Mes: julio 2019

TURBOCHARGER: COMPONENTS, WORKING PRINCIPLES, AND TYPES

31 Jul 2019 By INGENIERIA Y MECANICA AUTOMOTRIZ

A Turbocharger is a device that is used to increase the power of the engine or one can say the efficiency of an engine by increasing the amount of air entering into the combustion chamber. More air into the combustion chamber means more amount of fuel will be admitted into the cylinder and as a result, one will get more power from the same engine if the turbocharger is installed in it.

Very simply, a turbocharger is a kind of air pump taking air at ambient pressures (atmospheric pressure), compressing to a higher pressure and passing the compressed air into the engine via the inlet valves.

At the present time, turbos are used mainly on diesel engines, but there is now a move towards the turbocharging of production petrol engines.

The amount of engine that actually goes into the engine’s cylinder, compared with the theoretical amount if the engine could maintain the atmospheric pressure, is called volumetric efficiency and the aim of the turbocharger is to improve an engine’s volumetric efficiency by increasing density of the intake gas.

The turbocharger draws the air from the atmosphere and compresses it with the help of centrifugal compressor before it enters into the intake manifold at increased pressure. This results in more amount of air entering into the cylinders on each intake stroke. The centrifugal compressor gets power from the kinetic energy of the engine’s exhaust gases.

COMPONENTS OF TURBOCHARGER

The turbocharger has three main components
1. The turbine, which is almost a radial inflow turbine.
2. The compressor is almost a centrifugal compressor.
3. The center hub rotating assembly.

No photo description available.

A turbocharger is made up of two main sections: the turbine and the compressor.

The turbine consists of a turbine wheel and turbine housing. It is the job of the turbine housing to guide the exhaust gas into the turbine wheel. The energy from the exhaust gas turns the turbine wheel, and the gas then exits the turbine housing through an exhaust outlet area.

The compressor also consists of two parts: the compressor wheel and the compressor housing. The compressor’s mode of action is opposite that of the turbine. The compressor wheel is attached to the turbine by a forged steel shaft, and as the turbine turns the compressor wheel, the high-velocity spinning draws in air and compresses it. The compressor housing then converts the high-velocity, low-pressure air stream into a high-pressure, low-velocity air stream through a process called diffusion. The compressed air is pushed into the engine, allowing the engine to burn more fuel to produce more power.

WORKING PRINCIPLE

A turbocharger mainly consists of two main sections: the turbine and the compressor. The turbine consists of a turbine wheel and the turbine housing whose purpose is to guide the exhaust gases into the turbine wheel. The kinetic energy of the exhaust gases gets converted into the mechanical after striking it on turbine blades. The exhaust outlet helps the exhaust gases to get exit from the turbine. The compressor wheel in the turbocharger is attached to a turbine with the help of steel shaft and as the turbine turns the compressor wheel, it draws the high-velocity, low-pressure air stream and converts it into high-pressure, low –velocity air stream. This compressed air is pushed into the engine with the more quantity of fuel and hence produce more power.

The waste exhaust gases of the engine are utilized to drive a turbine wheel, which is connected to a compressor wheel by a shaft. The compressor or air wheel sucks in air through the air filters and passes this into the engine.
As the waste gases are expelled from the engine, they are directed to the turbine or hot wheel of the turbo and so completes the cycle.

1. Capture

Instead of escaping through the exhaust pipe, hot gases produced during combustion flow to the turbocharger. The cylinders inside an internal combustion engine fire in sequence (not all at once), so exhaust exits the combustion chamber in irregular pulses.
Conventional single-scroll turbochargers route those irregular pulses of exhaust into the turbine in a way that causes them to collide and interfere with one another, reducing the strength of the flow. In contrast, a twin-scroll turbocharger gathers exhaust from pairs of cylinders in an alternating sequence.

2. Spin

The exhaust strikes the turbine blades, spinning them at up to 150,000 rpm. The alternating pulses of exhaust help eliminate turbo lag.

3. Vent

Having served their purpose, exhaust gases flow through an outlet to the catalytic converter, where they are scrubbed of carbon monoxide, nitrous oxides, and other pollutants before exiting through the tailpipe.

4. Compress

Meanwhile, the turbine powers an air compressor, which gathers cold, clean air from a vent and compresses it to 30 percent above atmospheric pressure, or nearly 19 pounds per square inch. Dense, oxygen-rich air flows to the combustion chamber.

The additional oxygen makes it possible for the engine to burn gasoline more completely, generating more performance from a smaller engine. As a result, the Twin Power engine generates 30 percent more power than a non-turbocharged one of the same sizes.

It follows the following process

1. The engine’s air intake sucks in cool air and sends to the compressor.
2. The compressor compresses the incoming air and heats it up. It then blows out the hot air.
3. The hot air cools down when passing through the heat exchanger and enters the cylinder’s air intake.
4. The cold air burns inside the combustion chamber at a faster rate because of carrying more oxygen.
5. Due to the burning of more fuel, the energy output will be bigger faster, and the engine will be able to send more power to the wheels.
6. Hot waste gasses will leave the chamber and blows past the turbine at the exhaust outlet.
7. The turbine rotates at a high speed and spins the compressor too as both are mounted on the same shaft.
8. The exhaust gasses leave the car through the exhaust pipe. They waste less energy than an engine not having a turbocharger.

TYPES OF TURBOCHARGER

1. Single-Turbo

Single turbochargers alone have limitless variability. Differing the compressor wheel size and turbine will lead to completely different torque characteristics. Large turbos will bring on high top-end power, but smaller turbos will provide better low-end grunt as they spool faster. There are also ball bearing and journal bearing single turbos. Ball bearings provide less friction for the compressor and turbine to spin on, thus are faster to spool (while adding cost).

Advantages
• A cost-effective way of increasing an engine’s power and efficiency.
• Simple, generally the easiest of the turbocharging options to install.
• Allows for using smaller engines to produce the same power as larger naturally-aspirated engines, which can often remove weight.

Disadvantages
• Single turbos tend to have a fairly narrow effective RPM range. This makes sizing an issue, as you’ll have to choose between good low-end torque or better high-end power.
• Turbo response may not be as quick as alternative turbo setups.

2. Twin-Turbo

Just like single turbochargers, there are plenty of options when using two turbochargers. You could have a single turbocharger for each cylinder bank (V6, V8, etc). Alternatively, a single turbocharger could be used for low RPM and bypass to a larger turbocharger for high RPM (I4, I6, etc). You could even have two similarly sized turbos where one is used at low RPM and both are used at higher RPM. On the BMW X5 M and X6 M, twin-scroll turbos are used, one on each side of the V8.

Advantages
• For parallel twin turbos on ‘V’ shaped engines, the benefits (and drawbacks) are very similar to single turbo setups.
• For sequential turbos or using one turbo at low RPM and both at high RPM, this allows for a much wider, flatter torque curve. Better low-end torque, but the power won’t taper at high RPM like with a small single turbo.

Disadvantages
• Cost and complexity, as you’ve nearly doubled the turbo components.
• There are lighter, more efficient ways of achieving similar results (as discussed below).

3. Twin-Scroll Turbo

A turbo is powered by exhaust gases that are redirected to spin turbine blades and force air into the engine. Now, an engine’s cylinders fire in sequence, meaning that exhaust gases enter the turbo in pulses. As you can probably imagine, these pulses can easily overlap and interfere with one another when powering the turbo, and a twin-scroll turbocharger solves this issue by using a divided-inlet turbine housing and a specific exhaust manifold that pairs the right cylinders to each scroll. In a four-cylinder vehicle, you can then have the first and fourth cylinders powering one scroll, and two and three powering another. This means that there are less pulse overlap and less lag.

Advantages
• More energy is sent to the exhaust turbine, meaning more power.
• A wider RPM range of effective boost is possible based on the different scroll designs.
• More valve overlap is possible without hampering exhaust scavenging, meaning more tuning flexibility.

Disadvantages
• Requires a specific engine layout and exhaust design (eg: I4 and V8 where 2 cylinders can be fed to each scroll of the turbo, at even intervals).
• Cost and complexity versus traditional single turbos.

4. Variable Geometry Turbocharger (VGT)

A variable geometry turbo (VGT) is an expensive and complex power solution that’s especially prevalent in diesel engines. A VGT has a ring of aerodynamically-shaped vanes in the turbine housing that can alter their area-to-radius ratio to match the revolutions of the engine. At low revs, area-to-radius ratio creates more pressure and velocity to spool up the turbo more effectively. At higher revolutions, the ratio increases to let in more air. The result is a wider boost range and less lag.

Advantages
• Wide, flat torque curve. Effective turbocharging at a very wide RPM range.
• Requires just a single turbo, simplifying a sequential turbo setup into something more compact.

Disadvantages
• Typically only used in diesel applications where exhaust gases are lower so the vanes will not be damaged by heat.
• For gasoline applications, the cost typically keeps them out as exotic metals have to be used in order to maintain reliability. The tech has been used on the Porsche 997, though very few VGT gasoline engines exist as a result of the cost associated.

5. Variable Twin-Scroll Turbocharger

A variable twin-scroll turbo combines a VGT with a twin-scroll setup, so at low revolutions, one of the scrolls is closed completely, forcing all the air into the other. This results in good turbo response and low-end power. As you speed up, a valve opens to allow air into the other scroll (this is a completely variable process, meaning the valve opens in small increments), you get good high-end performance. You get the sort of performance from a single turbo that you’d normally only be able to get from a twin-turbo set-up.

Advantages
• Significantly cheaper (in theory) than VGTs, thus making an acceptable case for gasoline turbocharging.
• Allows for a wide, flat torque curve.
• More robust in design versus a VGT, depending on the material selection.

Disadvantages
• Cost and complexity versus using a single turbo or traditional twin-scroll.
• The technology has been played with before (eg: quick spool valve) but doesn’t seem to catch on in the production world. There are likely additional challenges with technology.

6. Electric Turbochargers

A very recent development is the introduction of turbos with electric compressors. An example is BorgWarner’s booster, which is an electrically powered compressor. The compressor provides an instant boost to the engine until the turbocharger has spooled up enough. A similar version of this can be found in Audi’s SQ7. With the instant boost, lag becomes a thing of the past, but again, the system is expensive and complex. A compressor needs a motor, which in turn needs to be powered, so this is not a simple system to implement.

Advantages
• By directly connecting an electric motor to the compressor wheel, turbo lag and insufficient exhaust gases can be virtually eliminated by spinning the compressor with electric power when needed.
• By connecting an electric motor to the exhaust turbine, wasted energy can be recovered (as is done in Formula 1).
• A very wide effective RPM range with even torque throughout.

Disadvantages
• Cost and complexity, as you now must account for the electric motor and ensure it remains cool to prevent reliability issues. That goes for the added controllers as well.
• Packaging and weight become an issue, especially with the addition of a battery onboard, which will be necessary to supply sufficient power to the turbo when needed.
• VGTs or twin-scrolls can offer very similar benefits (though not at quite the same level) for a significantly lower cost.

WATER COOLING VS AIR COOLING

30 Jul 2019 By INGENIERIA Y MECANICA AUTOMOTRIZ

A vehicle’s engine-cooling system serves not just to keep the engine cool, but to also keep its temperature warm enough to ensure efficient, clean operation. System components include a radiator to dissipate heat, a fan or fans to ensure adequate airflow for radiator cooling, a thermostat valve that opens when the desired operating temperature is reached and a water pump (or coolant pump) to circulate coolant through the engine, hoses and other components. Most vehicles now employ an expansion tank that allows the coolant to expand, and exit, the cooling circuit when hot, and to return when the car is turned off and the engine cools.
The cooling system also incorporates elements of the cabin’s ventilation system, because engine heat is used to warm the car’s interior.

While running, an engine continuously produces heat and converts it into power.
This heat is derived by burning fuel in the engine.
But as we all know, there is no engine in the world which is 100% efficient.
There is always some amount of heat energy which gets wasted. If we do not transmit this heat energy into the atmosphere, this heat will overheat the engine.
This overheating will result in engine seizing. In engine seizing, due to excess heat piston gets melted inside the cylinder.
It avoids this trouble of overheating a car is provided with an engine cooling system.

An engine cooling system is a system integrated with the engines. It carries away excess heat from the engine with the help of a flowing fluid.
This fluid can be air or water.

Or we can say there are two types of cooling systems
1. Liquid or indirect cooling system
2. Air or direct cooling system

LIQUID OR INDIRECT COOLING SYSTEM

In a liquid cooling system, an engine is surrounded with water jackets. With the help of a pump, this water gets circulated in this water jacket.
Water flowing in these jackets takes out heat from the engine. This hot water then flows through a radiator, where it gets cooled from the cold heat blown through a fan.
In this system, the water takes heat from the engine and that water gets cooled by the air and then again gets circulated to the engine.
This is an indirect cooling process, where the actual cooling thing that is air is not directly cooling the system. The air is cooling the water and water is cooling the engine.
Liquid or indirect cooling system is mainly used in big engines, like that of cars and trucks.

Advantages

1. The compact design of engines
2. It provides even cooling to the engine
3. The engine can be installed at any location of the vehicle. It is not necessary to install an engine at the front.
4. It can be used in both small and big engines

Limitations

1. Here water jacket becomes one extra part of the engine.
2. Water circulation consumes power, thus reduces engine efficiency.
3. In case of failure of the cooling system, serious damage could happen to the engine.
4. Cost of the system is considerably high.
5. It requires routine maintenance, and thus puts extra maintenance cost burden.

AIR OR DIRECT COOLING SYSTEM

In a direct cooling system, an engine is cooled directly with the help of air flowing through it. It is the same cooling system which is used to cool our bike engines.
As we can see here, the air is in direct contact with the engine hence it is also known as a direct cooling system.
Air cooling system is used for small engines, like that of bikes and grass cutter, etc.

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Advantages

1. Design of the engine becomes simpler.
2. Repair is easy in case of damages.
3. Absence of bulky cooling system makes system maintenance easily.
4. No danger of coolant leakage.
5. The engine is not subjected to freezing troubles.
6. Weight of the system is less.
7. It is a self-contained unit, as it does not requires a radiator, header, tanks, etc.
8. Installation of the air-cooled system is easy.

Limitations

1. It is applicable to only small and medium-sized engines.
2. It can only be used at the places where ambient temperatures are lower.
3. Cooling is not uniform.
4. Higher working temperature as compared to water-cooled engines.
5. It produces more aerodynamic noise.
6. Specific fuel consumption is slightly higher.
7. Lower maximum allowable compression ratios.
8. The fan, if used consumes almost 5% power generated by the engines.

Characteristics of an efficient engine cooling system

Following are two main characteristics of an efficient engine cooling system.

1. It should be capable of removing about 30% of the heat generated in the engine while maintaining an optimum working temperature in the engine.
2. It should remove heat at a faster rate when the engine is hot and remove the engine at a slow rate when the engine is cold.

¿Qué significan las letras que tienen los rines ya sea en su cara interior o exterior?

28 Jul 2019 By INGENIERIA Y MECANICA AUTOMOTRIZ

JWL» (Japan Light Wheel Alloy) es una compilación de estándares definidos por el gobierno japonés para garantizar la seguridad del vehículo para las ruedas de aluminio. Cada rueda puesta al mercado debe ser probada para cumplir con los estándares de JWL antes de que una rueda pueda ser lanzada al mercado en Japón.

Estas normas son generalmente aceptadas en todo el mundo como aceptables para la mayoría de las condiciones de la carretera. Ése es porqué usted verá estas marcas en el europeo y otras ruedas del país asiático.

Japón Light Alloy Wheel Association, manteniendo un estrecho contacto con sus compañías miembro, realiza estudios de investigación y técnicos relacionados con la fabricación, comercialización y distribución de llantas de aleación ligeras para automóviles.

Estas actividades también incluyen el mercado y la investigación técnica dirigida a desarrollar la nueva demanda para los productos de la industria más muchas otras actividades relacionadas.

Para lograr estos objetivos, la asociación alemana de la rueda de la aleación de Japón apunta mejorar calidad de la 
rueda de la aleación ligera del automóvil y promueve la responsabilidad de su producto en el mercado automotor-Después.

Los objetivos principales incluyen también lo siguiente:
Para mantener estándares de seguridad, apoya la norma técnica «JWL» y «JWL-T» y promueve el sistema de registro «JAWA» VIA.

JWL. 
Rueda de la aleación ligera de Japón. La norma técnica para las llantas de aleación ligera para automóvil de pasajeros 
aprobado por el Ministerio de Transporte (MOT).

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JWL-T. 
Japón Camión y autobús de la rueda de la aleación ligera. 
La norma técnica para las ruedas de disco de aleación ligera para camiones y autobuses aprobado por el Ministerio de Transporte (MOT).

VÍA. 
Sistema de Registro de la Asociación de Inspección de Vehículos. La marcación VIA sólo se puede grabar en la rueda si se registra en el Japan Light Alloy Automotive Wheel Testing Council después de estrictas pruebas de calidad realizadas por la instalación de pruebas autorizada sobre la adaptabilidad del 
estándar técnico JWL o JWL-T.

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JAWA 
Para establecer el orden del diseño de la rueda en nuestra industria, 
«JAWA» promueve Voluntary Wheel Design Protection Registration System.
«JAWA» también presta su apoyo a los esfuerzos para encontrar soluciones al sistema de reciclaje de materiales.

¿Cómo funciona la válvula EGR?

28 Jul 2019 By INGENIERIA Y MECANICA AUTOMOTRIZ

En los motores más modernos, el funcionamiento de la EGR se rige por la señal de los sensores de temperatura del motor, régimen del motor y carga de aceleración. En función de estos la ECU del coche comandará la EGR, abriéndola o cerrándola. Por norma general, las EGR están abiertas (metiendo gases quemados al motor) cuando circulamos con el motor caliente, a baja carga y a regímenes de motor bajos.

Si se cumplen los parámetros para la apertura de la EGR, veremos que esta se acciona de dos formas, según su naturaleza. Puede ser por un actuador de vacío o por un actuador eléctrico. Las segundas son las más eficaces y las que ahora equipan casi todos los vehículos, ya que permiten controlar mejor el grado de apertura de la válvula. Algunos vehículos equipan válvulas EGR refrigeradas por un intercambiador de calor que utiliza el refrigerante del motor. De esta forma, se reduce la temperatura de los gases a la hora de introducirlos en los cilindros y la producción de emisiones de NOx es todavía menor.

Cuando la válvula EGR está abierta en la cámara de combustión se mezclan los gases recirculados con los gases frescos de la admisión. En este caso los segundos son menores que si la válvula estuviese cerrada y por tanto en las explosiones se genera menos calor, de ahí la reducción de las emisiones de NOx.

Como no es difícil intuir, el funcionamiento la válvula EGR resta potencia al motor. Cuanto más frío sea el aire que entra al motor y más oxígeno tenga, más potencia tendrán las explosiones y por tanto, mejor será el rendimiento del vehículo. Por ese motivo, cuando demandamos mucha aceleración, la EGR permanece cerrada, para tener todas las prestaciones del motor.

Cómo comprobar el ajuste de las válvulas de la cabeza de motor?

28 Jul 2019 By INGENIERIA Y MECANICA AUTOMOTRIZ
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Las holguras de las válvulas son pequeñas brechas entre la parte superior de los vástagos de la válvula y la parte del mecanismo que presiona sobre ellos para abrirlas.

Compruebe las holguras en intervalos regulares según se especifique en el programa de mantenimiento del auto y ajústela de ser necesario. Restablezca la holgura cada vez que se saque la culata.

Antes de empezar, asegúrese de conocer el tipo de mecanismo de válvula que comúnmente se llama engranaje de válvula (montado en el motor) y su holgura. El manual del auto debería indicarle la holgura, pero si no es así, consulte con un distribuidor o en el manual de servicio del auto.

Primero debe saber el orden de encendido del motor, cuál es el cilindro Nº 1, cuáles son las válvulas de admisión y de escape, y que balancín o levas lo hace funcionar. Realice un plan con toda esta información en un papel.

Encuentre la holgura correcta para las válvulas de admisión y escape, y si éstas deberían ser ajustadas con el motor caliente o frío.

FIRING ORDER: ITS PURPOSE AND ORDER IN DIFFERENT NUMBERS OF CYLINDERS

28 Jul 2019 By INGENIERIA Y MECANICA AUTOMOTRIZ

The firing order is the sequence of power delivery of each cylinder in a multi-cylinder reciprocating engine. This is achieved by sparking of the spark plugs in a gasoline engine in the correct order, or by the sequence of fuel injection in a Diesel engine. When designing an engine, choosing an appropriate firing order is critical to minimizing vibration and achieving smooth running, for long engine fatigue life and user comfort, and heavily influences crankshaft design.

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The firing order of an engine is the sequence in which the power event occurs in the different cylinders. The firing order is designed to provide for balance and to eliminate vibration to the greatest extent possible. In radial engines, the firing order must follow a special pattern since the firing impulses must follow the motion of the crank throw during its rotation. In inline engines, the firing orders may vary somewhat, yet most orders are arranged so that the firing of cylinders is evenly distributed along the crankshaft.

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PURPOSE OF FIRING ORDER

These are some factors which must be considered before deciding the optimum firing order of an engine. 
• Engine vibrations
• Engine cooling 
• Development of back pressure.
• Engine balancing and
• Even flow of power.

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FIRING ORDERS OF VARIOUS NUMBER OF CYLINDERS

1. 3-cylinder

Firing order
1-2-3 Saab two-stroke engine
1-3-2 BMW K75 engine

2. 4-cylinder

Firing order
• 1-3-4-2 Most straight-4s, Ford Taunus V4 engine
• 1-2-4-3 Some English Ford engines, Ford Kent engine
• 1-3-2-4 Yamaha R1 crossplane
• 1-4-3-2 Volkswagen air cooled engine

3. 5-cylinder

Firing order
• 1-2-4-5-3 Straight-5, Volvo 850, Audi 100

4. 6-cylinder

Firing order
• 1-5-3-6-2-4 Straight-6, Opel Omega A
• 1-6-5-4-3-2 GM 3800 engine
• 1-2-3-4-5-6 GM 60-Degree V6 engine
• 1-4-2-5-3-6 Mercedes-Benz M104 engine
• 1-4-5-2-3-6 Chevrolet Corvair
• 1-4-3-6-2-5 Mercedes-Benz M272 engine, Volkswagen V6’s
• 1-4-2-6-3-5 Toyota HZ engine

5. 7-cylinder

Firing order
• 1-3-5-7-2-4-6 7-cylinder single row radial engine

6. 8-cylinder

Firing order
• 1-8-4-3-6-5-7-2 1988 Chrysler Fifth Avenue, Chevrolet Small-Block engine
• 1-8-7-2-6-5-4-3 GM LS engine, Toyota UZ engine
• 1-3-7-2-6-5-4-8 Porsche 928, Ford Modular engine, 5.0 HO
• 1-5-4-8-7-2-6-3 BMW S65
• 1-6-2-5-8-3-7-4 Straight-8
• 1-8-7-3-6-5-4-2 Nissan VK engine
• 1-5-4-2-6-3-7-8 Ford Windsor engine
• 1-5-6-3-4-2-7-8 Cadillac V8 engine 368, 425, 472, 500 only
• 1-5-3-7-4-8-2-6 Ferrari Dino V8 (F355)
• 1-2-7-8-4-5-6-3 Holden V8

7. 10-cylinder

• 1-10-9-4-3-6-5-8-7-2 Dodge Viper V10 
• 1-6-5-10-2-7-3-8-4-9 BMW S85

8. 12-cylinder

Firing order
• 1-7-5-11-3-9-6-12-2-8-4-10 Ferrari 456M GT V12
• 1-7-4-10-2-8-6-12-3-9-5-11 Lamborghini Diablo VT
• 1-4-9-8-5-2-11-10-3-6-7-12 Caterpillar Inc. 3412E
• 1-12-5-8-3-10-6-7-2-11-4-9 Audi VW Bentley W12 engine
• 1,12,7,6,3,10,11,2,5,8,9,4 Rolls-Royce Merlin
• 1,12,4,9,2,11,6,7,3,10,5,8 Lamborghini Aventador

9. 16-cylinder

Firing order
1-12-8-11-7-14-5-16-4-15-3-10-6-9-2-13 Cadillac V16 engine

10. 20-cylinder

Firing order
• 1-12-8-11-7-14-5-16-4-15-3-10-6-9-13-17-19-2-18-20 Cadillac V20 engine

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SUSPENSION SYSTEM: COMPONENTS, TYPES AND WORKING PRINCIPLE

26 Jul 2019 By INGENIERIA Y MECANICA AUTOMOTRIZ
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A system of mechanical linkages, springs, dampers that is used to connect the wheels to the chassis is known as a suspension system. It has usually done two works-controlling the vehicle’s handling and braking for safety and keeping the passengers comfortable from bumps, vibrations etc.

It also helps to maintain correct vehicle height and wheel alignment.it also control the direction of the vehicle and has to keep the wheel in a perpendicular direction for their maximum grip. The suspension also protects the vehicle itself and luggage from damage and wear. The design of the front and rear suspension of a car may be different.

COMPONENTS OF THE SUSPENSION SYSTEM

A suspension system irrespective of their type has some main components in common that are:-

1. Knuckle or Upright-

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It is the component of the suspension system that is mounted over the wheel’s hub through which the wheels and the suspension of the vehicle connect with each other by the linkages provided.
A knuckle is provided with the king-pin and the caster angles that help the front wheels of the vehicle to steer in right or left direction which in turn steers the vehicle.
A knuckle provides housing for central bearing over which the wheel’s hub rotates along with the rotation of the wheels.

2. Linkages-

linkages are the rigid connections that are used in the suspension system to connect the mainframe of the vehicle with the knuckle of the wheels through mechanical fasteners.

On the basis of the type of suspension used linkages are of 3 types-

i. Wishbones or A-arm – 
It is the type of the mechanical linkage which is in shape of the alphabet A, the pointy end of the A-arm is fastened to the knuckle and the other 2 ends of the A-arm are fastened to the mainframe of the vehicle.
On the basis of the application of the vehicle, either a single A-arm or double A-arm are used.

ii. Solid axle or live axle- 
It is the type of linkage which is used to connect the mainframe of the vehicle with the knuckle on the wheel, this is the solid axle casing that supports the overall weight of the vehicle, this type of linkage can be seen in trucks.

iii. Multiple links- 
Instead of using double wishbone or solid axle linkage various high-end cars are adopting multiple link type of suspension in which multiple solid links are used to connect the mainframe of the vehicle to the knuckle on the wheel.

3. Shock absorbers or springs-

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They are the flexible mechanical components that are used to absorb shock provided by the road condition and is placed between the linkages ( wishbone. Solid axle, multi-links) and the mainframe such that the road shock is minimised before transmitting to the mainframe of a vehicle.

On the basis of the application and type of suspension used shock absorbers are of many types that are-

i. Spring and damper type shock absorber- 
It is the type of shock absorber in which a pneumatic or hydraulic piston is known as the damper is used that provides damping by absorbing the road shocks.

This damper is surrounded by a compression coil spring which is an elastic mechanical constraint that compresses when force is applied by the bump and recoil back or regains its original shape and size when the force is removed.

It is used to maintain the surface contact of the tyres with the road by providing stiffness (resistance to compress), also maintain the damper at its original length after absorbing the shock.

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ii. Leaf spring- 
It is the type of spring in which a number of ductile metal plates called leaf are arranged in a special pattern i.e. one over one in ascending order of their length, leaves of the leaf spring shock absorber are pre-stressed such that when the shock is transferred by the wheels these pre-stressed leaves being ductile tries to regain their original shape i.e. straighten,. Due to which shock is absorbed by the leaves.

This type of shock absorber can be easily seen in trucks on the road in which leaf spring shock absorber is used in between the solid or live axle and the mainframe of the vehicle.

iii. Air spring- 
It is the latest type of shock absorbers which can be easily seen in Volvo buses, in air spring shock absorbers the damping of shock is a function of air compression, which means air is used as a shock absorber.
The air needed for different load conditions is controlled and monitored by the Electric control unit of the vehicle.

TYPES OF SUSPENSION SYSTEM

1) INDEPENDENT SUSPENSION SYSTEM

This system means that the suspension is set-up in such a way that allows the wheel on the left and right side of the vehicle to move vertically independent up and down while driving on an uneven surface. A force acting on the single wheel does not affect the other as there is no mechanical linkage present between the two hubs of the same vehicle. In most of the vehicle, it is employed in front wheels.
This type of suspension usually offers better ride quality and handling due to less unsprung weight. The main advantage of independent suspension is that they require less space, they provide easier steerability, low weight etc.. Examples of Independent suspension are

No photo description available.

i. Double Wishbones

It is an independent suspension system design using two wishbone-shaped arms(called A-ARM in USA and WISHBONE in the UNITED KINGDOM)to locate the wheel. Each wishbone or arm has two mounting points to the chassis and one joint at the knuckle. The angle movements of the compressing and rebounding wheels can be managed by using arms of unequal length.
The main advantage of the double-wishbone suspensions is that they allow easy adjustments of camber, toe and other properties. This type of suspension also provides increasing negative camber gain all the way to full jounce travel. On the other hand, it takes more space and is slightly more complex than the other system like Macpherson strut. It also offers less design choice.

ii. MacPherson Strut

This type of independent suspension got its name from Earle S. McPherson who developed this design. The MacPherson strut is a further development of the double-wishbone suspension. The main advantage of the MacPherson is that all the parts providing the suspension and the wheel control can be combined into the one assembly.

It makes it easy to fit in transverse engine. This design is very popular due to its simplicity and low manufacturing cost. The disadvantage is that it is more difficult to insulate against road noise. for this, an upper strut mount is necessary, which should be decoupled as possible. It also requires greater clearance height.

2) DEPENDENT SUSPENSION SYSTEM

IN Dependent Suspension there is a rigid linkage between the two wheels of the same axle. A force acting on one wheel will affect the opposite wheel. For each motion of the wheel caused by road, irregularities affect the coupled wheel as well.
It is mostly employed in heavy vehicles. It can bear shocks with a great capacity than independent suspension. Example of this system is

I. Solid Axle.
A solid axle or beam axle is a dependent type suspension. It is mostly used in rear wheels in which the rear axle is supported and located by two leaf springs. The vertical movement of one wheel influences the other. They are simple and economical to manufacture.
They are so rigid that there is no change in track width, toe-in and camber on a full bump which helps in the low wearing of tyres. The main disadvantage is that the mass of the beam is included in the unsprung weight of the vehicle which results in low ride quality. The cornering ability is also poor due to zero camber angle.

3) SEMI-INDEPENDENT SYSTEM

This type of system has both the characteristics of a dependent as well as independent suspension. In semi-independent suspension, the wheel move relative to one another as in independent suspension but the position of one wheel has some effect on the other wheel. This is done with the help of twisting suspension parts. Example of semi-independent is

i. Twist Beam
The twist-beam suspension also known as the torsion-beam axle. These are mostly based on C or H shaped members. The cross beam of the H-shape holds the two trailing arms together and provides the roll stiffness to the suspension.
It is mostly used in the rear wheel of the cars. It is very favourable due to its low cost and it is very durable. It is simple in design and is very light in weight. But on the other side camber angle is limited and the roll stiffness is also not very easy. Toe characteristics may be unsuitable.

DISC BRAKES: CONSTRUCTION, WORKING PRINCIPLE, TYPES, AND ROTOR MATERIALS

26 Jul 2019 By INGENIERIA Y MECANICA AUTOMOTRIZ

Brake rotors of disc brakes rotate with the wheels, and brake pads, which are fitted to the brake calipers, clamp-on these rotors to stop or decelerate the wheels. The brake pads pushing against the rotors generate friction, which transforms kinetic energy into thermal energy.

This thermal energy generates heat, but since the main components are exposed to the atmosphere, this heat can be diffused efficiently. This heat-dissipating property reduces brake fade, which is the phenomenon where braking performance is influenced by the heat. Another advantage of disc brake is its resistance to water fade, which occurs when the water on the brakes significantly reduces braking force. When the vehicle is in motion, the rotor spins at high speeds and this rotational motion discharges the water from the rotors themselves, resulting in stable braking force.

CONSTRUCTION

The brake rotor (disc) which rotates with the wheel, is clamped by brake pads (friction material) fitted to the caliper from both sides with pressure from the piston(s) (pressure mechanism) and decelerates the disc rotation, thereby slowing down and stopping the vehicle.

1. Rotor: 
Circular disc bolted to the wheel hub that spins with the wheel. Rotors are most commonly made of cast iron or steel; however, some very high-end cars use a carbon-ceramic rotor. Rotors can be slotted or drilled for better heat dissipation.

2. Brake pads: 
The component that pushes into the rotor, creating the friction that slows and stops a car. They feature a metal portion called a shoe and a lining that is attached to the shoe. The lining is what actually comes in contact with the rotor and wears away with use. Linings are made of different materials and fall into three categories: organic, semi-metallic and ceramic. The lining material chosen will impact the length of brake life, the amount of noise heard when the brakes are applied, and how quickly the brakes bring a car to a halt.

3. Piston: 
Cylinder connected to the brake system hydraulics. The piston is what moves the brake pads into the rotor when the driver presses the brake pedal. Some brake systems have a single piston that moves both pads, while others have two pistons that push the brake pads from each side of the rotor. Others still have four, six, or even eight pistons for higher braking power, at the expense of added cost and complexity.

4. Caliper: 
Housing that fits over the rotor and holds the brake pads and pistons, as well as contains ducting for brake fluid. There are two types of brake calipers: floating (or sliding) and fixed. Floating calipers “float” over the rotor, and only have pistons on a single side. When the driver presses the brakes, the pistons press the brake pads on one side into the rotor, which causes the caliper to slide over so that the pads on the non-piston side of the caliper also contact the rotor. Fixed calipers are bolted in place, and instead, have pistons on both sides of the rotor that move when the driver applies the brakes. Fixed calipers apply brake pressure more evenly and clamp more firmly on the rotor, however floating calipers are found on most cars and are perfectly adequate for everyday driving.

5. Sensors: 
Some vehicles have brakes that contain sensors embedded in the brake pads which work to tell the driver when the pads are worn out. Other brake sensors play a part in the vehicle’s ABS system.
Disc brakes are generally used in passenger cars, but due to their stable performance at higher speeds and resistance to brake fade, they are gradually spreading into the commercial vehicle segment, where drum brakes were traditionally chosen for their longer service life. There are two types of disc brakes.
The «opposed piston type disc brake» has pistons on both sides of the disc rotor, while the «floating type disc brake» has a piston on only one side. Floating caliper type disc brakes are also called sliding pin type disc brakes.

WORKING PRINCIPLE

When the driver steps on the brake pedal, the power is amplified by the brake booster (servo system) and changed into a hydraulic pressure (oil-pressure) by the master cylinder. The pressure reaches the brakes on the wheels via tubing filled with brake oil (brake fluid). The delivered pressure pushes the pistons on the brakes of the four wheels. The pistons in turn press the brake pads, which are friction material, against the brake rotors which rotate with the wheels. The pads clamp on the rotors from both sides and decelerate the wheels, thereby slowing down and stopping the vehicle.

• When the brake pedal is pressed, the high-pressure fluid from the master cylinder pushes the piston outward.
• The piston pushes the brake pad against the rotating disc.
• As the inner brake pad touches the rotor, the fluid pressure exerts further force and the caliper moves inward and pulls the outward brake pad towards the rotating disc and it touches the disc.
• Now both the brake pads are pushing the rotating disc, a large amount of friction is generated in between the pads and rotating disc and slows down the vehicle and finally, let it stop.
• When a brake pad is released, the piston moves inward, the brake pad away from the rotating disc. And the vehicle again starts to move.

TYPES OF DISC BRAKES

There are two types of disc brakes. One is called the «opposed piston type disc brake» which has pistons on both sides of the disc rotor, and the other is the «floating type disc brake» which has a piston on only one side. The floating type disc brakes are also called the sliding pin type disc brakes.

1. Opposed Piston Type Disc Brakes

The opposed piston type is a disc brake which has pistons on both sides of the disc rotors.
The opposed piston type disc brake features stable braking force as well as a high level of controllability.
The swept areas of the brake pads are enlarged to increase braking force, and here opposed piston types are favored. This is because of its advantage where the number of pistons can be increased to realize even distribution of pressure on the rotors from both sides. Depending on the size of the brake pads, there are several types, including the 4-pot type which has two pistons on each side for a total of four, and the 6-pot type which has three pistons on each side for a total of six.

2. Floating Type Disc Brakes

Floating type is a disc brake which has a piston on only one side and is also called the sliding type disc brake.
On the floating type disc brakes, the piston pushes the inner brake pad against the rotor when the brakes are engaged. This generates a reaction force that moves the caliper itself along with the slide pin, pushing the outer pad against the rotor to clamp it from both sides.

Many passenger car disc brakes are of the floating caliper type since this type has a relatively simple and lightweight construction, which allows for lower manufacturing costs.
Floating type disc brakes for commercial vehicles
Disc brakes are used mainly for passenger cars, but due to their consistent performance at higher speeds and resistance to brake fade, they are gradually spreading into the commercial vehicle segment, where drum brakes were traditionally chosen for their resistance against wear.

TYPES OF ROTOR

1. Smooth Rotors
Smooth rotors are identified by their flat, smooth surface. For most cars and trucks on the road, smooth rotors are original equipment (OE) because of their versatility for many driving conditions. The main benefit of smooth rotors is that they tend to wear evenly, helping your brake pads last longer. If you want to keep the smooth rotor but still go for the upgrade, look for premium metal that absorbs more heat.

2. Drilled or Dimpled Rotors
Drilled rotors are identified by the pattern of holes that have been drilled all the way through the rotor disc. Dimpled rotors are similar, though instead of holes there are dimples that have been drilled to the rotor’s minimum thickness level, retaining more structural integrity than a fully drilled rotor. These rotor types help the brake pads to better grip the rotor, giving it more initial bite and increasing stopping power.
*Note that drilled or dimpled rotors are typically found in combination with slotted rotors.

3. Slotted Rotors
Slotted rotors are recognized by carved lines found on the rotor. These carved slots help to cool the rotor during high-performance use. They also help to remove dirt and other debris from the disc and brake pad, helping to maintain consistent contact for more efficient braking. Slotted rotors are perfect for vehicles that see frequent, heavy towing.

4. Drilled/Dimpled and Slotted Rotors
Rotors that are both drilled (or dimpled) and slotted, while effective, are best for trucks that want the added aesthetic, such as those with wheels that have a more open design. Not only will they look great through an open-wheel, but the drilled holes assist with an initial bite while the slots are designed to remove dust and debris from between the rotor and brake pad.

ROTOR MATERIALS

Brake rotors can be made of six different materials, each with its own advantages. Let’s take a look at each.

1. Cast Iron
This is the very definition of old school when it comes to a brake rotor. It’s one or two pieces and gets the job done. In fact, it’s the most common material for brake rotors. The right design (usually two-piece) can even work well in a performance vehicle. However, it’s also the heaviest option, which affects the overall weight of your car and its handling, since that weight is right up there with your front wheels.

2. Steel
Steel has been the racer’s choice for years because a steel brake rotor is thinner, weighs less and handles heat better. The downside: Steel rotors aren’t as durable as some others, and warped rotors can cause noise and a pulsating pedal when you brake.

3. Layered Steel
Layering sheets of steel together and laminating them makes them resistant to the warping you might find in a straight steel brake rotor. It’s a favorite of racers who don’t want frequent brake rotor replacement and repair, but manufacturers are currently only targeting professional racers and production is limited, so it’s not terribly common in passenger vehicle applications.

4. Aluminum
Aluminum brake rotors dissipate heat quickly, but they also melt at a lower temperature than other options. Aluminum is a favorite for motorcycles, which weigh less and are easier on the rotors when braking than a heavy car, truck or SUV.

5. High Carbon
These are iron, but with a lot of carbon mixed in. They can take a lot of heat and dissipate it quickly. The metallic content helps the rotor avoid cracking under high stress, and brake noise and vibration are reduced as well. The only downside is the price, which is significantly higher than straight iron or aluminum.

6. Ceramic
What’s your favorite supercar? Ferrari? Porsche? Lamborghini? Odds are it’s packing ceramic brake rotors. They offer the highest heat capacity (85 percent higher than cast iron) and superior dissipation, and they maintain a more consistent force and pressure as the temperature of the rotors rises. Ceramic is the highest-performance brake rotor available today.

ADVANTAGES AND DISADVANTAGES

Advantages

1. It is lighter than drum brakes.
2. It has better cooling ( because the braking surface is directly exposed to the air)
3. It offers better resistance to fade.
4. It provides uniform pressure distribution
5. Replacement of brake pads is easy.
6. By design, they are self-adjusting brakes.

Disadvantages

1. It is costlier than drum brakes.
2. Higher pedal pressure is required for stopping the vehicle. This brake system is installed with vacuum booster.
3. No servo action is present.
4. It is difficult to attach a suitable parking attachment.

TYPES OF AUTOMATIC TRANSMISSION

24 Jul 2019 By INGENIERIA Y MECANICA AUTOMOTRIZ

1. Traditional Automatic Transmission

It also is known as self-shifting transmission, n-speed transmission or torque converter automatic, this is the standard type of automatic transmission to be found in most of the cars these days. Unlike a manual gearbox, it does not use a clutch to change gears. Instead, a hydraulic fluid coupling or a torque converter does this job. It connects to the Electronic Control Unit of the engine and allows for precise control of the vehicle.

It is a type of transmission that automatically changes gear ratios as the vehicle moves. The benefits of an AT center on giving drivers freedom from shifting gears manually. Other advantages include a smooth and precise engine control. Note that AT can be found in many non-MT vehicles.

Automatic cars perform smoothly, but the shifting of the gears is not quick all the time, earning them the name ‘slushbox’. The impression has been changing though, thanks to some brilliant transmission models such as the ZF 8-speed, which you will find in many cars ranging from Jaguars to BMWs.

2. Automated-Manual Transmission

Also known as semi-automatic transmission (SAT) or paddle-shift gearboxes, a semi-automatic transmission is a type of automatic transmission that it involves the driver making gear changes similar to a manual transmission. However, it does not have a clutch unlike an MT, and it makes use of electronic equipment such as sensors, actuators, and processors to simulate manual and make gear change precise and smooth.

This automatic transmission type utilizes a regular clutch and gear setup but automates the action by the use of sensors, actuators, processors, and pneumatics.

The cars featuring this transmission provide better performance on highways. They are not recommended for city driving because the engines feel jerky under hard acceleration.

3. Continuously Variable Transmission (CVT)

A continuously variable transmission or CVT is technically another type of automatic transmission. However, it does not use mechanical gears unlike an AT and instead, makes use of belts or pulleys to enable seamless gear shifting based on rations and depending on engine speed. Compact design and step-less acceleration are some of the advantages of a CVT while different engine feel and cost are some of its downsides.

It allows seamless gear shifting with numerous range of ratios and facilitates the engine to spin at the maximum RPM (speed).

Two more types of CVT are there. The Hydrostatic CVT uses hydrostatic motors and variable-displacement pumps for transferring power to the engine. On the other hand, the Toroidal CVTs use discs and power rollers for this purpose.
The transmission allows the engine to operate at the maximum efficiency with seamless acceleration. It is good for fuel economy, and the repair and maintenance are not expensive. However, the engine creates much noise under acceleration and load. Plenty of models use this gearbox, and some of the crowd favorites are Chevrolet Spark, Ford C-Max, Nissan Sentra, and more.

4. Dual-Clutch Transmission (DCT)

Another type of automatic transmission is the dual-clutch transmission system or DCT. Also known as a twin-clutch transmission or a double-clutch transmission, it does not have a torque converter and primarily involves the use of two separate clutches for odd and even gear sets, thus allowing a seamless shift to higher and lower gears. It also does not have a clutch pedal and instead, a computer operates both clutches. Hence, it offers the ease of an AT with the performance of an MT.

It is a hybrid of an automatic and manual transmission. There is no torque converter in DCT. You will use two separate shafts for gear changing, one for odd-numbered and another for even-numbered gears. Both the shafts have their own clutch.

You can shift to a higher or lower gear in a fraction of second and the transformation from automatic to the manual is also seamless. However, the DCT gearboxes can’t escape the complaints of noisy clutches, scratching sound, and rough shifts.

5. Direct Shift Gearbox(DSG)

It is almost similar to the DCT but without its annoying problems. It uses two clutches instead of a torque converter, and its mechanism works by simple disengaging of one clutch and engaging the other second one for changing the gears. This transmission offers faster gear shifting and smoother pulling away than the traditional models.

Modern DSG units provide better fuel efficiency than even the manual gearboxes. The DCT is a dry transmission that does not need the driver to change the gearbox fluid ever. It leaves the clutches dry and wears out their frictional quality eventually. The results are abrupt shifts, slow responses to gear shifting, and jerky transmission. On the other hand, DGS is a wet transmission that keeps the clutches lubricated. The result is decade-long service with lighting gear-changing performance. However, you have to change the fluid on a regular basis (every 40k miles), which could be costly.

Many automobile manufacturers such as Skoda, VW, Porsche, and Audi use this model in their cars but under different names. For example, Porsche calls it PDK gearboxes while the name changes to DSG S-Tronic units for Audi models.

6. Tiptronic Transmission

It is one of the automatic transmission types that functions just like a manual gearbox. However, it’s different from manual operation in the sense that it uses a torque converter in the place of a clutch pedal, does have the option for auto shifting, and does not let the driver have full control over the gears.

A Tiptronic transmission gives a driver an option to drive either in automatic mode or manual mode. Introduced by Porsche in the 90s and adopted by other manufacturers soon after, this type of automatic transmission has no clutch but, when used in manual mode, it allows direct upshift and downshifts selection using paddled behind the steering wheel or by using the gear lever itself. When used in automatic mode, the computer does the gear shifting.

What unique about this unit is it has the option to override the automatic mode. It means that you can drive your car as an automatic along with being able to switch into the manual mode when required such as getting up a hill or going downward in a steep road.

The cars using this unit has an inbuilt safety feature so that any driver error does not result in the damage of the gearbox. A number of manufacturers use this type of automatic transmission but it was first seen in Porsche 911 (in 1990) and then adopted by BMW and Chrysler.

Automotivee World

IC ENGINE: COMPONENTS AND THEIR FUNCTIONS, TYPES AND TERMINOLOGY

23 Jul 2019 By INGENIERIA Y MECANICA AUTOMOTRIZ

It is an engine in which combustion of fuel take place inside the engine. When the fuel burns inside the engine cylinder, it generates a high temperature and pressure. This high-pressure force is exerted on the piston (A device which free to moves inside the cylinder and transmit the pressure force to crank by use of connecting rod), which used to rotate the wheels of vehicle. In these engines we can use only gases and high volatile fuel like petrol, diesel. These engines are generally used in automobile industries, generation of electric power etc.

Advantages of I.C. engine

 It has overall high efficiency over E.C. engine.
 These engines are compact and required less space.
 Initial cost of I.C. engine is lower than E.C. engine.
 This engine easily starts in cold because of it uses high volatile fuel.

COMPONENTS OF IC ENGINE

1. Cylinder block
Cylinder is the main body of IC engine. Cylinder is a part in which the intake of fuel, compression of fuel and burning of fuel take place. The main function of cylinder is to guide the piston. It is in direct contact with the products of combustion so it must be cooled. For cooling of cylinder, a water jacket (for liquid cooling used in most of cars) or fin (for air cooling used in most of bikes) are situated at the outer side of cylinder. At the upper end of cylinder, cylinder head and at the bottom end crank case is bolted. The upper side of cylinder is consisting a combustion chamber where fuel burns. To handle all this pressure and temperature generated by combustion of fuel, cylinder material should have high compressive strength. So it is made by high grade cast iron. It is made by casting and usually cast in one piece.

2. Cylinder head
The top end of the engine cylinder is closed by means of removable cylinder head. There are two holes or ports at the cylinder head, one for intake of fuel and other for exhaust. Both the intake and exhaust ports are closed by the two valves known as inlet and exhaust valve. The inlet valve, exhaust valve, spark plug, injector etc. are bolted on the cylinder head. The main function of cylinder head is to seal the cylinder block and not to permit entry and exit of gases on cover head valve engine. Cylinder head is usually made by cast iron or aluminum. It is made by casting or forging and usually in one piece.

3. Piston
A piston is fitted to each cylinder as a face to receive gas pressure and transmit the thrust to the connecting rod. It is a prime mover in the engine. The main function of piston is to give tight seal to the cylinder through bore and slide freely inside the cylinder. Piston should be light and sufficient strong to handle gas pressure generated by combustion of fuel. So the piston is made by aluminum alloy and sometimes it is made by cast iron because light alloy piston expands more than cast iron so they need more clearances to the bore.

4. Piston rings
A piston must be a fairly loose fit in the cylinder so it can move freely inside the cylinder. If the piston is too tight fit, it would expand as it got hot and might stick tight in the cylinder and if it is too loose it would leaks the vapor pressure. To provide a good sealing fit and less friction resistance between the piston and cylinder, pistons are equipped with piston rings. These rings are fitted in grooves which have been cut in the piston. They are split at one end so they can expand or slipped over the end of piston. A small two stroke engine has two piston rings to provide good sealing but a four-stroke engine has an extra ring which is known as oil ring. Piston rings are made of cast iron of fine grain and high elastic material which is not affected by the working heat. Sometimes it is made by alloy spring steel.

5. Connecting rod
Connecting rod connects the piston to crankshaft and transmits the motion and thrust of piston to crankshaft. It converts the reciprocating motion of the piston into rotary motion of crankshaft. There are two end of connecting rod; one is known as big end and other as small end. Big end is connected to the crankshaft and the small end is connected to the piston by use of piston pin. The connecting rods are made of nickel, chrome, and chrome vanadium steels. For small engines the material may be aluminum.

6. Crankshaft
The crankshaft of an internal combustion engine receives the efforts or thrust supplied by piston to the connecting rod and converts the reciprocating motion of piston into rotary motion of crankshaft. The crankshaft mounts in bearing so it can rotate freely. The shape and size of crankshaft depends on the number and arrangement of cylinders. It is usually made by steel forging, but some makers use special types of cast-iron such as spheroidal graphitic or nickel alloy castings which are cheaper to produce and have good service life.

7. Engine bearing
Everywhere there is rotary action in the engine, bearings are needed. Bearings are used to support the moving parts. The crankshaft is supported by bearing. The connecting rod big end is attached to the crank pin on the crank of the crankshaft by a bearing. A piston pin at the small end is used to attach the rod to the piston is also rides in bearings. The main function of bearings is to reduce friction between these moving parts. In an IC engine sliding and rolling types of bearing used. The sliding type bearing which are sometime called bush is use to attach the connecting rod to the piston and crankshaft. They are split in order to permit their assembly into the engine. The rolling and ball bearing is used to support crankshaft so it can rotate freely. The typical bearing half is made of steel or bronze back to which a lining of relatively soft bearing material is applied.

8. Crankcase
The main body of the engine at which the cylinder are attached and which contains the crankshaft and crankshaft bearing is called crankcase. It serves as the lubricating system too and sometime it is called oil sump. All the oil for lubrication is placed in it.

9. Valves
To control the inlet and exhaust of internal combustion engine, valves are used. The number of valves in an engine depends on the number of cylinders. Two valves are used for each cylinder one for inlet of air-fuel mixture inside the cylinder and other for exhaust of combustion gases. The valves are fitted in the port at the cylinder head by use of strong spring. This spring keep them closed. Both valves usually open inwards.

10. Spark plug
It is used in spark ignition engine. The main function of a spark plug is to conduct a high potential from the ignition system into the combustion chamber to ignite the compressed air fuel mixture. It is fitted on cylinder head. The spark plug consists of a metal shell having two electrodes which are insulated from each other with an air gap. When high potential current supply to spark plug it jumping from the supply electrode and produces the necessary spark.

11. Injector
Injector is usually used in compression ignition engine. It sprays the fuel into combustion chamber at the end of compression stroke. It is fitted on cylinder head.

12. Manifold
The main function of manifold is to supply the air fuel mixture and collects the exhaust gases equally from all cylinder. In an internal combustion engine two manifold are used, one for intake and other for exhaust. They are usually made by aluminum alloy.

13. Camshaft
Camshaft is used in IC engine to control the opening and closing of valves at proper timing. For proper engine output inlet valve should open at the end of exhaust stroke and closed at the end of intake stroke. So to regulate its timing, a cam is use which is oval in shape and it exerts a pressure on the valve to open and release to close. It is drive by the timing belt which drives by crankshaft. It is placed at the top or at the bottom of cylinder.

14. Gudgeon pin or piston pin
These are hardened steel parallel spindles fitted through the piston bosses and the small end bushes or eyes to allow the connecting rods to swivel. It connects the piston to connecting rod. It is made hollow for lightness.

15. Pushrod
Pushrod is used when the camshaft is situated at the bottom end of cylinder. It carries the camshaft motion to the valves which are situated at the cylinder head.

16. Flywheel
A flywheel is secured on the crankshaft. The main function of flywheel is to rotate the shaft during preparatory stroke. It also makes crankshaft rotation more uniform.

TYPES OF I.C ENGINE

I.C. engine is widely used in automobile industries so it is also known as automobile engine. An automobile engine may be classified in many manners.

According to number of stroke:

1. Two stroke engine
In a two stroke engine a piston moves one time up and down inside the cylinder and complete one crankshaft revolution during single time of fuel injection. This type of engine has high torque compare to four stroke engine. These are generally used in scooters, pumping sets etc.

2. Four stroke engine
In a four stroke engine piston moves two times up and down inside the cylinder and complete two crankshaft revolutions during single time of fuel burn. This type of engines has high average compare to two stroke engine. These are generally used in bikes, cars, truck etc.

According to design of engine:

1. Reciprocating engine (piston engine)
In reciprocating engine the pressure force generate by combustion of fuel exerted on a piston (A device which free to move in reciprocation inside the cylinder). The piston starts reciprocating motion (too and fro motion). This reciprocating motion converts into rotary motion by use of crank shaft. So the crank shaft starts to rotate and make rotate the wheels of the vehicle. These are generally used in all automobile.

2. Rotary engine (Wankel engine)
In rotary engine there is a rotor which frees to rotate. The pressure force generated by burning of fuel is exerted on this rotor so the rotor rotate and starts to rotate the wheels of vehicle. This engine is developed by Wankel in 1957. This engine is not used in automobile in present days.

According to fuel used:

1. Diesel engine
These engines use diesel as the fuel. These are used in trucks, buses, cars etc.

2. Petrol engine
These engines use petrol as the fuel. These are used in bikes, sport cars, luxury cars etc.

3. Gas engine
These engines use CNG and LPG as the fuel. These are used in some light motor vehicles.

According to method of ignition:

1. Compression ignition engine
In these types of engines, there is no extra equipment to ignite the fuel. In these engines burning of fuel starts due to temperature rise during compression of air. So it is known as compression ignition engine.

2. Spark ignition engine
In these types of engines, ignition of fuel start by a spark, generated inside the cylinder by some extra equipment (Spark Plug). So it is known as spark ignition engine.

According to number of cylinder:

1. Single cylinder engine
In this type of engines have only one cylinder and one piston connected to the crank shaft.

2. Multi-cylinder engine
In this type of engines have more than one cylinder and piston connected to the crank shaft

According to arrangement of cylinder:

1. In-line engine
In this type of engines, cylinders are positioned in a straight line one behind the other along the length of the crankshaft.

2. V-type engine
An engine with two cylinder banks inclined at an angle to each other and with one crankshaft known as V-type engine.

3. Opposed cylinder engine
An engine with two cylinders banks opposite to each other on a single crankshaft (V-type engine with 180o angle between banks).

4. W-type engine
An engine same as V-type engine except with three banks of cylinders on the same crankshaft known as W-type engine.

5. Opposite piston engine
In this type of engine there are two pistons in each cylinder with the combustion chamber in the center between the pistons. In this engine, a single combustion process causes two power strokes, at the same time.

6. Radial engine
It is an engine with pistons positioned in circular plane around the central crankshaft. The connecting rods of pistons are connected to a master rod which, in turn, connected to the crankshaft.

According to air intake process:

1. Naturally aspirated
In this types of engine intake of air into cylinder occur by the atmospheric pressure.

2. Supercharged engine
In this type of engine air intake pressure is increased by the compressor driven by the engine crankshaft.

3. Turbocharged engine
In this type of engine intake air pressure is increase by use of a turbine compressor driven by the exhaust gases of burning fuel.

ENGINE TERMINOLOGY

1. Top dead center (T.D.C.)
In a reciprocating engine the piston moves to and fro motion in the cylinder. When the piston moves upper direction in the cylinder, a point at which the piston comes to rest or change its direction known as top dead center. It is situated at top end of cylinder.

2. Bottom dead center (B.D.C.)
When the piston moves in downward direction, a point at which the piston come to rest or change its direction known as bottom dead center. It is situated in bottom side of cylinder.

3. Stroke (L)
The maximum distance travel by the piston in single direction is known as stroke. It is the distance between top dead center and bottom dead center.

4. Bore (b)
The inner diameter of cylinder known as bore of cylinder.

5. Maximum or total volume of cylinder (Vtotal)
It is the volume of cylinder when the piston is at bottom dead center. Generally, it is measure in centimeter cube (c.c.).

6. Minimum or clearance volume of cylinder (Vclearance)
It is the volume of cylinder when the piston is at top dead center.

7. Swept or displace volume (Vswept)
It is the volume which swept by the piston. The difference between total volume and clearance volume is known as swept volume.

Swept volume = Total volume – Clearance volume

8. Compression ratio
The ratio of maximum volume to minimum volume of cylinder is known as the compression ratio. It is 8 to 12 for spark ignition engine and 12 to 24 for compression ignition engine.

Compression ratio = Total volume / Clearance volume

9. Ignition delay
It is the time interval between the ignition start (spark plug start in S.I. engine and inject fuel in C.I. engine) and the actual combustion starts.

10. Stroke bore ratio
Stroke bore ratio is the ratio of bore (diameter of cylinder) to length of stroke. It is generally equal to one for small engine and less than one for large engine.

Stroke bore ratio = inner diameter of cylinder / length of stroke

11. Mean effective pressure
The average pressure acting upon the piston is known as mean effective pressure. It is given by the ratio of the work done by the engine to the total volume of engine.

Mean effective pressure = Work done by engine / Total volume of cylinder

Sistema de carga: Componentes, funciones, operaciones y trucos de diagnostico

20 Jul 2019 By INGENIERIA Y MECANICA AUTOMOTRIZ

CHARGING SYSTEM: COMPONENTS, FUNCTIONS, WORKING PRINCIPLE AND DIAGNOSIS TIPS

The vehicle is equipped with many electrical devices to drive safely and comfortably. The vehicle requires electricity not only while driving but also while it stops.

Therefore, the vehicle has a battery for a power supply and a charging system to generate electricity by the engine running. The charging system supplies electricity to all the electrical devices and charges the battery.

The Charging system is an important part of the electrical system. It provides electrical current for the lights, the radio, the heater, the engines electrical systems, and other electrical accessories. It also maintains the batteries in a charged state, recharging them as necessary.

The charging system has three main components: the alternator, the voltage regulator, and the batteries.

The alternator generates electrical power to run accessories and to recharge the batteries. It is normally driven by a belt located off the crankshaft. Mechanical energy from the crankshaft is converted by the alternator into electrical energy for the batteries and accessories.
The voltage regulator acts as an electrical traffic cop to control the alternator output. It senses when the batteries need recharging, or when the vehicles electrical needs increase and adjust the alternator’s output accordingly.

The batteries are a reservoir of chemical electrical power. Their primary purpose is to crank the engine. They also supply power to vehicle accessories when the electrical load is too great for the alternator alone.

Three-phase alternating current

(1) When a magnet rotates within a coil, a voltage will be created between both ends of the coil. This will give rise to an alternating current.
(2) The relation between the current generated in the coil and the position of the magnet is as shown in the figure. The largest amount of current is generated when the N and S poles of the magnet are closest to the coil. However, the current flows in the opposite direction with each half-turn of the magnet. Current that forms a sine wave in this manner is called “single-phase alternating current”.

COMPONENTS AND FUNCTIONS

In general, the components of the charging system are composed of alternators and regulators. However, the charging system needs to add some additional components so that the electricity generated can be supplied to the battery and to all electrical loads safely and precisely. The component, consisting of;

1. Battery

The function of the battery is as a storage of electrical energy. Like a warehouse, the battery will store all the electrical energy generated by the alternator and then this stored electricity is removed when necessary.

2. Fuse and Fusible links

Fuse and fusible links have different functions even though have the same shape. The fusible link can be called as the main fuse which is placed near the battery positive terminal. The function of this fuse is to protect the entire electrical system of the car from excessive currents. Generally, the fusible link has a capacity of up to more than 60 Ampere.

While the function of the fuse is as the safety of a series of specific electrical wiring, in conventional charging system there are two fuses with the same capacity (it’s about 10-15 Ampere). A fuse is used as a voltage regulator fuse and another fuse is used to secure the CHG and Voltage relay.

3. CHG Lights

CHG lamp or commonly also called “charging warning light” is an indicator light to indicate the present failure of the charging system. When the ignition key ON then this light will light up normally, as well as when the engine life of this lamp should turn on, if it is dead then it could mean the charging system failure.

4. Ignition key

The ignition key works as a switch. The charging system will be activated automatically when the engine is running, but to generate a magnetic field on the rotor coil must be done by a switch.

The ignition switch is used as a switch to connect and disconnect power (positive battery current) from battery to rotor coil. When the ignition key is ON, then the electricity from the battery to the coil rotor will be connected. However, when the ignition key is turned OFF then the power supply will be cut off. So it is not possible the alternator generates electricity when the ignition key is OFF even the engine crankshaft rotates.

5. Regulator

The function of the regulator is to regulate the voltage generated by the alternator. Why should it be there? because the voltage generated by the alternator depends on the engine’s RPM. This means that if the engine RPM is low, the alternator voltage is also low, but if the engine RPM is high then the alternator voltage is also high.

The regulator will be used to keep the voltage generated by the alternator not exceeding 14 volts even if the engine run in high RPM. This voltage setting aims to protect the electrical components of the vehicle to prevents over-voltage.

There are two types of regulators, namely type or conventional type and type of IC. The point type/conventional uses two coils to adjust the alternator output voltage. While the IC Regulator uses an IC circuit (Integrated Circuit) to regulate the output voltage.

6. Altenator

The function of the alternator is to convert a partial engine’s rotating energy into electricity. The alternator input comes from the engine pulley connected through a V belt, the rotation of the rotor will cause the intersection of the magnetic force line with the stator coil so that the electrons flow on the stator coil.

The electricity in the stator coil is not directly connected to the battery, but it must pass through the diode bridge to rectify the current. This is done because the current in the stator coil is AC (Alternate Current).

7. Charging Wire

The function of the charging wire is to connect every component of the charging system, there are at least two types of wires: standard wire and B + wire. The standard wire has a small diameter like the car’s electrical wiring in general, the function of this wire is connecting each terminal on the entire charging system.

While the B + wire has a larger diameter than the standard wire and almost matches the stater wire. The function of this wire is to connect the terminal B alternator with Battery.

WORKING PRINCIPLE

The flow of electricity in the charging system

Electricity in each position of the ignition switch.

Ignition switch ACC or LOCK

Ignition switch ON (when the engine is not running)

When the ignition switch is in the ON position, current flows from the battery to the alternator. The reason for this is as follows. The alternator generally used for the vehicle generates electricity by rotating the magnet. The magnet is not the permanent magnet but the electromagnet that generates magnetic force by flowing electricity inside. Therefore, it is necessary to supply electricity to the alternator before starting the engine to prepare for generating electricity.

Ignition switch ON (when the engine is running)

FUNCTIONS OF ALTERNATOR

The alternator plays a major role in the charging system. The alternator has three functions of generating electricity, rectifying current and regulating voltage.

(1) Generation
Transmitting the engine revolution to the pulley via the v-ribbed belt turns the electromagnetic rotor, generating alternating current in the stator coil.

(2) Rectification
Since the electricity generated in the stator coil is alternating current, this cannot be used for the DC electric devices installed on the vehicle. To use the alternating current, the rectifier is used to rectify the alternating current into direct current.

(3) Regulation of voltage
IC regulator regulates the generated voltage to make the voltage constant even when the alternator speed or the amount of current flowing into the electric devices change.

CHARGING SYSTEM DIAGNOSIS

The following general information has been assembled as a guide for charging system diagnosis. Refer to the appropriate Original Equipment Manufacturer’s service manual for specific information pertaining to charging system diagnostic procedures and safety precautions for your vehicle.

BENCH TESTING

If an alternator test bench is available, follow the procedures found in the bench tester’s instruction manual to conduct an alternator performance test. This test will determine if the alternator output is within its performance specification, preventing unnecessary alternator replacement.
If the alternator output is within specification during bench testing, resolve problems in the remainder of the vehicle’s charging circuit and other electrical circuits that may affect charging circuit performance. Refer to the appropriate vehicle manufacturer’s service manual for the procedures and circuit schematics necessary to identify and correct additional charging circuit problems.
If the test bench results show the alternator’s output performance to be out of specification, replace the alternator. Follow the vehicle manufacturer’s recommended procedures to inspect the remainder of the charging circuit and other electrical circuits that may affect charging circuit performance.

NOTE: If the bench test identifies the regulator as defective, it may be possible to replace the regulator (internal or external) and return the alternator to service. If the regulator is replaced and the alternator returned to service, follow the vehicle manufacturer’s recommended procedures to inspect the remainder of the charging system and other electrical circuits that may affect charging circuit performance.
Whether or not a test bench was used to determine the condition of the alternator, the following Helpful Tips have been assembled to help isolate conditions that may affect charging circuit performance.

HELPFUL TIPS

1. What is the condition of the battery?
• A visual inspection and a performance test of the battery must always be performed before inspecting the charging system. The battery must be fully charged (12.6 volts) and the battery cables, terminals, and casein good, clean condition. This includes the frame and body grounds as well (refer to Battery Visual Inspection and Performance Testing).

2. Does a charge lamp, amperage (amp) gauge or voltmeter indicate a charging system problem?

Charge Lamp:

• Ignition ON engine not running – The charge lamp should illuminate.
• Ignition ON engine running – The charge lamp should illuminate briefly then turn OFF.
• Weak Battery – A weak battery can cause the charge lamp to illuminate during high amperage draw.
• Low Idle – A low idle can cause the charge lamp to illuminate dimly.
• Poor Wiring – Corroded, broken, loose or frayed wires/ connections could cause the charge lamp to illuminate during idle.
• Open Charge Lamp – Some charging systems will not properly operate if the charge lamp bulb fails.

Amp Gauge:

• Ignition ON engine not running – The amp gauge should read zero or slightly below.
• Ignition ON engine running – The amp meter should display a current output above zero. It will display a different level of charge depending on what electrical circuits are operating. A negative charge indicates the battery is discharging more quickly than the charging system can supply current.
• Wires and connectors – Corroded, broken, loose or frayed wires/connections could cause zero or erratic readings on the gauge.

Voltmeter:

• Ignition ON and engine not running – Gauge readings should be between 12.0 and 12.6 volts with the ignition ON and the engine not running. Readings below 12 volts could indicate insufficient charging, low battery, corroded, broken, loose or frayed wires/connections.
• Ignition ON and engine running – Gauge readings should be between 13.0 and 14.5 volts with the ignition ON and the engine running. A reading exceeding 14.5 volts could indicate a bad battery, failed regulator or poor wire connections. A reading below 13.2 volts could indicate a failed alternator or corroded, broken, loose or frayed wires/connections.

3. Are any fuses open?

• Check the fuses in all the fuse box(es). An open fuse indicates circuit problem(s) that may have an effect on the charging circuit. Check the owner’s manual or the manufacturer’s service manual for the location of each fuse box.

4. Is the fusible link(s) open?

• There may be several fusible links controlling battery voltage to the vehicle’s electrical circuits. If a fusible link is open, the supply voltage will be completely lost to all electrical systems or to the electric circuit(s) that the open fusible link controls. Check the owner’s manual or the manufacturer’s service manual for the location of each fusible link.

5. Is the alternator’s drive belt tension within specification?

• Too loose – If the drive belt is too loose, it will slip around the pulley causing the alternator to charge irregularly or not at all.
• Too tight – If the drive belt is too tight, internal bearing damage will cause premature alternator failure.

6. Are the alternator’s drive belt in good condition and the proper size?

• Worn or too narrow – If the alternator’s drive belt is worn or too narrow, it will slip around the pulley, causing the alternator to charge irregularly or not at all.
• New drive belt – The life of a new alternator drive belt is approximately 10 minutes. It is important to check and adjust the belt’s tension to the “used” specification after the initial 10 minutes of operation.

7. Has the vehicle been modified or additional equipment installed after it left the factory?

• Accessories – Non-factory accessories such as phones, computer outlets, televisions, refrigerators, stereo equipment or lights, among others, can overburden alternator performance and cause premature failure.
• Improper accessory installation – Improper accessory installation procedures can cause charging problems. Some of these problems may include poor ground points, loose connections or improper wiring.

8. Has any work been performed on the vehicle?

• Electrical ground points – Check the ground circuits between the battery and engine and also from the vehicle body to the frame for high resistance. Many times when a vehicle has been repaired, the ground point(s) are disturbed or not re-secured properly.
• Multiple electrical grounds – With multiple ground vehicles, each electrical circuit is assigned to one or more ground points. The poor ground at one ground point may cause feedback through another ground point causing unusual circuit activity.

EXHAUST GAS RECIRCULATION (EGR) SYSTEM: WORKING PRINCIPLE, DESIGN, AND BENEFITS

18 Jul 2019 By INGENIERIA Y MECANICA AUTOMOTRIZ

Diesel engines tend to emit higher Nitrogen Oxide (NOx) which is harmful to humans. This is because of high temperatures in the engine cylinders because of the higher compression ratio. To control and decrease the NOx, manufacturers employ ‘Exhaust Gas Recirculation’ technology in engines.

The term EGR stands for Exhaust Gas Recirculation. It is a part of modern-day diesel engine vehicles which helps to decrease the Nitrogen Oxide (NOx) emissions. Exhaust Gas Recirculation is the technique used for reducing the nitrogen oxide in both the internal combustion diesel engines as well as petrol engines.

WORKING PRINCIPLE

The exhaust gas added to the fuel, oxygen, and combustion products increases the specific heat capacity of the cylinder contents, which lowers the adiabatic flame temperature.

In a typical automotive spark-ignited (SI) engine, 5% to 15% of the exhaust gas is routed back to the intake as EGR. The maximum quantity is limited by the need of the mixture to sustain a continuous flame front during the combustion event; excessive EGR in poorly set up applications can cause misfires and partial burns. Although EGR does measurably slow combustion, this can largely be compensated for by advancing spark timing. The impact of EGR on engine efficiency largely depends on the specific engine design, and sometimes leads to a compromise between efficiency and NOx emissions. A properly operating EGR can theoretically increase the efficiency of gasoline engines via several mechanisms:

• Reduced throttling losses.

The addition of inert exhaust gas into the intake system means that for given power output, the throttle plate must be opened further, resulting in increased inlet manifold pressure and reduced throttling losses.

• Reduced heat rejection.

Lowered peak combustion temperatures not only reduces NOx formation, but it also reduces the loss of thermal energy to combustion chamber surfaces, leaving more available for conversion to mechanical work during the expansion stroke.

• Reduced chemical dissociation.

The lower peak temperatures result in more of the released energy remaining as sensible energy near TDC (Top Dead-Center), rather than being bound up (early in the expansion stroke) in the dissociation of combustion products. This effect is minor compared to the first two.

EGR is typically not employed at high loads because it would reduce peak power output. This is because it reduces the intake charge density. EGR is also omitted at idle (low-speed, zero loads) because it would cause unstable combustion, resulting in rough idle.

Since the EGR system recirculates a portion of exhaust gases, over time the valve can become clogged with carbon deposits that prevent it from operating properly. Clogged EGR valves can sometimes be cleaned, but replacement is necessary if the valve is faulty.

DESIGN

A vacuum controlled EGR valve regulates the number of exhaust gases admitted into the cylinders. It consists of a spring-loaded vacuum diaphragm. It links to a metered valve which controls the passage of the exhaust gases. Ported vacuum from a calibrated signal port located above the throttle valve connects to the EGR vacuum chamber.

At idling, the EGR valve is in the closed position because of the spring pressure and lower ported vacuum. The engineers designed it so because if the exhaust gases recirculate at the idling, then it would cause rough/erratic idling. Upon opening of the throttle applies the ported vacuum and gradually opens the tapered valve. This causes the exhaust gas to flow into the intake manifold.

However, when the throttle opens fully, there is no vacuum in the intake manifold. So, it closes the tapered valve and stops the exhaust gases from entering the intake manifold.

BENEFITS

The Exhaust Gas Recirculation system recirculates a part of the exhaust gas back into the engine cylinders through the combustion chamber. The logic behind the EGR system is very simple. The exhaust gas is hotter than the fresh air sucked by the engine. So, the exhaust gas significantly reduces the contents of the cylinder for combustion. Because of the absence of oxygen (O2), the exhaust gases have nothing to burn as they contain neither fuel nor oxygen particles.

Thus, it results in lower heat discharge and cylinder temperatures. It reduces the formation of nitrogen oxide (NO2) as well. The dormant exhaust gas present in the cylinder also limits the peak temperatures. It also reduces the loss that arises because of throttling in petrol engines while improving the engine life by reducing the cylinder temperatures. The three-stage catalytic converter further reduces the NOx to acceptable levels.

LIMITATIONS

The engineers designed the EGR system in such a way that it recirculates the exhaust gases only when the engine forms the Nitrogen Oxide (NOx). Thus, the EGR system DOES NOT affect the ‘Full-Load’ operation.

The Exhaust Gas Recirculation system also has a thermal control valve in the vacuum line which prevents the operation of EGR at lower engine temperatures. This system is useful especially in the diesel engines where the catalytic converter cannot stimulate the chemical reduction due to high oxygen contents. So, the NOx emission remains the same in such conditions.}

Automotive World

Mariposa/Moneda/Válvula del Motor o cuerpo de aceleración (Electronic Throttle Body)

16 Jul 2019 By INGENIERIA Y MECANICA AUTOMOTRIZ

Las mariposas en un motor tienen la función de controlar la cantidad de aire que circula hacia los cilindros de éste mediante un circuito de colectores de admisión, por lo que son muy importantes.

En los motores más antiguos, solo se necesitaba una mariposa para controlar el aire que succionaban los pistones y, dependiendo del tipo de motor, podían ser una por cada cilindro.

En la actualidad, existen mecanismos que controlan mucho mejor la entrada del aire hacia los cilindros por lo que el sistema de admisión varía en función del tipo de motor y del sistema de admisión variable, ya que con éste se pretende aprovechar al máximo la dinámica del aire para llenar mejor los cilindros y aumentar el rendimiento de los motores.

Existen mariposas controladas por aire y mariposas controladas eléctricamente, pero la función es la misma. Como es lógico, las controladas eléctricamente son más caras. También están las principales que van controladas mecánicamente mediante cable.

¿Qué sucede cuando se estropean las mariposas?

De normal, los fallos provocados por averías de mariposa se deben a la falta de aire en los cilindros, lo que en su mayoría de casos va a provocar una pérdida de potencia y aumento de consumo.

Cuando esto sucede, se pueden apreciar “tirones” en marcha, sobre todo cuando necesitamos potencia y si la que falla es la mariposa principal, el motor podría no arrancar ya que “estrangulamos” totalmente la entrada de aire.

Otra forma de notar que las mariposas fallan es que el motor tiraría humo negro ya que la combustión no la haría completa al faltarle aire.

4 STROKE VS 2 STROKE ENGINES

16 Jul 2019 By INGENIERIA Y MECANICA AUTOMOTRIZ

4 STROKE ENGINES

* 4 stroke engine completes 2 rotations of the crankshaft after completing one cycle.
* Power is produced once every 4 strokes of the piston.
* Engine design is a bit complicated due to valve mechanism which is operated through gear & chain mechanism.
* No need of adding oil or lubricant to fuel.
* Top side of the piston is flat.
* Mixture remains only in the combustion chamber.
* 4 stroke engines are heavier.
* 4 stroke engines make less noise.

2 STROKE ENGINES

* 2 stroke engine completes 1 rotation of crankshaft after completing one cycle.
* Power is produced once during 2 strokes of the piston.
* 2 stroke engine has ports which make its design simpler.
* Addition of oil is required.
* A bump or protuberance may be needed on the top side of the piston.
* Air-fuel mixture enters through inlet port & travels to combustion chamber passing through the crankcase.
* 2 stroke engines are lighter comparatively.
* 2 stroke engines are louder comparatively.

ADVANTAGE AND DISADVANTAGES

4 STROKE ENGINE:-

ADVANTAGES

1. More torque:- In general, 4 stroke engines always make extra torque than 2 stroke engine at low RPM. Although 2 stroked ones give higher torque at higher RPM it has a lot to do with fuel efficiency.

2. More fuel efficiency:- 4 stroke engines have greater fuel efficiency than 2 stroke ones because fuel is consumed once every 4 strokes.

3. Less pollution:- As power is generated once every 4 strokes & also as no oil or lubricant is added to the fuel; 4 stroke engine produces less pollution.

4. More durability:- We all know that more the engine runs, quicker it wears out. 2 stroke engines are designed for high RPM. If an engine can go for 10000 rpm’s before it wears out; a 4 stroke engine with 100 rpm will run for 100 minutes than the other 2 stroke engine which has a higher rpm of 500 & will run for only 20 minutes.

5. No extra addition of oil:- Only the moving parts need lubrication intermediately. No extra oil or lubricant is added to fuel.

DISADVANTAGES

1. Complicated design:- A 4 stroke engine has complex valve mechanisms operated & controlled by gears & chain. Also, there are many parts to worry about which makes it harder to troubleshoot.

2. Less powerful:- As power gets delivered once every 2 rotations of the crankshaft(4 strokes), hence 4 stroke is less powerful.

3. Expensive:- A four-stroke engine has much more parts than 2 stroke engine. So they often require repairs which leads to greater expense.

2 STROKE ENGINE:-

ADVANTAGES

1. Simple design & construction:- It doesn’t have valves. It simply has inlet & outlet ports which makes it simpler.

2. More powerful:- In 2 stroke engine, every alternate stroke is power stroke unlike 4 stroked one in which power gets delivered once every 4 strokes. This gives a significant power boost. Also, the acceleration will be higher & power delivery will be uniform due to the same reason.

3. The position doesn’t matter:- 2 stroke engine can work in any position as lubrication is done through the means of fuel (as the fuel passes by through whole cylinder & crankcase).

DISADVANTAGES

1. Less fuel efficiency:- For every alternate power stroke, fuel gets consumed every alternate stroke. This makes the engine less fuel efficient although it results in uniform power delivery.

2. Oil addition could be expensive:- Two-stroke engines require a mix of oil in with the air-fuel mixture to lubricate the crankshaft, connecting rod and cylinder walls. These oils may empty your pockets.

3. More pollution:- 2 stroke engine produces a lot of pollution. The combustion of oil added in the mixture creates a lot of smoke which leads to air pollution.

4. Wastage of fuel:- Sometimes the fresh charge which is going to undergo combustion gets out along with the exhaust gases. This leads to wastage of fuel & also power delivery of the engine gets affected.

5. Improper combustion:- The exhaust gases often get trapped inside the combustion chamber. This makes the fresh charge impure. Therefore maximum power doesn’t get delivered because of improper incomplete combustion.

Automotive world

Clasificación SAE y API

13 Jul 2019 By INGENIERIA Y MECANICA AUTOMOTRIZ

Clasificación SAE (Society of Automotive Engineers)

Esta clasificación tomó como referencia el grado de viscosidad del lubricante en función a la temperatura la que se somete el motor durante su funcionamiento, por lo que no clasifica a los aceites por su calidad.

La marca de certificación y el símbolo de servicio API identifican la calidad de los aceites de vehículos de gasolina y diesel.

Clasificación

El sello de API también conocido como “STARBURST”, indica que el aceite cumple con la normativa vigente de

protección del motor y con los requisitos de economía de combustible ILSAC.

Tambien conocido como “DONUT”

Moresa

Para que sirve el O/D (OverDrive) en tu caja automática?

10 Jul 2019 By INGENIERIA Y MECANICA AUTOMOTRIZ

Cuando el aviso de “O/D OFF” esta encendido, quiere decir que el overdrive está apagado; y cuando el aviso está apagado, quiere decir que el overdrive está encendido (lo sé, suena algo confuso pero es solo cuestión de leer lo que dice el tablero)

  • Overdrive activado o encendido: el indicador “O/D OFF” está apagado
  • Overdrive desactivado o apagado: el indicador “O/D OFF” está encendido

¿Para qué sirve el overdrive?

Veamos las diferencias, sin overdrive:

  • El carro dispone de hasta 3 cambios o cajas
  • Los cambios de caja resultan más largos, es decir el cambio automático de 1a a 2a tarda más, etc
  • El motor realiza más revoluciones
  • El motor en funcionamiento presenta más ruido
  • Hay un mayor consumo de combustible
  • Al frenar o disminuir la velocidad se hace con frenado de motor
  • Se pierde inercia, por el punto anterior
  • Es ideal para cuando se va lento (dentro de la ciudad por ejemplo), cuando hay constantes frenados, cuando se lleva carga, cuando se está en un terreno con pendientes o pantanoso

Con overdrive:

  • El carro dispone de 4 cambios o más (según la especificación del carro)
  • Los cambios de caja resultan más cortos, es decir el cambio automático de 1a a 2a tarda menos
  • El motor realiza menos revoluciones
  • El motor en funcionamiento presenta menos ruido
  • Hay un menor consumo de combustible
  • Al frenar o disminuir la velocidad no se hace con frenado de motor, solo se aplica freno de disco o del que disponga el carro
  • No se pierde inercia, por el punto anterior
  • Es ideal para cuando se va rápido (sobre carretera por ejemplo), cuando no se lleva carga

En resumen cuando necesitemos que el carro haga un poco más de esfuerzo, debemos tener el overdrive apagado (aviso encendido de “O/D OFF”), y cuando queramos que haga menos esfuerzo y vaya más rápido debemos activar el overdrive. También hay que tomar en cuenta que para activar el overdrive se puede estar en marcha de 0 a 60 km/hr o un poco más dependiendo del carro que tengamos; y para desactivar el overdrive se puede hacer cuando estemos en marcha a poca velocidad, o cuando el carro no esté en movimiento.

¿Para qué sirve el botón Shift Lock en un auto?

10 Jul 2019 By INGENIERIA Y MECANICA AUTOMOTRIZ

Si tienes un coche automático, te habrás encontrado con el botón Shift Lock muy cerca en de la palanca que utilizas para cambiar entre las diversas posiciones de manejo. Aquí te decimos para qué sirve y cómo te puede ayudar a salir de un apuro.

El botón Shift Lock en el auto

El botón Shift Lock te puede sacar de un apuro en más de una ocasión

Muchas personas manejan sus autos con transmisión automática sin tener la remota idea de la existencia del botón Shift Lock. Aunque suele estar en una zona visible cerca de la palanca o selector, la mayoría ignora para qué funciona y la forma correcta de utilizarlo.

La incorporación del Shift Lock en los autos de transmisión automática es una necesidad, dado que el control de los cambios no depende del conductor, a diferencia de lo que sucede en un vehículo con una caja manual de velocidades. De esta manera, conocer el funcionamiento del sistema de bloqueo de cambios se convierte en un tema de seguridad.

Cuando nos ponemos detrás del volante de un coche automático, tenemos que presionar un botón ubicado en la palanca de velocidades para moverlo entre las diferentes posiciones, ya se Neutral, Estacionamiento, Drive o Reversa. Lo único que se necesita es tener pisado el freno y presionar el botón para desplazar la palanca a conveniencia, un mecanismo que también evita que se cambie de posición de forma accidental y que termine por dañar la caja de velocidades.

En algunas ocasiones o contratiempos, existe la posibilidad de que la palanca de la transmisión se quede trabada. Aquí es donde resulta de gran utilidad el botón Shift Lock, ya que solo tendremos que seguir una serie de pasos muy sencillos para poder utilizar el auto de nueva cuenta o, dependiendo de la situación, remolcarlo al lugar que nos convenga.

El botón Shift Lock permite “destrabar” la palanca de forma mecánica

Algunos de los escenarios que te obligarían a utilizar Shift Lock sería que te quedaras sin batería en el vehículo en posición de Estacionamiento (P), una de las situaciones más frecuentes que suele dar dolores de cabeza. Por más que se pise el freno para intentar desplazar la palanca a Neutral (N) y así poder mover la unidad, esto no dará resultados hasta que destrabemos el selector de forma mecánica.

De esta manera, el botón Shift Lock permite que se desactive de forma manual el enclavamiento de la posición P y volver a Neutral para permitir el remolque. La palanca puede quedar inmovilizada por otros factores o averías, como puede ser un falso contacto en uno de los interruptores que son presionados por el pedal de freno. Sin importar cuál sea la razón, mediante este botón se podrá cambiar de posición con el vehículo apagado y sin pisar el freno.

Lo primero que tenemos que hacer es colocar el freno de mano y retirar la llave del encendido. Acto seguido, se levanta la tapa del Shift Lock con un desarmador plano, teniendo extremo cuidado de no dañar los acabados. Con la misma llave del vehículo, se presiona la tecla hacia abajo y, al mismo tiempo, intentamos mover la palanca a posición Neutral. Para terminar el trabajo, colocamos la cubierta de plástico, introducimos la llave y presionamos el pedal de freno. Si no se trata de un asunto de batería, podemos intentar encender el motor; en caso contrario, estaremos listos para iniciar con el remolque de la unidad.

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MANUAL TRANSMISSION: COMPONENTS, TYPES, WORKING PRINCIPLES AND APPLICATIONS

09 Jul 2019 By INGENIERIA Y MECANICA AUTOMOTRIZ

A manual transmission is a house of various components like gears, shafts and various selecting mechanism that is arranged in special fashion to provide appropriate torque and speed ratios to compete with the challenges provided by the different road conditions, the shifting from high torque to high speed and vice-versa is performed manually by symmetrical pushing and pulling of the gear lever by the driver.

The vehicle with MT usually comes with an n-speed manual with or without reverse configuration where ‘n’ denotes the number of speed ratios or shifts for example-Maruti Suzuki swift comes with 5-speed 1-reverse manual transmission.

COMPONENTS OF A MANUAL TRANSMISSION

1. Clutch Pedal:
The clutch pedal is a hydraulically controlled piece of gear that disengages the clutch when you depress it.

2. Clutch:
This is a system of components which is used to transmit engine torque to the transmission. It consists of a pressure plate, diaphragm spring, clutch disc, throw-out bearing, and other smaller components. The clutch disc is a friction pad which is sandwiched between the flywheel and the pressure plate.

3. Flywheel:
As it relates to manual transmissions, the flywheel is the component which delivers engine torque to the clutch disc. This circular mass has a smooth surface which the clutch disc interacts with.

Understanding how a clutch works are fairly important to understanding the transmission overall.

4. Selector Fork
This arm is used to move the collars along the output shaft (to select gears) and can be moved using the gear shift.

5. Collar(s)
The collar is what is used to select different gears. It slides between gears and can mesh with them. The collar is splined to the output shaft, whereas the gears rotate with the layshaft (and thus are on bearings on the output shaft). By locking the collar with a selected gear, engine torque passes from the layshaft to the output shaft.

6. Synchronisers
These are located between the gears and the collar and allow for the collar to engage the gear even if there is a speed differential between the two. Essentially, this aids in matching the speed of the gear and the collar.

7. Shafts
There are usually 3 shafts used in a manual transmission those are-

(i) Main-Shaft- 
It is the shaft that is also called the output shaft and is placed in front of the clutch shaft and in parallel to the lay-shaft. Gears, gear lever along with the meshing devices such as dog clutches and synchromesh devices are mounted over this shaft.

(ii) Lay-shaft or Counter Shaft- 
It is the shaft used as an intermediate shaft between the clutch shaft and the main shaft, it is usually mounted below and parallel to the main shaft, and act as an engine output carrier from the clutch shaft to the main shaft.

(iii) Clutch-Shaft- 
It is the shaft that carries the rotational output from the engine’s flywheel to the transmission with the help of clutch that engages and disengages the output from the engine.

8. Gears
Various sized gears are used to allow for different wheel speeds. Larger gears will provide more torque but have lower maximum speeds. Smaller gears (with fewer teeth) will provide less torque but will allow the car to travel at a higher speed.

There are mainly 4 types of gears used in the manual gearbox those are-

(i) Spur Gear: 
Used in old sliding mesh gearbox these types of gears have straight cut teethes.

(ii) Helical Gear:
They are the modified version of the latter as they have angular cut teethes.

(iii) Bevel:
They are best of all above gears having a conical cross-sectional area with angular cut teethes.

(iv) Idler-gear: 
It is the small gear used as a reverse gear usually mounted over the layshaft.

TYPES OF MANUAL GEARBOX USED

There are 3 types of manual gearboxes used since the introduction of the transmission that is-

1. Sliding Mesh Gearbox

This is the oldest type of gearbox used. In this type of gearbox shifting occurs by the sliding of gears over the splined main-shaft in order to mesh with the appropriate gear on the lay-shaft whose one gear is in constant mesh with the clutch shaft gear in order to carry rotational motion for the conversion(high torque or high speed)as required by the drive, this gearbox requires special technique for the shifting that is usually known as double-declutching and also the meshing was so noisy and harsh, that gives rise to the development of a new gearbox system.
Note-They usually came with the max of 3-speed manual shifts.

2. Constant Mesh Gearbox

This is the modified version of the later which was introduced to over the limitations of the later, in this type all the gears on the main-shaft, lay-shaft and clutch-shaft are in constant mesh with each other and the selection of the appropriate gear is done by the special meshing devices known as dog clutches which slides over the splined main-shaft in order to select the appropriate gear as need by the drive. This system flushes away the double-de-clutching problem and made the drive less noisy as the spur gears of the sliding mesh is replaced with the helical or bevel gears ,but the shifting of gear is still not smooth and also there is a lot of wear and tear of the dog clutches due to the different rotational speed of the shafts while meshing, which leads to the high maintenance.
Note – it came with 4 or 5-speed 1-reverse manual shift configuration.

3. Synchromesh Gearbox

This is the latest type of gearbox used from decades as this system overcomes all the limitations provided by the constant mesh gearbox or sliding mesh gearbox and also improves the output capabilities of the manual transmission system, in this type the dog clutches from the constant mesh gearbox is replaced by the synchromesh devices which first bring the main-shaft and lay-shaft at same speed by the frictional contact, then meshing of the appropriate gear occurs which makes the system smooth and also decreases the maintenance of the gearbox, today this system usually comes with 5-speed 1-reverse manual transmission configuration.

Note-it is coming with a 5-speed 1-reverse configuration.

WORKING OF MODERN MANUAL TRANSMISSION

Today almost all the vehicles with a manual transmission on the road are equipped with synchromesh gearbox as it is more reliable, needs less maintenance, and the selection of gear is not complex with This type of gearbox whose working is as follows-

• When the driver presses the clutch pedal in order to shift the gear, the disengagement of the engine flywheel and clutch shaft occurs which lets the driver select appropriate gear according to the need of the drive.

• When the gear lever is pushed or pulled by the driver in order to select the particular gear, the synchromesh device which is attached to the particular link slides towards the selected constantly meshed pair of gears.

• At first, this synchromesh device makes the frictional contact with the selected pair and the shafts in order to bring the rotating shafts at the same speed.

• Then the pair of gears having an appropriate gear ratio has meshed with the synchromesh device in order to obtain output given by the pair of gears, which is then transferred to the main shaft.

• Then this output with appropriate torque or speed is transferred to the final drive when the driver releases the clutch pedal which completes the shifting of gear.

• When it comes to the selection of reverse gear the contact of the synchromesh device is made with the idler gear which in turn reverses the rotation of the main shaft and the drive starts moving in a reverse direction.
Note – As constant meshing of gears and Continuous sliding of synchronizing devices is there so constant supply of lubricating oil should be there in order to avoid wear and tear of the components of the manual transmission.

APPLICATION

Specifically, manual transmission covers 52% of the total automobile market which means more than half the vehicle on the roads is equipped with MT.

1. All the heavy vehicles such as trucks, loaders, etc. Are equipped with MT.

2. Almost all the bikes on the road are having a manual gearbox with usually 4 or 5-speed shifts with no reverse.

3. The formula race cars use a manual transmission with quick response shifting mechanism.

4. Almost all commercial cars use MT due to their low cost except high-end cars like Audi, BMW, etc.

(Automotive World)

INJECTION SYSTEM: COMPONENTS, TYPES AND WORKING PRINCIPLES

06 Jul 2019 By INGENIERIA Y MECANICA AUTOMOTRIZ

“ Fuel injector is an electronically controlled mechanical device that is responsible for spraying (injecting) the right amount of fuel into the engine so that a suitable air/fuel mixture is created for optimal combustion.”

The technology was created in the early 20th century and implemented on diesel engines first. By the final third of the 20th century, it had also become popular among regular gasoline engines.

The electronic control unit (ECU at engine management system) determines the precise amount and specific timing of required gasoline (petrol) dose for every cycle, by collecting information from various engine sensors. So, the ECU sends a command electrical signal of the correct duration and timing to the fuel injector coil. In that way opens the injector and allows petrol to pass through it into the engine.

The one terminal of the injector coil is directly supplied by 12 volts which are controlled by the ECU, and the other terminal of the injector coil is open. When ECU determined the exact amount of fuel and when to inject it, activates the appropriate injector by switching the other terminal to the ground (mass, i.e. negative pole).

COMPONENTS

The objectives of the fuel injection system are to meter, atomize and distribute the fuel throughout the air mass in the cylinder. At the same time, it must maintain the required air-fuel ratio as per the load and speed demand on the engine.

* Pumping elements:

To move the fuel from the fuel tank to the cylinder.

* Metering elements:

To measure the supply of the fuel at the rate demanded by speed and load conditioning on the engine

* Metering control:

To adjust the rate of the metering elements for change in load and speed of the engine.

* Mixture control:

To adjust the ratio of the fuel and air as demanded by the load and speed.

* Distributing elements:

To divide the metered fuel equally among the cylinder.

* Timing control:

To fix the start and stop of the fuel-air mixing process.

TYPES OF FUEL INJECTORS

1. Top-Feed – Fuel enters from the in the top and exits the bottom.

2. Side-Feed – Fuel enters on the side on the injector fitting inside the fuel rail.

3. Throttle Body Injectors – (TBI) Located directly in the throttle body.

TYPES OF FUEL INJECTION SYSTEMS

1. Single-Point OR Throttle Body Fuel Injection

Also referred to as a single port, this was the earliest type of fuel injection to hit the market. All vehicles have an air intake manifold where clean air first enters the engine. TBFI works by adding the correct amount of fuel to the air before it is distributed to the individual cylinders. The advantage of TBFI is that it’s inexpensive and easy to maintain. If you ever have an issue with your injector, you’ve only got one to replace. Additionally, since this injector has a fairly high flow rate, it’s not as easy to clog up.

Technically, throttle body systems are very robust and require less maintenance. That being said, throttle body injection is rarely used today. The vehicles that still use it are old enough that maintenance will be more of an issue than it would with a newer, lower mileage car.

Another disadvantage to TBFI is the fact that it’s inaccurate. If you let off the accelerator, there will still be a lot of fuel in the air mixture that is being sent to your cylinders. This can result in a slight lag before you decelerate, or in some vehicles, it can result in unburned fuel being sent out through the exhaust. This means that TBFI systems are not nearly as fuel efficient as modern systems.

2. Multiport Injection

Multiport injection simply moved the injectors further down towards the cylinders. Clean air enters the primary manifold and is directed out towards each cylinder. The injector is located at the end of this port, right before it’s sucked through the valve and into your cylinder.

The advantage of this system is that fuel is distributed more accurately, with each cylinder receiving its own spray of fuel. Each injector is smaller and more accurate, offering an improvement in fuel economy. The downside is that all injectors spray at the same time, while the cylinders fire one after the other. This means that you may have leftover fuel in between intake periods, or you may have a cylinder fire before the injector has had a chance to deliver additional fuel.

Multiport systems work great when you are traveling at a consistent speed. But when you are quickly accelerating or removing your foot from the throttle, this design reduces either fuel economy or performance.

3. Sequential Injection

Sequential fuel delivery systems are very similar to multiport systems. That being said, there is one key difference. Sequential fuel delivery is times. Instead of all injectors firing at the same time, they deliver fuel one after the other. The timing is matched to your cylinders, allowing the engine to mix the fuel right before the valve opens to suck it in. This design allows for improved fuel economy and performance.

Because fuel only remains in the port for a short amount of time, sequential injectors tend to last longer and remain cleaner than other systems. Because of these advantages, sequential systems are the most common type of fuel injection in vehicles today.

the one small downside to this platform is that it leaves less room for error. The fuel/air mixture is sucked into the cylinder only moments after the injector opens. If it is dirty, clogged, or unresponsive, your engine will be starved of fuel. Injectors need to be kept at their peak performance, or your vehicle will start to run rough.

4. Direct Injection

If you’ve started to notice the pattern, you can probably guess what direct injection is. In this system, fuel is squirted right into the cylinder, bypassing the air intake altogether. Premium automobile manufacturers like Audi and BMW would have you believe that direct injection is the latest and greatest. With regards to the performance of gasoline vehicles, they’re absolutely right! But this technology is far from new. It’s been used in aircraft engines since the second world war, and diesel vehicles are almost all direct injection because the fuel is so much thicker and heavier.

In diesel engines, direct injection is very robust. Fuel delivery can take a lot of abuse, and maintenance issues are kept to a minimum.

With gasoline engines, direct injection is found almost exclusively in performance vehicles. Because these vehicles operate with very precise parameters, it’s especially important to maintain your fuel delivery system. Although the car will continue to run for a long time when neglected, the performance will quickly decline.

METHODS OF FUEL INJECTION

There are two methods of fuel injection in the compression ignition system

1. Air blast injection
2. Air less or solid injection

1. Air blast injection

This method was originally used in large stationary and marine engines. But now it is obsolete. In this method, the air is first compressed to very high pressure. A blast of this air is then injected carrying the fuel along with it into the cylinders. The rate of fuel injection is controlled by varying the pressure of the air. The high-pressure air requires a multi-stage compressor so as to keep the air bottles charged. The fuel ignites by the high temperature of the air caused by the high compression. The compressor consumes about 10% of the power developed by the engine, decreasing the net output of the engine.

2. Airless or solid injector

In this method, the fuel under high pressure is directly injected into the combustion chamber. It burns due to the heat of compression of the air. This method requires a fuel pump to deliver the fuel at high pressure around 300kg/cm^2. This method is used for all types of small and big diesel engines. It can be divided into two systems

1. Individual pump system: in this system each cylinder has its own individual high-pressure pump and a measuring unit.

2. Common rail system: in this system the fuel is pumped by a multi-cylinder pump into a common rail, the pressure in the rail is controlled by a relief valve. A measured quantity of fuel is supplied to each cylinder from the common rail.

This is all about the fuel injection system. If you have any query regarding this article, ask by commenting. If you like this article, don’t forget to share it on social networks. Subscribe our website for more informative articles. Thanks for reading it.

WORKING PRINCIPLES

The injectors are controlled by the Engine Control Unit (ECU). First, the ECU obtains information about the engine conditions and requirements using different internal sensors. Once the state and requirements of the engine have been determined, the fuel is drawn from the fuel tank, transported through the fuel lines and then pressurized with fuel pumps. Proper pressure is checked by a fuel pressure regulator. In many cases, the fuel is also divided using a fuel rail in order to supply the different cylinders of the engine. Finally, the injectors are ordered to inject the necessary fuel for the combustion.

The exact fuel/air mixture required depends on the engine, the fuel used and the current requirements of the engine (power, fuel economy, exhaust emission levels, etc.)

(Automotive World)

What Is Otto Cycle? What Are The Processes In Otto Cycle

05 Jul 2019 By INGENIERIA Y MECANICA AUTOMOTRIZ
Otto Cycle

Otto Cycle is the theoretical thermodynamic cycle which describes the working of a spark ignition engine. This type of spark ignition engines is the most common type of engines used in automobiles. Today we will attempt to study it and understand what comprises of this Otto Cycle.

The Otto cycle is the study of what happens to a mass of gas when it is subjected to changes in pressure, temperature, volume, adding heat and removing heat. The system is the term given to the mass of gas that is subjected to these changes. Otto Cycle also studies the effect of this system on the environment. The effect in question here is the net output or the work generated by the Otto Cycle to move the automobile in which the engine is installed.

otto cycle

The name Otto Cycle comes from the name of the person who has put forward the theory of this system.His name was Dr Nicolas August Otto.
The Otto Cycle comprises a top and bottom of the loop process which is called isentropic process. This process is frictionless and adiabatic. And an isochoric process which happens at left and right side of the loop and has the constant volume.

The reason we consider the Otto cycle as a theory is because of its premise that it operates in a completely efficient system where no energy is lost. However, we know that in reality, it is still not possible.

The isentropic process implies that during compression cycle there will be no loss of mechanical energy and considers that no heat will either enter the system or leave it.
In theory, heat flows through the left pressurizing process and some of it passes back through the right depressurizing process. The difference of heat here gives the net mechanical work generated.

The Following Are The Four Processes In Otto Cycle-

Process 0-1 :

Also known as the intake stroke

Mass of air at constant pressure is fed into the cylinder/piston

Process 1-2:

Also known as Compression stroke.

In this process, the isentropic compression of the charge happens. This happens due to movement of the cylinder from bottom dead center to top dead center.This is the time when air-fuel mixture is compressed.

Process 2-3 :

This is also known as Ignition phase.

Here the piston for a moment of time rests at the top dead center. There is a little air-fuel mixture present at the top during this process. Heat is then introduced into the system which ignites the air-fuel mixture. Due to this, the volume remains constant whereas the pressure rises.

Process 3-4 :

Also known as Expansion stroke.

The rise in pressure due to ignition causes the piston to move to bottom dead centre.Gases are expanded isentropically and hence the system works on the piston.In simpler terms, the expansion of gases leads to movement of piston here.

Process 4-1 :

Also known as Heat Rejection phase.

The piston comes to rest at bottom dead center for a while. This drops the gas pressure immediately as the heat is removed using a heat sink at the cylinder head. The gas returns to its original state as was in step 1.

Process 1-0 :

Also known as the Exhaust stroke.

The exhaust valve opens in this process as the piston moves from Bottom dead center to top dead center. The remainder gas is expelled and the process again starts from 0-1.

So here we have in theory how an Otto process works.

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