The engine is the heart of any automobile. It is responsible for the generation of power to propel the vehicle as and when desired. Like any power generating machine, engines also need fuel for operation. This is generally catered to the engine in the form of diesel or gasoline.
Engines used in cars are primarily internal combustion (IC) engines. Cars are equipped with a four stroke engine for their operation. Two stroke engines have become obsolete now.
Working of a four stroke engine
Any automotive engine consists of a cylinder where the fuel mixture gets exploded. This explosion creates a force that pushes a piston back in a tightly closed container. The movement in the crankshaft turns a flywheel. The mechanical power and motion of the crankshaft is transmitted for the desired operation of the automotive. The reciprocating motion of the piston in the cylinder is continued for a continuous action. The movement of the piston in the cylinder can be classified into four strokes namely: suction stroke, compression stroke, power stroke and exhaust stroke.
- Suction stroke: During this stroke the exhaust valve remains closed and the inlet valve is opened. The piston is moved downwards. Either mixture of fuel or air or only air is introduced inside the cylinder based on the fuel used. The pressure inside the cylinder is maintained below the atmospheric pressure in this stroke by moving the piston downwards so that fuel can seep in due the pressure difference.
- Compression stroke: During this stroke both the inlet and the exhaust valves are closed and the air-fuel mixture or the air alone is compressed by piston which moves towards the top dead center (TDC). Since work is done on the mixture by the piston, the temperature of the mixture rises. If it is a diesel engine, the fuel is introduced at this point. Due to high temperature of the air, the fuel is ignited. In case of a petrol engine, air-fuel mixture ignition is done with help of a spark plug.
- Power stroke: After the ignition takes place in the cylinder, a large amount of heat is generated in the cylinder and the pressure that is built up pushes the piston downwards. Both the valves remain closed during this process. The power thus generated by the piston is transferred to the crankshaft through a connecting rod that is converted into useful work.
- Exhaust stroke: During this stroke, the inlet valve is closed and the remaining gases in the cylinder are forced out by the upward movement of the piston. The exhaust valve opens to facilitate this. The cylinder is now prepared to receive a fresh charge into itself.