2-stroke engines!

The name 2-stroke itself explains that 2- stroke engines use engine cycle which lets the car run in 2 steps, in layman language. 2-stroke engines are usually light and hence cannot generate much power when compared to 4-stroke engines. So they are mostly used when low RPMs are required.

The two strokes in this are namely Compression Stroke and Combustion Stroke. The main difference between a two-stroke engine and a four-stroke engine is the reduced number of strokes. The question which arises first is ‘Where are intake and exhaust strokes?’. Well both the intake and exhaust of fuel and gas take place simultaneously. This happens at the piston comes down to bottom center at the end of combustion stroke. As the piston comes down, the exhaust gases leave and fresh fuels come in.

2-stroke engines need to be oiled separately because oil sump as in 4-stroke engine cannot be attached to a 2-stroke engine. 4-stroke engines use automatic lubrication and oil is stored in oil sump inside the crank case. 2-stroke engines cannot be given oil sump automatic lubrication because the inlet and exhaust valves in 2-stroke engines are placed on the sidewalls of the cylinder (as in the figure above). So, if an oil sump is attached to the 2-stroke engine and automatic lubrication is enabled, the oil will block the valves and hence inlet and exhaust can’t take place.
2-stroke engines cannot be used in cars and other automobiles where speed is required because of their less efficiency in Spark Ignition (SI) engines at higher speed and less economical in Compression Ignition (CI) engines. So, 4-stroke engines are used when higher RPMs are required.