Differences Between a 4-Stroke and a 2-Stroke Engine

The below table can be read like the table of comparison between the two types of engines and also as the merits and demerits of the two designs.

2 stroke and 4 stroke comparison

S.no
4-Stroke Engine
2-Stroke Engine
1 One working stroke for every 4 strokes or 2 revolutions. One working stroke for every 2 strokes or one revolution.
2 As the number of cycles is less, power output is less for the same cylinder size. Power is more for the same cylinder size. More suitable for diesel power plant.
3 The weight of the engine is more for the same output power. The weight of the engine is considerably less. So, it is more suitable for marine engines.
4 The operating temperature is less. So, less consumption of lubricating oil. The operating temperature is more. So, more consumption of lubricating oil. Special piston cooling is necessary for large engines.
5 Variation of torque is more. So, a heavier flywheel is necessary. A smaller flywheel is enough as the torque is more uniform.
6 Noise is less. Noise is more due to frequent exhaust.
7 Higher thermal efficiency. Thermal efficiency is less due to possible wastage of fuel-air mixture through the exhaust port.
8 Due to the valve mechanism, the design and manufacture of the engines are difficult and the cost is more. Easier in design and manufacturing cost is less.
9 The straight piston is used. A deflector piston is used.

Vinodh Reddy is an Editor-in-chief of ME Mechanical. He holds Bachelor of Engineering (Honours) degree in Mechanical Engineering from BITS-Pilani.

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