Difference between 2 Stroke and 4 Stroke Engine

A stroke is an important topic that must not be left behind when discussing on automobile engine. As we all know most modern vehicles are designed either with two stroke or four stroke. But before discussing on differences between two stroke and four stroke engine I should clarify on meaning of stroke in an engine.

Stroke in an engine is the space covered by the piston from top dead center (TDC) to the bottom dead center (BDC). That is, the stroke is the cylinder distance between piston. Two stroke engine is when piston move two times in the cylinder while four stroke is when it move four times in the cylinder.

One of the main difference between two stroke and four stroke engine takes place in the crankshaft. It rotates one time between two stroke. That is, crankshaft complete one revolution in one power stroke in two stroke engine while in four stroke engine, it complete two revolutions in one power stroke. These implies that the two stroke give more power when compared with four stroke engine but consume less fuel in four stroke.

Fig show some difference between two stroke and four stroke in an automobile engine.

At the end of this article, the reader is expected to have basic understanding on meaning of stroke in an engine and difference between two and four stroke engine. The followings detailed below are some other differences between two stroke and four stroke engine.

  1. two stroke engine has one revolution of crankshaft within one power stroke while four stroke has two revolution of crankshaft between one power strokes.
  2. Two stroke engine generate high torque compare to 4 strokes engine that generates less torque due to 2 revolution of crankshaft between one power strokes.
  3. Two stroke engine uses port to inlet and outlet of fuel while four stroke uses valve as it inlet and outlet of fuel.
  4. Two stroke engines require lighter flywheel compare to other engines because it generates more balanced force due to one revolution for one power stroke while four stroke requires heavy flywheel because it generates unbalance force due to two revolutions for one power stroke.
  5. In two stroke, engine charge is partially burn and mix with the burn gases during inlet. It is due to port mechanism while In four stroke engine charge is fully burn and does not mix with burn charge in ideal condition.
  6. In two stroke easy lubrication occurs due to lubrication oil mix with the fuel while four stroke engine is complicated in building lubrication.
  7. More lubricating oil required in two stroke engine because some oil burns with fuel while less lubricating oil required in four stroke engine.
  8. Two stroke engines give less thermal efficiency while four stroke engines give more thermal efficiency.
  9. Two stroke engines has high power to weight ratio compare to others while 4 stroke engines have less power to weight ratio.
  10. Two stroke creates more noise. It is less noise in four stroke.
  11. Two stroke engines are less efficient and generate more smoke while four stroke engines are more efficient and generate less smoke.
  12. Two stroke engines are comparatively cheaper while four stroke engines are expansive due to valve and lubrication mechanism.
  13. Two stroke engines are easy to manufacture while four stroke engines are hard to manufacture.
  14. Two stroke engines are generally lighter while engines are comparatively heavier than 2 strokes due to heavy flywheel and valve mechanism.
  15. Due to poor lubrication in two stroke engines more wear and tear occurs while in four stroke less wear and tear occurs due to perfect lubrication.

I hope you enjoyed reading this article, we’ve discussed on difference between two stroke and four stroke engine. Be free to ask question, remember we’re here to help you. Please don’t forget to share this article and thanks for reading!

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