For all of you who are curious in how a four-stroke engine works, you are in for a big treat. On this part of the site, we will be talking about four-stroke engines and how they work.

Before reading this, please check out How a Two-Stroke Engine Works page first.(If you have not already.) Now the concept of the four-stroke engine is a bit different. In a two-stroke engine you have a piston doing all the work; working as a intake and an exhaust valve. It also does the compression. This is what makes a two-stroke engine lighter than the four-stroke engine. In a four-stroke engine, there are fuel injectors that squirt out fuel onto the piston then igniting. One of the main differences between a two-stroke engine and a four-stroke engine, is that in a four-stroke engine you must add oil separately. You must not mix it in with the gas. In a two-stroke engine you add oil and gas in the same container causing both to enter the engine and igniting, then the fumes exit through the exhaust. Two-strokes actually pollute more than four-strokes making them a bigger hazard to the environment. That is why cars are powered by four-stoke engines. If you compare the power between these two types of engines, you will notice that the two-stroke is lighter and more powerful than the four-stroke. But in a four-stroke engine you have more power control of the engine. So these two issues actually even out quite a bit.

The four stroke engine was first demonstrated by Nicholas Otto in 1876, hence it is also known as the Otto cycle. The technically correct term is actually four stroke cycle. The four stroke engine is probably the most common engine type nowadays. It powers almost all cars and trucks.

The four strokes of the cycle are intake, compression, power, and exhaust. Each corresponds to one full stroke of the piston; therefore, the complete cycle requires two revolutions of the crankshaft to complete.

Back to Top