Can you name and describe the four strokes that make up one full cycle of a 4-stroke engine?

Answer 1

The Otto cycle, know as the four stroke cycle is as follows.

Induction

Compression

Power

Exhaust

This is a simplified explanation of a petrol engine, the basic details are correct. Most are also relevant to a CI engine. It is not meant to be a definitive answer and is only a description for the basic operation.

Induction:

The inlet valve opens and the piston moves down the cylinder causing a partial vacuum and drawing an air/fuel mixture into the cylinder through the inlet manifold.

Compression:

The inlet valve closes and the piston moves up the cylinder compressing the air/fuel mixture. The compression ratios vary.

Power:

Near the top of the compression stroke a spark is induced and the air/fuel mixture is ignited. This causes the gasses to expand rapidly and forces the piston down the cylinder.

Exhaust:

The exhaust valve opens and the piston moves up the cylinder expelling the burnt gasses out through the exhaust manifold. The exhaust valve closes and the cycle starts again.

1. intake: In this stroke air (and in non-fuel-injected engines gasoline) is drawn in.
2. compression: In this stroke air (and in non-fuel-injected engines gasoline) is compressed (just before the end of this stroke in fuel-injected engines the gasoline is injected, then a spark ignites the fuel/air mixture).
3. expansion: in this stroke the burning fuel/air mixture pushes against the piston, doing work.
4. exhaust: in this stroke the burnt fuel/air mixture is pushed from the cylinder to make room for a fresh charge on the next intake stroke.

Intake, compression, power, exhaust.

The first stroke down takes the air/fuel mixture in thus intake, then as the cylinder rotates up, the mixture compresses. The fuel is ignited and the power stroke starts down and as the cylinder goes back up it is the exhaust phase where it expels the burnt fuel and then starts the first stroke again