The Four-Stroke Engine

A four-stroke auto engine is a type of internal combustion engine that converts fuel into mechanical energy to power a vehicle. A stroke is a movement of the piston up or down in the cylinder. The four strokes in the engine cycle are intake, compression, combustion, and exhaust.

It looks like this:

4-Stroke-Engine-with-airflows numbers

  1. Intake: The first stroke begins with the intake valve opening, allowing a mixture of air and fuel to enter the cylinder. This mixture is drawn in as the piston moves downward, creating a vacuum.

  2. Compression: The intake valve closes and the piston moves back up, compressing the fuel and air mixture in the cylinder. This creates a high-pressure environment, making it easier for the fuel to ignite.

  3. Combustion, or Power: When the piston reaches the top of the cylinder, a spark plug ignites the compressed fuel and air mixture, causing a controlled explosion. The resulting energy pushes the piston back down, producing the engine's power.

  4. Exhaust: The exhaust valve opens, and the piston moves back up, pushing the exhaust gases out of the cylinder and through the exhaust system. This prepares the engine for the next cycle by creating a vacuum in the cylinder and bringing in a fresh fuel-air mixture.

The four-stroke engine cycle repeats continuously, with each stroke powering the next. The rotation of the engine's crankshaft converts the up-and-down motion of the piston into rotational energy that drives the wheels of the vehicle.