# Working Principle of Automobile Engines

How a car engine cylinder turns burning fuel into motion, through its intake, compression, power and exhaust strokes, with the valves and crankshaft that drive the wheels\.

By clever\-badger\-517b89f7

Topic: Machines

[Open the interactive Jig](https://ask.jig.com/j/coPIbDyXFHtN)

## Transcript

### 1. Fuel becomes motion

This is one cylinder of a car engine, cut open so you can see inside\. Every turn of a car's wheels starts here, with tiny bursts of burning fuel\. Watch how a push becomes a spin\.

Drag anywhere to turn the engine and look around\.

### 2. Meet the moving parts

The piston slides up and down inside the cylinder\. The connecting rod links it to the crankshaft, which turns round and round\. Valves open and close the doorways for gas, and the spark plug lights the fuel\.

### 3. 1\. Intake: breathe in

The piston slides down and the intake valve opens\. Like pulling the plunger of a syringe, this sucks in a mix of air and a little fuel\. The blue cloud is that fresh mix filling the cylinder\.

### 4. 2\. Compression: squeeze

Both valves close and the piston rises\. The mix is squeezed into about one tenth of the space it had\. Squeezed gas gets hot and ready to burn fiercely\.

A typical car engine squeezes the mix about ten to one\.

### 5. 3\. Power: the push

The spark plug makes a tiny spark and the squeezed fuel burns in a flash\. The hot gas expands and shoves the piston down hard\. This is the only stroke that makes the engine go\.

It is a fast, controlled burn, not an explosion\.

### 6. 4\. Exhaust: breathe out

The exhaust valve opens and the rising piston pushes the burnt gas out toward the exhaust pipe\. Then the whole cycle starts again: in, squeeze, push, out\.

### 7. Perfect timing

Behind the engine, a toothed belt links the crankshaft to the two camshafts\. Their egg\-shaped bumps press each valve open at just the right moment\. The camshafts turn once for every two turns of the crankshaft\.

Four strokes take two full turns of the crankshaft\.

### 8. From piston to wheels

The heavy flywheel keeps the crankshaft spinning smoothly between pushes, and its turning goes on through the gearbox to the wheels\. Most cars have four cylinders taking turns, so one is always pushing\.

Only about a third of the fuel's energy becomes motion; the rest leaves as heat\.