← How It Works

How a Car Engine Works

A six-step lesson with 3D models. Take the engine apart, run the mechanism, and see how fuel turns into wheel rotation.

  • 6 steps
  • about 5 minutes
  • rotatable model
Full screen
Step 1

The internal combustion engine

An engine turns fuel into rotation. The fuel burns inside the engine — hence the name. The rotation goes to the transmission, and from there to the wheels.

Inair and fuel
Outcrankshaft rotation
Step 2

What an engine is made of

Engine blockThe core of the engine: it holds the cylinders the pistons move in.
Cylinder headCovers the cylinders from above. It holds the valves and spark plugs.
Pistons and rodsThe piston takes the gas pressure, and the connecting rod passes it to the crankshaft.
CrankshaftA shaft with "throws": it turns piston travel into rotation.
CamshaftOpens the valves at the right time. Spins at half the crankshaft's speed.
Head gasketSeals the joint between block and head so gases can't escape.
Step 3

The piston pushes — the crankshaft turns

Gases push the piston down, the connecting rod passes on the push, and the crankshaft turns the up-and-down motion into rotation — like bicycle pedals.

The heavy flywheel at the end of the crankshaft keeps spinning by inertia and smooths out the jolts between piston pushes.

Step 4

Four strokes

  • 1. IntakeThe piston moves down with the intake valve open — the cylinder draws in air and fuel.
  • 2. CompressionValves closed, the piston moves up and compresses the mixture.
  • 3. PowerThe spark plug fires, the mixture ignites — gases push the piston down.
  • 4. ExhaustThe exhaust valve is open, and the piston pushes out the spent gases.

Over four strokes the crankshaft makes two turns. Only the third stroke pushes the piston; the engine coasts through the rest on inertia.

Step 5

Why multiple cylinders

The power stroke happens in only one stroke out of four, so a single-cylinder engine would run jerkily. That's why the cylinders work in turn: in an inline four, the order is 1 → 3 → 4 → 2. At any moment one of the pistons is pushing the shaft, and the engine runs smoothly.

Next

What to read next

Engine Repair Booksmodel-specific manuals — with disassembly, dimensions, and torque specs Oil Changeguides by make Spark Plug Replacementguides by make Timing Belt and Chain Replacementguides by make Engine Overhaulguides by make

3D models: Engine — JuanG3D, V6 car engine — Blendoriano (Sketchfab, CC BY 4.0), simplified for the site, parts animated.