How a car engine works
A gasoline car engine converts chemical energy in fuel into heat and then mechanical motion. Burning an air-fuel mixture raises the pressure inside a cylinder. That pressure pushes a piston, and a connecting rod transfers the force to a rotating crankshaft.
From a moving piston to turning wheels
A piston travels up and down inside a cylinder; it does not turn the wheels directly. Its connecting rod pushes on an offset crankshaft journal. This geometry converts reciprocating motion into rotation. The transmission and final drive then adapt that rotation before it reaches the driven wheels.
Why the engine needs four strokes
In a four-stroke gasoline engine, each cylinder takes in a fresh charge, compresses it, produces a power stroke and clears the burned gas. One complete cycle takes two crankshaft revolutions. The spark plug starts combustion near the end of compression; the expanding gases supply useful work during the power stroke.
What four cylinders change
An inline-four places four cylinders in a single row. Their power strokes occur at different times, spreading the delivery of torque through the cycle. In a typical evenly firing four-stroke inline-four, a power stroke begins every 180 degrees of crankshaft rotation. The flywheel helps smooth changes in rotational speed between these events.
Air, fuel, oil and coolant have different jobs
The intake system supplies air, and fuel injectors meter the fuel. Engine oil reduces friction and carries heat away from loaded surfaces. Coolant carries heat from the block and cylinder head to the radiator. Oil and coolant normally circulate through separate passages; neither is the charge intentionally burned in the cylinder.
Explore the mechanism in 3D
Start with the complete assembly, then select a piston and follow its connecting rod down to the crankshaft. Use the section view to see internal relationships and the exploded view to separate assemblies. The model is a simplified four-cylinder, double-overhead-cam learning aid, not a manufacturing drawing.
Does every car engine use spark plugs?
No. Diesel engines ignite injected fuel using the heat of compressed air. Battery-electric cars use electric motors instead of combustion engines. This guide and explorer focus on a four-stroke gasoline engine.
Connect the steps
- Fuel and air
- Combustion pressure
- Piston force
- Connecting rod
- Crankshaft rotation
A piston cannot drive a wheel directly
The piston moves back and forth while the crankshaft turns. The connecting rod changes angle as its big end follows the crankshaft journal. At the top and bottom of the stroke the piston reverses direction even though the crankshaft continues turning. The flywheel helps carry rotation through parts of the cycle where a cylinder is not delivering power.
Try it in 3D
Select a piston, then follow the connecting rod to the crankshaft. Compare the direction of each part’s movement during a complete cycle.
Open the related explorer →Does every downward piston movement produce power?
No. The intake stroke also moves the piston downward. Valve state and the stage of the cycle tell you what that movement is doing.