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How a Car Works · Chapter 01

The chain: fuel → wheels.

The whole car in one story — how tiny, precisely-timed explosions become the smooth pull you feel from the pedal. Five ideas, each with its live demo.

· STORED FIRE

A tank of stored fire

Petrol is absurdly dense stored energy — heat, waiting. Everything that follows is one chain: release the heat, catch it as pressure, turn the pressure into rotation, and carry that rotation down to the road.

FUELstored energyFIREburning releases itPRESSUREhot gas expandsROTATIONpistons turn the crank

TAKEAWAYFuel is stored heat; the whole car is a machine for turning heat into rotation.

· THE EXPLOSIONS

Tiny, precisely-timed explosions

The engine releases that heat in thousands of small, exactly-timed burns. Each cylinder breathes in, squeezes, burns, and exhales — four strokes of 180°, so one full cycle takes two turns of the crank.

air + fuelexhaustspark1 · intake1 · intake2 · compression2 · compression3 · power3 · power4 · exhaust4 · exhaust
DEMOThe Four-Stroke CycleScrub the crank, watch the strokes — the whole demo runs off one angle.

TAKEAWAYOne cycle = two crank revolutions: intake, compression, power, exhaust — 180° each.

· TWIST × TURNS

Twist, then multiply it

A burn pushes; a crank turns the push into twist. Torque is how hard each push twists; power is that twist times how fast you keep pushing. The pedals tell the whole story.

TORQUE — how hard you pushleveragepushtorque = push × leveragePOWER — how fast you keep pushingturns/minpower = torque × turning speed

TAKEAWAYTorque = push × leverage; power = torque × turning speed. Gears trade speed for twist.

PIT NOTE

This is why a race engine revs to the sky — not for more twist, but for more turns per minute. The same push, more often, is more power.

· THE DRIVELINE

Down the driveline

From the crank the twist runs through the clutch and gearbox — which multiply it — along the driveshaft to the differential, the gear set that lets two wheels on one axle turn at different speeds in every corner.

DEMOThe DifferentialOne axle, two wheels, different speeds — watch the gear set split the difference.

TAKEAWAYThe differential lets one axle turn two wheels at different speeds — every corner needs it.

· THE HONEST BILL

Four postcards of rubber — and the honest bill

All of it lands on four patches of rubber, each about the size of a postcard. And honestly: most of the fuel’s energy never gets there — it leaves as heat down the exhaust and through the radiator.

33%exhaust heat29%coolant & radiated heat8%friction & pumping30%motion — the useful bit100% of the petrol's energy, typical car engine at cruise

TAKEAWAYOnly ~30% of the fuel’s energy becomes motion; the rest leaves as heat.

FOR THE SELF-CHECK

What to remember

  1. 01Fuel is stored heat; the whole car is a machine for turning heat into rotation.
  2. 02One cycle = two crank revolutions: intake, compression, power, exhaust — 180° each.
  3. 03Torque = push × leverage; power = torque × turning speed. Gears trade speed for twist.
  4. 04The differential lets one axle turn two wheels at different speeds — every corner needs it.
  5. 05Only ~30% of the fuel’s energy becomes motion; the rest leaves as heat.
Test yourself → optional
NEXT · CH 02The engineThe heart of the chain, at surface level — then the deep dives.