Lesson 1 · about 12 minutes · 6 parts

How a car actually works.

Not a glossary of parts. One story: a single firing of fuel, followed all the way from the spark to the road, with every mechanism moving under your own hand.

Why an engine is really a fire lit thousands of times a minute
How up-and-down becomes round-and-round
Why a gearbox exists, and what low gear actually buys you
The clever gear that lets two wheels turn at different speeds
How brakes stop a tonne of metal, and where the energy goes

Play with the engine on the right first, then start.

Part 1 · One becomes four

One cylinder gives one push, then coasts. So engines carry several.

A four-cylinder engine fires its cylinders one after another, so there is almost always one on its power stroke pushing the crank round. Four uneven shoves blur into one steady spin. That spin is the only thing the rest of the car ever works with, and everything from here is about shaping it.

Key ideaCylinders take turns firing so the crank gets a steady stream of pushes, not one shove and a long pause.

Part 2 · Feeding the fire

Before it can burn, the mixture has to be drawn in and squeezed.

On the intake stroke the piston drops and pulls air in past the open intake valve, roughly fourteen parts air to one of petrol, sprayed in as a fine mist. Both valves shut, the piston rises and squeezes it, and only then, just before the top, the plug ignites the compressed mixture. Fire it too early or too late and the push lands at the wrong moment.

Key ideaThe spark fires just before the top of the compression stroke, into a mixture that is already squeezed. Timing is the whole trick.

Part 3 · Trading turns for twist

The engine spins fast. The wheels need to push hard.

An engine makes its power spinning quickly, but a car has to move a tonne of metal from a standstill. Those are opposite demands, so a gearbox sits between them and trades one for the other.

Low gear turns the engine many times for each turn of the wheels: less speed, much more push. High gear does the reverse. Pick a gear and watch the trade.

A clutch or a torque converter lets the two sides part so you can stop without stalling. Some cars change ratio with two clutches or a belt instead of stepping through fixed gears.

Key ideaLow gear multiplies the engine's twist to get you moving. High gear trades that twist back for speed.

Part 4 · Splitting the drive

Two wheels, one bend, different speeds.

Through a corner the outer wheel travels a longer path than the inner one, so it has to turn faster. Bolt both to one shaft and they fight. The differential drives both wheels yet lets them turn at their own speeds. Steer it into a bend and watch them separate, then put one wheel on ice and see its one real weakness.

Key ideaThe differential drives both wheels but lets the outer one spin faster in a bend. Its weakness: it will also feed a wheel that has no grip.

Part 5 · Turning motion back into heat

Braking does not destroy speed. It converts it.

Press the pedal and you are really pushing fluid down a line. Because liquid does not compress, that push reaches all four wheels at once, and a small force at your foot becomes a large clamp at the pads.

The pads grip a spinning disc, and the car's motion turns into heat in the metal, which the disc sheds into the air. The energy is not gone, it has changed form. Hold the pedal and watch the speed fall as the discs warm.

Key ideaOne push on the pedal clamps all four wheels through fluid, and the car's speed leaves as heat.

Part 6 · Where it all lands

Everything a car does, it does through four palms of rubber.

All that fire, gearing and braking finally reaches the road through four small patches of tyre, each about the size of your hand. Every bit of accelerating, cornering and stopping is shared across the same little patch. Ask it for too much at once and it lets go, which is what a skid is.

Key ideaEverything passes through four hand-sized patches of rubber. Grip is a budget, and you can overspend it.

The supporting cast

The systems that keep the fire fed, cooled, lit and pointed the right way. Not the main story, but a car will not run without them.

Breathing

Air intake

Strains dust from the air and feeds the cylinders. A turbo or supercharger packs in extra air so more fuel can burn.

Supply

Fuel system

A pump lifts petrol from the tank at the back and sends it forward to the injectors, which spray it as a fine mist.

Heat

Cooling

Coolant carries engine heat to the radiator at the front, where moving air throws it away. A thermostat holds the best temperature.

Out

Exhaust

Collects the burnt gas, cleans the worst of it in the catalytic converter, quiets it in the muffler, and lets it out at the back.

Spark and charge

Electrical

The battery starts the engine and feeds the plugs. Once running, the alternator recharges it and powers the lights and screens.

Ride

Suspension

A spring takes each bump and a damper stops the bounce, so the body stays level and the tyres stay pressed to the road.

Aim

Steering

The wheel turns a small pinion that slides a toothed rack side to side. In a bend the inner wheel turns a touch sharper than the outer one.

Life

Oil and lubrication

A pump pushes oil through the engine so metal slides on a thin film instead of grinding. It carries heat and grit away to the filter.

Lesson complete

You now know how a car turns fuel into motion.

An engine is a controlled fire: intake, compress, ignite just before the top, then exhaust.
Pistons push a crank, and several cylinders firing in turn make that push steady.
A gearbox trades the engine's fast spin for the hard push a car needs to move.
A differential drives both wheels while letting them turn at different speeds in a bend.
Brakes clamp all four wheels through fluid and turn motion into heat.
All of it reaches the road through four patches of rubber the size of your hand.