How a Car Engine Works

I'm Jake O 'Neill, creator of Animagraffs,

and this is how a car engine works.

Let's start at a single piston,

the powerhouse of the engine, and work our way outwards.

The 4 stroke cycle.

When a piston travels to the end of its range,

whether up or down, that's a stroke.

Car engines use a 4 stroke cycle, and it goes like this.

First, intake.

The piston descends,

sucking an air-fuel mixture into the cylinder through the

intake port, with both intake valves open.

Next, compression.

With all valves closed, the piston comes back up,

compressing the fuel and air mixture for more powerful

combustion.

Then, the power stroke.

An electrical spark ignites the compressed fuel and air

mixture,

and the resulting combustion forces the piston to the

bottom of the cylinder again.

A connecting rod transfers this power to the crankshaft.

Finally, exhaust.

The piston comes back up,

pushing the spent mixture out through open exhaust valves

and the exhaust port connecting multiple pistons.

For smooth power delivery, pistons take turns firing.

The firing order for this engine is one, three, four, two.

Camshafts, with specially shaped cams,

push spring-loaded valves open in turn.

Cam gears and a timing belt or chain links everything to

the crankshaft, and it all spins together.

The crankshaft translates piston power out of the engine.

It has counterweights to balance against the pistons for

perfectly smooth revolutions.

This is what RPM means.

We're counting the number of full crankshaft revolutions

per minute.

The engine block holds the crankshaft and cylinders and the

cylinder head holds valves, ports, cams, etc.

The geared flywheel sits at one side of the crankshaft for

connection to a transmission.

It's also where the starter connects to the system.

This engine has four cylinders arranged in a single row,

but there are many other possible configurations,

like six cylinders with three on each side,

angled in a v-shape, or eight.

Despite different design goals,

the basic engine parts are all there.

Now let's look at other systems that support this

combustion process.

Air intake.

Air comes in through the air filter and then into the

intake manifold where it mixes with fuel before being

sucked into individual cylinders through intake ports.

Fuel.

The fuel pump carries gas from the tank through a fuel

filter to the engine where fuel injectors emit a precisely

timed spray of gas into the intake port.

Cooling.

Engines get very hot during operation and require a cooling

system.

Coolant channels around the cylinders and through the

cylinder heads carry a special liquid called antifreeze to

keep temperatures within safe operating range.

It's called antifreeze because it won't freeze in icy

weather.

After cooling hot engine parts,

coolant circulates through the radiator.

The radiator has a network of small tubes and fins.

Coolant passes through these channels while air pulled in

by the radiator fan blows by the tubes,

cooling the hot liquid for recirculation.

A water pump keeps the coolant system flowing and properly

pressurized.

The thermostat regulates coolant temperature by either

routing coolant back through the engine or to the radiator

for further cooling.

Electrical.

The spark plug delivers the electrical spark that ignites

the fuel-air mixture for combustion.

The metal core is insulated from the outer metal casing

with porcelain.

The spark jumps between these conductive surfaces.

A coil pack delivers electrical current to the spark plugs

as directed by the ECM, or Engine Control Module.

The ECM is a computer that directs many core engine

functions like spark timing, valve open and close timing,

air to fuel ratio, etc.

The alternator works like a power generator,

converting the engine's mechanical energy into electricity

to charge the battery or run other electrical systems while

the engine is running.

The battery provides power to the starter for engine start.

Oil.

Motor oil is used to lubricate, clean, prevent corrosion,

improve sealing,

and cool the engine by carrying heat away from moving

parts.

Rings around the top of the piston head keep oil out of the

combustion process,

while otherwise allowing the cylinder to be lubricated.

Oil galleries are channels through the engine block and

cylinder head that carry oil to various engine parts.

Oil flows through the engine and back to the oil pan for

recirculation.

Oil rests in the oil pan when not in circulation.

The oil pump keeps oil properly pressurized and flowing.

And the oil filter keeps oil clean from contaminants.

Exhaust.

The exhaust manifold collects gases from multiple cylinders

into one pipe.

Exhaust flows through the catalytic converter which

captures toxic chemicals in engine exhaust and then out

through a muffler that reduces exhaust noise.

And finally,

here's the full functioning engine with all the basic

systems we've discussed.