Understanding your engine

Get to know what’s going on the hood of your car with this handy guide.

 

There is a good chance that the magical workings of the thing in your car, van, or motorcycle that makes it go along the road will never be something that you have to worry about. These days, if it goes wrong, someone will come along with a laptop and analyse something to find out what the problem is. However, if you understand how your engine works, it can give you a head start on narrowing down where any problem might be.

 

What does it do?

All engines do the pretty much the same job – they generate power that is translated into mechanical movement. You put fuel, or ‘energy’, in one end and that is converted by the engine into movement. For internal combustion engines, the fuel is usually petrol, diesel or LPG.

 

How it works

When you put fuel into your tank, you’re topping up a reservoir of flammable liquid. When you start up, this liquid is pumped to the engine, mixed with air and this mixture is set alight inside the pistons. In petrol engines, this combustion is caused by a spark from a spark plug or an electronic system, in diesel engines the fuel is mixed with highly compressed air at high temperature, which causes ignition. As the fuel burns, it increases the pressure in the piston, making it move. This movement of the pistons is converted mechanically, so it turns the up and down motion into a circular motion of the crankshaft. The crankshaft is attached to the gearbox via a clutch, and from the gearbox to the driving wheels. 

 

Simple VS. Complex

Simple engines may have one or two cylinders: more complex engines may have up to 12. Each piston is fired in sequence to maintain the pressure on the camshaft to revolve. The amount of times your camshaft turns is measured in revolutions per minute (RPM, or revs). The more fuel you send to the engine by pressing the accelerator, the faster the engine turns.

Burning fuel results in exhaust gases. These gases are pushed out of the pistons through valves and sent down a pipe which usually exits the car under the body at the back.

 

Lubrication

Because your engine is full of moving metal parts, it will be lubricated with oil. This oil is pumped around the engine and prevents metal parts wearing on each other. The oil also collects any minute pieces of metal loose in the engine. Your oil level should be measured regularly to prevent it falling too low and you can check it by using the dipstick.

 

Cooling System

At operating temperature, petrol and diesel engines are very hot. To mitigate this, they are usually cooled with water. The water in your cooling system will be made colder by airflow over the radiator, which is usually at the front of the engine compartment, as you drive along. This cooled water is pumped around the engine and returned to the radiator to cool again. When the weather is cold, you can draw the heat from the hot water to heat the inside of your car.

 

Alternator

There are other auxiliary pieces of equipment attached to your engine. The alternator is driven by a belt and generates electrical energy to recharge the battery. The starter motor is an electric motor which turns the main engine when you turn the key.

In summary, burning fuel and air results in an up and down motion of the pistons. This motion is translated into a circular motion of the camshaft and that, ultimately, is what propels your vehicle. The engine is lubricated with oil and cooled by water, both of which are moved around the engine by pumps driven by the engine.