The cylinder is the power unit of the engine. This is where fuel is burned and converted into mechanical energy that powers the vehicle. The number of cylinders in a typical car could be four, six or eight.
The cylinder is made of metal and is sealed shut. It contains a piston that moves up and down, compressing the fuel, which ignites and causes combustion. There are two valves at the top of the cylinder; an inlet valve and an outlet valve. The inlet valve is where the fuel and air enter the cylinder from the carburettor or electric fuel injector, and the outlet valve is where exhaust gases escape.
The exhaust gases created during combustion in the cylinder rotate an axle known as the crankshaft. These are connected to the bottom of the cylinder which in turn powers the gearbox that drives the wheels.
The more cylinders there are, the more pistons are combusting the fuel, and therefore more power is generated.
Cylinders can be laid out under the bonnet in a straight line, in two rows or in a flat arrangement. Engines with cylinders in a straight line are known as an inline engine (i.e. I4 or L4). These usually have less than six cylinders. Those in two rows are referred to as a V engine, as they are usually in a 'V' formation and have more than six cylinders. UK Engines with a flat arrangement generally have four to six cylinders.
If an engine cylinder is not working efficiently then there may be overheating, leaking or misfiring. These can be obvious problems that can be detected by smell, smoke or visible leaks.
If you have a problem with the cylinders, you would be able to detect a sweet and rubbery smell when inside the car. This smell can be created by coolant leaking into the cylinders.
Grey smoke is a good indicator that your cylinders are not working efficiently and the engine is overheating.
Leaks can be obvious, particularly on dry days. If there's a puddle of liquid underneath your car you might want to check its coolant levels.
Cylinder pressure should be balanced to maintain efficient combustion and good engine condition. Low pressure will be easily identifiable as the main indicator is an engine misfire when it is started, or poor performance when driving.
The pressure can be measured using a compression gauge. You can do this yourself if you have one or you can ask a mechanic to do it for you.