Engine Components - EngineKnowHow

The main engine components in both a spark and compression ignition engine are:

Engine: BMW N55, Source: BMW AG


Engine Block – The body of the engine which contains the cylinders.

Cylinder – The cylinders in which the pistons run.  The cylinders are housed in the cylinder block.

Piston – Translates the combustion energy from the fuel / air mixture into linear motion and to the crankshaft.

Piston Rings – Rings which sit in grooves on the outside of the piston with the top rings sealing the combustion chamber whilst the bottom rings scrape oil down the cylinder walls.

Connecting Rod – also known as “Conrod”, connects the pistons to the crankshaft and converts the linear motion of the pistons to the rotational motion of the crankshaft. Connected to the pistons via a gudgeon pin and the small end bearings and connected to the crankshaft via big end bearings.

Crankshaft – A shaft driven by the connecting rods which produces the work which can be transferred out of the engine. Connected to the engine block by the main bearings.

Oil Sump / Pan – The casing which is positioned below the crankshaft and connects with the engine block to enclose the crankcase. Acts as the oil reservoir for the oil / lubrication system in wet sump engines.

Cylinder Head – Sits atop the engine block and seals the cylinders and contains the spark plugs and/or the fuel injectors in addition to the valve mechanisms.

Inlet / Exhaust Valves – Valves which admit the fresh charge into the combustion chamber and then allow the combustants to exit the combustion chamber. Typically always poppet valves.

Valve Springs – Springs which sit on the inlet / exhaust valves and act to close the valves.

Camshaft – A shaft which acts against the valves via lobes to push open the valves with one cam lobe per valve. Situated in the cylinder head in newer engines and driven off the crankshaft via gears, chains or belts it rotates at half the speed of the crankshaft.

Intake / Exhaust Manifold – Connect either with the intake or exhaust ports to provide the fresh air to the ports into the combustion chamber or to collect the combustion products from the exhaust ports.

Timing Chain / Belt – Transmits the rotation of the crankshaft to the camshafts.

Injectors – Inject fuel either into the combustion chamber on direct injection engines or into the inlet ports on port fuel injection engines and generally connected to a fuel rail.

Oil Pump – Mounted in the sump of engines and provides lubrication to the engine.

Fuel Pump – Provides the fuel to the engine / fuel rail / injectors and increasingly mounted in the engine due to the higher fuel pressure requirements of direct injection engines.

Water Pump – Pumps the coolant around the engine to manage engine temperatures and typically mounted externally to the engine.


Engine: Honda