Oil pump (internal combustion engine)

An oil pump is an internal combustion engine component that circulates oil under pressure to the engine's rotating bearings,sliding pistons and camshafts.This lubricates the bearings, allows the use of higher capacity fluid bearings, and also helps cool the engine.In addition to its primary purpose of lubrication, pressurized oil is increasingly used as hydraulic fluid to power small actuators.One of the first notable uses of this was for hydraulic lifters in camshaft and valve actuation.More recent uses may include tensioners for timing belts or transmissions for variable valve timing systems.

Water Pump 

The type of pump used varies. Gear pumps trochoidal pumps and vane pumps are commonly used.Piston pumps have been used in the past, but are now rarely used on small engines.To avoid priming, the pump is always installed low, submerged in water or near the oil level in the sump. Short suction line with simple wire mesh filter to bottom of sump.

Pump Drive

For simplicity and reliability, a mechanical pump is used, driven by the mechanical gear train of the crankshaft.It is beneficial to reduce the pump speed,so the pump is usually driven from the cam (if installed in the cylinder block) or the distributor shaft, which turns at half the engine speed.Putting the oil pump low uses a nearly vertical drive shaft driven by a helical gear from the camshaft.Some engines, such as the 1964 Fiat Twin Cam engine, were originally OHV engines with an oil pump driven by a conventional camshaft in the cylinder block.When developing the DOHC engine, the previous oil pump arrangement was retained and the camshaft became a shortened stub shaft.Even though the distributor position was moved from the previous block mount to the cylinder head camshaft mount, the oil pump drive remains in the same position, the unused distributor position is now covered by a blind plate.Small engines or scooters may have an internal gear pump mounted directly on the crankshaft.For reliability, an external drive mechanism is rarely used, either a separate belt drive or external gears,although camshaft driven pumps usually rely on the same timing belt.Sometimes an extra separate belt is used where a dry sump pump is added to the engine during tuning.

The electric oil pump is not used, also for reliability. Some "turbo timer" electric auxiliary oil pumps are sometimes fitted on turbocharged engines.These are the second oil pumps that continue to run after the engine has stopped, supplying cooling oil to the turbocharger's hot bearings for a few minutes while they cool down.These are auxiliary pumps and are not intended to replace the main mechanical pump, the oil pump.An electric pump as the main engine pump would again require a large electric motor, which would probably be cheaper to drive directly from the engine.For example, the oil pump of a BMW S65 engine delivers an oil volume of 45 LPM (liters per minute) at approximately 5.5 bar pressure.This pump requires a very large motor to drive it.