Variable Oil Pump Description Chevrolet Volt I

The engine is equipped with a variable displacement vane oil pump. It is indirect regulated by the oil pressure out of the main oil gallery. The purpose of this indirect regulation is to keep a defined maximal pressure in the main oil gallery independently of the individual pressure drop between the pump outlet and the main gallery inlet and the individual oil flow to the consumers (bearing clearances differ, wear differs, •••) The purpose of the variable displacement is to reduce the power consumption of the pump to reduce the overall fuel consumption of the engine. The oil flow of a static displacement oil pump is linear to the speed of the pump. This would lead to a too high oil pressure after a certain engine speed (ca. 1000 rpm at cold oil temperature, ca. 3000 rpm at hot oil temperatures). To reduce that high oil pressure normal pumps have a relieve valve: a portion of the pressurized, already pumped oil is fed back to the intake of the pump. This is waste of power. The oil flow of a Variable Displacement Vane Pump (VDVP) as used in Fam 0 Gen 3 is linear to the speed and to the excentricity of the rotor to the slide. The slide is moveable, so it is possible to reduce the oil flow for a given speed by reducing the excentricity. With a lower flow the oil pressure is reduced; pump oil flow equals now engine oil flow.