Benefits of Variable Discharge Oil Pump on Performance of 3 Cylinder SI Engine

Lubrication system is a critical factor for engine health. But it creates parasitic load and increased fuel consumption of the engine. The oil demand of an engine depends on engine speed, load, bearing clearances, operating temperature and engine's state of wear. Ideally, the oil pump should adapt the delivery volume flow to actual engine oil demand and should avoid unnecessary pumping of oil which causes increased power and fuel consumption. However in a conventional mechanical oil pump, there is no control on the oil flow and it is purely a function of operating speed. A variable discharge oil pump (VDOP) is an approach to reduce the parasitic losses wherein the oil flow is regulated based on the mechanical needs of the engine. This study is based on the results of a two stage VDOP installed on a 1.2 litre, 3 cylinder MPFI engine. The oil supply is regulated by a solenoid control which receives command from Engine Control Unit (ECU). The study was done in two stages. In the first stage, experiments were conducted under steady state conditions on engine dyno by operating VDOP in two modes one as a conventional mechanical pump and another as a two stage oil pump .Experimental results shows a BSFC benefit of ∼2.5 % between the two modes. In second phase, experiments were conducted under New European Drive Cycle (NEDC 90) and observed an overall benefit of ∼0.5 KMPL (kilometer per litre). On the downside, it is observed that the engine out NOx emissions increases due to increase in oil temperature during the low pressure phase.