GDi High Efficiency Fuel Pump for Fast Engine Starts and Reduced Cam Loads

Gasoline direct injection (GDi) fuel pumps use a plunger reciprocating in a sleeve to deliver pressurized fuel. Current industry-standard clearances between the plunger and sleeve create internal fuel leakage rates which are large enough to negatively affect pumping efficiency at low engine speeds. A polymer seal located between the plunger and sleeve has been developed to minimize the fuel leak solving the low engine speed efficiency problem.

This paper will present analytical, experimental and validation testing results of improved pumping efficiency attained with this new seal. With the plunger seal, pumping efficiencies are shown to improve by a few percentage points at high engine rpms (erpm) but can double at low (cranking and idle) rpms, without degradation of performance after durability testing. Considering the rate of pressure rise during engine cranking, pumps with the plunger seal exhibit faster system pressure build which is independent of system pressure and cranking speed. Additional benefits of improved efficiency such as pump and cam downsizing will also be discussed where a decrease in maximum cam load and torque are predicted.