Browse Publications Technical Papers 2019-01-1196
2019-04-02

GDi High Efficiency Fuel Pump for Fast Engine Starts and Reduced Cam Loads 2019-01-1196

Current GDi fuel pumps use a plunger that is inserted into a bearing (for example a sleeve) where the sleeve ID is match-honed to a to obtain a close clearance fit with the plunger. This close clearance fit has to be large enough to prevent metal-to-metal seizures by allowing some fuel between the plunger and sleeve for cooling/lubrication, however, then this clearance becomes a detriment for low engine rpm pumping efficiency. This clearance allows too much “internal” fuel leak at low rpm which prevents fast and high enough pressure build in the high pressure fuel system. This new invention puts a specially developed seal at the plunger/bearing interface to minimize/eliminate the fuel leak solving the low rpm efficiency problem. This is achieved without the need to tighten the clearance between the plunger and bearing which would compromise the pump’s robustness to seizures. Along with improved low rpm efficiency, this new high efficiency pump also exhibits gains in efficiency at higher rpms enabling plunger and/or pump cam downsizing. The advantage of downsizing is reduced cam loading leading to lower cam stresses, cam drive torque, and the potential to downsize valvetrain components. This paper will present analytical and experimental results of improved pumping efficiency and examples of pump/cam downsizing with the associated reduced cam loading. Additionally, results from validation testing and reduction in efficiency loss over pump lifetime will be discussed.

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