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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.

To meet future particulate number regulations, one path being investigated is higher fuel pressures for direct injection systems. At operating pressures of 30 MPa to 40 MPa, the fuel system components must be designed to withstand these pressures and additional power is required by the pump to pressurize the fuel to higher pressures than the nominal 15MPa to 20MPa in use today. This additional power to the pump can affect vehicle fuel economy, but may be partially offset by increases in combustion efficiency due to improved spray mixture preparation. This paper examines the impact on fuel economy from increased system fuel pressures from a combination of test results and simulations. A GDi pump and valvetrain model has been developed and correlated to existing pump torque measurements and subsequently used to predict the increase in torque and associated impact on fuel economy due to higher GDi system pressures.

Fuel systems associated with Gasoline Direct Injection (GDi) engines operate at pressures significantly higher than Port Fuel Injection (PFI) engine fuel systems. Because of these higher pressures, GDi fuel systems require a high pressure fuel pump in addition to the conventional fuel tank lift pump. Such pumps deliver fuel at high pressure to the injectors multiple times per engine cycle. With this extra hardware and repetitive pressurization events, vehicles equipped with GDi fuel systems typically emit higher levels of audible noise than those equipped with PFI fuel systems. A common technique employed to cope with pump noise is to cover or encase the pump in an acoustic insulator, however this method does not address the root causes of the noise. To contend with the consumer complaint of GDi system noise, Delphi and Magneti Marelli have jointly developed a high pressure fuel pump with reduced audible output by concentrating on sources of noise generation within the pump itself.