High Pressure Fuel Circuit

Courtesy of NISSAN NORTH AMERICA, INC.

ECM controls fuel rail pressure by controlling the quantity control valve according to a signal transmitted from the fuel pressure and temperature sensor and adjusting fuel pressure necessary to the direct injection in the high pressure circuit to approximately 20 MPa (200 bar, 204 kg/cm ² , 2, 900 psi).

The high pressure circuit has control items as follow.

• Fuel feed
• Fuel pressure control

Fuel Feed 

The high pressure fuel pump pressurizes fuel sent from the fuel pump up to approximately 20 MPa (200 bar, 204 kg/cm ² , 2900 psi) and pumps the pressurized fuel to the fuel rail. In addition, the high pressure fuel pump has a fuel pressure damper to control pressure fluctuation occurring at rapid acceleration, contributing to the reduction in fuel fluctuation. Since the high pressure fuel circuit does not have a return circuit, the pressure increases up to 27 MPa (270 bar, 275.4 kg/cm ² , 3, 915 psi) due to temperature rise in the high pressure fuel circuit after engine stop or in deceleration mode.

Fuel Pressure Control 

The fuel pressure and temperature sensor detects fuel pressure in the fuel rail and converts the detected fuel into a voltage signal to transmit it to ECM. ECM controls the quantity control valve according to a PWM signal and adjusts fuel pumped to the high pressure fuel pump. This adjusts fuel pressure in the fuel rail to approximately 3 - 14 MPa (30 - 140 bar, 30.6 - 142.8 kg/cm ² , 435 - 2, 030 psi) according to the operating state of the engine. After the engine stops, the power is not distributed to the quantity control valve. Accordingly, the high pressure fuel pump stops pumping fuel. For fuel pressure, it is maintained even after the engine stop.