Fuel Supply, High-Pressure Side
Fuel Supply High-Pressure Side DFI
The high-pressure side of the direct fuel injection system is matched to the requirements of the 6-cylinder turbo engine.
Main differences compared with 9X7 DFI naturally aspirated engines are:
- 6-piston fuel high-pressure pump
- Adapted high-pressure rails
- Multi-port injectors (6 ports)
The above key features based on the current 911 Carrera DFI models have been changed or modified to meet the specific requirements of the new 911 Turbo. The higher power output of the new 911 Turbo and the related fuel requirement necessitates an increase in the maximum fuel flow. This is mainly achieved by a 6-piston fuel high-pressure pump, which ensures a delivery rate that is approx. 30 % higher than the 3-piston fuel high-pressure pump used in the 911 Carrera models.
Similar to with the current 911 models, mixture formation in the new 911 Turbo engine is based on homogeneous direct fuel injection. The mixture of air and fuel is distributed as evenly as possible in the combustion chamber to enable optimum combustion, which thus reduces fuel consumption and exhaust emissions while increasing torque. In the new 911 Turbo, this process injects the fuel directly into the combustion chamber at a fuel pressure of up to 1957 psi (135 bar) (911 Carrera: 1740 psi/120 bar). The higher pressure in the new 911 Turbo offers a further increase in the maximum amount of injected fuel and supports mixture formation with even finer atomization of the fuel. Efficient mixing of the air and fuel is assisted by the special shape of the tumble intake ports.
6-Piston Fuel High-Pressure Pump
The 6-piston fuel high-pressure pump with quantity control valve provides the high pressure of between 580 to 1957 psi (40 to 135 bar) needed for injection. The high-pressure pump is driven via the intake camshaft of the left cylinder bank.
Adapted High-Pressure Rails
The same fuel high pressure is supplied by the high-pressure pump via the high-pressure line to the fuel rails of banks 1 and 2 and to all injectors. The volume of the high-pressure rails is matched to the turbo engine.
NOTE: 3 piston 911 version pump shown in above picture.
Multi-Port Injectors (6 ports)
The use of multi-port injectors is also new. Compared with the swirl injectors used in the 911 Carrera models, these injectors offer a greater useful bandwidth for fuel injection. In addition to fine and sensitive injection at small flow quantities, the multi-port injectors in the new 911 Turbo enable a maximum flow that is up to 40 % higher. In the new 911 Turbo, the fuel is injected into the cylinder through 6 orifices on each injector with individually matched spray and cone angles.
This type of fuel injection using multi-port injectors creates individual cone-shaped clouds of fuel, which enable very fine atomization and quick evaporation of the fuel. The heat energy required to evaporate the fuel is extracted from the combustion air. This cooling reduces the cylinder charge volume and additional air can be drawn into the cylinder through the open intake valve. In turbo engines in particular, this effect improves cylinder charging and therefore engine performance.
The injectors are solenoid-operated and are positioned beneath the intake ducts of each cylinder. They inject the fuel under high pressure directly into the combustion chamber. To open an injector, the activation voltage is briefly raised to up to 75 V by way of a voltage booster in the DME control unit.
Fuel Quantity Control Valve
The quantity control valve installed at the inlet port of the high-pressure pump regulates the fuel high pressure. Control current 0 to approx. 2 A.
When the engine is running, the high pressure measured by the pressure sensor is regulated to a pressure of between approx. 580 to 1957 psi (40 to 135 bar) by the quantity control valve (at the input of the high-pressure pump). Note: Cayenne Turbo DFI version shown
Fuel Pressure Sensor
The pressure sensor on the high-pressure rail measures the fuel high pressure (measuring range from 0 to 2479 psi/170 bar).