Fuel Rail: Description and Operation

Fuel Supply

Fuel High Pressure System in V8 DFI Engines







The fuel high pressure system in V8 DFI engines is made up of the these parts/components.

TECHNICAL MANUAL: Always read and observe the specifications in the Technical Data when securing all fuel lines in the high pressure area.

Fuel Temperature Sensor (on low pressure side)







At start of production, all Cayenne V8 engines have a fuel temperature sensor on the low pressure side, which will be replaced by a temperature model in the DME in later production. Depending on the amount of fuel required and the fuel temperature, the DME control unit, together with the flow control valve, regulates the amount of fuel on the high pressure side upstream of the high pressure injectors.


High Pressure Line

The high pressure line connects the high pressure pump to the fuel rail.

Central High Pressure Rail







The central high pressure rail in V8 engines is located in the engine's inner V. From here, the fuel is supplied via individual lines to the fuel injectors for cylinders 1 to 8. The high pressure rail provides the same pressure for all injectors. The volume of the high pressure rail is adapted according to the amount of fuel the engine needs (V8 naturally aspirated engine 100 cm3, V8 Turbo 150 cm3).

- The rail volume is determined by the required pressure variation behavior and the shortness of the starting time.

High Pressure Fuel Line