Fuel Supply, Low-Pressure Side

Fuel Supply, Low-Pressure Side







General Information

The engine is designed to provide optimum performance and fuel consumption if unleaded unleaded fuel 93 octane ((R+M)/2). When fuel with 90 octane ((R+M)/2) is used, the engine's knock controller automatically adapts the ignition timing.

The maximum filling capacity of the fuel tank is approx. 17.7 gl. (67 liters), including approx. 3.1 gal. (12 liters) reserve capacity. On USA vehicles, a carbon canister with tank leakage diagnostics module (DMTL) for tank leakage testing is installed on the right of the luggage compartment, similar to the 9X7 models.

The fundamental difference in the fuel supply for the 997 Turbo DFI is that the pressure regulator (72.5 psi/5.0 bar rel.) and the fuel filter (similar to 997 DFI) have been integrated in the tank. This has made it possible to eliminate the fuel return from the engine, including the fuel cooler.

Similar to the 997 DFI, there are 2 fuel pumps in one pump chamber. Electric fuel pump 1 is controlled via the control unit in the right plenum panel depending on consumption and electric fuel pump 2 is activated additionally depending on demand based on a calculated consumption of >110 l/h.

Both electric fuel pumps are activated briefly when the ignition is switched on. The fuel is delivered into the filling chamber of the fuel pumps by the sucking jet pumps. These are operated with low pressure and are located in the low-lying tank pockets on the left and right. After the electric fuel pumps, the fuel flows through the fuel filter to the pressure regulator. The excess fuel that has been delivered is routed in the tank from the pressure regulator directly into the pump chamber. As a result, a fuel low pressure of approx. 72.5 psi (5 bar) is present at the quantity control valve of the DFI high-pressure pump.

NOTE:
- The procedures for checking the fuel pressure, holding pressure and delivery rate of the 2 electric fuel pumps are described in the Technical Data.
- Observe the safety instructions in the Technical Data when working on the fuel system.

Internal Design of the Fuel Tank with RLFS







Fuel delivery unit 911 Turbo DFI with 2 fuel pumps:

- RLFS fuel system without return line (and without fuel cooler)
- 2 sucking jet pumps (SSP) deliver the fuel into the pump chamber (PT)
SSP-HP - High-pressure sucking jet pump (0.5 mm)
SSP-NP - Low-pressure sucking jet pump (1.05 mm)

- Two electric fuel pumps (EKP) at the bottom in the pump chamber (PT)
EKP1 - Fuel pump 1 is controlled via control unit
EKP2 - Fuel pump 2 is activated only when required (>110 l/h)

- KF - Fuel filter in the tank (lifetime filter)
- DR - Pressure regulator in the fuel tank (rel. fuel pressure 72.5 psi/5 bar)