Fuel Injection - BOSCH AFC - EUROPEAN Models: Description: Notes

NOTE: The Bosch AFC Fuel Injection system is used on all models. Variations may exist between model applications with the addition of auxiliary control systems. This article covers the Bosch AFC system in general, with manufacturer's differences noted. Federal Vanagon models do not use an oxygen sensor, so disregard oxygen sensor information for these vehicles.

The Bosch Air Flow Controlled (AFC) fuel injection system is an electronically controlled system operated by incoming air flow. The AFC fuel injection system also contains a feedback system which measures oxygen content of exhaust gases and maintains the air/fuel ratio at about 14.7:1.

The fuel injection system consists of an electric fuel pump, fuel pressure regulator, fuel injectors, Electronic Control Unit (ECU), air flow meter, air temperature sensor, throttle switch, coolant temperature switch (cylinder head temperature switch on Vanagon), oxygen sensor, catalytic converter and electrical relays.

In addition, all models except Porsche 944 are equipped with a cold start system to aid in cold engine starts. The cold start system consists of an auxiliary air valve, cold start injector and thermo time switch. An air conditioning solenoid valve is installed on Renault models equipped with air conditioning to provide additional air when compressor is activated.

Fiat Spider 2000 Turbo models are equipped with a boost enrichment circuit, load enrichment circuit and an overboost protection circuit which provide necessary information to ECU on turbo operation.

California Vanagon models are equipped with a speed limit switch between throttle switch and ECU which deactivates the oxygen sensor at engine speeds in excess of 3000 RPM. BMW, Porsche 944 and Renault Fuego Turbo models are equipped with electronic engine control. On these vehicles the ECU controls ignition timing in addition to fuel injection.

Fig 1: Fiat AFC Fuel Injection System

Courtesy of BMW OF NORTH AMERICA, INC.

Fig 2: BMW AFC Fuel Injection System

Courtesy of BMW OF NORTH AMERICA, INC.