Fuel Injection - BOSCH AFC: Description
The Bosch Air Flow Controlled (AFC) fuel injection system is an electronically controlled system. The Electronic Control Unit (ECU) monitors electrical signals from various sensors, indicating changing operating conditions; such as intake air volume and temperature, coolant temperature, engine load, acceleration/deceleration and exhaust gas oxygen content (some models). The ECU analyzes these signals and determines the fuel injection duration necessary for optimum air/fuel ratio. See Figure.
An air flow meter, mounted between the throttle chamber and air cleaner, is the major control unit in addition to the ECU. The air flow to the engine is monitored by the ECU and fuel is adjusted accordingly by timing injector delivery. Injector delivery is based upon amount of intake air required for one engine rotation. The AFC system maintains constant fuel pressure and maintains proper air/fuel mixture by adjusting quantity of fuel to amount of intake air.
A "Closed Loop" feedback system is incorporated into the Bosch AFC fuel injection system by various manufacturers. The system consists of an oxygen sensor (2 on TR8) mounted in the exhaust manifold, special 3-way catalytic converter and special electronic control unit with feedback monitor system. Some systems also employ a modulating valve or frequency valve. Oxygen sensor feedback systems are used on the following models:
- All BMW Models
- Calif. Datsun 280ZX & 810
- Calif. Fiat Brava, Strada & X1/9
- All Fiat Spider 2000
- All Jaguar Models
- All Porsche 928
- Calif. Toyota Cressida & Supra
- All Triumph Models
- Calif. Volkswagen Vanagon