In 1974 Opel introduced, with the Manta GTE model, the first electronic fuel injection from Bosch onto the market in which the barometer cans are substituted by the air volume meter. In addition, parallel to this, the principle of pressure measurement is still used by some manufacturers today.
How it works
Even though an air vane swivels with the intake of air, the rotary angle is however, not precisely proportional to that of the air volume intake. A rotary potentiometer converts the movement of the air vane through complicated resistance trajectories, according to the air volume intake, into a signal and passes this on to the control device. A compensation flap turns at the same time in a dead area and dampens any oscillations of the air vane which may appear. The pressure control valve is now connected through its spring chamber with the inlet manifold of the engine and regulates the inlet manifold pressure to 2-3 bar of injection pressure. The pressure difference between distributor pipe and inlet manifold thereby remains constant. The injection amount depends precisely on the injection pulse-length. The throttle switch no longer has contacts for the acceleration. An acceleration enrichment is reached through the slightly stronger oscillating air vane, which also signals an acceleration to the control device more quickly. In all cases, an further enrichment is carried out for a certain amount of time. The triggering of the injection is now taken over directly by the contact-breaker points. However, all injectors inject only at every second contact release. Due to the fact that one could not yet determine the air volume, and at this time no Lambda sensor existed, a height corrector had to help correct the injected fuel amount in large heights. Because it was not often installed directly on the engine, garages had a lot of problems with failures in this component. It was simply forgotten.