In the Opel Vectra, depending on the engine, there are two different injection systems that, in terms of the basic principle, work similarly, but differ in the injection mode and the way the intake air is measured:
The concept of partially sequential injection is understood as follows: with each revolution of the crankshaft, half of the required amount of fuel is simultaneously injected into all cylinders. So the cylinder receives the amount of injected fuel it needs in «two doses», with the first half injected into the stationary intake air ahead of the closed intake valve. On the next revolution of the crankshaft, the second half is injected into the incoming intake air with the intake valve open.
With fully sequential injection, each cylinder, in accordance with the ignition sequence, immediately receives its entire amount of fuel into the open intake valves. The advantage of this injection is a uniform formation of the air-fuel mixture in all cylinders, better exhaust gas performance and lower specific fuel consumption.
Measuring the intake air is necessary in order to dose the right amount of fuel into the amount of air that is currently sucked in. Simtec injection systems with an air mass meter have a heated plate in the intake air stream for this purpose and measure the cooling of the plate (strong cooling = a lot of air). Multec-S injection systems with an intake manifold pressure sensor infer the amount of intake air based on the pressure ratio in the intake path.
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