Table of contents: Launch ↓ Warm-up ↓ Idling ↓ Acceleration ↓ Lambda regulation ↓ Altitude correction ↓
Only the differences from the mechanical system are described here.
Launch
After starting the engine, an increased amount of fuel is supplied for a few seconds for the so-called post-start boost. The temperature sensor informs the control unit of the coolant temperature, and it commands the pressure regulator to increase the pressure on the control slot. Higher pressure ensures that more fuel is supplied to enrich the mixture. The amount of fuel depends on the coolant temperature.
Warm-up
When the engine warms up, the pressure regulator reduces the pressure value. This ensures normal fuel supply.
Idling
On a low-power engine, an auxiliary air duct is provided by the control unit (in the central mounting block) can only be set to the "open" or "closed" position. The above-described precise stabilization of engine speed is carried out by the control unit on the five-cylinder engine.
Acceleration
When the engine is cold, when the accelerator pedal is pressed, a richer mixture is injected. Operation in this mode is carried out in the same way as when increasing the speed after starting.
Lambda regulation
For the normal operation of the catalyst, a constant transition from a slightly over-enriched to a slightly lean mixture is necessary. The lambda probe reports the composition of the exhaust gases in the exhaust manifold at the moment to the control unit, which in a split second gives an "order" to the pressure regulator to increase or decrease the fuel pressure and, accordingly, determines the required amount of fuel supplied.
Altitude correction
On a 2.3-liter engine, atmospheric pressure influences the mixture preparation, which prevents too much fuel from being supplied to the engine when driving in high-altitude areas where the air is thinner.
(The original source of the article can be found on the website AUDImanual)