SAAB WIS ONLINE

Fuel injection

Fuel injection


Fuel injection in the Saab Trionic system is sequential, which means that injection follows the engine's firing order.

Injection duration is calculated by the engine control module mainly on the basis of the following information:


• pressure in the intake manifold

• intake air temperature

• engine speed

• engine coolant temperature

• oxygen content of the exhaust gases

• knocking, if any

• throttle position


Pre-injection


As soon as the engine starts to rotate and the electronic control module receives pulses from the crankshaft position sensor, the main relay and fuel pump relay operate, causing all injectors to open simultaneously and squirt a small amount of fuel into the intake valves. Injector opening duration is determined by the coolant temperature.

The purpose is to achieve short starting times. After this initial injection of fuel, the system reverts to regular sequential multipoint fuel injection.