| Throttle Position Sensor.
It's a potentiometer (like a volume control on a stereo). When you wind the throttle open all you're doing is turning the butterfly valves to fully open in the throttle bodies. You're also turning the TPS.
Depending on where the TPS is set at it produces a different voltage. From that signal the ECU can work out how far you've got the throttle wound on, therefore how much the butterflies are open, therfore how much airflow is going into the engine and therefore how long a pulse it needs to send to the injectors and keep them squirting enough fuel in for the air/fuel ratio to be right.
The ECU takes a whole bunch of other stuff like the engine temperature, the crank position and the RPM the engines is at into account as well before it decides how much fuel to spit in, but that's about the size of it. |