i mean, not literally how does it go up and down LOL......what is the output based on? combination of speed, pedal pressure, etc? i am somewhat technically challenged here, but would like to know.

thanks

 

The engine computer knows how much fuel it has metered into the cylinders (electronic fuel injection), and it knows how far you've travelled from the odometer. Those parameters are all part of the standardized OBD2 engine diagnostics protocol.

It determines how much fuel to meter based on current speed, throttle position, rpm/gear, air temp & pressure, and type of fuel.

 

The ECU knows your speed in MPH,and it knows the fuel flow in gallons per hr .60m/h/3 g/h=20 m/g Luck,Charlie there is a flowmeter in there somewhere-or an indirect flowmeter based on the pressure and number of squirts, duration of squirts of the Fuel injectors(or fuel pump).Luck,Charlie