me a bit confused, if i am the ecu and i am firing the injectors, i should precisely know how much fuel i am throwing in, and i am getting the vss signal too hence i know the speed too, so theoretically i should be very precise in telling the mileage per liter.....
now the errors can be induced by error in vss, idling on lights, error in fuel level sensor.
but if i am cruising than the reading should be pretty precise, as only the error in vss remains, the idling part goes away and the error in fuel level sensor will only give error in range, but mileage per liter should be as precise as vss is..
and abroad almost everything with four wheels has navigation, so you can further reduce the vss error with gps help...
now if i calculate the mileage at 120 km/h cruising @ 3k rpm in 4 cylinder vehicle
i am doing reverse calculation as i have no idea for how long injectors inject or how much is there flow rate
3k rpm = 6k power strokes per min
in an hour there will be 360000 power strokes
lets say our car do 20 km/l, we use 6 litres in an hour
so it will be 60000 strokes per liter
0.01667 milli liters per stroke
now if my injector has 10 milli liter per sec capacity at the given pressure difference above manifold
than if i inject for 1.667 msec every stroke i will be gettting the 20km/liter mileage
in all this calculation there are no assumptions.
now i know that milometers are not accurate, logically the calculation tells they should be, hence i am missing some thing....