Quote:
Originally Posted by Cocktails
Doesn't the trip work out MPG by fuel level in tank?
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Nobody outside of BMW knows how the trip computer measures fuel consumption. But it is safe to assume it is NOT by measuring the fuel level in the tank. There rate that fuel comes out of the tank is far too slow to measure instantaneous fuel consumption, which the Beemer does. Also variables like centrifugal forces going around a corner and fuel sloshing to the side of the mean measuring fuel level in the tank is a non-starter for the trip computer. However filling your tank up to full and calculating fuel consumption from volume of fuel added and distance travelled is a great way for you to measure fuel consumption yourself.
The car trip computer probably measures fuel consumption by fuel injection pressure and length of the injection pulse. When you remap, you mess with the length of the injection pulse. There is no reason to think that the car trip computer knows the car has been remapped, so it may be calculating fuel consumption based on pre-remap parameters which are now no longer valid.
In short, any claimed change in fuel consumption following a remap needs to be proved by comparing distance travelled divided by fuel added for several fill-ups before and after the remap.