Originally Posted by Roy Smith
fuel injection recyles the fuel it did not use so by passing the fuel flow meter showing a lower rate of fuel use.
That's about right in that most fuel injected engines have a small amount of feedback, although this is normally inside the engine into a small reservoir and not back into the fuel tank. Unlike diesel which does return fuel to the tank, and for which you need two fuel flow meters so that the difference can be measured and therefore show 'actual' fuel consumed.
Also make sure it is not too close to a bend in the pipe where air locks could occur.
I spent some time calibratin my Navman but I'm still not happy so will be doring some trialing this season.