[mwebb]

from a vacuum gauge to this ...
if you are just looking for a relative value as a vacuum gauge would sorta kinda provide in a gasoline powered engine ...

you can plumb in a MAF sensor ,
any MAF sensor into the air intake , they have a 5 volt reference and a ground and a signal
which you will need to provide a power supply for
some have a temp sensor as well
just monitor the MAF signal

lower = better FE

Originally Posted by So_SiMpLe_

Right so by the rpm and throtle position is possible to find the fuel consumption!

There's a speed sensor that is easy to fix in my car's gearbox and give speed by voltage!

I have to think about a thing like that and I'll search the classifieds!

The volume of air is not dependent on the throttle position, if you go @ 40km/h in 5th gear and the engine really almost "dead" if you press full throttle you get full pump injection but the volume of air stays almost the same!