It is called a vacuum gauge and was done back in the 50's.

The higher vacuum you maintain, in theory, the better your mileage. When
you press the accelerator your vacuum drops and that means you are using
more gas.




> wrote in message
oups.com...
> Given ever higher price for gas it would be nice to be
> able to monitor ones driving habbits to get the best MPG
> posible.
>
> In a EFI engine the fuel consumption is based on the on
> time for the injector(s). Has anyone seen any DIYS circuits
> for intergrating the injector duty cycle.
>
> I have been playing with a laptop PC versio, but it isn't
> too healthy to be watching a LCD while driving.
>
> I am hoping to find a way to reduce this info to a single
> analog meter so that all you have to do is maximise or
> minimisethe needle position.
>
> Terry
>