On the 12 valve is there a way to monitor instant MPG?

 

I dont understand the question....

Milage is usually calculated by taking the miles divided by gallons used = MPG.

As for the trip computer, I dont find mine accurate and never bother looking at it anymore.

 

I've checked around before, these are the only devices I could find, well over $1000
http://www.floscan.com/ModelSelectio...lEngineMfg.asp

 

I'm trying to perfect my hydrogen unit and it would be easier with instant MPG instead of waiting till the tank is empty and calculating it then. I don't expect the instant MPG to be perfect, but to get a general idea of what is going on.

 

Well, you don't need miles per gallon, you need a fuel consumption rate... I take it that you will be fumigating a constant ratio of hydrogen per the amount of fuel being injected; for a long-use and daily-driving application I can imagine that you'd need a pretty accurate way of regulating hydrogen input.

You can either get this based on how much fuel is going to the engine, or how much air is going to the engine.

The first option is to measure the air going in, which is the way all of the professional propane fumigation kits work. I think that they use an electrically adjustable venturi that just meters in a ratio of hydrogen versus CFM of air flow into the engine, like a carburator. I think that would be the best way to induct hydrogen, although I don't know what your system exactly looks like. Alternately I would assume that you could use an air-flow sensor and electronically inject a relative amount of hydrogen, but that seems overly complicated to me...

Or I take it that you could fit some kind of fuel-flow gauge on the lines going to and away from the injection pump. Don't know what you could use, but in theory that would work. I don't think I've ever seen anybody do anything like that though.

 

That's the way the Flo-Scan gauge I linked to works, measures supply and return flow then subtracts them.
The way a 24 valve mpg gauge works is by inputting the throttle position, rpm and mph to give the readout. It doesn't measure true fuel flow, any engine modifications at all screws it up.