Calculating Fuel Econ. from pulse times and mph

[Clare Snyder]

Roger Heflin wrote:
> 
> Hello,
> 
> I have been trying to calculate fuel econ. from injector pulse times.
> I have a batch fire vehicle, I believe I know what the number of times
> per rpm that the injectors fire.  I think the injecotrs fire once per
> rpm (is this right).  I know the injector rating (lb/hr), there ford
> svo injectors which I believe means they are rated at 39 psi, my car
> is running at 45 psi, so the injectors are doing 45/39 * 30 lb /hr.
> Also the computer says the injecotr is on x.x ms.  I am assuming that
> is what the computer it telling the injectors to do.  Are the ramp
> up and ramp down times similar enough that you can assume that that
> time is close enough, or are there some transient things that cause
> the actual open time to be less than or greater than that number?
> What I am really tring to do is figure out what the absolute best
> gas mileage my car could get, if it was only crusing, with no braking
> or acceleration, and also determine how badly different things affect
> the gas mileage.
>                                 Roger Heflin
> 
What you want to do is determine the ACTUAL fuel usage, as well as the
ELECTRICAL time on of the injectors, then calculate the amount of flow
per second of injector on time. Then all you have to do is have your
computor, or whatever you are using, add this given fuel amount every
second of real time. By inputting distance into the equasion, you can
get MPG as well as GPH consumption. The CompuCruise system did this and
was very accurate after a good calibration run. For a simple fuel
totalizer, a calculator can be used. Have a circuit sum the injector on
time, resetting every totalled second, with the reset closing the= key
of the calculator. 0+(constant)=======. The constant is the # of partial
gallons consumed per injector second. Every time the + key is closed, it
gets added to the total. As for the circuit to time the "injector on"
time, I can't help you, but lots of EEs out there surely can come up
with something complicated, or mabee even simple:}
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