computer project
Zublin, Bryan (SD-MS)
BZUBLIN at po2.gi.com
Sat Jun 17 02:13:38 GMT 1995
Roberto L. Landrau landrau at mitre.org writes:
> With
> constant fuel pressure, I presume the flow rate is proportional to
> the pulse width, offset by the injector "dead" or "turn-on" time.
> The fuel pressure in my car varies as a function of vacuum (or intake
> air pressure) level. Would I have to add a fuel pressure sensor in
>order to compute fuel flow?
You need to determine the "duty cycle" of the injectors to calculate the
flow rate. For example, if an injector is firing every 10 mS, and the ON
pulse width is 1 mS, the duty cycle is 10%. Therefore, it is flowing 10% of
its maximum flow rate (this ignores the dead time). Of course, you need to
know what the maximum flow rate of the injectors is in order to complete the
calculation. This can be measured if you have an injector, fuel pump, and
pressure regulator.
I think that you can assume that the pressure is relatively constant,
because most EFI systems have a fuel pressure regulator that is referenced
to the intake manifold (I think this is what you were referring to). This
maintains the same pressure across the injector.
Bryan Zublin
bzublin at gi.com
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