Misc ?? EFI

[Bruce Plecan]

-----Original Message-----
From: Scot Sealander <Sealand at clarityconnect.com>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Saturday, November 21, 1998 6:05 PM
Subject: Re: Misc ?? EFI


snip

>
>Take this example.  If you know the amount (mass) of air that is in the
>cylinder and divide that by the desired AFR, you get the amount of fuel
>needed for that cylinder.

For figuring that mass, (correct me if I'm wrong):
Engine displacement * RPM/no of cyl * VE

so that product divided by 14.7= amount of fuel needed (#/hr ?)
That can't be right, I'm missing something there in the first
equation, no mention of #s

  Multiply the result by the injector constant,

Why then more than one injector constant?.  I've heard mention of
as many as 3 for a single calibration.

>and you get the amount of time needed for the injector to deliver the
>required fuel.
>
>Now when in closed loop, the desired AFR is 14.7 to one.  The O2 sensor
>just happens to work perfectly for us at that AFR. The calculated fuel PW
>is dithered slightly rich/lean, and the O2 sensor lets the ECM know if
>it is actually moving rich/lean.  If not, appropriate CL action is taken.
>
>If CL control takes the integrator a certain amount away from a neutral
>value, over time the BLM will move to correct the fuel PW, returning the
>Int to neutral.
>
>So the fuel equation may be:
>
>AirInCyl/AFR * injector constant * Int * BLM.

= 14.7???
>
>If everything is perfect, then commanding a richer AFR will take the
>correct proportion of fuel, and it will be the newly commanded AFR.
>Notice that to be right, the AirInCyl term has to be right, and the
>BLM and Int should be neutral.  Also the injector should be maintained
>with the same pressure drop across it (fuel pressure to manifold
>pressure, assuming port injection), so that it remains linear across it's
>commanded pulse widths.
>
>I have seen people say that the commanded AFR has nothing to >do with
reality, but that is only true if the terms in the equation are >not being
accurately measured/used, or the injector is seeing >varying fuel pressure
deltas across it.

I've got to restate what I was trying to express when I said that,
rereading that, after what you've stated, I see your point.
Again thanks
Bruce
>
>Scot Sealander    Sealand at clarityconnect.com
>