Replacing L-Jetronic flap-type AFM with silicon pressure sen

[Tony Bryant]

> I've sorta asked the same thing .... I think you're gonna be told by
> those that know (not me) that pressure is not mass, ergo your
> "tracking" will wander as humidity, temp and barometric pressure
> change.  I was told (I think that's what they said) that I
> could get reasonable mass approximations by knowing the pressure
> differential across the throttle, the throttle opening, and
> the temp.
> 

This intrigued me enough to investigate it, I found the formula in 
the appendix of Heywood's I.C.E. fundamentals, for the flow through 
an orifice. The only problem is that it specificies Cd, (Discharge 
co-efficient[1]), is only "experimentally determinable". (Fudge 
factor if you ask me...)

Does anybody know what figures are reasonable for Cd at almost 
closed, and fully open?

Alternatatively does anybody have flow figures for a real throttle 
body, speicifing angle, and flow? (as measured on a constant 
depression flow bench)

[1] Cd is not the same as Coefficient of drag.

Thanks...

$$$ MAKE CAR FAST $$$
bryantt at psc.fp.co.nz