Replacing L-Jetronic flap..........

[RABBITT_Andrew at mail.orbeng.com.au]

>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...)

It's not so much a fudge factor, as a factor that makes a simple model 
of a complex phenomena work.  I've some good papers on modelling of 
throttles and it gets real complex very quickly.

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

probably less than 1, but if we talk pulsing flow, the mean flow rate 
will be higher for the same dP compared with steady state flow.

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

Throttles are not constant dP devices when used on 4-stroke ICEs.