Buckeye19

Hello all,

I’m trying to find some info on the actual injectors used in the early Porsche CIS fuel systems. I’m looking at the early cars because I need something on the smaller end of the spectrum. If I remember correctly, they open at a line pressure of about 160 psi, and cycle closed again once pressure drops to ~140 psi (please correct me if I’m wrong).

If anybody has an idea of the flow rate at say 100% duty cycle at 160 psi I would greatly appreciate it. I am guessing they are around an equivalent of 200cc/min based on engine demand, but I was hoping somebody has some hard numbers somewhere. Thanks a bunch for any info you have.

-Brett

Peter Zimmermann

Brett: Early CIS injectors open at approximately 3 bar of pressure (about 43 psi) and they have no metering function. For testing purposes Porsche has always used cc/min (or 30 sec.) calculations to measure fuel pump delivery. I don't remember ever reading how much the injectors flow, the critical tests were spray pattern and leakage.
Pete

Buckeye19

Thanks for the info Pete.

The last set of CIS injectors that I saw cycled/cleaned with a pressure gauge were 930 turbo injectors. Possibly they open at higher pressures? Otherwise I'm not sure why the 160 psi number was stuck in my head, because it seems I was way high.

Peter Zimmermann

Believe it or not, 911 Turbo injectors open at even lower pressure. Their spec is 2.0 - 3.2 bar. Maybe you remember someone testing MFI (mechanical fuel injection) injectors, which open at very high pressure, if I remember correctly somewhere between 180 and 250 psi (roughly between 13 - 18 bar). Hope this helps!
Pete