Thread: CIS Horsepower
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Thierry25 Thierry25 is offline
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Join Date: Feb 2009
Location: FRANCE (Besanšon)
Posts: 310
Originally Posted by 911st View Post
I would like to see a flow test compairing the 3.3 & 3.6 injectors. Untill then I must remain a bit suspect.

CIS injectors are not like EFI injectors. I suspect that if the 3.6T injectors are bigger, then they would still flow the same fuel at most the rpm but could alow more fuel up top so they should not cause any tuning issues.

I suspect the way to more fuel through the CIS system is more system pressure and a fuel pump that suports this at some point would become a requirement. With the right pump it might be possable to put a fuel pressure reg (rising rate?) in line on the return line to effect fuel flow. However, the WUR return line would probably have to have its own path to the gas tank.

I belive of the main ways the 3.6T gets more fuel is a different WUR that runs lower control pressure on boost to support its 360HP.

I wonder if the 3.6T metering cone is any differant as to profile than the 3.3's to accomidate the 10% higher air flows?

If one was to go to the real dark side with CIS it would be interesting to use a V8 fuel head and plumb the extra two injectors in before the throtle plate. It would require a significant increase in control pressure or a reduction in the windage of the metering plate by cliping.
Hello Keith

The metering cone on the 3.6T is larger than 3.3 you believe it ? So for the same air flow , the metering plate moves less !

The wur of the 3.6 T provides higher control pressure than the 3.3T...

But 3.6T injectors have much higher flow !

Conclusion: Porsche use higher flow injector for the 3.6T. In order to control these larger injector at low RPM, they increased the metering cone OD and they increased the control pressure.
965 C2T / 1991 3.3 TURBO
Old 11-22-2009, 09:01 AM
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