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Thierry25 Thierry25 is offline
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Join Date: Feb 2009
Location: FRANCE (Besanšon)
Posts: 310
Originally Posted by JFairman View Post
Maybe the K-jetronic ECU is programmed differently in the 964 turbo to make the lambda valve bleed off more lower chamber pressure at large throttle switch positions. That would send more fuel to the injectors.

I don't know as I've never even seen a 964 turbo up close and don't know what all the subtle differences are in state of tune.

I remember someone posting pics of the 964 turbo and 930 fuel system specs from a book and I remember they were all the same accept for boost control pressure and I don't know where that post was and I think I remember reading it the other way around - I thought I read that the 964 turbo WUR was set to lower boost CP than the 930 one.
If it was thats probably where the extra fuel is coming from under boost.

I have no idea what thread that was in and don't feel like trying to find it right now.
That's true that if you are not familiar to 964T, it a bit difficult for you to follow me. ( As it is sometime difficult for me to follow you on 930 territory ).

To be honnest with you I have the full original Porsche workshop files on my hand. ( both 3.3T and 3.6T)

The 3.3 T kjet ECU supply the same stable 50% duty cycle at WOT to the freq valve ( which is the same as 3.3T). There is absolutely no lambda regulation at WOT.

Fuell pressure system is the same ( 6.1 to 6.8) The warm control pressure is the same 4.5 b . On boost, the control pressure is 1.1 bar shifted on the 3.6T while it is 1.3 shifted on 3.3 T ( Sorry I made mistake it is not 0.4bar less but 0.2 bar only )

By the way, while I tuned my KJET-BOOST controller system on my car . With the stock pumps (before to switch to 044 front fuel pump) , I made the test to trigger the lambda freq valves at stable 75% duty cycle on all RPM. As you can see on the following curve, it brings a lot of fuel ( the car almost stalled) in the mid rpm)....but it doesn't bring same fuel increase at high rpm

965 C2T / 1991 3.3 TURBO
Old 01-06-2010, 02:33 PM
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