Pelican Parts Forums - Throttle positiong sensor back-date.

Pelican Parts Forums (http://forums.pelicanparts.com/)

- Porsche 911 Technical Forum (http://forums.pelicanparts.com/porsche-911-technical-forum/)

- - Throttle positiong sensor back-date. (http://forums.pelicanparts.com/porsche-911-technical-forum/948851-throttle-positiong-sensor-back-date.html)

Throttle positiong sensor back-date.

I have a 1974 911 2.7 CIS. Following Wayne's suggestions, I swapped in 964 cams and 9.5:1 pistons. I also swapped in a CIS from a 1979 911SC and ported my heads to match.
The 1974 cis system had a throttle position sensor on the throttle body which causes the air/fuel mix to enrich when on hard throttle. The 1979 cis system changes the air/fuel mix by adding or removing vacuum to the warm up regulator. (When the throttle is closed, vacuum from below the butterfly valve is conveyed to the interior of the WUR causing an increase in control pressure leading to a lean mix. When the throttle is open, the vacuum drops and the mixture is enriched.)
Here's my question: would I get a performance advantage by installing my mechanical TPS from my old '74 throttle body onto my new '79 throttle body?
(I suspect that Porsche dropped the old style, mechanical TPS in favor of the vacuum and WUR setup in order to meet fuel efficiency and emission standards.)

Will a '74 style TPS give me harder acceleration compared to the '79 style vacuum/WUR setup?

The silence is deafening. LOL Sorry I got nothing.

Thanks Mikl911...! ('74 cis holds many mysteries....)

Basic CIS troubleshooting..........

Quote:

Originally Posted by artwangler (Post 9504614)

Thanks Mikl911...! ('74 cis holds many mysteries....)

Art,

I received your email this morning and here are some answers to your inquiries:
a). The vacuum connection to your WUR-045 is incorrectly installed. Vacuum from throttle body is located below the butterfly valve and you got it right. However, WUR-045 uses the side port for vacuum and you are using the top. Reverse your installation.
b). Since you have a decel valve and WUR-045, the TPR (throttle pressure regulator) is no longer needed. And your CIS is now vacuum assisted.
c). Your question about the ignition distributor could be answered correctly if you furnish us with some related information:
What is the ID number on the ignition distributor?
What is the engine number/type stamped on the crankcase?
A picture of the distributor showing the vacuum hose would be helpful.

BTW, what problem/s are you experiencing now? Do you have a pressure gauge to measure your fuel pressures? Keep us posted.

Tony