CIS throttle plate / switch calibration

[Gretz]

This is for an 82 SC.

The two switch units on the throttle body indicate when the CIS system should richen the mixture and they are all based on degrees of the throttle being open. For instance, the one on the left side of the car should switch when the throttle is open 15*. To complicate matters, the throttle plate when closed is not exactly at 90*, as you can see on my car in the pic below.

Here’s my question:

Are we measuring the angle the throttle is open from the throttle plate being fully at 90* within the throttle body or are we considering whatever “fully closed” is on each car to be 0* and measuring from there? Obviously on my car, “fully closed” is already 5* or so off axis which changes the calibration considerably.

[Funracer]

I think this is one of those times where “about” is good enough. I just eyeballed mine at 15 degrees and it works ok.

[Gretz]

I’d love to be totally low key about it, but it seems like it can make a big difference. Like on the micro switch (attached to the cruise control bracket) is supposed to enrich at 15* but activates (don’t recall if it opens or closed) basically as soon as you touch the throttle. But if I reset the throttle plate to basically be at 90* with the throttle body, that would change completely.

If you read the actual specs from Porsche, it says that these switches should be replaced if they are out of spec, but you can usually calibrate them (especially the switch on the right side of the throttle body) I just need to know the starting point for the calibration.

[Funracer]

Originally Posted by Gretz

I’d love to be totally low key about it, but it seems like it can make a big difference.

Not in my experience. Left side switch is easy to adjust after the throttle plate is locked down where you want it. I play with my throttle plate occasionally and reset this one all the time, including again this morning.

Right side switch is easy to get close especially if you have your CIS on the bench which it looks like you do. This is from an 83, same as your 82 :https://youtu.be/0_WjDpe0alk?si=B6ZBgmxtsH346J-x