Temp at which aux. air regulator opens?

I've gotten very curious about the workings of the CIS on my '80 SC recently. The car basically runs well, but I can't fight my innate curiosity. Last night, after running the car for quite a while to make sure my spiffy new Bosch universal O2 sensor ($26 at Pep Boys, vs. $82 for the factory part) was performing as expected, I shut off the engine, and removed the line going in to my auxiliary air regulator. I wanted to look into it with a mirror to see if the valve was truly closed when the car was warm. I wanted to know this because my car idles slowly when cold, and then idles a little fast when warm. Sure enough, the valve was completely closed while the car was warm.

So I let things cool down overnight, so I could look to see if it had opened up when cooler. I looked this morning, and the valve was only partly opened. Maybe one fourth of the total valve area was available for air to flow through.

My question is this: How cold does it need to be before that thing should be all the way open? It was 60 degrees in my garage this morning, and I would have thought that it would be completely open. If it doesn't open all the way at those temps, but it should, that could help explain my initial low idle speed.

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Greg Slater
1980 SC
gslater@uswest.net

Which aux air regulator? Aren't there two of them. One of them is just a bi-metal valve, and I think it opens at very cold temps (below freezing). The other one has a bimetal strip and a heating element. I don't know the exact temp for it, but it seams that around 50 or 60 degrees I start getting a higher idle at startup.



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Bill Krause
'79 911SC Euro

It's the one that's easily accessible on the right side of the engine, pretty much straight out from cylinder #5. I wouldn't be too surprised if it was only partly opened at 60 degrees F, but it still seems like the startup process for a completely cold engine would benefit from having it fully open, if only briefly, at that temperature.

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Greg Slater
1980 SC
gslater@uswest.net

I checked mine a while back also and it was just partially opened. try spraying some carb cleaner or WD40 to free up the gate.
81SC

They're supposed to be only partially open at that temp. You have to get down to around 15-20 degrees to see that thing really open up. A while back I posted a thread on how to make it adjustable so you can adjust your fast idle speed. It was posted 08/05/00, and was titled "Adjusting fast idle speed on CIS".

Leon
78SC

[This message has been edited by leon (edited 09-08-2000).]