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Quick CIS adjustment altitude

Guys-
OK it's been a while since I tuned my fuel injection (Leask WUR) so I'm rusty.
So quick dumb question - if your car is tuned for higher altitude (5000+ ft) and you road trip sea level for a few days - and want the car to run right - is there a quick change you can do to correct AFRs? 3mm screw on the fuel head maybe?? My memory from the last time I drive a CIS car to sea level was it didn't run quite right down there...but maybe this car will be different...?

I would not want to reset my Leask WUR setting tho.

Thanks-
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'91 911 Turbo
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Last edited by turbo ride; 08-16-2017 at 09:54 AM..
Old 08-16-2017, 09:27 AM
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Never mind I miss read the last sentence.
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Last edited by Rich76_911s; 08-16-2017 at 09:47 AM..
Old 08-16-2017, 09:44 AM
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If you don't have a wide band AFR gauge you'll be shooting in the dark and if the stock air cleaner housing in in there you'll probably be best off leaving it the way it is unless you know what you're doing.
Old 08-16-2017, 10:09 AM
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I do have a wide band hooked up. But yeah I'm not going to deal with changing the settings on the WUR. I guess I was trying to remember if a quick adjustment of the 3MM on the fuel head would affect the whole range of running - or just idle....
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'91 911 Turbo
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Old 08-16-2017, 02:03 PM
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The 3mm allen head adjustment affects idle the most and also affects the rest of the range less and less as the rpms go up.
The gradual enrichment adjustment curve as rpms increase is a slope not a straight line because it's a mechanical linkage and the moving flowing air mass can change shape, compress a little under boost pressure, or expand a little under vacuum as needed to make it's way through the convoluted CIS intake air flow path.
I'm not smart enough to describe it better in an understandable way to someone that has no idea how it all works or may have never seen the air flow meter linkage mounted inside the cast aluminum top half of the air flow meter housing.

You'll never know unless you take the thing off and look in there and watch what happens as you move the air sensor plate up and down.
Also the 930 sensor plate moves in the opposite direction as an older SC sensor plate so the mechanical linkage is different.
Old 08-16-2017, 02:20 PM
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Your signature line lists a '91 C2 Turbo. The '91 has WUR -160 which includes altitude compensation. If you do not have a -160 then just lean out the mixture on the fuel distributor to the point where the idle ceases to oscillate. It's OK to do this by ear as you will need to re-adjust once you get back up the mountain.
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Old 08-16-2017, 04:39 PM
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Ok I had actually forgotten that it had altitude compensation. The last CIS car I had (1984 Audi ur-quattro) did not. I'll be curious to compare my AFRs at sea level. Thanks for the input guys.
Old 08-18-2017, 09:07 PM
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A 3000ft alt change makes mine change by around 0.5AFR
Alan
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Old 08-19-2017, 01:32 PM
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