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JBurer JBurer is offline
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Join Date: Nov 2008
Location: Austin, TX
Posts: 205
That's a great tip on the ignition timing sub-idle - thanks!

They test here for NOx levels, but only OBDII and later cars (1996 onwards). I'm fortunate in that I only have to pass the 2-step test, which evidently doesn't test NOx and doesn't require a load test. If I had a newer car, this would be much more difficult.

Will let you know how I make out... planning to try this again tomorrow.

Originally Posted by beepbeep View Post
Usually, you set up idle ignition timing quite low at idle RPM target (like 12 degrees @ 900 RPM) and raise it just below (like 18 degrees @ 800 RPM). As ignition is advanced, engine will pick up revs. So ignition advance at 800 RPM is used as guard against idle stalling.

Leaning out the mixture usually sends NOx values up but HC values down. If US emission laws don't care about lambda and NOx, you can lean out the idle until HC goes down. Also, you can raise idle RPM to 1000 revs or so (1250 seems to be max) in order to heat up the cat more.

Those tricks won't fly in Europe (they check NOx, lambda, HC and CO here) but might work in your case.
Old 10-10-2009, 06:27 PM
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