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Disconnecting or blocking the air pump hose is in the manual for SETTING your CO level when TUNING your engine or as in my case tuning the A/F ratio on a dyno. Which is tested pre-cat location.

On the other hand the air pump should be connected and should help emissions test as they are tested at the tailpipe and the extra O2 helps the cat burn unburnt HC's.

Schocki

Should be good for the idle and rolling test. The result of high NOX is due to the fact that the air is blown into the exahust before the monolith. This leans out the exhaust gases and causes high NOX.

Here is Rogers post about his problem until he disconnected the vacuum line...
https://rennlist.com/forums/showthre...iled+emissions

Bill51sdr

Um, respectfully, NOPE! NOX is a product of combustion, specifically heat in the combustion chamber. Adding air downstream of the combustion chamber has absolutely no effect on NOX levels, unless it is introduced at the midbed of the CAT, which is where NOX emissions are reduced. The 928 has a high compression engine which exacerbates the NOX problem... more compression, more heat, and especially if your combustion chambers are carboned up, thus actually increasing the effective compression in the cylinder. The air injection system when operating properly does not cause high NOX emissions.

Schocki

OK sorry about the misinformation, the only thing that remains unsolved are Roger's really low NOX numbers after he diconnected the air pump.
Explanation please! https://rennlist.com/forums/attachme...chmentid=58340

I also just checked the cat on my GTS, the air is injected in the last 3rd of the cat. The air is injected into the cat not before. Does this have any effects?

Schocki

Bill,
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