DIY_EFI Digest V4 #442

[Gary Derian]

My guess is that headers cool the exhaust causing the catalyst to run cooler
and less efficiently.  Try insulating them, but then you will need
stainless.

Gary Derian <gderian at oh.verio.com>
>
> I have a 1999 Infinity QX4 that I'm trying to get a set of headers
> emission legal (Smog Exempt) in California.  My first test failed
> because of high Nox.  This is determined by a formula they come up with
> that extends the results out to at least 50K at which point my Nox
> exceeded that limit.  (It would pass a standard street smog test no
> problem)  After some investigation I found an Infinity Service Bulletin
> that suggested adding a ground wire from the intake manifold to the
> righthand cylinder head.  Further diagnostics revealved a lazy or slow
> O2 sensor at which time I replaced all four.  After this I had the
> vehicle sniffed to verify any changes.  The Nox was down substantially.
> At this time I set all the SRT's and drove approx. 50 miles to make sure
> no DTC's popped up.  Off to the test lab again and failed again with
> high Nox.  This vehilce has no mods done to it.  Factory ECU. The only
> thing I can think of might cause this high Nox would be the design or
> flow of the tube off the header to the EGR on the engine.  Any ideas????
>
> JT
>