emissions
emissions
10-19-2006, 10:47 PM
#2
The Lady's Man
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Lots of threads on this. Start with o2 sensor, plugs (original copper ones). Then consider a cat and plug wires. Complete tuneup with rotors and caps if possible. I just did all of this.
10-19-2006, 10:57 PM
#4
The Lady's Man
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NOX was my issue too and these things fixed it right up. Sounds like a bigger problem than I can try to help with. Hopefully Dr. Bob will see this post. MAF?
10-19-2006, 11:38 PM
#6
Burning Brakes
High NOx comes from lean combustion, or advanced timing, or anything that results in high peak combustion temperatures. Given the new parts anticipated from your response could it be that you have low fuel pressure resulting in a slightly lean mixture?
10-20-2006, 12:57 AM
#7
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nox
being in CA, and the rolling dyno smog testing, I've had some experience with high nox/hydrocarbons and 928's. My GTS was in the 1400's for nox at both 15/25 mph and tried 5-6 tests, everything from water injection to cooler ? spark plugs, race fuel, etc. The smog tech was real nice and suggested after the 6th retest to try new cats b/c my OEM ones from 1993 were probably burnt from running too rich, at some point since 1993. Took out oem exhaust past exhaust manifolds, bought Ott x-pipe, 2 high flow random tech cats, and passed - have to get them really hot though - nox went from 1400 to 200. I just purchased an 88 S4 and failed nox at 1900-2000, on a pretest, high hydrocarbons and co2 also. This time I went straight for new Random Technology cats, universal 3" in and 3" out, welded on and passed at 12 on nox and hydrocarbons also. For what its worth.
I'm sure you've seen Louie's webpage:
http://www.performance928.com/cgi-bi...ss_parent=1128
I'm sure you've seen Louie's webpage:
http://www.performance928.com/cgi-bi...ss_parent=1128
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10-20-2006, 10:55 AM
#8
Rest in Peace
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We do a lot of EM repairs at our shop, on NOX the first things we check are the timing, the EGR system, if that checks out ok, we replace the three way convertors, I can not remember on not passing with a good convertor and the timing, and EGR system working.
The above post is correct in that high cumbustion chamber temps are what cause NOX.
The above post is correct in that high cumbustion chamber temps are what cause NOX.
Originally Posted by akitamike
being in CA, and the rolling dyno smog testing, I've had some experience with high nox/hydrocarbons and 928's. My GTS was in the 1400's for nox at both 15/25 mph and tried 5-6 tests, everything from water injection to cooler ? spark plugs, race fuel, etc. The smog tech was real nice and suggested after the 6th retest to try new cats b/c my OEM ones from 1993 were probably burnt from running too rich, at some point since 1993. Took out oem exhaust past exhaust manifolds, bought Ott x-pipe, 2 high flow random tech cats, and passed - have to get them really hot though - nox went from 1400 to 200. I just purchased an 88 S4 and failed nox at 1900-2000, on a pretest, high hydrocarbons and co2 also. This time I went straight for new Random Technology cats, universal 3" in and 3" out, welded on and passed at 12 on nox and hydrocarbons also. For what its worth.
I'm sure you've seen Louie's webpage:
http://www.performance928.com/cgi-bi...ss_parent=1128
I'm sure you've seen Louie's webpage:
http://www.performance928.com/cgi-bi...ss_parent=1128
10-20-2006, 11:57 AM
#9
Craic Head
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1429!
I failed with over 3600 two weeks ago.
Electrical tune-up (plugs, wires, caps, rotors, air filter, air pump filter) and I came down to 2400. This week I found a few vacuum leaks that were causing hesitation and (I'm hoping) bad readings going into the brain and screwing up the mixture.
I'm testing again this weekend just because it's free and I want to figure out what each adjustment does. I'll post after this and the next trick, if needed, is probably 02 sensor (my temp 2 sensor read oc on the multi-meter).
Good luck and post the solution for everyone.
I failed with over 3600 two weeks ago.
Electrical tune-up (plugs, wires, caps, rotors, air filter, air pump filter) and I came down to 2400. This week I found a few vacuum leaks that were causing hesitation and (I'm hoping) bad readings going into the brain and screwing up the mixture.
I'm testing again this weekend just because it's free and I want to figure out what each adjustment does. I'll post after this and the next trick, if needed, is probably 02 sensor (my temp 2 sensor read oc on the multi-meter).
Good luck and post the solution for everyone.
