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Old 02-09-2005, 01:53 PM
Duke2.6 Duke2.6 is offline
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Join Date: Mar 2003
Location: Southern California
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Your test sounds like the California ASM (acceleration simulation mode) test. The car is tested at 15 and 25 MPH using a load that simulates acceleration, which is more than what is required to maintain steady speed.

If the engine detonates during the test, NOx will skyrocket, however, if the temperatures were mild, which they usually are this time of year in Houston, I doubt that the engine would detonate as the load is not that great relative to engine output potential. If you don't notice detonation in normal driving, then it will likely not detonate during the test.

My last several tests have been with regular unleaded with no detonation related problems. My model does not have a detonation sensor, but I believe your model does. If detonation is detected the system will retard timing, and retarded timing reduces NOx since it reduces peak flame front temperature.
However, just to eliminate any potential unknowns, it wouldn't be a bad idea to fill it up with premium for the next test.

You should take your test report back to the shop and point out the O2 reading (it should be in the range of zero to a few tenths percent.)
As a minimum they should retest the car at no charge to you, and if the O2 readings are still preposterous, they have an equipment problem. If they give you the runaround, take the issue up with your state authorities who oversee emission testing. Such a huge and obvious error in O2 reading casts a pale on the validity of the entire test!

Duke

Last edited by Duke2.6; 02-09-2005 at 02:00 PM.
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