I just failed my MA emissions test because my NOx was too high. My HC's were .32 w/ a limit of 1.2, CO was .41 w/ a limit of 22.0, and NOx was 4.36 w/ a limit of 2.50. All readings are in gpm.

They did 7 runs with it for some reason, I think my rectangular LT1 tailpipes were giving them a hard time. I'm thinking the cylinder temp just got too hot and when they measured the last run, NOx was high. Should I try running 87 or 89 octane instead of 93, and bumping the timing down a bit, its at the factory 6* BTDC. With .32 gpm of HC's and .41 gpm of CO, I'm not too concerned with richening it up a little bit. I have a Catco 3" HF cat on it with about 15K miles, and all emissions equip is intact. Any ideas?

------------------
-Jason M. 1991 Camaro Z28

 

I should add, MA state inspection is now IM240 dyno. TIA

------------------
-Jason M. 1991 Camaro Z28

 

EGR controls NOx levels, maybe you should try replacing that? They're not that expensive, I don't think...

Running 93 gas I think lowers your emissions, when compared to 87 or 89.

------------------
89 iroc-z 305 tbi
k&n filtercharger, open element air filter. nuffin' else

 

Higher octane gas will increase emissions. The fact that higher octane gas burns slower means that your mixture will not burn complete. Lower octane gas will always provide a cleaner emission output. Nitrogen Oxides are produced by the cumbustion temperatures being too high. Yes the EGR redueces nox, because the returning exhuaust gas takes place of some of the air fuel mixture. So that would be one thing to do. Also, if you run some techtron, your combustion chambers will clean up, and reduce your compression ratio. Especially if you have alot of miles.

------------------
'82 Firebird, dead stock, 9 bolt disc rear, over 200,000 miles and still going strong, more to come...
http://www.spinfrenzy.com/stingerssx...easures.html#4

 

Thanks guys. Anyone else?

------------------
-Jason M. 1991 Camaro Z28