So here's the deal, i've gone to the inspection station 4 times now, and i still have not passed the emissions test, mainly cuz of my NOx levels.

All i'm running is a PFC, DP, Cat-Back with stock main CAT and turbos are set to non-sequential.

The first time i went, i failed cuz my NOx levels were only a little off: 1082 with 1042 being the std.

The second time i went back, i put my stock DP back in and got: 1110/1042

The third time i changed my spark plugs (BUR7EQ lead and BUR9EQ Trail), put my DP back on and added 1 gallong of denatured alcohol into a 11 gallons of 93 octane gas and i got: 1860/1042

The fourth time i tried i ran out the denatured alcohol and ran only 93 octane gas, and i hooked up the fan switch and had it running during the test, and i got: 1640/1042

I'm running out of ideas, and nothing seems to help. My next guess is to pull off the EGR sensor and inspect/clean it.

My question is, why would the NOx levels suddenly jump so high after changing out the spark plugs? i thinking about putting the spark plugs i had in earlier and going with those instead.

Any suggestions on how to lower NOx levels?

btw, i passed the HC and CO tests with flying colors.

 

Your NOx levels will drop a lot of if you EGR is functioning correctly (assuming that it isn't right now).

I had the same exact problem with another car of mine (not a rotary, but same problem...perfect HC/CO and high on the NOx). I raised the base fuel pressure by 10 psi and it cut the NOx in half. HC/CO went up a little, but since they were so clean to begin with, I had plenty of room there.

High NOx is indicative of high combustion temp. The ref told me that the 3 ways you usually get it down are: more fuel, EGR, or less timing. Since I'm in Cali, I couldn't retard the timing any less than spec, the car had no EGR. That left me with: add more fuel.

Sonny

 

If you are failing at idle, try setting the idle at around 950 for the test. Put it back after the test is over.

 

thanks for the advice guys, most likely i'll inspect the EGR first, then take sonny's suggestion and increase the base fuel pressure by 10 psi.

 

How far is the test center from you? In theory, the hotter the cat the more efficient it works. So you want to drive around and get it nice and HOT then go straight to the test center and have it tested. Another thing is that the ratio of alchohol to gas will probably work better at 1:5. Try those two and see if you can pass.

 

thanks for all the input guys...but here's quick follow-up to what happened.

Yesterday i went in for another test and I FINALLY PASSED!!! I ended up retarding ignition timing down 4 degrees in cells N03 - N10 and P01 - P07 in IGL and IGT MAP in my PFC, and i also increased fuel injection from 100% - 110%.

My final NOx reading was 772/1042

So my conclusion is for anyone with high NOx levels, adding denatured alcohol will only drastically increase NOx levels. So the key to reducing NOx levels is to run richer.

Thanks again for everyone's input.

 

Nice work, man!

Sonny

 

nox increase as the combustion temps do. hc emmisions decrease with heat. it is a sea-saw. the egr will re-route inert exhaust gasses to help with the temps and keep the nox level in check without going the route of putting in more fuel which may cause a hc failure. good job passing