OK consider this as my contribution to the NSX community. After 6 years of storage, I took my 91 NSX out of retirement. The challenge was passing SMOG.
The first time it failed, I ran 100 octane gas and ran the car nice and hot and got this:
The second time it failed, I used a bottle of "Guaranteed to Pass" following the instructions, and I cleaned the IAT sensor and 100 octane gas. We had to abort because the test didn't look good.
The third try passed. What I did was replacing both O2 sensors, ran it nice and hot with 100 octane gas. And I was amazed how much difference it made on the NOx number that failed the first couple of times. It went from 656 to 207 and passed with a huge margin (549 max).
The indicator was the %O2 was 0.1 when it should be 0.0. I never had a check engine light. So they are still somewhat working. But they are the originals when the car was built with 56k mile on them.
So I don't think we should ever reach close to the 549 maximum allowable NOx number like a lot of people are experiencing. Now we can all take a deep breath and exhale.
See you guys more often in local meets. Can't wait to put my GruppeM back on.
I am considering using stock 16" rear wheel and oem tires to effectively decrease my gear ratio from my current 265/35/18's, but calculated the overall diameter would decrease by 4% only, which would increase my 15mph 2nd gear engine speed from 1516 to 1576, which doesn't seem significant enough to increase EGR/catalyst. So far I'm just going to go at it again and try to get her cats hotter than last time. I had my EGR valve cleaned 2 years ago, but I noticed that the max numbers have dropped again vs from two years ago.