Subject: Re: High HC emissions -- redux by Scott7 on 2013/6/21 19:05:12
Quote:
bogus wrote: Those are all loosely based on CA SMOG tests.
There is a dyno involved, and a low speed test and a marginally higher speed test. 15 and 25mph, IIRC...
Now, there is one thing you are not talking about. The cats. Or, more than likely, the main cat.
Is NJ doing a visual or just a sniff test?
If it's just the sniff, I would replace the front y-pipe with one that has no cats, then, replace the single main cat with a new main cat.
When you get that close with the numbers, the cat is more than likely dead or dying.
Our Cherokee did that last year. It was in good tune, for sure, but it also wasn't passing. Threw on a new magnaflow cat and the numbers crashed down to earth. I mean CRASHED. I don't remember the specifics, but HC's went from failing at 500 or 600 to passing with under 50.
If you have the $$, try to retrofit an LT1 style system. That would allow for dual cats and dual exhaust and will add about 30hp to the thing.
If you buy a cat, get one that meets CA OBDII standards. They are more expensive, but they also last much much longer.
I agree with Andy on this, take a close look at your cat. I've had the pleasure of replacing that single cat multiple times to pass Colorado's sniffing tests. Recently I converted the system to two individual small cats, no y-pipes, and have had no problems since. I'm on my 4th year with this set-up, yesterday I went through emissions testing and passed with flying colors, examples: HC GPM reading O.6832 (Limit 2.0000), CO GMP reading 4.9566 (Limit 20.0000), NOx GPM reading 1.0589 (Limit 4.0000).
