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I have passed 3 times without a cat in the Denver metro. However, the last 2 times I used an extremely modified emissions tune and was running a mix of gas and e85. Since my cat is gutted I pass visual too. It took 3 tries to get the tune, but in the end it passed with everything well under the limits and it didn't hurt power as much as I thought it would.
It can be done without a cat, but I doubt it can with a stock or common tune.
Do you have your results by chance? I'm curious what the limits are in Denver and how they compare to CA.
Denver area is the hardest emissions to pass in the US that I know of.
I've had a lot more difficulty passing here than anywhere else in the US, in-fact, the world...
Actual emissions - not the 'visual' nonsense.
They put the car on a dyno, and run about a 5 min drive-cycle getting up to 50-60mph. The simple difference between a "tech" who is heavy/quick on the throttle to one who is soft can easily make or break passing (they won't let you drive you own car).
Combine that with the car being down 20-25% power due to altitude, and it takes quite a bit of throttle % to actually complete the drive-cycle, which will often kick the car out of closed-loop.
The CA guys seem to have this strange pride about how difficult their emissions are, but from what I've seen the only real difficult part is the visual.
+1 on CA really not being that bad sniffer-wise. Visual is the killer, compounded by the CARB E.O. requirement for modifications.
Having stuff WAY pre-OBD-II really helps us.
The guy doesn't even look for the DME or anything, just checks the vacuum diagram and pokes around under the hood tracing hoses.
The CA guys seem to have this strange pride about how difficult their emissions are, but from what I've seen the only real difficult part is the visual.
Trust me, that sense you're picking up is not pride.
My '86 failed visual once with a totally stock setup. Whatever. That's why they have more than one smog place.
I think the 700-ish ppm NOx number at 25 mph is hard to get to. It used to be 1800 - 2000 ppm. I don't know if the Colorado drive cycle described above is more forgiving or more ways to fail.
If there is a recipe that makes passing CA easy, I would love to hear it. Otherwise I'm sure I'm looking at big bux this November.
No, it's not pride. Just wanna drive my car, and I hope others can too.
Not all aftermarket cats are bad, with Tom and Josh's help I had to purposely lean my mixture to get higher readings on my Fabspeed cat. The operator said no way the state would believe those numbers, they are way too good. So we adjusted to make it just pass.
Do you have your results by chance? I'm curious what the limits are in Denver and how they compare to CA.
Here are the emissions results from my 951 in 2012 with not cat but an extreme emissions tune. I don't know the conversion of GPM to PPM, but as Joshua said the way they perform the test is very different here, too.
from the results i saw, it all points to the cat, you can even plug in the numbers on a lambda calculator to see how rich/lean it is running. acetone, sea foam, i am anti all for the most part.. they have pros and cons. Unless you have an obvious exhaust leak before the cat, extremely high miles and carbon build up in the CC's (combustion chambers) or shaved your cylinder head to the max , you just need a cat (based on your emmisions report)
And now the exciting conclusion, it passed!!! 951max chips, new O2 sensor, and a better cat did the trick, all numbers well below limits. Looked up the magnaflow carb model for the 951, and then got the same one in 3". Tech liked that well enough, he was a friendly guy and likes 944s I suppose. Now to pay the over a grand in California sales tax (I wonder if all my pelican receipts count towards that???)
Thanks for all the input and advice, I'll post the numbers when I'm back in the car tomorrow-
When I last bought a catalytic converter the DEC seemed the only solution for our cars in CA. Magnaflow lists Part #332006. That appears to be a universal, where the DEC is direct fit. NCLA951's must be a variant of this. Do others have experience with this cat? It would be nice to know if there is a reliable alternative to the DEC.
01-06-2016, 07:30 PM
