if you've passed the sniff test with one or more cats gutted/removed, or high-flow cats installed, what combination resulted in a pass?

or, if I was running my car strictly off-road, but wanted to be eco-conscious, which cat(s) will give me the best bang for my tree-hugging ways, while still preserving the max possible power?

e.g. if the uppipe was gutted, and the third cat was 'deleted', would a high-flow cat in the downpipe be enough to tame the WRX to meet CARB levels for a smog test? (I would think yes, assuming a quality high-flow cat that hasn't been treated to leaded 110, etc.)

looking for the best balance between performance (removing the most restriction) without compromising emissions beyond what CARB would like. hypothetically, the resulting configuration should be able to pass a sniffer test, assuming it didn't fail visual.

 

The Version one helix catted downpipe passed for me. That was the only cat I had.

 

I'm not an expert on the subject, but I have heard it told to me by those that are that the downpipe is the single most important cat.

One cat should pass you though.

Good Luck.

 

OK legally you have to have stock cats on

all 3

realistily if you can get by the visual inspection the stock dp will get you by
depending on what mods you have YMMV

 

So, stock dp should be sufficient to meet emissions standards...

And a Helix catted dp has been known to pass emissions.

So, are there other aftermarket dp's with hi-flow cats that perform similarly, and/or a mileage at which they stop meeting the numbers, when the sole cat.

And, with the proper tune, would a larger turbo still meet emissions factors? Intuition tells me that the larger turbo should inherently produce fewer particulates overall at lower rpm's, since the cfm from the compressor will be lower at 2500rpm. A lack of tune might force the computer to spend more time making corrections, impacting emissions, and the wrong AFR targets would do the same.

Assuming the cam grind isn't so aggressive a bystander would notice, is there a case where a single hi-flow cat, or stock cat, in the dp wouldn't be sufficient to control emissions at 2500rpm or less?

I think there's two applications for this. One is a tune that is emissions-conscious in cruising conditions.

 

Some guys on nastysock have claimed if you can get the car hot enough then it can pass the sniffer without cats.

 

I think that only implies to the up-pipe cat.

 

.....

 

All this smog talk makes me sad. I got my first smog due next month boo.

 

jerk lol
i had to do mine also

my baby isnt new anymore

 

My buddy had a Cobb catted turboback.... shot the cat through the tailpipe within a week.

 

Not yet. But yeah its not too bad. I think overall if you put the stock downpipe back on. Your okay no matter how crazy your setup is I think. As long as they're cool with the visual thats all.

 

5 years it went by so fast =(

 

You mean 6? I did mine last spring, will have to again next spring. Honestly though, I only have a turboback+up pipe so its not a big deal, I don't even swap out the UP. And taking the turboback off gives me an excuse to change to a different set up each time.

 

oh snaps you're right. I'm just to lazy swap out my DP. I hate wrenching anything on that car lol.