High Flow Cats
Safety Car
Joined: Mar 2017
Posts: 3,759
Likes: 935
From: Orlando Florida
Astounding lack of information on the net about actual catalytic converter flow. Intuitively, the greater the flow, the lower the catalytic action taking place, and the greater the odds of a check engine light. Included with that will be weight. Less cells equaling less material and therefore less weight. I see Magnflow has CA legal universals they list as 5 lbs -- so two would be 10 lbs less the equivalent straight pipe or OEM cat they replace - could be a net loss in weight. Unless you want flanges or even better electric cutouts. I bet there's a youtube of how that would sound...
Last edited by redzg; Apr 19, 2020 at 09:13 AM.
Burning Brakes
Joined: May 2014
Posts: 760
Likes: 213
From: Detroit
Astounding lack of information on the net about actual catalytic converter flow. Intuitively, the greater the flow, the lower the catalytic action taking place, and the greater the odds of a check engine light. Included with that will be weight. Less cells equaling less material and therefore less weight. I see Magnflow has CA legal universals they list as 5 lbs -- so two would be 10 lbs less the equivalent straight pipe or OEM cat they replace - could be a net loss in weight. Unless you want flanges or even better electric cutouts. I bet there's a youtube of how that would sound...
Melting Slicks
Joined: Feb 2007
Posts: 3,297
Likes: 398
From: Raleigh Suburbs
Last I knew, it's NOT legal in CA to replace with high flow convertors, I may be mistaken, but supposed to replace *only* if defective/damaged, with stock replacements.
Hopefully this has changed, as modern high flow convertors are actually *better* at clean emissions, and flow more cfm to boot.
It should deepen and louden the sound some, not as significant, as running no convertors.
Hopefully this has changed, as modern high flow convertors are actually *better* at clean emissions, and flow more cfm to boot.
It should deepen and louden the sound some, not as significant, as running no convertors.
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Melting Slicks
Joined: Nov 2017
Posts: 2,306
Likes: 747
The only cats that are 100% legal in CA are OEM cats or CARB approved aftermarket cats. If you're looking into ANY aftermarket cats, make sure they have a CARB approval for your specific model and model year.
For anything other than those two choices: you can get away with anything until you get caught
For anything other than those two choices: you can get away with anything until you get caught
Advanced
Joined: Mar 2020
Posts: 72
Likes: 57
Melting Slicks
Joined: Feb 2007
Posts: 3,297
Likes: 398
From: Raleigh Suburbs
Seriously though the Magnaflow CARB certified convertors are interesting, I'm sure it's one of the latest best technologies on how it works, giving minimal loss of performance with those convertors, but it remains to be seen! 
Melting Slicks
Joined: Feb 2001
Posts: 2,797
Likes: 356
From: Northville, MI
High flow cats vs factory C5 cats: 1 hp difference at most. If you had cats from a 70's era car they were very restrictive, with the C5 cats to today there is virtually Zero difference vs aftermarket cats other than weight. As I recall past discussion on the cats, the OEM were warranted to 60,000 miles by the EPA laws with free replacement. The PCM has non-programmable firmware of exhaust flow/cats/content/etc required by the EPA for cars in the US. Professional tuners and a few individuals can reprogram around it but I am not sure if they can eliminate the code--they can make it non-reporting.
Burning Brakes
Joined: May 2003
Posts: 1,232
Likes: 427
From: LI NY
