High-Flow Cat?

[steve8091]

I am currently replacing my exhaust (catback and header) and am wondering if I stand to gain anything from replacing the stock cat with a "high flow" cat while I am under there. Does anyone have experience with these? Can someone explain, in technical terms, what would create the higher flowrate?

Thanks.

[civicuser]

just get a test pipe. its just a strait pipe w/ a bung for the o2 sensor. it just bolts on to the rest of the exaust.

[steve8091]

I am looking for something (at least moderately) street legal. I am not interested in dumping a great deal of harmful compounds into the atmosphere, either.

[got v-tec?]

Originally Posted by steve8091

I am currently replacing my exhaust (catback and header) and am wondering if I stand to gain anything from replacing the stock cat with a "high flow" cat while I am under there. Does anyone have experience with these? Can someone explain, in technical terms, what would create the higher flowrate?

Thanks.

stock cats r alot more restrictive. the only differance is the screen inside the cat. lets say both screens have 150 holes the stock one can fit 1 toothpick in each hole while the high flow can fit 3 in each hole.

[superbluecivicsi]

Originally Posted by steve8091

I am looking for something (at least moderately) street legal. I am not interested in dumping a great deal of harmful compounds into the atmosphere, either.

The hi flo cat will pass smog if smogged as soon as it is bolted on. After that it is no good. just give it a few days of exhaust fumes. after that then youll be dumping good amounts of exhaust fumes into the atmosphere. Its good if its a mock up to look like a stock cat, in case a cop looks under the car. I have a Jackson Racing hi flo cat for sale off my 99 si if your interested. It wont pass smog though, I replaced it with a test pipe, something i should of done in the first place.

[GScivic7]

get a carsound/magnaflow cat. You can generally pick one up for around $100 and you will pass smog.

[steve8091]

Originally Posted by got v-tec?

stock cats r alot more restrictive. the only differance is the screen inside the cat. lets say both screens have 150 holes the stock one can fit 1 toothpick in each hole while the high flow can fit 3 in each hole.

It sounds like the construction of these are so simple that you really just need to select a chemical surface area - higher for cleaner emissions, lower for better flow. I had imagined that a more complex design might exist that did not rely on the same catalytic conversion process.