Exhaust high flow cat for hp gain

[stom_m3]

It look like from Eugene's post that the cats are the cork in the system. Has anyone ever tried running high flow cats? I would like to stay smog legal for my OBD2 stuff and I don't want to run simulators. Thoughts, ideas?

I should also say that Eugene also had Hiop headers but the comparison showed the difference with and without the trackpipe only.

I wonder why none of the exhaust manufacturers have done this yet?

[eclou]

Steven,

Mufflers are just cans with some baffling in them. Although you can get really fancy using acoustical engineering to change the sound quality without any baffling material (ala Flowmaster), most folks can just guestimate what they want to do, or incorporate existing designs. There is no EPA approval required.

The level of sophistication increases greatly when it comes to developing a cat converter. It actually has to work to emissions specs and be licensed and approved. I don't think that Matt/Rob L/ Ben L/Hugh Bros want to deal with that. That's the big boy's territory. Easier to just find some 3rd party hi-flows and weld some tubes to the,.

Eugene

[stom_m3]

Eugene good point about certification of the cats.

I'm hoping someone on this board has explored the high flow scenario though. Taking a quick look on the web, it seems as though high flow cats run ~$100-$110. I guess the hardest job would be welding the pipes to fit the stock application. I wonder if it would still pass CE lights or not.

[madsedan]

I had looked into this and had many conversations with Random Tech in Atlanta, they offered to give me a 3" metal substrate cat for a little over $100, cost, if I would dyno before/after and give them copies to use for research in offereing a "kit" to install bigger hi-flow cats on a 95 M3. I don't have any money to spend on stuff like this right now so its on the back burner. I did acquire a slightly hacked up set of mid-pipes with dual cats from a 96 M3 to try and do on my car. Because one of the pipes are cut short about 5" and there is a "5th" hole from a/f meter sensor I cannot just bolt them on the car and will try to see how/where I could cut my cat pipes and splice in the dual cats from the 96. I will post results when I get a chance to finish the project.
Most of us have known for a while that the single cat on the 95 M3 was a big bottle neck, the strong results of AA's pipes just back that up.
If anyone wants to trade a used set of AA track pipes for a set of 95 and a set of 96 M3 midpipes with cats let me know