Inlinefour.com sells a 2.5" collector flange to be used with the JDM headers(and retain stock cat) for $70. Would continued use of the stock cat(w/flange) be a major restriction with a JDM header? Or is replacing the stock unit far and above a better plan?

Thanks,
Chris

 

Look at the flow test results (compare ITR Stock to a CarSound cat)..

1) Catco (metal core) 2.25" 223.8 cfm
2) Catco (metal core) 2.5" 271.9 cfm
3) Catco (std. core) 2.25" 338.2 cfm
4) Catco (std. core) 2.5" 388.0 cfm
5) Random Tech 2.25" 297.1 cfm
6) Car Sound 2.25" 342.7 cfm
7) Test Pipe 2.25" 407.1 cfm
8) Stock NSX 242.1 cfm
9) Stock Type R 223.6 cfm
10) Stock Integra 218.3 cfm

This test I believe was conducted by CompTech. I don't know which series of Carsound cat the above 2-1/4" was, 54006 or 94006. It was too bad that they didn't test the 2-1/2" cats from CarSound. I recently received an email from Carsound which gave their flow rate for the 94006 at 14" of vacuum. The above tests by Comptech were reported to be conducted at 28". Carsound estimated the 94006 would flow around 400 CFM at 28".

You make the choice.

 

jdmhondaparts.com has the 2.5" flared pipe and the flange for $40 ($15 for the flange and $25 for the flared piece of pipe). $70 is rediculous for that stuff. A local muffler shop could probably do the same thing even cheaper.
Just my $.02.

 

Get a flange that keeps it 2 1/2 and get a carsound cat. You might want to buy that flange from the inline. I had a hard time finding someone who had or could make a flange that big. One shop even tried a mustang 5.0 and camaro z-28 flanges and they weren't big enough.

 

If you want to use the stock cat just keep the stock manifold or something like a DC. Why buy something to get a large collector and then neck it down? The cats are modified to bolt directly to the JDM header and B pipe. Think about an adapter for the B pipe not the stock cat.