I 've done many searches and I 'm a little confused.

My Integra has a DC JDM 4-1 ITR header, 2.5" T1R resonated Test Pipe, and T1R 2.5" exhaust.

I need to temporarily replace the TP with a used ITR cat so I can pass emissions inspection that was instituted in my county (NY) this year.

Will I have any issues with the USDM ITR cat connecting to the 2.5" catback exhaust? I believe the header side shouldn't be an issue, but what size is the downstream pipe of the ITR cat? I think it's 2.25". How much work is required to get it to fit on my 2.5" exhaust? Can any mechanic do it? The muffler shops here don't want to touch it. As soon as they hear the words aftermarket and catalytic converter, they are quick to tell me to "have a nice day". My mechanic said on the phone he should be able to get it to fit but he would have take the TP down first and then put the CAT up to see what needs to be done..

I am also hoping that the length of the USDM ITR cat won't be an issue. I think the USDM ITR cat is 17" long and my TP is about 16.5". Does anyone else have a JDM ITR header with a 2.5" exhaust and the stock ITR cat?
Any help would be greatly appreciated cause I need to get the car inspected fast and back on the road. I miss driving it.

 

of course its not gonna fit, the collector on the header is 2.5" and the flange on the b pipe is 2.5" as well. You're just going to have to switch it all out with your complete stock exhaust or a full jdm itr exhaust. BTW, thats the SAME exact setup I have on my R and I had to swap everything out as well when I did my smog

 

^^^ Agreed. Check the archives. The cats are two different lengths, and if I recall, USDM is longer. Although the rear exit is a 'standard' 2.5" 3 bolt (Chevy), the body is too long, so you can't just shorten the cat exit pipe by cutting down the end of the USDM cat. Not to mention that the USDM cat has good value for exactly this purpose, so cutting it up is not a good idea. PM if you need me to measure my USDM cat.

Best to either just install the complete stock ITR exhaust, or buy a JDM length Carsound or other cat, either new or used, and install that just for smog. It will be the correct length and flanges - straight bolt on. Then either sell it on HT, or keep it in your kit box for next time.

I did not check in your sig, but if you are in Cali, or another tight jurisdiction, neither of these will fly because they wont like the header. I forget if the total length of the USDM header and USDM cat is the same as the combo of the JDM header and cat. (Which would allow you to run the USDM manifold & cat, and mod or bolt up to the T1R catback.

 

Just get a JDM length cat. You wont lose much power and it will be better for the environment.

 

Thanks, I 'm not in Cali and they don't care about the header. As long as there are no CEL's and the smog particles are within range, my mechanic said it 'll be fine. If not he 'll tune the car so that it can pass, as long as I have a good CAT and the O2 sensor.

The reason I am (still) confused is because when I bought the T1R exhaust from RandMotorsports (was it Dave?) last year, I told him that I had a JDM 4-1 header and also asked him what lenth CAT would I need because I was thinking of getting a Carsound at the time. He said I would need ITR USDM length cat and then talked me into getting the 2.5" T1R Test Pipe which again when we measured it the other day, was 16.5" long.

I had others here tell me through PM's that their USDM ITR CAT fits fine with their JDM header but they said they all have either stock exhaust or USDM aftermarket exhausts (2.25"?). Now these are people that want to mostly sell their ITR cat to me.

Someone else told me they believe the JDM cat is like 13", while the USDM is 17", which would mean that the USDM exhaust is shorter than JDM, or the JDM header's collector is longer than USDM.

Anyway, I 'm also thinking if all I have to worry about is 1/2" (My TP 16.5" vs. USDM ITR cat 17"?), maybe we can shift the exhaust out a little by 1/2" and not have to worry about cutting the ITR cat. I 'm only doing this to pass inspection, and putting the TP back on the same day. I don't have the OEM ITR exhaust or header. This is a GSR and have sold most of my exhaust parts. I would not dream of putting anything else back on the car. The JDM header with the 2.5" resonated TP and T1R Power exhaust has made the car a lot quicker.

 

the usdm cat will not bolt up to a jdm header's collector. the only thing you need to worry about in terms of the length of the cat is whether you use a usdm or jdm length back pipe...that will take out the what length is the cat variable.