i just bought the itr full cat back system. i know it wont fit on the headers so im picking up the jdm dc headers. just want to get this straight. the itr cat back is 2.25" and the headers is also 2.2"am i correct?? TIA

 

The DC JDM 4-1 has a 2.5" collector. The ITR cat-back is 2.25" OD, but actually "bottlenecks" to < 2.0" where it bolts to the cat. You will need a custom cat. to bolt the DC JDM 4-1 to the ITR, or any other cat-back.

 

so im guessing i need to customize the flanges or something. or customize the whole cat?

 

Well there really isn't any sense in upgrading to a JDM 4-1 if you are going to keep the stock cat., so I would upgrade the entire unit to a custom 2.5" one.

 

well i have a gsr and i want to keep most mods OEM. or of some sort. any decent headers out that that will bolt on to the cat??

 

My point was that the stock cat. is a severe bottle-neck. It doesn't make sense to invest in a good header and bolt it to the stock cat.

 

icic... i get your point.... hmm... so i might as well upgrade the whole piping and cat to a 2.5 instead of having the itr 2.25?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by lDarkCloudl &raquo;</TD></TR><TR><TD CLASS="quote">icic... i get your point.... hmm... so i might as well upgrade the whole piping and cat to a 2.5 instead of having the itr 2.25?</TD></TR></TABLE>

That would be my choice.

 

damn. well i don't have the money for that. i might as well use the itr. any headers that will be good for the itr??

 

Well there is no reason why you can't install the header & cat. now and then upgrade the exhaust at a later time. If funds are limited, I'd just concentrate on the header and cat. for now. Your original plan for the DC JDM 4-1 will be just fine.

 

well. thing is i odn't have the headers yet. originally i thought the jdm dc 41 is 2.25. i have the itr cat piping and exhaust. now it's what header to get to bolt on to it. thnx for your help man... ive wouldve been pissed later if i had to find out while im working on myh car

 

So you have the stock ITR cat. as well? If you really don't plan on replacing that, you can either stick with a USDM-sized header, or have a larger flange welded to the stock cat. I really do have to stress that replacing the cat. with a high-flow version is a much better choice though.

 

Here is the problem: fitment
The ITR exhaust is made for a Header/Cat combo which is about 6-8 inches further from the engine than the stock GSR. If you use the stock GSR Header/Cat, the ITR will mount to all your hangers perfectly, but will leave a 6-8 inch gap between the stock cat and the ITR exhaust. I had to get my ITR exhaust lengthened at a muffler shop to fit up. The JDM ITR headers have a longer pipe and if you use that header, with some sort of custom cat, you can fit all the pieces together with no welding.
If you don't want to spend much more money, your only options are to get the ITR exhaust lengthened, get a custom pipe made to fit between the stock cat and the ITR exhaust, or just get a test pipe to directly connect the Headers with the ITR exhaust, leaving the cat out completely.

 

one word..
donuts..

tee hee hee

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LuckyNuts &raquo;</TD></TR><TR><TD CLASS="quote">Here is the problem: fitment
The ITR exhaust is made for a Header/Cat combo which is about 6-8 inches further from the engine than the stock GSR. If you use the stock GSR Header/Cat, the ITR will mount to all your hangers perfectly, but will leave a 6-8 inch gap between the stock cat and the ITR exhaust. I had to get my ITR exhaust lengthened at a muffler shop to fit up. The JDM ITR headers have a longer pipe and if you use that header, with some sort of custom cat, you can fit all the pieces together with no welding.
If you don't want to spend much more money, your only options are to get the ITR exhaust lengthened, get a custom pipe made to fit between the stock cat and the ITR exhaust, or just get a test pipe to directly connect the Headers with the ITR exhaust, leaving the cat out completely.</TD></TR></TABLE>

He already has the ITR cat.-back (and from what I can tell from his posts, the cat. too). He's planning on replacing the header anyway, so if he buys an ITR/LS/00+ GS-R header, it will bolt on just fine. If he decides to go the JDM route, he's going to have to modify the cat. anyay.

 

yea i have the full cat back. say i go with the jdm dc 41 still and customize the flanges. will it fit onto my gsr just fine and will the 2.5" header be restricted from the 2.25" cat back??

 

If the OEM JDM collector is 2.5in and the OEM JDM b-pipe is 2.25 inch, then it shouldn't be restricted, since that's what Honda decided would work! Exhaust velocity is important, not pipe size.
So....could you use all JDM OEM parts? (header, cat, exhaust) It seems they would all fit together since they all came from the same car.

 

sorry, not b-pipe. I meant that the collector is 2.5" and the cat-back portion is 2.25"

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LuckyNuts &raquo;</TD></TR><TR><TD CLASS="quote">If the OEM JDM collector is 2.5in and the OEM JDM b-pipe is 2.25 inch, then it shouldn't be restricted, since that's what Honda decided would work! Exhaust velocity is important, not pipe size.
So....could you use all JDM OEM parts? (header, cat, exhaust) It seems they would all fit together since they all came from the same car.</TD></TR></TABLE>

my cat back is USDM. so im figuring that if i get jdm headers i gotta customize something. thanks for all your help. so i might get the USDM ITR headers since i can get that close to free.