I am trying to figure out what to do for my new catalytic converter setup when I replace me old one and could use some assistance. I know the JDM ITR header has a 2.5in collector and that the JDM exhaust goes down to a 2.25in from I believe the catalytic converter.
But I also noticed a 2.5in 3 bolt flange will bolt up to the stock ITR exhaust's flange that is 2.25in.
My question, is there anything wrong just making the setup 2.5in all around without running a reducer pipe of 2.5in to 2.25in at the catalytic converter? I know I won't get the best power with this setup, but I also value the quiet exhaust and the stock looking exhaust tip.
This was what I was looking to do in the pictures. My current exhaust had piping reduced from 2.5 to 2.25 in, but I used a 2.5in flange which welded up without an issue, but I did not realize this at the time. But I feel if I do get rid of my stock ITR catback, having the 2.5in already will make it better for potential future upgrades.
Pictures of what I was mocking up along with my old cat. Test pipes are good for exhaust piping
Exhaust sizing questions with JDM ITR header and USDM exhaust
Exhaust sizing questions with JDM ITR header and USDM exhaust
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-Andrew Wong
- jayhaire
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Re: Exhaust sizing questions with JDM ITR header and USDM exhaust
It's been over a month without a reply.
I want to help. I've had a few setups over the years:
- JDM ITR 4-1 header, carsound cat, JDM mugen catback
- JDM ITR 4-1 header, JDM ITR cat, JDM ITR catback...no reducer at the end of the cat nor the beginning of the b-pipe.
I want to help. I've had a few setups over the years:
- JDM ITR 4-1 header, carsound cat, JDM mugen catback
- JDM ITR 4-1 header, JDM ITR cat, JDM ITR catback...no reducer at the end of the cat nor the beginning of the b-pipe.
Re: Exhaust sizing questions with JDM ITR header and USDM exhaust
I have a jdm itr header and a Oem ek9 exhaust. The ek9 and dc2 catalytic converter are the same thing. From my experience a Usdm Oem catalytic converter would not bolt to the jdm b pipe. The spacing on your pic appears to be able to accommodate both the Usdm and jdm spacing. The reducer isn’t necessary imo for fitment . Performance maybe . I don’t think decibels are going to vary much if you are using quality tubing. That thin stuff will be louder.
- coolhandluke
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Re: Exhaust sizing questions with JDM ITR header and USDM exhaust
From memory:Stin1 wrote: ↑Sun Aug 01, 2021 1:47 pm I have a jdm itr header and a Oem ek9 exhaust. The ek9 and dc2 catalytic converter are the same thing. From my experience a Usdm Oem catalytic converter would not bolt to the jdm b pipe. The spacing on your pic appears to be able to accommodate both the Usdm and jdm spacing. The reducer isn’t necessary imo for fitment . Performance maybe . I don’t think decibels are going to vary much if you are using quality tubing. That thin stuff will be louder.
JDM ITR header has a 2.5'' collector / USDM 2.25''
JDM ITR cat has a 2.5'' inlet and 2.36'' outlet / USDM 2.25''
JDM ITR exhaust is 2.36'' / USDM 2.25''
*All sizes interior diameter
Type-R Expo
Current: 98-1040 Stolen 12/22/21
Previous: 98-0197, 01-0187, 98-0731, 97 #00171
Current: 98-1040 Stolen 12/22/21
Previous: 98-0197, 01-0187, 98-0731, 97 #00171
Re: Exhaust sizing questions with JDM ITR header and USDM exhaust
Thanks everyone for the size and listed combos.
Go figure, the 2.25in vibrant flange that was also supposed to be 2.25in was also 2.5in lol.
When I see @coolhandluke on the sizes, I was basically trying to mimic the JDM ITR cat. But since the 2.5in flange bolts up to the stock exhaust. I am just going forward with that. Not looking for absolute power and I like the stock exhaust quietness
I noticed this as I looked at my exhaust. The flange I ran with the reducer on my current setup was sold to me as 2.25in and then welded to the reducer by a friend. Didn't realize the flange was actually 2.5in when I compared it to the various test pipes and flanges I bought. Looks like I shouldn't have an issue running the stock exhaust again.Stin1 wrote: ↑Sun Aug 01, 2021 1:47 pm I have a jdm itr header and a Oem ek9 exhaust. The ek9 and dc2 catalytic converter are the same thing. From my experience a Usdm Oem catalytic converter would not bolt to the jdm b pipe. The spacing on your pic appears to be able to accommodate both the Usdm and jdm spacing. The reducer isn’t necessary imo for fitment . Performance maybe . I don’t think decibels are going to vary much if you are using quality tubing. That thin stuff will be louder.
Go figure, the 2.25in vibrant flange that was also supposed to be 2.25in was also 2.5in lol.
When I see @coolhandluke on the sizes, I was basically trying to mimic the JDM ITR cat. But since the 2.5in flange bolts up to the stock exhaust. I am just going forward with that. Not looking for absolute power and I like the stock exhaust quietness
-Andrew Wong
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