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2G 3" downpipe to go with R&D Thermal Catback Exhaust

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Utz_3

10+ Year Contributor
58
8
Apr 15, 2012
Miami, Florida
Hello, I have a 99' GS-T currently running a stock exhaust and o2 housing. I want to upgrade to a Thermal CBE because i love the way it sounds. I have searched to see which downpipe i'd go with finally deciding to go with the Megan Racing V2 2.5" inlet (to accommodate for my stock o2 housing) and 3" outlet for better flow. But with my bad luck, as it just so happens that Megan Racing does not have the 3" outlet downpipes (i read somewhere here in the forums because they messed up their last batch that they made) so they have them with 2.75" outlet. Anyways I tried finding it from other vendors or here in the classifieds, but haven't found one.

So my question is what other downpipe could i go with for my Thermal CBE?

I thought of going with a Punishment Racing full 3" downpipe, but I feel like i'd get a lot of boost creep and I know because i have read it on here that i will have fitment issues because i have a stock o2 housing :(... I also searched on ebay and found an OBX brand 3" downpipe, anybody have any first hand experience with these?or the CX Racing 3" downpipe also sold on ebay? any fitment issues?

Thank you.

ps. sorry of the long post.
 
It doesn't really matter where you get it. Although I'm a big supporter of buying name brand parts, especially to keep the companies that still have interest in our cars in business, but its just some metal pipe welded to a flange. As long as you have the right flanges, all three would work exactly alike.
 
i have the same set up the thermal tapers down to 2.5 where it meets the downpipe the megen works fine

Thanks for the input, yes I know that the Thermal CBE comes with a 2.5" flange to fit the stock cat, I will just have that replaced with a 3" flange. Also, after reading up some more I now want to go with a full 3" turbo back exhaust, and either porting my o2 housing or getting a 3" tubular style o2 housing to prevent boost creep. However, I haven't really found any 3" o2 housings for our cars. I found the following on eBay, but not sure if that o2 housing will have fitment issues with my small 16g. Anybody have any ideas? to help get a 3" turbo back?

http://www.ebay.com/itm/95-99-MITSU...-98-/310659398795?hash=item4854be3c8b&vxp=mtr
 
I am doing the same thing and getting a Thermal Cat back. I am really interested in getting the PR downpipe for my GSX. I know it says it won't fit but can't find WHY?? Ive heard it will and it won't. On the O2 housings, Punishment sells them as well and it says they are 2.5" not sure what the stock one is but they claim 28% better exhaust flow which means faster spool if it does.
 
Megan Racing downpipe with Thermal R&D:rocks:
 

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The only 3" Downpipe that I've ever been happy with is Buschur Racing. Fits well, good quality flex section. I'm running it with the Thermal RD on a 2Gb AWD.
 
I run a pr down pipe mated to a 3" thermal. Material quality is great but fitment was horrible. Flange at cat was clocked wrong to begin with. Second, it was about two inches short. And lastly it was about an inch short were it mates to the o2 housing therefore it interfered with the oil pan. I know there's othera that have ran into this issue with this dp.
 
Honestly, most people do not even need a 3in exhaust and could get by just fine on a 2.5in exhaust. Many aftermarket down pipes are only 2.5in because they try to make them fit the stock o2 housing (which many don't mate well anyway). I like to retain stock heat shielding to keep away from more sensitive components such as the alternator. The EvoIII o2 fit the bill nicely, and has larger ports than the 1g or 2g. The only drawback is the odd angle the o2 housing has that requires modification to the down pipe to fit. I personally run an EvoIII o2 housing, RRE down pipe (angled for EvoIII o2 housing), and a Buschur Racing cat-back. The best combination I have run using all quality parts. The Thermal is decent, but I do not care for the huge tail pipe.
 
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I run a pr down pipe mated to a 3" thermal. Material quality is great but fitment was horrible. Flange at cat was clocked wrong to begin with. Second, it was about two inches short. And lastly it was about an inch short were it mates to the o2 housing therefore it interfered with the oil pan. I know there's othera that have ran into this issue with this dp.

This is what I am afraid of. I feel like PR made their downpipe to only fit well with their o2 housings, which are very nice, but kind of expensive. I would like to port my stock o2 housing or go with a bigger than stock tubular o2 housing if any exist?

Honestly, most people do not even need a 3in exhaust and could get by just fine on a 2.5in exhaust. Many aftermarket down pipes are only 2.5in because they try to make them fit the stock o2 housing (which many don't mate well anyway). I like to retain stock heat shielding to keep away from more sensitive components such as the alternator. The EvoIII o2 fit the bill nicely, and has larger ports than the 1g or 2g. The only drawback is the odd angle the o2 housing has that requires modification to the down pipe to fit. I personally run an EvoIII o2 housing, RRE down pipe (angled for EvoIII o2 housing), and a Buschur Racing cat-back. The best combination I have run using all quality parts. The Thermal is decent, but I do not care for the huge tail pipe.

I would like to just upgrade once for future goals, that's why i've changed my mind and would like to just got with 3" now. I considered the evo 3 o2 housing, but yes, i have read that flange is angled funky. Everywhere I turn i seem to run into fitment issues. :banghead:
 
The only 3" Downpipe that I've ever been happy with is Buschur Racing. Fits well, good quality flex section. I'm running it with the Thermal RD on a 2Gb AWD.

I will check that out, was this mated to a stock o2 housing? also you are awd, i'm fwd, downpipes are different, but i will look into it thanks.

Megan Racing downpipe with Thermal R&D:rocks:

I am considering going this route. I just wanted a "true" 3" downpipe, but there seems to be way too many fitment issues :cry:
 
I have only a flange connecting the down pipe to the o2 housing. I used pipe clamps for everything else. No fuss with mating flanges...I just cut all the flanges and reduced portions off to make all of it 3in.
 
Utz_3
I've been using the Buschur with a few different O2 housings over the years. First it was a stainless O2 from FP with a green, then later with a 3052

I've been through apexi and Greddy. The apexi rusted, the Greddy flex section completely crumbled when I accidentally backed into a parking spot and hit a curb stop. I had the apexi N1 exhaust then the dunk.
 
Utz, I also run their recirc, o2 housing with the down pipe. Which is great by the way, in quality and fitment. Pr us a great company and build great products. The problem is the they don't actually make these down pipe. They just resell them. By the way it definitely won't work with the stock o2 because of the angle. Yeah need an aftermarket or I believe the evo 3 o2 will wok as well.
 
Utz, I also run their recirc, o2 housing with the down pipe. Which is great by the way, in quality and fitment. Pr us a great company and build great products. The problem is the they don't actually make these down pipe. They just resell them. By the way it definitely won't work with the stock o2 because of the angle. Yeah need an aftermarket or I believe the evo 3 o2 will wok as well.

Yea, I like the recirculated PR o2 housings, however they're a bit expensive. Also you wrote a couple of post above that the downpipe was too short? That you had problems putting the exhaust together (PR o2 housing, PR 3" fwd downpipe, and Thermal CBE)? how did you solve your problem? did you have to have the downpipe modified to reach?


I run a pr down pipe mated to a 3" thermal. Material quality is great but fitment was horrible. Flange at cat was clocked wrong to begin with. Second, it was about two inches short. And lastly it was about an inch short were it mates to the o2 housing therefore it interfered with the oil pan. I know there's othera that have ran into this issue with this dp.
 
The flange is cut off and welded back on at the appropriate angle for the EvoIII o2 housing.
 
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Utz, I have a 98 gsx
Pr o2 housing, 3" awd pr dp, thermal cbe
The problem was with the dp itself. Pr doesn't make them they just resell them. Fitment with everything else was spot on. Simple trip to the exhaust shop correct everything. As far as o2 housing being expensive, you have to pay to play. Don't cheap out and buy a no name ebay junk, only to have to buy a high quality once it cracks.
 
Utz, I have a 98 gsx
Pr o2 housing, 3" awd pr dp, thermal cbe
The problem was with the dp itself. Pr doesn't make them they just resell them. Fitment with everything else was spot on. Simple trip to the exhaust shop correct everything. As far as o2 housing being expensive, you have to pay to play. Don't cheap out and buy a no name ebay junk, only to have to buy a high quality once it cracks.
I got confused by your username i suppose thinking you also had a gst.

Utz, sorry. I never expected that.

its ok, thank you for trying to help :thumb:
 
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