My friend and I (mosly my friend) just finished the install on my Hahn stage II turbo kit and now my car is in despirate need of a good exhaust system...
1. Should I get a custom 2 1/2" - 3" non-mandrel bend, cat back done at a muffler shop or somthing?
2. Should I order some $400-600 mandrel bend cat back (made for a non-turbo eclipse) from someone like Apexi (no bigger than 2 1/2 ")?
3. (This is the big one I've been tring to figure out)Can/Will a GST Cat Back system Bolt up to a GS/RS... if it does should I get the 3" Aftermarket catback?

I have been going crazy for the past few weeks tring to figure this out so all help is very much welcomed! Thanks

Hahn Stage II w/ FMIC, N1 3" Catback Exhaust, Custom 2 1/2" downpipe, Walbro fuel pump, Unorthodox maincrank pulley, Eibach Sporline Springs, GYB G2 Struts, OBX short throw shifter, Nitto 450 tires, 17" Eneki RP05 Rims, Smoked Taillights, Custom side marker lights, and few other minor cosmetic mods.

what u want is as little backpressure as possible so i think ur best route would be a 3 inch exhaust

built turbo 99 rs-back to stock and parted out
Now: 2003 S2000 Aem ems, 1000cc injectors, inline pro 3mm headgasket, T67 turbo, full race manifold, Tial 44m wastegate, Tial 50mm bov, 255 fuel pump, kaaz 1.5 lsd, comptech bearing caps, j's 4.77 gears, and so much more

I just got my Hahn Stage II as well and destroyed my stocker cat getting the downpipe out ... so I need a cat and I want to setup a nice cat-back as well. My big question is about the cats themselves. My gut feeling is that the cats in the GST and GS/RS are the same b/c the GST/GS/RS exhausts are the same other than the muffler (please correct if I'm wrong guys). If that's true, that would of course mean any aftermarket cat-back for the "GST" (Greddy Evo, APexi N1, Thermal R&D) should bolt up. (??) Although, I've heard rumors of problems coming over the rear axle with 3"ers. Is this true?

HOWEVER, the thing that throws me, is whenever I search aftermarket cats there are always different part numbers for the GS/RS cat and the GST cat although, the diameter specs and stuff seem to be the same. I even sent a question into a manufacter about this and they said they couldn't asnwer my question! BAW! So, the big question in all this, are the GS/RS and GST cats the same or not?? The even bigger question is: Will an aftermarket GST cat bolt up to stock downpipe? And, just to be more specific, I mean, flanges and lenght.

To answer your ^^^^ question on the exhaust diameter - if you can afford to go 3" you definately want to do that, just do it right the first time. A 2.5 will work, and alot of guys run them with turbos on this board, but more flow is always better

.
Yes officer, the windows are mirrored.

1999 GS Special Edition

just a guess, but the cat for a gst/x might have a different flange to mate to their dp, which is obviously different than ours.

just curious, but how did you destroy your cat taking off the dp?

- Dan

HRC Stage 2|30lb injectors|S-FMU|Walbro255HP|AFX UDP|B&M Short Shifter w/ Symborski Shift Kit|Rear Strut Bar|Power Slot Rotors|more...

I run a Thermal R&D 3" cat-back. The one made for the GST. And I am sure that any other GST catback will fit. We have the same bends. I am not sure about the cat question. I can maybe see issues with the DP fitment of the GST and the flexpipe fit of the RS/GS to stock cat. But I recommend my exhuast to anyone with the cash to buy it.


http://www.cardomain.com/id/jasvbts2k2
"The ONLY Honda I'd mod would be ASIMO"

Amazingly, I learned the answer to the cat just today. The cats are different, because my brother ordered a test pipe for his GST... the flange doesn't fit my stock downpipe... ours is rotated at a different angle.


1996 Eclipse RS / 5-Speed / Body Components by Aerogear / Coated in Magnetic Red Metallic v2 - More at http://home.insightbb.com/~mgalyan/
Mark Galyan - Greenwood, Indiana

Hey Sear how is your set up with that R&D exhaust? Is it very noticeable?

intricatelines.com/ -graphics and vinyls

"Tell them of us and say,
For their tomorrow,
We gave our today."
-- The Kohima Epitaph

>Hey Sear how is your set up with that R&D exhaust? Is it
>very noticeable?

How do you mean? Sound, looks? It sounds great. Mean. I don't think it's loud but I read somewhere the db's were over 100 at WOT! I can live with it. Haven't heard any other better. But really any exhaust with turbo is going to be loud inside, turbo, bov, fuel pump, etc.




http://www.cardomain.com/id/jasvbts2k2
"The ONLY Honda I'd mod would be ASIMO"

I also have the Thermal R&D 3" catback. I would highly reccomend it.

95 Avenger
ATX->MTX Swap
Holset HX40 @ 26 psi

Ya know, I feel like an idiot now. Everybody and their mothers dead goldfish knows that the downpipes on the GST and GS/RS are different, so of course the flange on the DP side of the cat is going to be different, thus ... making the cats different. Well, no more pounding the brain ... I need to get myself a GS/RS cat.

Oh, ... how I destroyed it: When I was trying to get off my stock DP I couldn't budge the top bolt loose (the one towards the underside of the car) on the cat with a 4' breaker bar or air gun. Eventually the head of the bolt sheared off. At that point the only way to get the DP disconnected from the cat was to sacrafice the cat, b/c obviously I need the DP for the turbo install. Anyone else have that problem?

.
Yes officer, the windows are mirrored.

1999 GS Special Edition

yeah. when i did my HRC stage 1 installation last august i noticed that my cat was rusted to hell to the stock downpipe. i ended up disconnection the muffler, and dropping the entire exhaust system, then dragging it out from under the car in order to cut the stock downpipe. that's why i can't simply get a cat back, because everything is just 1 huge piece of rust. i hate new england winters - my car has endured 7 of them.

EDIT: once the ERT downpipe comes out (i can't wait O.o) i'll get a high flow cat, and a nice cat-back system. it'll be a big improvement over my current semi-clogged cat (it smells like sulfur) and my dented stock downpipe.

2016 WRX STi Limited (current)
2001 A4 1.8tqms (donated)
1991 GVR4 #1933 (sold)
old.dsmregistry.com/detail.php?carid=218 (dismantled)

well it's a bit easier to get the cat to cat-back nuts off, b/c they're just nuts on studs. the cat to dp are bolts which are insane to get off. i ended up just dropping both the cat and the dp and having a muffler place get the bolts out. they welded it and crap, the bolts were actually melted. i wanted to get it apart while it was off the car, so i would be ready for the new ert dp.

- Dan

HRC Stage 2|30lb injectors|S-FMU|Walbro255HP|AFX UDP|B&M Short Shifter w/ Symborski Shift Kit|Rear Strut Bar|Power Slot Rotors|more...

>" My gut feeling is that the cats in the GST
>and GS/RS are the same b/c the GST/GS/RS exhausts are the same
>other than the muffler (please correct if I'm wrong guys). If
>that's true, that would of course mean any aftermarket
>cat-back for the "GST" (Greddy Evo, APexi N1, Thermal R&D)
>should bolt up. (??) Although, I've heard rumors of problems
>coming over the rear axle with 3"ers. Is this true?"

Will this work? Any aftermarket GST Exhaust will bolt up? If this is true this would seem to be the best way to go. BTW those of you with the 3" Thermal... how much $ did it run you and how do you like it so far?

Hahn Stage II w/ FMIC, N1 3" Catback Exhaust, Custom 2 1/2" downpipe, Walbro fuel pump, Unorthodox maincrank pulley, Eibach Sporline Springs, GYB G2 Struts, OBX short throw shifter, Nitto 450 tires, 17" Eneki RP05 Rims, Smoked Taillights, Custom side marker lights, and few other minor cosmetic mods.

>
>Will this work? Any aftermarket GST Exhaust will bolt up? If
>this is true this would seem to be the best way to go. BTW
>those of you with the 3" Thermal... how much $ did it run you
>and how do you like it so far?
>


I got it free, traded a friend for my stock exhuast when he sold his car. But, i love it, sounds great, excellent quality, like i said above, i would highly recommned it.

95 Avenger
ATX->MTX Swap
Holset HX40 @ 26 psi

I got it used for $400. But I was ready to buy a new one. Definately the best exhaust in my opinion.


http://www.cardomain.com/id/jasvbts2k2
"The ONLY Honda I'd mod would be ASIMO"

I personally like th Apexi N1 cat back for the gst on our cars, that's what I am using now. the piping goes from 3 inch to a whopping 3.3 inch at the rear section. i like it, ground clearance is a little small, but not super bad.

lates
james

Rest In Peace Heidi Doggy

>>My gut feeling is that the cats in the GST and GS/RS are the same b/c the GST/GS/RS exhausts are the >>same other than the muffler(please correct if I'm wrong guys).

From the cat back, the RS/GS/GST exhaust is the same. The rear flange on the cat is at the same angle for all 3 cars. The difference is on the front flange. The downpipe-to-cat flange is different on the GST than on our cars. That's why you can use a GST catback, but you MUST use a RS/GS cat.


>>Although, I've heard rumors of problems coming over the rear axle with 3"ers. Is this true?"

3" piping can be a tight fit. My Thermal goes under the rear axle, not over.


>>BTW those of you with the 3" Thermal... how much $ did it run you
>>and how do you like it so far?

I love my Thermal! Nice deep tone at idle and cruising, but it makes some noise at WOT! I got mine used for $280.

You are not your job.
You're not how much money you have in the bank.
You're not the car you drive.
You're not the contents of your wallet.
You're not your fu**ing post count.

97 Eclipse GS - *SOLD*
01 Audi A6 2.7T
01 YZF-R6

>>>Although, I've heard rumors of problems coming over the rear
>axle with 3"ers. Is this true?"
>
>3" piping can be a tight fit. My Thermal goes under the rear
>axle, not over.

I have never had a problem with the pipe scrapping thought I have scratched the muffler on low banks. Here is pic to show you this..




http://www.cardomain.com/id/jasvbts2k2
"The ONLY Honda I'd mod would be ASIMO"

Hmmm, that ground clearance doesn't look that bad at all. I often wondered why the exhaust went up and over the axle stock. It sounds like a lot of us are banking on the new ERT DP .... if it comes out I'll get one!


.
Yes officer, the windows are mirrored.

1999 GS Special Edition

I have the Thermal 3" too. I love it. It sounds awesome and gives you the performance you're looking for. Of course you get what you pay for though. I think I dished out about $650 for mine...yikes. The only gripe I ever had was at 4K WOT it made this loud raspy sound. It didn't do it anymore after the turbo went on, so now there's no gripes at all. I very much recommend the Thermal

____________________________
HAD: '98 Eclipse RS

HAVE: '04 Grand Prix GTP Comp G

i have a 3" atr exhaust, if you can find one i would highly recommend it ..its stainless steel, all slip fittings and it goes over the axle so no low clearance issues...i put some sound deading matter over the axle to prevent it from rattling my brains out but overall its a great exhaust...atr's are huge w/ the 4g63 guys for a good reason..the sound is very similar to a thermal, nice sounding w/ good performance

400whp or bust.