2G STM catback compatibility

[Mitchel63]

I purchased STM's catback exhaust. They say that it will bolt up to any downpipe that ends in the stock location. Most downpipes are built to replace the stock DP and catalytic converter, so they would end in the stock location. I have an Apexi DP....it is not compatible with STM's catback and they are telling me it is because the DP does not end in the stock location. I also have my old RRE DP on hand....it is the exact same length as my new Apexi unit. Both matched up perfectly to an RSR catback.

My question is this....has anybody purchased just an STM catback? If so, what downpipe are you using? I really want to make this work, but I run an external wastegate on a 2.5in O2 housing, so using their 3in DP is not an option.

Thanks!

 

[Dsmkauai]

If it's short get a test pipe or high flow cat. Do you have the stock dp and cat you can measure the apexi and rre against?

 

[Mitchel63]

It's too long. The DP and catback overlap by about 2 inches. I don't have a stock setup around anymore to measure against. I personally just think they made the break between their DP and catback in the wrong place, but hopefully I am wrong and somebody can chime in with a DP that will work!

 

[eviltsi]

I designed, built and tested this product on my 100% stock gsx.

First, the cat was removed, jigged and replaced with a test pipe. I then worked backwards off of that to develop the catback with the stock downpipe still in place. Only after the catback was completed did I remove the downpipe to make that portion. I can say, without a shadow of a doubt, it goes to the stock locations.

Now, the apexi catbacks came with an adapter that necked down to meet the stock cat with a flange that would actually seal, because the 3" is too big....IF you buy their downpipe, it replaces that adapter to make the exhaust 3" throughout. This is where your extra length is coming from.

Sorry for the inconvenience, but I did not take other products into consideration when I developed ours. Your easiest way out is to modify your preexisting downpipe.

 

[Mitchel63]

So can you answer my question of what downpipe will work with your catback, other than yours?

 

[eviltsi]

I have never used our catback with anyone else's downpipe, so I can not.

I can however make our downpipe with a 2.5" flange at the o2 housing if you so choose.

 

[Aproductions]

Same boat. I bought the catback. My punishment racing downpipe did not fit so I ordered the STM downpipe too. That did not fit to my megan racing o2 so yet again I had to order the o2 from STM. At least I know its high quality and all matching now from the turbo back.

P.s. I am still waiting for my o2 housing

 

[Mitchel63]

Eviltsi....thank you for the straight answer and also for suggesting a solution. Also thank you for producing new parts for a somewhat dying platform....the community really appreciates it!

Unfortunately, for several reasons, I'm not interested in running your downpipe. The part you made is beautiful, it just isn't going to work for me.

I do think that if you are going to sell these components separately, your website should be more clear. You say your catback will bolt up to any DP ending in the stock location. Which you have proven to me to be a true statement. However, I feel like most people would think that all downpipes end in the stock location, when in actuality, it appears to be none.

Aproductions....thanks for chiming in! They were making me feel like I'm the only one to have this issue. Your new setup will be badass for sure!

 

[Type1DSMr]

Same boat. I bought the catback. My punishment racing downpipe did not fit so I ordered the STM downpipe too. That did not fit to my megan racing o2 so yet again I had to order the o2 from STM. At least I know its high quality and all matching now from the turbo back.

P.s. I am still waiting for my o2 housing

Well that's good to know on the fitment with the Punishment downpipe. This thread helped clear up which exhaust I should get for the gsx, STM or Thermal. Now I know, if you already have other exhaust parts go with another brand, but if you need a full kit STM is the way to go. Thanks

 

[Aproductions]

For me I did not want an exhaust with a bottleneck like the thermal and I did not want to cut anything and modify it. I could have cut the punishment flange and clocked it the other way and re welded but I am not doing that to a new exhaust.

 

[Jacolu3]

Has anyone tried this exhaust with a ST rear sway bar?
My hks doesn't work with the st sway bar. It pushes the axle back down.
Just wondering if it will work

 

[Mitchel63]

For me I did not want an exhaust with a bottleneck like the thermal and I did not want to cut anything and modify it. I could have cut the punishment flange and clocked it the other way and re welded but I am not doing that to a new exhaust.

What bottleneck does the thermal have? I was under the impression it was straight pipe with a straight thru muffler??

 

[Mitchel63]

Looked closer at the pics and the Thermal does have a smaller flange where it bolts to the downpipe. That's silly. Thanks for pointing that out....guess I keep shopping!

 

[Type1DSMr]

Yeah I finally realized what you guys are talking about where it bottle necks down to 2.5 inch. Lucky for me, the Thermal on my car has been cut off and a 3 inch section and flange has been welded in place.

 

[AdR]

About 90% of the exhaust systems in the market today have some kind of bottleneck, either by the smaller diameter tubing coming out at the O2 housing, a 2.5" flange somewhere, a crushed section at the O2 like the ebay ones, or some kind of reduction in the catalytic section. They just try to make them compatible with oem parts without thinking that they should probably sell the complete thing and make it right the first time. The only ones that actually do just that are STM reason why I've asked for reviews and unfortunately very little people have actual system from the website in their hands and installed (some have modified versions, others have bought it and haven't installed or received it yet).

I personally sourced the parts to make a custom quality stainless steel mandrel 3" exhaust and honestly it's only about $200 cheaper than STM's... By the time you factor your time, welding wire, electricity and effort, you might as well have bought their setup.

 

[EShield]

I know this is an old post, but I want to post my experience. I had an old Megan 3" downpipe around, it was 1-2 inches too long and pushed the exhaust to the side and down, raising the muffler tip into the bumper. I just cut about 1.5 inches off where the Megan couples together with the band clamp to shorten it. I am going to hang it tonight and report my results.

I should also mention I have a no-name O2 housing that came with the car, but looks to be equivalent of a Megan.

 

[EShield]

Cut off exactly the width of the band clamp from the Megan downpipe to shorten it and it bolts right up to the STM catback.