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04 Cayenne TT
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Discussion Starter #1
Well as I'm pondering my exhaust situation, I thought I would post it out there since I don't claim to know it all and am relatively new to the Subaru platforms.

I was going to either run the Prodrive or TXS axleback to go with the TXS stealthback I already have. However, there's a few things with the TXS stealthback that have become issues with me. One is that this must be a first generation downpipe or something because there is no bung for an O2 sensor in the DP. There is one after the cat, but I've had to stretch out the harnss for that and as a consequence, I wrapped some black pastic cable wrap around it so this yellow harness wiring isn't just dangling there. This is one dislike of the TXS I have. Back to the absence of the bung. I have a ZT-2 already wired up but have not put the wideband in. I wanted to put it somewhere in the DP to reduce the amount of wiring I had to run. I've been to three different muffler shops/welders and none of them want to mount it for less than $75. And that's if I take it off the car. Kind of a rip-off to me, but it compounds the fact that this is another thing about the TXS that I wish it had. I figured it would be cheaper than that. And then there is the matter that the TXS hangs down lower. I much have lost at least 2-3 inches of ground clearance. I just don't like the way it sits.

Now on the good side, I think the 4" DP is definitely a good idea for pressure drop across the turbo. I like the fact that the TXS piping is all 3" and that they do not neck it down for any reason except at the end for the axleback. Mated to the STi axleback, it is nice and quiet. And the cat in the system will easily pass a visual inspection for emissions.

But here's the thing: living with the TXS is slowly becoming a sore spot on a vehicle I am loving to own. So it's going to have to go (people wanting a stealthback cheap take note!). So I'm now looking to switch exhausts all together. I've narrowed it down to two setups.

The Cobb turboback, and a Maddad stealthback with a Prodrive axleback.
The Cobb is a no brainer for fit and uses a FXT specific muffler so it should be reasonably quiet. Peaty's invaluable information on those pieces along with noise data that can be compared to the unabomber manifesto on nasioc shows it's on the quiet side. There is a bung for the wideband in the DP, and there is a cat on the bottom for a visual inspection. I'm not 100% convinced that the cat in the Cobb would pass since it doesn't have the heat shield most inspectors would be familiar with. It's a full 3" but has minor neckdowns at the connections.

The Maddad has the fake cat in the rear section and that should suffice for any visual inspection. There is a cat in the DP but it is up towards the turbo. And if you haven't seen this DP, it is a divorced wastegate design where the bypass tube does not join the main exhaust pipe until after the cat. It does not come with a bung for the wideband, but they can add one there before shipping. Like the Cobb, this one has the stock bracket that holds the tubing up by the end of the transmission (the TXS does not because it hangs down too low to use it). Piping is 3" like the Cobb and does neck down at the connections as well. The prodrive looks great but is a 2.5" system. I don't particularly think this is a huge deal since Prodrive has some big hp gains (claims) over the STi muffler (on the STi) so it must not be that restrictive.

I really like the Maddad fake cat in the rear section for inspections and that would add to the sleeper look if anyone pokes their head under there. But I'd have to add the O2 sensor (not sure how much but I feel confident it won't be $75). I can't find anyone that is runing a Maddad and Prodrive setup so I'd be the first. Shopping around it appears that this setup is about $110 cheaper than the Cobb.

But the Cobb is ready as is - no mods necessary. Bolt-on and go and there are many Subs out there running this system with no problems.

Link to the Maddad:
http://www.daddysscp.com/dcart4/product.php?productid=43&cat=5&page=1
 

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I have a stromung catback w/no problems (same as Cobb but slightly lesser stainless steel and less polishing). If I were to do it again, I would go stromung catted DP/midpipe and stromung catback just to keep it all one manufacturer so theres no fitment issues. The only reason for using a Helix DP is because it was off my old wrx.

my helix DP bolts up fine to the stromung catback and isnt all that loud, its the perfect balance between too quiet and loud enough. the only thing I had to do was get the flange welded all the way around where the catback mates to teh downpipe. the stromung is tapered and setup to take the stock donut gasket on the stock DP so they only spot welded around the flange. This left gaps where air could get out because the Helix DP has a flat 3" gasket.

it was a $10 fix at a local muffler shop

as far as sleeper goes, the stromung is perfect because its only polished on the canister and tip, the piping is brushed and so is the end of the canister.




^^^on this last pic you can see the spot welds on the flange, it took 10 min to fix.

I had a avi video link up on the old website but I dont know how to access it :( If you want I can email you the AVI file (10mb)
 

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11 sec club
04 Cayenne TT
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Discussion Starter #3
I was thinking that Stromung was the same as the Cobb like you say as far as fitment and dimensions. A Cobb DP and the Stromung cat-back should fit just as well as all Cobb, correct?
 

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agentorange said:
any sound clips?
I have one but it was linked on the old site and I cant find it :( I do have a 10mb avi file on my hard drive that I can email
 

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DOHCammin said:
I have one but it was linked on the old site and I cant find it :( I do have a 10mb avi file on my hard drive that I can email
Send one to me please. I have the stromung DP, and when funds, oh hell who am I kidding, when I can spend the money and not have my wife chew me out for it, I will be buying a stromung high flow 3rd cat midpipe and cat back to have a complete stromung TBE. In the mean time, I could burn the sound onto a CD and play it as I drive. :)
 

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the head said:
I'm not 100% convinced that the cat in the Cobb would pass since it doesn't have the heat shield most inspectors would be familiar with.
You can alsways take the heat shield off of the factory mid-pipe and just put it on the Cobb DP.. The factory mid-pipe heat sheild just bolts together and sort of clam shells around the piping and cat. Easy way to make it apear stock. :) Saw a post over on NASIOC where a guy did that and it look just like the factory one, but had a Stromung high-flow midpipe inside the heat sheild.
 

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fxtacy said:
Send one to me please. I have the stromung DP, and when funds, oh hell who am I kidding, when I can spend the money and not have my wife chew me out for it, I will be buying a stromung high flow 3rd cat midpipe and cat back to have a complete stromung TBE. In the mean time, I could burn the sound onto a CD and play it as I drive. :)
pm me your email address.
 

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11 sec club
04 Cayenne TT
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Discussion Starter #12
I went with the Cobb TBE. I'm sure it will suit my needs. Tne Maddad stuff was going to take a while to get here since I wanted an O2 sensor bung added (they will be offering bungs on all of their systems in the future).

I'll take pics of the Cobb and TXS side-by-side when I do the swap.
 
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