STI axelback

[NICKZ]

hey guys,

I tried searching for this and didnt find much. Im looking at picking up a 2005 STI axelback to put on my 2003 legacy and I had just a couple quick questions. Number one, Im not sure how true this is but i heard that the STI exhaust creates back pressure for the turbo and this can actually do more harm then good...is this true or is someone just bull shitting me??? Next, I would most likely purchase some sort of mid-pipe to , not sure what yet, but i should be able to take that to my local exhaust shop and they should be able to set it all up for me correct (i dont think this is something i could do) Also Im a little apprehensive about buying used parts like this, the guy said it had no leaks or dents, but is there anything i should look for condition wise??? anything else you guys feel like i should know or would be helpful would be greatly appreciated...Thanks for the knowledge guys.

[chuckthefuk]

Back pressure does not harm forced induction systems, it just limits their efficiency. If what you heard was true then Catatytic converters would cause the same "harm" since it causes restriction in the exhaust path.

Going with a 2.5" axle back is overkill on a N/A EJ25. 2.25" is the highest that should be used IMO. 02' WRX and up use 2.25" mid pipes and axle back. Most subaru's follow the same path for the exhuast system so reusing the stock hanger locations is a snap! There is also the benefit in reusing the "crushed donut" gasket instead of some cheap flex pipe that most shops offer.

If there are no leaks, no dents, and no excessive corrosion (rust) then you should be good. You will have to change the mounting point (hanger) for the axle back. But the exhaust shop will do this for you at no extra charge.

My current setup is UEL headers with universal hi-flow cat and wrx mid-pipe, wrx axle back and a canister style muffler. Although a Stromung or proper baffled muffler would help me out, but MEH. whatever.

The only benefit you will have with an STi muffler is the fact that its shiny and says STi. But too each their own. Good luck.

-Chuck

[impreza_GC8]

^ I agree mostly except to add that the stock STI axleback is NOT 2.5" in diameter, it is the same 2.25 as the WRX axleback is.
The hangers will need to be relocated and a custom/modified midpipe will need to be used.

[chuckthefuk]

\stock STI axleback is NOT 2.5" in diameter, it is the same 2.25 as the WRX axleback is.
The hangers will need to be relocated and a custom/modified midpipe will need to be used.

04+ STi has a 2.5" midpipes and axle backs. I purchased one under the assumption that it was 2.25" but nope turns out it was 2.5". But hey who knows what you had.

-Chuck

[NICKZ]

Well i wouldnt be buying one but i found a good deal and i want something that is gonna give me a little more rumble then the nonexistent one i have now. Everything that i found did say it was 2.5" but im not worried about it, i realize it might be a little much but theres a wrx in my future so at least it will be something i can use later down the road.

[chuckthefuk]

You want rumble? That classic BOXER rumble. EZ!! spend the $180 on the ebay UEL headers.. There very good quality and its an instant BOXER rumble.

-Chuck

[rougeben83]

^ I agree mostly except to add that the stock STI axleback is NOT 2.5" in diameter, it is the same 2.25 as the WRX axleback is.
The hangers will need to be relocated and a custom/modified midpipe will need to be used.

sti is 60mm. wrx is 55mm

and you're wrong on this whole "backpressure" business. First, turbo cars need even less restriction than an n/a car to make power, second, the turbo exhausts are much freerer flowing than the n/a exhausts so it will be louder.

[impreza_GC8]

I'm not necessarily going to turn this into an argument but it is my impression that Subaru shared its exhaust parts during certain years. I agree that the STI "should" have a larger exhaust but after owning an STI exhaust and dealing with a lot of people's cars I have come to find that some STI's did not come equipped with the theoretically larger exhuast. In fact, some STIs didn't even have the STI tip. This is a true statement, my STI exhaust purchased from an old man who owned an 05 STI does not say STI anywhere on it yet he is the only owner of the car and never changed it. This is not the only time I have come across this. My STI exhaust is identical in appearance to a stock 06-07 WRX exhaust, yet came off an 05 STI.

[rougeben83]

I'm not necessarily going to turn this into an argument but it is my impression that Subaru shared its exhaust parts during certain years. I agree that the STI "should" have a larger exhaust but after owning an STI exhaust and dealing with a lot of people's cars I have come to find that some STI's did not come equipped with the theoretically larger exhuast. In fact, some STIs didn't even have the STI tip. This is a true statement, my STI exhaust purchased from an old man who owned an 05 STI does not say STI anywhere on it yet he is the only owner of the car and never changed it. This is not the only time I have come across this. My STI exhaust is identical in appearance to a stock 06-07 WRX exhaust, yet came off an 05 STI.

viewtopic.php?f=11&t=10919&hilit=muffler (https://sl-i.net/FORUM/viewtopic.php?f=11&t=10919&hilit=muffler)

perhaps it should then be that if you have an 'STI' embossed tip, you have the larger exhaust.