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Old 03-12-2013, 05:09 PM   #1
tmartin1978
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pearl

Default Cat-Back or Turbo back?

07 STI with 80K miles.

Here's my issue. My stock air box broke. I replaced it with an SPT air intake. Love the sound, btw. But, I've lost a TON of power and am looking to opening up the car's breathing a bit. An added problem is a rather large drop in MPG. Just filled up this morning with 209 miles on the previous tank of gas. Not totally sure what that works out to, but I think it's somewhere between bad, and complete $hit.

So, I've been talking with MKC Performance in Kansas City. Well respected shop. He suggested a tune and a COBB boost controller. That's all fine and good. He also suggested that to get any noticeable horsepower gain, I'd need to free up the exhaust a bit. He recommended a Cat-Back because of budget concerns.

I'm curious is anyone can suggest a Cat-Back exhaust that is relatively quiet (compared to the stock STI). This car is my daily driver. Only model I've looked at is the Borla Hush, but I'm not thrilled about the 2 pipes out the back.

So, If anyone has the time to read this long, wordy post, I'd appreciate any and all info. Or, just point me in the right direction to some info on this site.

Thanks all!
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Old 03-12-2013, 05:12 PM   #2
alecb
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I would go with a downpipe before a catback. If you end up going with a downpipe, for the love of god make sure you get a tune. If you end up going with a catback, just search around YouTube, there are hundreds of videos of different exhausts.
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Old 03-12-2013, 05:15 PM   #3
Navendra94
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A Catback won't really make a that much of a difference in power. I'd just get a new downpipe ( downpipes are the REAL difference in power on these cars ) and a tune. Sounds like your car needs a service also... I'd look into getting the car "freshened up" and then getting a new Downpipe with ProTune. As for CatBack exhausts, for the GD Body, people have said that the Cobb CBE is fairly quiet. If your stock CatBack is in good shape, by all means you can just leave it and mate up a new Downpipe to it. I wouldn't know since i have a GR. If I was you... I'll do this , once again :

- FULL Service
- Downpipe + Tune
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Old 03-12-2013, 05:25 PM   #4
tmartin1978
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Quote:
Originally Posted by Navendra94 View Post
A Catback won't really make a that much of a difference in power. I'd just get a new downpipe ( downpipes are the REAL difference in power on these cars ) and a tune. Sounds like your car needs a service also... I'd look into getting the car "freshened up" and then getting a new Downpipe with ProTune. As for CatBack exhausts, for the GD Body, people have said that the Cobb CBE is fairly quiet. If your stock CatBack is in good shape, by all means you can just leave it and mate up a new Downpipe to it. I wouldn't know since i have a GR. If I was you... I'll do this , once again :

- FULL Service
- Downpipe + Tune
First, thanks for the info.

I just had the 75K service at my Subaru dealer, and they installed the intake at that time. He reflashed the ECU, and said everything was good to go. Maybe I should challenge that...

So, I really don't need to change the stock STI exhaust if I get a new downpipe? Just trying to wrap my head around this...

SPT Intake.
New Downpipe.
Tune.
Rock on?

Thanks all..
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Old 03-12-2013, 05:31 PM   #5
Gallo2011
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If a catback rather than a downpipe was your "tuner's" first thought to open up the exhaust and free up horsepower, I suggest thanking him for his time and looking elsewhere.
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Old 03-12-2013, 05:32 PM   #6
guroove
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Quote:
Originally Posted by tmartin1978 View Post
But, I've lost a TON of power and am looking to opening up the car's breathing a bit. An added problem is a rather large drop in MPG.
Ok, you really need to focus on fixing this before you even think about throwing more mods at this car. Chances are something is broken. Something big and expensive, like the engine. Stop driving it until you get this sorted out. You need to have everything looked over twice.
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Old 03-12-2013, 05:33 PM   #7
vision.dynamix
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Quote:
Originally Posted by tmartin1978 View Post
So, I've been talking with MKC Performance in Kansas City. Well respected shop. He suggested a tune and a COBB boost controller. That's all fine and good. He also suggested that to get any noticeable horsepower gain, I'd need to free up the exhaust a bit. He recommended a Cat-Back because of budget concerns
Step 1. Never go to that shop again.
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Old 03-12-2013, 05:39 PM   #8
tune_up_or_shut_up
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Get a downpipe and tune. The stock downpipe is really holding you back when it comes to freeing up power.
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Old 03-12-2013, 05:40 PM   #9
guroove
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Let's just make this perfectly clear, it is NOT NORMAL for a car to suddenly lose power or to experience a drop in mpg. Something is mechanically wrong. You don't modify a car to regain power that was lost. FIX IT FIRST.
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Old 03-12-2013, 05:45 PM   #10
isotopesope
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you probably lost power because your car isn't properly tuned for that intake and you're running lean, potentially ruining your motor. no bueno.

how does a stock airbox break? and why not replace it with another stock one instead of upselling you a performance intake you're not tuned to run properly.

how did they "reflash" the ecu? with an open source tuning program or an accessport or...? sounds like that dealership is no good either.

you need to get your car running properly first (meaning probably getting a replacement stock airbox), THEN determine your tuning method (pro-tune, open source, accessport...), THEN researching which modifications to do, THEN begin modifying it.

Last edited by isotopesope; 03-12-2013 at 05:50 PM.
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Old 03-12-2013, 05:48 PM   #11
tmartin1978
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To be clear, the loss of power is mainly in 2nd gear. Noticeable to me, being that I drive it daily. Probably not so noticeable to those who don't. I probably misspoke when I wrote a loss of a TON of power. But it is there. Also, I've been told by many that adding a new intake, and forcing more air in to the motor without a tune can absolutely drop the MPG.

I just had a FULL service at a Subaru dealer (same place I've taken it since the car was purchased), and they say there is nothing wrong with it. Engine sounds fine. Turbo spools fine. Runs smooth. Just less power and efficiency.
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Old 03-12-2013, 05:55 PM   #12
SDoBB
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And why did you think this was acceptable? You brought the car in to fix an issue and they put an intake on without a tune and tell you your cars ok just less power and efficiency? Step back and think about this for a minute.
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Old 03-12-2013, 05:55 PM   #13
guroove
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Running slightly leaner should improve both mpg and power unless something went wrong, and the engine either got damaged, or the ECU is compensating for the change in a bad way.

First, I would check that everything is installed securely, and all the clamps are on as tightly as possible. Then I'd reset the ECU and have it relearn everything.

To answer your question about the exhausts, a cat back won't do anything for you except make it loud. All you need for stage 2 is a downpipe, but a full turboback would be better. A BCS and a tune are never a bad idea if everything is in good mechanical shape.
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Old 03-12-2013, 06:07 PM   #14
tmartin1978
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Really? If I thought it was acceptable, I wouldn't be asking for others opinions. The stock air box replacement was more expensive than the SPT intake. That was the only factor in my decision. Subaru claims the bolt on SPT intake is fine for a stock car. There are no other mods at this time.
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Old 03-12-2013, 06:20 PM   #15
Gallo2011
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Quote:
Originally Posted by tmartin1978 View Post
my Subaru dealer installed the intake. He reflashed the ECU, and said everything was good to go. Maybe I should challenge that...

I really don't need to change the stock STI exhaust if I get a new downpipe.

New Downpipe.
Tune.
Rock on.
Used your own words to give you some direction.
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Old 03-12-2013, 06:34 PM   #16
HinshawWRX
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We don't know what your budget is, so we can't do a lot for you. You can easily find cheap downpipes and catbacks in the classifieds. I would not goto that tuner again if he suggested a catback.

Read UNABOMBERS MANIFESTO to educate yourself a bit.
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Old 03-12-2013, 10:33 PM   #17
Whitefire818
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If I were you I would find a nice used stock airbox. Should be less than $50. Sell the SPT intake and reflash your ECU back stock until you have enough money for a proper turbo back exhaust and accessport or protune.

I was in a similar situation as you. Bought my car with a CAI and 650cc injectors installed on a poor tune. Went back to stock, then installed a turboback exhaust and accesport and now my car is running better than ever.
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Old 03-13-2013, 09:58 AM   #18
tmartin1978
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Thanks all. Really appreciate the honesty.
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Old 03-14-2013, 11:30 AM   #19
Bov_Rider
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a tuner suggesting a catback before a downpipe? hmmmm he probably meant a TBE. get a catless DP (not a cheap quality), tune your car then get a catback for the exhaust sound and if you are not looking to have the rumble sound, keep the stock catback. I went invidia N1 race but it is very loud. SPT, Perrin, Cobb, Invidia G200 are more calm compared to the N1 race but Cobb and SPT are more close to stock. calm and no drone.
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