downpipe/cat back install questions - Subaru WRX Forum
 
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post #1 of 15 Old 02-03-2008, 12:04 PM Thread Starter
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downpipe/cat back install questions

I just ordered:
- Cobb catted bellmouth downpipe
- Cobb heat shield
- HKS Carbon-Ti cat back exhaust

Now for my questions...
1. My 07 WRX has just under 11,000 miles on it. Should I buy a new gasket that goes between the turbo and downpipe, or is it ok to reuse my stock gasket?
2. Should I buy a new gasket (oem donut style or other) that goes between the downpipe and cat back or is it ok to reuse the stock gasket?
3. Should I buy new exhaust hangers or will the stock ones work fine for this setup?
4. Will I need to rent/borrow an 02 sensor removal tool from Auto Zone or do I not have to worry about that on my car?
5. Does anybody forsee any other problems/issues that I may run into?

I still haven't decided whether or not I will attempt this install myself or seek help from a mechanic friend of mine who has access to a lift and other equipment. I've already done the silencer delete mod, short shifter install, front and rear shifter bushing installs, and cleared/painted headlights mod by myself, so I think I might be able to tackle the exhaust too. From what I've read, I think I'll be ok doing it myself with ramps, jackstands, and simple hand tools when the weather warms up a little more. I've just never done this before, so I'm really not sure what to expect. Anybody have any advice?

I already have a Cobb AP too, so I'll be flashing to Stage 2 immediately after the install. I'm already pretty excited to hear the boxer rumble and feel the extra power!

John
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post #2 of 15 Old 02-03-2008, 12:30 PM
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1. you could reuse it, but i would buy a new one.
2. I not familiar with the cobb dp but i think that it mounts differently than the stock donut, it should be a 3" 2 bolt gasket
3. stock hangers are fine
4. the downpipe o2 is pretty easy to get to, you can also use a 22mm, or a 7/8 open end wrench, shit you can even use a all 16th's (cresent wrench) just soak it with rust off, or liquid wrench.
5. the stock heat shields are a pain sometimes, but yours is an 07 so there should be that much rust on the bolts.

its pretty easy to do a TBE, just take your time. If you get frustrated just walk away for 10-15 min, or move on to something else

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post #3 of 15 Old 02-03-2008, 12:34 PM
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Exhaust and dowmpipe are easy DIY mods. You should replace the gaskets just to be safe. Make sure you torque everything back up to spec and evenly so the gaskets crush correctly. The exhaust should come with hangers, or you may reuse your factory hangers. As for the O2 sensor, just reuse your factory sensor, I had no issues that way. Good luck and enjoy the boxer rumble and extra HP.

D-Rock
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post #4 of 15 Old 02-11-2008, 09:21 PM
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i reused all of my gaskets, and yes you will need to get a 7/8 wrech to remove your 02 sensor. all of your exhaust hangers will match up. the only problem that you may have is the seal between your downpipe and catback leaking some. I cured this problem by geting grade 8 bolts and nuts 5/16 thread i believe the same length as your stock bolts. The stock bolts are shouldered and i couldn't get the leak to stop even with the shoulder of the stock bolts bottomed out.
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post #5 of 15 Old 02-11-2008, 09:35 PM
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cobb dp uses stock dount gasket to connect to catback... they say its reusable but maybe you should by another gasket just in cae if you dont use it return it
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post #6 of 15 Old 02-12-2008, 03:33 AM
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i would go new withthe downpipe gasket but the donut should be ok to reuse. worst comes to worst you can put copper rtv silicone on the DP gasket

a 1/8 or 22mm wrench will be fine for the o2, you can do that when the part is off the car.

other than 14mm and 10mm tools there is not much to it
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post #7 of 15 Old 02-12-2008, 07:22 AM
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Quote:
Originally Posted by MilesFox View Post
a 1/8 or 22mm wrench will be fine for the o2
I know you meant 7/8, but I'm just gonna put it out there so there's no confusion....not to mention it's stated above. Yeah man show everyone has given you some good input. I was hesitant to do the DP myself but once you get into it it's really a breeze dude. Just make sure you have all the necessary tools and you'll be fine. Tools you'll need (taken from scoobymods, modified to fit your install by me):

1) Penetrating spray such as Liquid Wrench, PB blaster, WD-40. I used PB.
2) 10, 12, 13 and 14mm wrenches. I used the ratcheting kind....very helpful if you have extra $$$.
3) 10, 12, and 14mm sockets. As with Vishnu, I would STRONGLY recommend a Flex-head and deep sockets if you can get a hold of them. I did this without either a flex head (used wobble extensions) or deep sockets.
4) 22mm O2 sensor sockets (or 7/8 open end wrench). I bought mine at Autozone, but I hear that you can borrow one from them.
5) Long flat-head screw driver, phillips screwdriver.
6) Breaker bar. I think mine is 18" or so.
7) Several extensions for socket set.
8) Needle-nose pliers
9) 2 jack stands
10) Floor Jack
11) Ramp
12) Shop light or headlight.
13) Torque wrench.
14) Anti-seize
15) Zip lock bags to organize bolts/nuts

If anyone else has any siggestion of what tool you need chime in. Also man show, a good ref point (disregard the uppipe part) is: BEST DAMN WRX DOWNPIPE UPPIPE install cobb stage 2 - ScoobyMods
Good luck and enjoy!

Mike
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post #8 of 15 Old 02-12-2008, 08:56 PM Thread Starter
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Sweet... I'm really glad everyone is always so helpful here.

Here's a little update: my HKS Carbon-Ti cat back arrived last Friday and I was so excited that I put it on myself that night. I reused the donut gasket on the factory downpipe for now since it looked practically brand new. Everything went pretty smoothly (except trying to get those factory spring bolts back on - they gave me a bit of trouble). I absolutely love the way it looks and sounds. A+++ Today, my Cobb catted dp arrived. I also decided to order a new gasket for between the turbo and dp. It was relatively inexpensive and if it'll help me avoid an exhaust leak, it'll be worth every penny - if not, oh well, at least I'll have a little peace of mind. That should be here tomorrow or the next day hopefully. I also contacted my mechanic friend and he agreed to help me install the dp this coming Saturday afternoon. I read through the instructions that came with the Cobb dp and although the Cobb dp can be used with the factory donut-style gasket, they recommend that I use the gasket that came with the cat back. My cat back came with a pretty nice looking flat metal gasket, so I think I'll probably use that instead of the factory rubber donut. Hopefully everything will go smoothly and I'll flash Stage 2 this weekend! Keep your fingers crossed!

Thanks again for all the advice and info too!

Any kind souls out there wanna make a donation to my bank account? It's looking rather empty right now. I sure hope I'll be happy with Stage 2 for a long time... this mod bug is killing me.

John
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post #9 of 15 Old 02-13-2008, 11:37 AM
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Quote:
Originally Posted by man show View Post
Any kind souls out there wanna make a donation to my bank account? It's looking rather empty right now. I sure hope I'll be happy with Stage 2 for a long time... this mod bug is killing me.
Thats what i thought as well, but i was only at stage 2 for 6 months before i wanted more.

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235.8 WTQ

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post #10 of 15 Old 02-13-2008, 11:41 AM
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Stage 2 power for me is definitely satisfying for me. Currently getting a tune via internet from Dom and getting things dialed in rather than an OTS map makes a very noticable difference. I suggest looking into one of these options of a custom tune.

Mike
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post #11 of 15 Old 03-10-2008, 10:08 PM
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so did u instal the dp yet? let me know how did the instalation go? feel the power? im gettin my hks downpipe next week already installed my greddy ti-c catback ( love it!)
cobb and silencer delete tomorrow some time. cant wait for stage two!!!!
any other things u might be doin to it soon?
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post #12 of 15 Old 03-11-2008, 08:29 AM
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HKS makes the worst DP in the business. You should cancel your order if you haven't gotten it yet or send it back. It's not a bellmouth or divorced wastegate design. You won't get the same kind of gains, that's why it's so cheap.

Mike
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post #13 of 15 Old 03-11-2008, 08:23 PM Thread Starter
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Quote:
Originally Posted by thebear View Post
so did u instal the dp yet? let me know how did the instalation go? feel the power? im gettin my hks downpipe next week already installed my greddy ti-c catback ( love it!)
cobb and silencer delete tomorrow some time. cant wait for stage two!!!!
any other things u might be doin to it soon?
Yeah, I actually ended up installing the downpipe myself in my garage with some help from my dad since my mechanic friend was busy that weekend. Before I did it, I read through a couple different write-ups about downpipe installs and familiarized myself with the whole process and made sure I had all of the necessary tools. The only thing I had to get was an O2 sensor removal tool from Auto Zone - which I didn't actually have to get since a wrench would have worked just fine, but it did make things a little easier. I'm really enjoying the extra power over stock, but for some reason, my car still seems to be holding back a little. Maybe it's just the way the Cobb OTS maps are written. Ideally, I'd like to get a protune, but I want to wait until I have a few more mods that would significantly benefit from a tune. I'm sort of not really sure where to go from here because everything I get now (power-wise) will be in preparation for a bigger turbo (bigger injectors, fuel pump, TMIC, etc.). I haven't really researched any of that stuff yet, so I'm not sure what order to get it all in, etc.

Also, I agree with Longshot... the HKS downpipe really isn't very good. It's basically the same as the stock dp (flat plate design) minus the catalytic converters and slightly larger pipe diameter. There are other relatively inexpensive options (if that's why you got it) that will probably give you better power gains and make the smile on your face even bigger. I would consider returning/selling your dp and getting a different one if I were you. Good luck and enjoy Stage 2!

John
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post #14 of 15 Old 03-13-2008, 08:25 AM
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Hey Man_Show.

Glad your Stage 2!

Where at in Frederick do you live?? I live in Baltimore County but visit IAG Performance in Westminster every once in a while.

They are installing my Prodrive Springs and doing an alignment next Saturday.

~Jeff~
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post #15 of 15 Old 03-13-2008, 06:15 PM Thread Starter
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Thanks man. Right now, I live right down the street from Fort Detrick. I've never heard of IAG Performance, but I just checked out their website and it looks like a pretty nice shop. Are you talking about next Saturday - as in the 15th or the 22nd? ### the Hagerstown meet with Rob from CSS is on the 15th, but I think I might miss it because I have to work all morning. Unless the thing goes late into the afternoon... who knows.

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