Cobb Tuning SS 3" Cat-Back Exhaust System [Archive] - ScoobyMods

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Peaty
09-27-2003, 07:52 PM
Got the system from Cobb Tuning here:

http://cobbtuning.com/forester/powerpackages.html#muffler.

Well known Subaru vendor and good guys to deal with.

The back box section is nicely welded as are the bends and flanges. I knew it was going to be a 3" diameter but when you have it in front of you it looks huge, like a stove pipe.

The install was pretty simple. Everything you need is supplied, some bolts and a gasket for the axle back section. You reuse the donut, bolts, springs and nuts at the cat flange section.

What you'll need:

Eye protection - Lots of stuff under there to fall in your eyes

Gloves - You'll be working around heat shields, they are sharp

Band-aids - If you don't think gloves are a good idea

12mm and 14mm wrench or sockets - Remove bolts and nuts

Ramps and or Jack Stands - Get the car safely in the air

Optional:

Some heavy duty hangers - I got a set of Kartboy Hangman hangers (www.kartboy.com) Cobb makes them too. These prevent the exhaust from moving around.

Never seize - I like to put this on all bolt threads when I work on exhaust stuff.

Hi temp Silicone - I put some on the axle back flange just to be sure it won't leak.


First get the car safely in the air. I used Rino ramps and then a floor jack to raise the suspension a little. I then put jack stands under to rest the frame on.

Install was pretty simple, I removed the mid pipe first. Undoing the cat flange( 14mm and 12mm open end) then the other end by the muffler section 2-14mm open ends) Then undo the hanger last and drop the whole part down.

Then move onto the axle back section. It's supported with 3 hangers. I found it best to remove them in this order. (before you do wrap a towel around the tail pipe chrome part. If it gets away from you you will scratch the under part of the bumper)

If you undo the drivers side rear hanger's bolt with a 14mm open end you can then lower that side and slip out the opposite side. It's tricky but supporting the whole thing then you can undo the one in front of the muffler. I've also done it by removing the one in front first then the two back ones. Either way it's easier with a helper :)

If you are going to re use the hangers just move them to the new system. If you have some nice Kartboy or other urethane hangers remove the steel sleeve from the drivers side rear hanger and put it in the KB bushing.

Info on KB hangers here:


http://www.scoobymods.com/forums/showthread.php?s=&threadid=174&highlight=hangman

The mid-pipe has one hanger and it's larger (longer) than the other three. That one I reused because the KB hangers were shorter. I don't ever remember seeing a hanger that big on any of the other Subaru's I've worked on.

Next it's time to put the new system on. I put the mid-pipe on first then the rear section. It's pretty straight forward. I do like to use never seize on threads when it comes to working with exhaust systems. Reuse the hardware by the cat converter, there are new nuts and bolts for the axle back section and a gasket.

That's about it, not too tough.

If you have a rear diff protector you are going to have to remove it. I tried to notch out the protector to clear the flange but it didn't work. The flange cleared but the rear bolt that holds the protector impacts the pipe.

Peaty
09-27-2003, 07:53 PM
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09-27-2003, 07:54 PM
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Peaty
09-27-2003, 07:55 PM
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Peaty
09-27-2003, 07:56 PM
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09-27-2003, 07:56 PM
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09-27-2003, 07:56 PM
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09-27-2003, 07:57 PM
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Peaty
09-27-2003, 08:02 PM
Undo the cat flange

Peaty
09-27-2003, 08:02 PM
Then the other end

Peaty
09-27-2003, 08:03 PM
Undo the hanger

Peaty
09-27-2003, 08:05 PM
Then remove the rear section, here are shots of the new system in place:

Peaty
09-27-2003, 08:06 PM
cat flange

Peaty
09-27-2003, 08:08 PM
back flange

Peaty
09-27-2003, 08:09 PM
closer to the back box

Peaty
09-27-2003, 08:10 PM
tail pipe

Peaty
09-27-2003, 08:11 PM
tail pipe 2

Peaty
09-27-2003, 08:12 PM
Tailpipe 3

Peaty
09-27-2003, 08:40 PM
OK when I got back from my first drive with the new system. I did do some sound bites while driving. I clipped the mic to the headrest. I've converted them to MP3's

Keep in mind sound our loudness of an exhaust is pretty subjective.

Where before the XT sounded pretty sedate and kind of sorta like a Boxer, now there is no mistaking it. You can hear the throbbing of the motor most definitely now. Is it obnoxious? No I don't think so, it's too new and different for me to make a real call yet. My wife did comment that when I pulled up into the garage she could "Feel the house pulse". It's nothing like my RS though because she knew I was coming home when I pulled into the subdivision. :)

Cruising down the highway there is more wind noise than the exhaust note. I have to live with it more but that's my topline as of now.

I did listen to the sound bites and they seem a lot louder than the exhaust actually is. Humm, I have to turn my subwoofer down I guess.

Kastle attached the zip below. In the Zip there are 4 files, one of the Stock XT exhaust. This was taken inside my garage w/ the door open. The Mic was only about 3 feet from the tailpipe to the side by the wheel arch on the drivers side. There is another w/ the Cobb system. Then there are two taken during me driving. Again keep in mind the mic makes things sound a lot louder. I plan on doing this again and turning down the gain on the mic.

kastle
09-27-2003, 09:01 PM
Peaty's sound zip file..http://www.scoobymods.com/mods/impreza/audio/images/PeatyXTcobbSS.zip

Peaty
10-12-2003, 04:48 PM
Here are some results that I will update when I get more information. We had a few people not show up yesterday and I never got a chance to do a stock Forester XT But for the heck of it I did mine with the Cobb SS Catback and my friend Mike's stock STi.

I used the method in the PDF above for lack of anything better that I could find. THis one:

http://ohv.parks.ca.gov/pages/1140/files/j1287_199807.pdf


Forester XT Stock System:

58.0 dBA at 750 RPM
62.0 dBA at 900 RPM
65.0 dBA at 1,250 RPM
68.0 dBA at 2,000 RPM
68.0 dBA at 3,000 RPM


Forester XT w/ Cobb Tuning 3" SS Cat-Back exhaust:

72.0 dBA at 750 RPM
74.5 dBA at 900 RPM
79.5 dBA at 1,250 RPM
81.0 dBA at 2,000 RPM
83.4 dBA at 3,000 RPM



Forester XT w/ Cobb Tuning Uppipe, downpipe (w/hi-flo cat) and catback.


74.6 dBA at 750 RPM
76 dBA at 900 RPM
78 dBA at 1,250 RPM
85 dBA at 2,000 RPM
88 dBA at 3,000 RPM


Interior sensor pointing up ~24" above handbrake:

Idle / not in motion

50.0 dBA at 750 RPM
54.0 dBA at 900 RPM
60.0 dBA at 1,250 RPM

Note: Normal conversation came out at 62- 65 dBA in interior.


Impreza STi Stock exhaust:

67.3 dBA at 750 RPM
70.0 dBA at 1,000 RPM
75.5 dBA at 1,250 RPM
75.7 dBA at 3,000 RPM

Interior

48 dBA at 900 RPM

-------

Conditions were calm 68°F (20°C) low humidity. Here is how I placed the sound meter for each test:

Peaty
10-12-2003, 04:49 PM
Sound meter used:

Peaty
10-13-2003, 04:50 PM
FYI - Cobb has posted dyno results here:

http://www.wrxforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=000013;p=2

Peaty
06-25-2005, 09:10 AM
sound clip with downpipe w/ hi flo cat and catback:

http://www.peatpics.com/public/fileforyou/F-XT%20sound.zip

right click "save as"