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Old 11-19-2000, 09:11 AM   #1
Dazz
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Member#: 2312
Join Date: Sep 2000
Location: Montreal, Canada
Vehicle:
Red Impreza GC4 98
Silver Legacy BH6 2004

Cool exhaust modification info needed

Hi guys,

My 2.2 exhaust is stock and I'd like to modify it. I mean starting from de first cat to the end, I will remove the second cat, somebody have a suggestion for me, I don't want too much sound (I do Highway). I will probably put a Dynomax Ultraflo. I'd like to know what diameter I should use from the front to the end, for quietest ride, should I put a 18" glasspack or an afternarket resonator ???

Dazz
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Old 11-19-2000, 09:21 PM   #2
P.K. Motorsports
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Member#: 1110
Join Date: Mar 2000
Location: USA
Vehicle:
1999 RS
Silver

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I guess it's not illegal to remove the cats in Canada, eh? Well, if that were the case I'd first say this:

Go 2".

Your 2.2 will be overpiped with no second cat and 2.25". The RS can barely, IMO, support a true 2.25".

Rather than bumping up the stock pipe after the first cat, I would strongly consider welding on a 2" Y-pipe at the junction of the collectors and proceeding with a 2" aftermarket cat. They are not that expensive and that first cat will remain the bottleneck in your system if you don't do this.

After that you'll need a resonator. Without the first cat just putting a straight-through turbo muffler would be LOUD. It's OK to relocate the flex joint to just prior to the resonator. As for what kind of resonator, Magnaflows are 4" and a pretty snug fit. They're also overkill. A standard 14" long 3.5" diameter glasspack is plenty to quiet it down and cheaper. It won't last as long, but it is not difficult for a muffler guy to weld in a new one and that is years down the road. Also, if you dislike the exhaust you build it's good not to have too much invested in it.

Don't go to 2.25" at the midpipe. I did this and I think it results in a loss of gas velocity which is not helpful to performance.

Keep the pipe at 2" all the way to the muffler. If you must fit a 2.25" muffler try to delay the bump-up as long as possible.

Make sure the exhaust doesn't get constricted back to 1.75" after you go 2" at the flanges. This creates a chamber in the exhaust and can introduce peaks and troughs in the power delivery.

Good luck.
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Old 11-20-2000, 06:21 PM   #3
Dazz
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Join Date: Sep 2000
Location: Montreal, Canada
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Red Impreza GC4 98
Silver Legacy BH6 2004

Wink

Thanks PK, I appreciated your help. For the cat, your right, i'm not supposed removing it, but who care !!! You have a suggestion for the aftermarfet cat ? Everything ellse will do the job ?

Take care

Dazz

[This message has been edited by Dazz (edited November 20, 2000).]
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Old 11-20-2000, 10:12 PM   #4
P.K. Motorsports
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Silver

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If it's indeed illegal you may have a tough time convincing an exhaust guy to remove a factory cat.

If you can, I don't know too much about what kind of cat to get simply because removing stock cats and replacing with an aftermarket version is rarely done in California due to the laws and smog certification worries. I know Random Technologies makes high-flow cats, but you should investigate a little further.

The first step is to take off all the exhaust shielding. It will save time at the shop and it probably won't fit after the modifications anyway. Find a shop which sells the Dynomax (it that's what you want, they are noisy bastards). Talk with the guy about what you want, write it all down and stick to it. If the guy tries to start telling you that x and y is a dumb idea and you should appreciate the hard work Subaru has done in designing this exhaust, pick another shop. Then get it up on the lift and start at the Y-junction.

Good luck. Keep us posted.
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Old 11-21-2000, 06:01 PM   #5
Dazz
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Red Impreza GC4 98
Silver Legacy BH6 2004

Talking

Thanks again Dude...

Dazz
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Old 11-21-2000, 06:09 PM   #6
Tim Prudence
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Catco makes good, high-flow cats for about 1/6 the price of Random tech.
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Old 11-21-2000, 06:23 PM   #7
Fred Zaplitny
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I have the Borla cat-back, which is really made for the 2.2L. It says so right in the paperwork. It's 2" piping and very loud!
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Old 11-23-2000, 05:30 AM   #8
Dazz
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Location: Montreal, Canada
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Silver Legacy BH6 2004

Cool

You told me that the dynomax ultraflo is a noisy bastard! Somebody have another suggestion for the same price ?

Dazz
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