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Old 04-18-2002, 04:50 PM   #1
PatTheRat
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Member#: 12975
Join Date: Dec 2001
Location: Ottawa, Ontario CA
Vehicle:
2002 Impreza 2.5RS
Silver Metallic

Default Exhaust system questions

Hey guys,

Any suggestions here would be appreciated. I am sort of a newbie to intermediate here, so bear with me.

I am looking to add a little more HP to my stock RS. So far I have added an SPT performance exhaust (I know it doesn't really add any appreciable performance gains all by itself). I am going to be adding a CAI in the next couple of weeks. My question is this, what could I add to the exhaust system now to make some difference. I was thinking a mid-pipe in addition to the exhaust from SPT might give me some benefit in unison with the CAI. A header upgrade is basically out of my league pricewise, I wouldn't mind turning what I have now into a cat back system. Do you think I can make any gains with the SPT in the system?

Any thoughts?

Thanks for your help and patience, if I have put my foot in my mouth anywhere up there.
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Old 04-18-2002, 06:39 PM   #2
Keiho
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Graphite Gray Pearl

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Midpipe would help yes.

Not sure what muffler you have (SPT), but I'm guessing that it isn't the most free flowing muffler out there.

But to answer your question, yes a midpipe will help things out.
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Old 04-19-2002, 02:40 PM   #3
PatTheRat
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Silver Metallic

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Bump

Any more thoughts or suggestions?
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Old 04-19-2002, 05:15 PM   #4
Reciprocity
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The stock midpipe does have a resonator in it...which is a mild restriction to airflow...so putting on a new midpipe without a resonator will give you a bit more power. Plus it will make the car a bit louder...if you want that.

How much more power? I have no clue...sorry.

But if you want to take it a couple steps further you can have your exhaust system heat treated...coated with some material to keep the heat INSIDE the exhaust, which will promote better flow. There are a couple options...

1) Painted on coating: Some sort of ceramic type coating will work. It can be expensive...and unless you are going to be keeping those stock exhaust pipes on the car I wouldn't suggest it...due to cost.

2) Wrap: You can wrap the exhaust in a heat retention material...there are wraps out there. Problem with this is that if the exhaust is a mild steel...you could trap water against the exhaust and cause it to rust. I wouldn't suggest this if you live in a wet or snowy environment.

However...

There really isn't too much that can be gained from the exhaust. Think of it as 4 different pieces

Header: Can be replaced with something with a better flowing design, can be heat treated, probably the most expensive part of the exhaust system. There can be smog issues.

Cat: Can be replaced with a high flow model. CARB does not like people replacing them though...so this is where you could run into the biggest trouble with the smog police.

Midpipe: One of the cheapest parts. Can be heat treated. Unless you are dealing with a smog Nazi you shouldn't have trouble with an aftermarket one.

Exhaust (Can): Many many many options. Which one gives the most HP? There isn't going to be a huge difference here...honestly. For the can it's all about looks and sound.

A full replacement system (one that replaces all 4 pieces) will give you the biggest difference. Brullen and MRT are two complete systems...which can also be purchased in parts. Both will give you somewhere around...mmm...trying to remember...around 14 hp more. A mix and match system could get the same results...but possibly less.

I think that's about it...

NC
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Old 04-19-2002, 06:12 PM   #5
PatTheRat
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Location: Ottawa, Ontario CA
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2002 Impreza 2.5RS
Silver Metallic

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Very informative! Thanks very much.
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