I asked a similar question about a graph that was posted in the HP thread last night...

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...He said Smooth Bee the skins is fat
I don't beg cause I'm not in begonia
I dress warm so that I won't catch pneumonia
My rhymes are stronger than ammonia
I'm a diamond, you're a cubic zirconia

I'm sorry but you can't break the laws of thermodynamics just because you own a wrx

You are just increasing the back pressure by going to 2.5" and an engine obviously likes a certain balanced amount of this.

You can't?

Aww crap... Time to stop work on this perpetual motion machine...

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[COLOR="Gray"]550Nm off a 2L... Just wish it was in the dak dak...[/COLOR]

Regarding backpressure (when using a cat), see:

http://www.airpowersystems.com.au/us...wrx-hoe-r2.htm

There is no difference in backpressure noted between a 2.5" (R2) and 3" (R1) diff-back system, up to 525HP. Granted, this is just testing the APS system, and assumes that they used a thorough and accurate methodology for logging that data.

And no, I am not on commission from Michael South

datalog exhaust manifold pressure.

using a varex muffler, i can definately confirm that you WILL loose efficency as soon as you begin restricting anything below 3".

and yes, i have the data and results.

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Long live the WRC

compared to Michael South ?

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Speak to Shane @ SMC Tyres, Unit 6/385 Sevenoaks St Beckenham WA 6107. Mobile 0413 128 087. Tell him Maddog sent you!

michael south knows a lot about wrx's
especially ones with a 32mm restrictor

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MY93 Impreza GX 1.8L, 0hp, 0nm

At the end of the day, all this proves is that for a given application there are better alternatives. Its way to hard to just genericly place everything in one basket and say "yo this be teh shiznit!"

Pick your application do your own research and go for gold.

IF things were so easy, there would be no need to keep engineering engines and finding better ways to do things.

i reckon at the end of the day, prettymuch anything is better than the restrictive stock exhaust. except maybe a 6" exhaust on a td04

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MY93 Impreza GX 1.8L, 0hp, 0nm

Isn't it 34mm?

Stace, is using the Varex muffler able to reproduce the results of changing pipe size accurately? Isn't it just a butterfly valve?

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John Stamos fan club lifetime member