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Old 12-21-2012, 12:52 PM   #1
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Default What Size Exhaust Tubing for how much boost? (1.8)

I'm not sure if I can't find it our theres not sticky post?

Is there like a common knowledge for a certain amount of boost/hp for a certain size exhaust. Like Oh a slapon greddy kit is fine with 2.5".

A begi pushing doubled that HP needs 3".. etc..
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Old 12-21-2012, 12:54 PM   #2
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3" or greater
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Old 12-21-2012, 01:01 PM   #3
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3" with large free flow muffler- non turbo.

3" with large free flow muffler- low boost turbo/super charger 5-10lbs

3" with large free flow muffler- higher boost levels 12-xxlbs

These are rules to live by.

Last edited by Braineack; 12-21-2012 at 01:20 PM.
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Old 12-21-2012, 01:07 PM   #4
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With a turbo do not go less than 3" from the turbo straight to the back of the car if at all possible. Anything less is a compromise in spool and power.
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Old 12-21-2012, 01:13 PM   #5
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Just go 8"

Can't go wrong with 8"
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Old 12-21-2012, 01:16 PM   #6
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Old 12-21-2012, 01:20 PM   #7
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Miater, i had to fix your flawed post.
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Old 12-21-2012, 01:35 PM   #8
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lololol
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Old 12-21-2012, 01:41 PM   #9
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Quote:
Originally Posted by 18psi View Post
Just go 8"

Can't go wrong with 8"
Does Fae really believe your 3" is 8"?
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Old 12-21-2012, 01:50 PM   #10
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bullshit.


my BEGI 2.25" to 2.5" DP, to 2.25" cat, to 2.25" borla exhaust

to the same Begi 2.25" to 2.5" DP, 3" cat, and 3" catback:



same dyno. same boost*.



*was getting creep, so i lifted.
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Old 12-21-2012, 01:51 PM   #11
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Oh now you've gone and done it: Brain will school you
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Old 12-21-2012, 01:53 PM   #12
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ah, to be fair he does say he's running less boost.
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Old 12-21-2012, 02:21 PM   #13
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I know I'm in the minority here but does the exhaust size recommendation stay the same for supercharger applications as well or is there something different? Thanks.
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Old 12-21-2012, 02:26 PM   #14
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bigger is always better.

just sound like absolute **** on a SC.
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Old 12-21-2012, 02:46 PM   #15
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The only reason to not do a 3" exhaust on a turbo car is because you can't afford it AND you're too lazy to build one yourself.

N/A cars should get 2.25" straight-through systems.
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Old 12-21-2012, 03:03 PM   #16
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Quote:
Originally Posted by Braineack View Post
bullshit.
Lol, don't hate at me bro! Its not my data and its the only comparison I could quickly find.

Your results are obviously better. I believe Curly has something similar going from his Frankenstein exhaust to a 3" ARTech? Couldn't find it quickly.

Quote:
Originally Posted by comradefks View Post
I know I'm in the minority here but does the exhaust size recommendation stay the same for supercharger applications as well or is there something different? Thanks.
Ironically, I'm using Cordus old catted 2.5" FM turbo exhaust on my NB with the Rotrex and an BP6D exhaust manifold and factory downpipe. It's less than ideal, but it works for now. I will eventually be replacing manifold with a RB unit and the muffler with a 2.5" Magnaflow 5x11x22 because the ancient FM muffler has definitely seen better days. It's actually significantly quieter than expected, but it rasps on throttle stomps.
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Old 12-21-2012, 04:04 PM   #17
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Quote:
Originally Posted by comradefks View Post
I know I'm in the minority here but does the exhaust size recommendation stay the same for supercharger applications as well or is there something different? Thanks.
Turbo cars are much more sensitive to the exhaust size because the turbine acts as a backpressure multiplier.

The considerations for a SC car are different and more like doing the exhaust for an NA car (taking into consideration some additional flow). Things like sizing the pipe diameter and length to promote scavenging become important. Bottom line, on an SC car run a good header and an exhaust system matched to the header. That will likely be smaller than a 3".
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Old 12-21-2012, 04:15 PM   #18
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Quote:
Originally Posted by hornetball View Post
Turbo cars are much more sensitive to the exhaust size because the turbine acts as a backpressure multiplier.

The considerations for a SC car are different and more like doing the exhaust for an NA car (taking into consideration some additional flow). Things like sizing the pipe diameter and length to promote scavenging become important. Bottom line, on an SC car run a good header and an exhaust system matched to the header. That will likely be smaller than a 3".
^^ This. Everything I've read backs this up. The only person with an SC setup that I've seen that is running anything bigger is TrackDayHooky. At one point he was running one of the discontinued 949Racing 2.75" exhausts on a 400+HP C38 Rotrex build. No clue what that car has on it now.

Ok, back to the trubo stuff. Who has more apples to apples comparison data for exhaust upgrades?
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Old 12-21-2012, 04:23 PM   #19
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curly posted a dyno log thing not too long ago.
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Old 12-21-2012, 04:32 PM   #20
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For turbo exhaust you want a Choad

Short as possible and wide as possible.

My 4" isnt that loud. Very deep though. ***** deep
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