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Old 11-02-2006, 03:42 PM   #21
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Originally Posted by bripab007 View Post
easier to route/fabricate 2.5" exhaust, more difficult to construct 2.75-3.0" exhaust
But not prohibitive? I know sometimes it's worthless to guess, but at ballpark 200whp is it just a stupid idea? (bragging rights:gay: )¿

Wideopentuning's post indicates that it's basically worth it at any level.
I plan to do 3" but my motivation is suspect. After screwing around so much with my entire build, I just want to do one thing right and not have to think about the "redesign." Feel me?

white90na, thanks for the writeup.


EDIT: Wideopen, I plan to cut the Megan D/P after the last bend, as it straightens to the back of the car, then weld a flange. My "catback" would start there with a 2.5 to 3.0 gradual cone expander and be 3" the rest of the way. Do you see any restriction in the first couple of feet or so of 2.5? I noticed your example used a 3"turboback to achieve those numbers.

I'm somewhat familiar with exhaust gasses cooling/expanding as they flow along the pipe. Hopefully I've answered my own question here.
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Old 11-02-2006, 03:51 PM   #22
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I guess I'm confused...is what prohibitive? Does the difficulty of routing the 3" exhaust make that option prohibitive? Certainly not; plenty of people have done it. You'd just have to be a better welder/fabricator than me

Since there's no performance reason to not go with the largest possible exhaust on the turbo car, and you have the time, money and skill, why not go the 3" route?
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Old 11-02-2006, 04:00 PM   #23
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BEGi makes their downpipes from 2.5" to 2.75" at the flange.
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Old 11-02-2006, 04:02 PM   #24
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Originally Posted by bripab007 View Post
I guess I'm confused...is what prohibitive? Does the difficulty of routing the 3" exhaust make that option prohibitive? Certainly not; plenty of people have done it. You'd just have to be a better welder/fabricator than me
Ah, my bad. Yes, that's what I was asking. It all sounds good until that end part! I have one semester of MIG under my belt, thanks for the confidence!

Quote:
Originally Posted by bripab007 View Post
Since there's no performance reason to not go with the largest possible exhaust on the turbo car, and you have the time, money and skill, why not go the 3" route?
Agreed my friend.
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Old 11-02-2006, 04:16 PM   #25
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BEGi makes their downpipes from 2.5" to 2.75" at the flange.
Ah, sweetness, I think it will work just fine (i just don't know until I'm under the car - as usual). I've also thought about running just a cat, no muffler. Think the noise suppression would be sufficient for my tastes.

Also, I forgot duh I have a 3" high-flow cat and a 3" Ultra-Flo (Dynomax I think) muffler from my other car, so testing is free.
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Old 11-02-2006, 04:55 PM   #26
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whatever. go 3". it works great on my SIX PSI <200 rwhp car!
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Old 11-02-2006, 05:23 PM   #27
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I have one semester of MIG under my belt, thanks for the confidence!
Trust me...if I can weld (well, sorta...), anyone can.
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Old 11-03-2006, 01:06 AM   #28
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U of A. Sounds like you have a decent plan. It can be tough on a Miata to get away with a 3" downpipe with a high mounted turbo.
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Old 11-03-2006, 01:11 AM   #29
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yeah, the welder cut into the chassis on mine. there's pics on my garage thing. It will not be a bottleneck till 600hp though!
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