3"?? 2.75"?? is there a diff?? - Subaru WRX Forum
 
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#1 Old 10-02-2004, 11:27 AM
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3"?? 2.75"?? is there a diff??

I just want to clarify something coz I'm in a dilema on which to get...
I am considering a fujitsubo RM-01 exhaust and a tanabe hyper medalion exhaust..
The fujitsubo is 3" in diameter while the tanabe is 2.75"...
Tanabe says that 2.75" is just right to get the best performance but it seems that every other exhaust on the market, including fujitsubo, is utilizing 3"...
Does Tanabe know something that the other companies don't or does the .25" really make a difference???
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#2 Old 10-02-2004, 11:23 PM
 
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Doesn't really make a difference.
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#3 Old 10-03-2004, 09:37 AM
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I agree with playa. But I would go with the wider cross-section.

"I hear Buschur Racing does WRX UTECs now ... oh buddy!"
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#4 Old 10-03-2004, 11:53 PM
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2.75" - 23.76 sq. in.
3" - 28.27 sq. in.

I don't know much about fluid dynamics so I can't tell you how much a difference in flow that makes... but it's a 16% difference in area going from the 3" to the 2.75".

I'd go with the 3 inch. As far as I know, more flow = better.
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#5 Old 10-04-2004, 01:15 AM
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Exclamation excellent point

Quote:
Originally Posted by Chris
2.75" - 23.76 sq. in.
3" - 28.27 sq. in.
As far as I know, more flow = better.

Flow rate depends on both fluid velocity and the cross sectional area. Since back pressure in an exhaust is a bad thing (why we remove cats), and back pressure is indirectly proportional to the forwrd flow of exhaust gas ... it follows that a large cross sectional area, as Chris points out, will give you better flow characteristics (rate).
I can't believe i didnt think of that. This is why you have to look at an exhaust's cross sectional area and not just the "small" difference in the diameter of the piping.


:eek:

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#6 Old 10-04-2004, 07:21 AM
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With a turbo, bigger is always better.
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#7 Old 10-05-2004, 02:09 AM
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Quote:
Originally Posted by Cosmo
With a turbo, bigger is always better.
and that about sums it up.

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