GavinJ
Club Retro Rides Member
MGB 3.9 v8 Sebring
Posts: 927 
Club RR Member Number: 209
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Situation is 3.9 MGB v8 conversion running a very low ride height - exhaust needed with maximum clearance and time to fab one up? Question how much of a negative affect would rectangular pipe have on air flow?  My dad has a plentiful supply and I was thinking I could fab something up running very close to the body.... Opinions.... Oh and just for the hell of it.....  |
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Last Edit: Feb 9, 2011 18:30:29 GMT by GavinJ
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don't know what the effect would be to be honest. Used to own a MK3 astra 2.0 that had a square tail pipe and it sounded rude
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naffa
Part of things
Kingfisher Blue on 18"s
Posts: 364
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I don't have any science for this but I would think theres a very good reason why exhausts are still made from tube and not box section.
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Cheers Nathan  |
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it's cheaper to bend round pipe in long lengths, than it is to bend square tubing, without it collapsing and making a smaller internal diameter
Only thing you'd have to worry about really, is that rather than any internal rust evenly coating the inside, it may possibly collect more in the corners. That, and you can't stick it in a pipe bender, you'd have to cut and weld EVERY angle
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You're like a crazy backyard genius! |
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hodaz
Part of things
I wear this hat so they think I am one
Posts: 178
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If my Civil Engineering degree has tought me anything you just need to make sure that the diameter is the same. IE 1" square tube and a 1" pipe have the same hydraulic diameter, since the turbulence gets "trapped" in the corners of the square. So would it actually save any space since the areas that aren't round don't actually get used? Stuff flows better through circles for turbulent flow, which is why exhausts and pipes and stuff are circular.
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Last Edit: Feb 9, 2011 21:18:06 GMT by hodaz
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If my Civil Engineering degree has tought me anything you just need to make sure that the diameter is the same. IE 1" square tube and a 1" pipe have the same hydraulic diameter, since the turbulence gets "trapped" in the corners of the square. So would it actually save any space since the areas that aren't round don't actually get used? Stuff flows better through circles for turbulent flow, which is why exhausts and pipes and stuff are circular. So would a 2" * 0.5" rectangular section flow the same? |
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" East bound and down, loaded up and truckin' "
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hodaz
Part of things
I wear this hat so they think I am one
Posts: 178
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No much worse. The rough formula for hydraulic diamter is DH= (4A)/P Where A is area and P is wetted perimeter.
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box section cant be all that bad the exhaust ports on etype jags are square and the pipes from the boxes are squashed so they don't scrape
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Copey
Posted a lot
Posts: 2,845
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just look as nascar boom tubes! they must flow pretty well, lol
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1990 Ford Sierra Sapphire GLSi with 2.0 Zetec
1985 Ford Capri 3.0 (was a 2.0 Laser originally)
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