i was reading the exhaust guide sticky, great info by the way, it was very informative. anyways, i have been thinking about the options available when routing the system and all the bends required. i know that in any air system where flow is the goal, bends are restrictions, i have heard that for every 90 degrees there is 1-2psi of restriction, bends of course are inevitable.

here is my thought, i have seen on the intake side, both n/a and forced induction, where the designers open the pipe on the bends. i think its called radiusing but i cant remember. basically what they do is open the diameter in the curve.
-------\ its rough i know but this would be a 90 degree bend
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its sloppy i know, but i think it illustrates my thought. i dont yet fully understand the theory, and i am pulling it form memory but i think the idea is that as the air enters the bigger area its velocity slows down and makes the turn easier, then speeds back up when the pipe narrows back up. i think too that it reduces the pressure against the walls are the pipe and low pressure areas after the turn, both of these reduce turbulance which kills the flow.

the way i see it, they do this on the intake side and it supposedly works, and air is air, so why wouldnt it work on the exhaust. what do you guys think?

apparently the computer takes all the spaces out when you post. it was supposed to show a 90 degree bend, and the second one was to show the opened area in the curve.

 

I understand your theory and im thinking if you dont have a high performance or forced induction that it will probably hurt back pressure in a n/a format...

that being said i too have wondered similiar things. if you look at the exhaust pipe on a 2stroke dirt bike you see how they flair in the middle like you say. i was told long ago that it created a vacuum to help pull the exhaust out and that it was only good on two strokes. but this may be an idea you look up.

RM

 

hurt back pressure how? reading the sticky on this forum i got the impression the no matter the setup that backpressure was bad. the goal of any and all exhaust systems was minimal backpressure.

it is sort of similar to the two strokes, those are expansion chambers, beyond that i dont really know much about them. what im thinking about is somewhat different. its only on the turns, probably only the tight ones (i imagine that say a 45 degree bend is probably not worth the effort). i might be going about it wrong, but my goal is not to create a vacuum, only to reduce or eliminate the pressure or probably more accuratly the pressure drop around bends.

picture a square 90* bend. the air almost literally stops, turns, and then moves forward. this creates a high pressure area at or in front of the turn, and turbulance on the inside of the bend in the low pressure area after the turn.

mandrel bends address this, the air stays together more and moves through the bend more smoothly. the larger the radius the better. air is lazy and does not like to turn, and centrifigual force pushes air to the outside. the air on the outside of the turn slows down due to friction and there is a low pressure area on the inside of the turn, which draws the air towards its creating turbulance, both of them hurt flow. im wondering if opening up the inside portion of the bend, would reduce that pressure and smooth flow out more increasing performance.

as im thinking about it, i actually think it would be increasing the radius of the outside of the pipe instead of tightening the radius of the inside, though maybe the effect is the same.

 

You have the right idea, but I really doubt that this will amount to any real world difference. Dyno? Maybe a few numbers.

thinking out of the box. I like it.

 

theory meets reality. i dont know how much would be gained, but i know from first hand experience a little bit can make a difference, especially when combined with other little things. i would love to see some real world tests on this theory.