Do Bends Effect Power.. - Page 2 - Yamaha R6 Forum: YZF-R6 Forums
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post #11 of 41 (permalink) Old 02-06-2006, 01:01 PM
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Originally Posted by Agent4573
It's called head loss. Yes it effects the flow by increasing the pressure in the system needed to push the exhaust out at a certain speed, but because of the relatively low reynolds number of your exhaust gas flow, mandral bent tubing probably won't effect power output to a noticable amount. So your both right.
and I thought III brought it back from the dead..
the topic wasn't how much it affects it, it was whether it affects it at all.. and it does.
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post #12 of 41 (permalink) Old 06-07-2007, 07:20 PM
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Re: Do Bends Effect Power..

Originally Posted by imbobdole
I can't help but partially disagree with the above statement, although it is a little old. First off, I'm relatively new to motorcycles but not even close to new with engines. The analogy to the hose shooting out water isn't the best for a couple reasons:
1-If you really want to use water as a comparison, then time it from when you turn the hose on with it empty until your jug is full with both, you'll notice that it in fact does take longer for the water to reach the end of the hose. The fact is, when you have the hose on full blast with a constant pressure, a constant amount of water will be exiting regardless; water cannot expand nor compress such as gases can. Once the pressure is established it will flow out of the hose at a constant rate as long as the loops in the pipe do not effect the diameter of it, so that much is correct. The fact is, with an exhaust system you do not have a constant flow; you have individual cylinders firing, meaning that, despite that they're firing VERY rapidly and may seem like it's a constant flow, it is not. Not to mention that gases do not flow like liquids anyway. Water and exhaust flow are like comparing apples and oranges.

2-Even when bends do not affect pipe radius, they still CAN cause a performance issue, albeit a small one in this case. But since we're talking technical terms, they do affect the performance. With a completely straight pipe, the exhaust is being shot out and, in a perfect world, is not hitting anything at all. (Read:no restrictions) The fact of the matter is that when you have a bend in the pipe, it is hitting the wall at an oblique angle. When the exhaust hits that wall, it causes a restriction, and herego a detraction from overall performance.

All in all, the short answer actually is YES. The bends can case a detraction in performance, although it may actually be a small one. I'm not just blowing smoke here; I'm a Physics major. I personally have performed experiments similar to this and found results accordingly. Sorry for the lengthy response, but I can't think of another way to say it in lesser words. Happy holidays to everyone
My buddy is an auto mechanic and the hose is def a bad example. Exhaust flows in a spiral, bends are bad because it disturbs the the flow, but it really doesnt make a huge difference.
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post #13 of 41 (permalink) Old 06-07-2007, 07:43 PM
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Re: Do Bends Effect Power..

Originally Posted by imbobdole
I can't help but partially disagree with the above statement.....
I work with Nuclear steam generators & have a very good understanding of how gases/vapours flow and am 100% in agreement with bobdole.

We put bends/radius in steam piping to slow down flow.

But I think you would probably have a hard time measuring the power loss in a straight pipe vs. a pipe with bends, provided they are of the same length and volume, assuming no ovality occures during the bending process.

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post #14 of 41 (permalink) Old 04-07-2008, 01:13 AM
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Re: Do Bends Effect Power..

anyone wanna explain on another exhaust tpoic of flow etc regarding taper in the pipework? I'd think that would have more effect on performance than bends done correctly???
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post #15 of 41 (permalink) Old 04-21-2008, 05:59 PM
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Re: Do Bends Effect Power..

I heard the less bends the better,( according to street tunner, hot rod mags.
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post #16 of 41 (permalink) Old 05-22-2008, 12:20 PM
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Re: Do Bends Effect Power..

I heard that if you mix your fuel with lighter fluid and worcestershire sauce and bend your pipes conversly to x=y*x^Z/c+EMc^2 that you will gain maximum bhp or cause the universe to implode, i forget which one though.
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post #17 of 41 (permalink) Old 05-22-2008, 01:16 PM
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Re: Do Bends Effect Power..

Originally Posted by Wolf View Post
Try this test at home. Take a hose pipe and turn on the tap a set amount - say one turn. Time it a few seconds with the pipe dead straight and see how much water ends up in a measuring jug. Then gently loop the pipe, even in a complete circle and do the same again. If you are accurate you will ene dup with exactly the same amount of water each time. Exhaust gas is just the same...
Wait so a highly compressible gas is the same as a liquid, which is incompressible?

You need to take a basic fluid mechanics course.
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post #18 of 41 (permalink) Old 05-24-2008, 08:54 PM
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Re: Do Bends Effect Power..

We all ride Yamaha's, right?

Anyone care to do a history lesson on what got this company started?

The TUNING FORKS have a lot to do with Saxophones, and Saxophones share a bit in common with exhaust. That horn ain't straight.

My point? Bends can be good... Its not all about getting rid of the most all at once... its about tuning, and not just for sound... Yammie does this on purpose, guys.. great power at peak does NOT equal good racing. SMOOTH power does, and bends can help that (if done right). Physics of fluid/gas/sound movement do not explain this alone. This needs to be coupled with the characteristics of your motor (which can be changed with INTAKE, another bendy pipe.)

No Black/White answer here, I'm afraid... it's a bike by bike thing depending on your choices of what you change.

Godspeed Peter Lenz, Godspeed Super Sic. You will both be missed.
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post #19 of 41 (permalink) Old 07-08-2008, 08:53 PM
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Re: Do Bends Effect Power..

it is a simple answer as long as the bends radius does not change.
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post #20 of 41 (permalink) Old 09-04-2008, 06:35 PM
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Re: Do Bends Effect Power..

IMBOBDOLE...excellent, simple answer using the laws of physics
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