Mandrel bends
12-08-2005, 01:08 PM
#11
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Originally Posted by BigKID
It really depends on the size of the pipe, your flow requirements and the angle of the bend in question. Anything under 45* I would say crush/crimp bends will be fine as long as the pipe diameter is 2.5" for dual or 3" for single. If you have a 90* bend in your system, especially if it is a 2.5" or smaller, the flow is going to be severly hampered by a crush where a crimp wouldn't be as bad. The thing about a mandral bend is that no matter what the degree of the bend is, the pipe diameter stays uniform. On a crimp bend, the higher the degree of the bend, the more the pipe is ovaled or flattened. With a crimp bend the diameter is reduced as well as creating an unsmooth surface on the inner wall of the bend creating more turbulance in that area. If you exhaust guy is good, he should be able to fabricate you a good flowing exhaust with a series of shallow crush bends instead of a few deep (>45*) bends. If you look at my exhaust, I only have one 90* bend (over the axle). The rest are 45's eventhough they are mandral. If they weren't, I would have had it fabricated with a series of more shallow bends.
I ran a single 3". Actually took the pics of yours and told him "I want it to look like this" (hope you dont mind
) I think to go over the axle he make at least three bends though. I guess to keep them at shallower angles. Its not bad at any point, I was just wondering how much gain you really get with teh mandrel bends. I know it looks a lot better, just wondering if there was a REAL performance gain, or if its just more of a "everyone says its way better, so it must be" I work in th epetro chem industry and deal with flows on a daily basis, and can see where your velocity may be reduced a little from the restriction, but I couldnt really see where I would be choking it down. One thing about flow is that anytime you have a reduction in the flow (decreasing flow area) you will have a change in your velocity, OR pressure. If the pressure stays the same, your velocity will go up, and the opposite.
So I figured with the flow area being reduced, the pressure would increase just a hair, but didnt think it would e enough to worry about.Now when Im running lowwwwwwwww 10's ..............................
12-08-2005, 07:10 PM
#12
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I ran 2.5" non mandrel bent duals all the way to the rear of my old Formula, and still put down 395 rwhp with stock heads. Mandrel bends may have given me a couple more, but I doubt it would have been much at all.
12-09-2005, 10:16 AM
#13
A mandrel bend exhaust definately flow a lot better. However, the mandrel bends(IMO)makes the exhaust look complete. For instance, when I look at a exhaust, I want to see the bends not push in but rather a smooth conformed bend that matches the detail that you put into the paint, engine, or whatever of the truck. A nice exhaust really stands out in my opinion. Just my .02 guys.
12-09-2005, 11:51 AM
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I always assemble exhaust from mandrel bends. It just works as good as it can be that way. If you can't get that done... I'd definitely suggest running 3 inch pipes with regular bends where you would have gotten away with 2.5's mandrel bent.
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