Exhaust bend quality




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  1. #1
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    Default Exhaust bend quality

    Hello everyone

    I asked a local exhaust shop to bend a section of pipe for me over the weekend. When I collected the pipe today I was not happy with the quality of the bends.

    The salesman stated that the two kinks present at each bend (see attached photo) is normal for 63mm exhaust bends.

    Now I accept that pipe will narrow down around the bend when a normal bending brake is used. But I suspect the kinks is due to improper dies being used.

    Am I being a rude and difficult customer or was the wrong dies used?
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  2. #2
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    Default Re: Exhaust bend quality

    What is the wall thickness? Kinked because the walls are too thin for the bend diameter?

  3. #3
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    Default Re: Exhaust bend quality

    I think its an out of sight out of mind functional is accepted thing.I think with the thin pipe and being a hydraulically bent pipe from the center you will always get kinking,maybe not as bad as that. If you need better bends I suppose you could find a shop that uses thicker wall pipe and a mandrel bender.But your vehicle will still drive the same

  4. #4
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    Default Re: Exhaust bend quality

    I'd say that's fairly typical of a hydraulic type bend on commercial grade tubing. The deformations are symmetrical. As stated, increasing wall thickness or increasing the bend radius will provide a better bend. There's not much that the operator can control with this type of bending. The die sizes used look like the correct size from the outer indentations. If the dies were narrower, you'd see the sides being pressed in and if the dies were wider, you'd have a flatter inner profile.

    Ideally you want to pull the tube with the die over an internal mandrel that will help stretch the outer wall. Tube quality also plays a part. You need to go to a proper tube bender for a better quality bend, but know that the cost of doing a single bend is a lot higher.

  5. #5
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    Default Re: Exhaust bend quality

    I am no expert but had pipes bent on a bending brake that did not have similar kinks.
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  6. #6
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    Default Re: Exhaust bend quality

    Quote Originally Posted by plunger View Post
    I think its an out of sight out of mind functional is accepted thing.I think with the thin pipe and being a hydraulically bent pipe from the center you will always get kinking,maybe not as bad as that. If you need better bends I suppose you could find a shop that uses thicker wall pipe and a mandrel bender.But your vehicle will still drive the same
    If these bends are for an exhaust, they will cost more horsepower than a standard factory exhaust. The flow of gasses will be very disturbed with bends like that. The cross sectional area of the pipe shouldn't change through out the bend. Any exhaust builder worth his salt should know this.
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  7. #7
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    Default Re: Exhaust bend quality

    Nothing beats a mandrel bend. My 76mm downpipe.
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  8. #8
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    Default Re: Exhaust bend quality

    What's a mandrel bend vs hydraulic bend?

  9. #9
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    Default Re: Exhaust bend quality

    Both can be hydraulic but a mandrel bender has much tighter fitting dies. Some mandrel benders are hand turned depending on the size of pipe.
    It has a mandrel normally looks like a bullet or series of balls connected to each other. This holds the shape of the tube to put it simply. But it also has a wiper die and are expensive to make.

    Very late now but from memory you can turn to 3D of your pipe size so it can turn a much sharper radius without the pipe or tube collapsing.

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  11. #10
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    Default Re: Exhaust bend quality

    Yes, that would look much better if it was a mandrel bend.
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    Default Re: Exhaust bend quality

    This is what a mandrel & mandrel bends look like:
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  13. #12
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    Default Re: Exhaust bend quality

    Yup the bend look sort of normal for a exhaust shop bender The folds can be caused by either too thin or even by too thick pipe sidewall.
    If you are very finicky then yes find mandrel bends and cut and weld them. There is also the very expensive option of diary stainless bends - look fantastic but costs a fortune. These guys supply those.
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  14. #13
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    Default Re: Exhaust bend quality

    I got my Mandrel bends at a guy who was making a 3" roll cage, then found 2.4mm was too thin, and he was about to dump them. Got myself 4x90 and a 45. Slightly thick for the exhaust, but welds damn easy with a stick welder. Then I just picked up the best 3" 1.2mm length at the reject supply in Randfontien for R150. Exhaust done for a bargain till I had to put that stainless tripple braided flex piece in, that cost me 900.

    Maybe go check out the truck scrap yards and rescue some old exhausts. Some of them are as small as 60mm if you dont want to go too big.
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