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Making an exhaust pipe
by
jasonsansfleece
on 15 Jan, 2008 17:37
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So, There is no one anywhere near me who can mandrel bend a straight through exhaust pipe.
There are shops that use an exhaust pipe bender but that will slightly deform the pipe in the bends.
Couple of questions; To what extent would such deformation impair exhaust flow? This is a performance application. I've taken the trouble to match the ports although stock 1.6 port castings don't seem all that flow conducive.
If I were to take a pipe bender like this,
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=35336and fill the pipe with sand and cap the ends what sort of bend could I expect?
Any better or worse than the muffler shop? I like the idea of doing it my self.
I'm aware I could buy mandrel bent bends and weld the pipe up but that is way beyond my welding capability.
Anyway, any input appreciated,
Guy
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#1
by
Op-Ivy
on 15 Jan, 2008 19:57
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You could always just clamp the exhaust? I know many people that clamp their exhaust system together instead of welding.
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#2
by
BlackTieTD
on 16 Jan, 2008 12:12
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the 'ribs' in the corners of your standard muffler shop exhaust will restrict flow at those spots, as well as cause the airflow to be more turbulant. i don't think anyone is going to have exact numbers on that for you but in general, for performance use mandrel.
many have speculated as to how much you could improve a cheap pipe bender like that by filling the tubes with sand. i imagine that in order to have any effect, you'd have to have some very secure (welded or threaded?) end caps. haven't looked into it much but i'm sure a bunch of us would be interested in what you come up with if you try this out. let us know.
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#3
by
jimfoo
on 16 Jan, 2008 12:21
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So, There is no one anywhere near me who can mandrel bend a straight through exhaust pipe.
There are shops that use an exhaust pipe bender but that will slightly deform the pipe in the bends.
Couple of questions; To what extent would such deformation impair exhaust flow? This is a performance application. I've taken the trouble to match the ports although stock 1.6 port castings don't seem all that flow conducive.
If I were to take a pipe bender like this,
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=35336
and fill the pipe with sand and cap the ends what sort of bend could I expect?
Any better or worse than the muffler shop? I like the idea of doing it my self.
I'm aware I could buy mandrel bent bends and weld the pipe up but that is way beyond my welding capability.
Anyway, any input appreciated,
Guy
If the pipe is a tight fit, you can get good bends, but if it is a little loose in the shoe it will start to collapse.
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#4
by
saurkraut
on 16 Jan, 2008 12:52
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Don't give up on welding. Oxacetalene is easy. The 2.5" exhauste under my car is mandrel bends from NAPA and the welding rod is dry cleaner coat hangers.
I prefere the ones with the gold flux.
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#5
by
jasonsansfleece
on 16 Jan, 2008 19:29
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Saurkraut, I'm going to have to take my jacket to the dry cleaners :wink:
I like Op-Ivy's idea. Use an expanding tool and slide the pipe over the bends and clamp. Not as elegant as weld but I am not a welder.
If I had access to the bender in question rather than having to buy it and could test the fit of the shoe it might be worth a try.
But the more I think about it the clamp option wins. Expand the pipe, a little muffler assembly compound for fitment lubrication and final sealing, then adjust all the joints rotationally and longitudinally and clamp!
Thanks for the replies,
Guy
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#6
by
subsonic
on 16 Jan, 2008 19:57
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Libbybapa just used a homemade clamp tool that used a vise grip of some sort. One of the other members hooked him up with the details. Appeared to all be done with hand tools. Looked good. You may want to ask him about it.
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#7
by
TedV
on 16 Jan, 2008 20:52
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the sand bending I've seen has been by cap one end of a pipe, fill with DRY sand, then cap the other end with a small hole in the cap. Then using a torch, heat the metal cherry red, but don't melt it. The small hole is to let the heated, expanding vapor out of the pipe. Other wise you have something that resembles a pipe bomb with any moisture in the sand.
kind of a blacksmith art tho, have plenty of pipe and gas handy to practice with.
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#8
by
Dr. Diesel
on 18 Jan, 2008 19:26
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sounds to me like a trip to
www.techtonicstuning.com might be in order. They've got terrific, reasonably priced exhaust systems. All mandrel bent, of course.
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#9
by
935racer
on 27 Jan, 2008 10:57
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Honestly damn near any fab shop can make you a good mandrel bent exhaust using "U- bends". Finding a shop with an actual mandrel bender would be quite difficult depending on your location.
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#10
by
Dr. Diesel
on 27 Jan, 2008 12:02
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I've had awful luck finding anyone locally (except QuickTD) who is willing and/or able to do anything with any degree of quality. Up until recently The only two things I didn't do myself were exhaust and deep transmission internals.
Since my gasser rabbit project, and my diesel syncro project, I can tick exhaust off that list. My daily passat has a bearing noise in the tranny, so soon I'll have to pop that last cherry.
Here's some pics of the syncro downpipe
you can find the downpipe pics on the gas rabbit here:
http://www.cardomain.com/ride/2639240
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#11
by
rallydiesel
on 30 Jan, 2008 17:24
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Looks like he only had certain pre-made angles of pipe and had to piece them together.
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#12
by
Dr. Diesel
on 31 Jan, 2008 06:12
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yeah, those are all angles made from a section of 2.5" madrel U-bend. Cut the angle you need, and weld it on, step by step.
I'm working with a basic mig welder, unfortunately.
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#13
by
Baselyne
on 02 Apr, 2008 11:28
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oh man, this thread is so interesting, I will be giving you a call soon dr.diesel
your doing good work and I think you should be proud
even with the mig...your ballin
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#14
by
Op-Ivy
on 02 Apr, 2008 21:42
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Here's some pics of the syncro downpipe
Well done!