Making an exhaust pipe

[jasonsansfleece]

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

[Op-Ivy]

You could always just clamp the exhaust? I know many people that clamp their exhaust system together instead of welding.

[BlackTieTD]

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.

[jimfoo]

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.

[saurkraut]

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.

[jasonsansfleece]

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

[subsonic]

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.

[TedV]

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.

[Dr. Diesel]

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.

[935racer]

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.

[Dr. Diesel]

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

[rallydiesel]

Looks like he only had certain pre-made angles of pipe and had to piece them together.

[Dr. Diesel]

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.

[Baselyne]

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

[Op-Ivy]

Here's some pics of the syncro downpipe

Well done!