tubing bender

seattle##gs · Oct 24, 2017

who can bend some 1 3/8" tubing for exhaust without making a mess of it? I need 180 degrees in a very tight bend...tighter than the stock P11 high pipes.

RoadScholar · Oct 25, 2017

Virtually all your local muffler (silencer) shops have mandrel benders, some have at least one person that knows what they are doing. If you pay for results, rather then learning curve, you'll get what you want.

baz · Oct 25, 2017

Yep use a shop that has a mandrel bender,or for really tight bends use welding elbows and use a polyromy or similar to clean the welding up

Dances with Shrapnel · Oct 25, 2017

seattle##gs said:
who can bend some 1 3/8" tubing for exhaust without making a mess of it? I need 180 degrees in a very tight bend...tighter than the stock P11 high pipes.

You can try packing the pipe with sand first prior to running it through a piping bender. Without sand, muffler shop benders will likely yield a wrinkled inner radius. Not sure if a muffler shop bender can get you the radius you are looking for.

Nater_Potater · Oct 25, 2017

For the lazy-at-heart; https://www.summitracing.com/search...tOrder=Ascending&keyword=mandrel exhaust pipe in both mild steel and stainless. You won't find a muffler shop that'll even think of warming up the tubing bender for those prices.

Nathan

baz · Oct 25, 2017

Dances with Shrapnel said:
You can try packing the pipe with sand first prior to running it through a piping bender. Without sand, muffler shop benders will likely yield a wrinkled inner radius. Not sure if a muffler shop bender can get you the radius you are looking for.

no sand needed with a mandrel bender and no wrinkles either

grandpaul · Oct 25, 2017

Just add fire! Fire makes everything better.

Dances with Shrapnel · Oct 25, 2017

baz said:
no sand needed with a mandrel bender and no wrinkles either

That's true if you are really dealing true mandrel tubing bender. Most muffler shops only have plain tubing benders which will wrinkle a tight inside radius. I had it done before as an experiment and wrinkles was what I got. Others results may vary.

As others have pointed out, the way forward for one-offs is to purchase the bent tubes; cut and weld together.

seattle##gs · Oct 25, 2017

I ordered from Summit. I hope it's as good as the picture and the price is very reasonable. Thanks.

xbacksideslider · Oct 25, 2017

Broken link removed

Columbia River Mandrel Bending - they do custom bends.

They also sell boxes of bends in steel, aluminized steel, stainless, and aluminum in all diameters. I've used them for several turbo car exhaust projects, building head pipe to bumper over axle systems out of one $80 box of 3" aluminized bends.

acotrel · Oct 25, 2017

My friend use to specialise in tube bending and built his own mandrel benders. If you want a cheap exhaust system, it is sometimes better to go to someone like him and buy some bends and weld them together. The disadvantage is the weld flash on the inside of the joins. My 2 into 1 system was made like that and works very well.
If you try to do tube bending yourself, you would probably drive yourself insane. There is a lot to know about spring-back and deformation of the metal around the bends.

Dances with Shrapnel · Oct 25, 2017

I've used Headers by Ed. Neat site with all sorts of information.

http://www.headersbyed.com/

acotrel · Oct 25, 2017

I noticed on this page that Ed says 'tuning errors' can make some exhaust systems look better than others'. I am under the impression that you should build the exhaust system, then tune the motor to get the best out of it. And if it is not good enough, modify it and start tuning again. I would never tune a motor to suit a particular exhaust system, then fit and modify a different exhaust to try to get better results without re-tuning the motor. With a more restrictive exhaust system, I tend to advance the timing on the exhaust cam. Then the motor runs hotter so the jetting changes.

http://www.headersbyed.com/pc_dynoissues.htm

seattle##gs · Oct 26, 2017

All good sources. Summit is the cheapest and promises it by Friday. I have a P11 motor and trans in a Trackmaster frame and I cannot find any off-the shelf exhaust system that even comes close to working. I am an amateur tig welder but I know two people who can really help me.
I am guessing that the existing pipes are 18 gauge?
I have a single Mikuni and a Joe Hunt magneto. If I use open pipes m will I need bigger jets?

acotrel · Oct 26, 2017

If you replace a muffled exhaust system with separate pipes with megaphones, you are likely to burn a piston. In any case you need to jet to suit changes in the exhaust system, cam timing, fuel and ignition timing. Often the required changes are only slight, but if you are already running very lean ... ?

Fast Eddie · Oct 26, 2017

seattle##gs said:
All good sources. Summit is the cheapest and promises it by Friday. I have a P11 motor and trans in a Trackmaster frame and I cannot find any off-the shelf exhaust system that even comes close to working. I am an amateur tig welder but I know two people who can really help me.
I am guessing that the existing pipes are 18 gauge?
I have a single Mikuni and a Joe Hunt magneto. If I use open pipes m will I need bigger jets?

Maybe you’ll need bigger jets, maybe not, it depends on many factors. I once swapped the very restrictive stock silencers off of a late Harris Bonnie, for Commando style, straight through pea shooters. ‘Obviously’ this would need jetting up, so I took a guess but it was too rich, so I went down, and down in jet size until it was right... and ended up with stock main jets!

Didn’t P11s only have little, straight through ‘silencers’? If so, I’d try it at stock settings (or Mikuni equivalent) first.

A straight pipe isn’t really going to perform that differently to a straight through silencer in practice.

acotrel · Oct 26, 2017

The biggest problem is not about getting more power, but complying with the noise laws. In the past I modified a 2 into 1 exhaust on a race bike until it started to go, then the noise became painful. I have the same problem with my Seeley - it performs beautifully, but it is too loud.

tubing bender

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