950 Supermoto Turbo Build Thread

Maineroads,

It feels like two lifetimes ago but I was a race car fabricator/engineer as a young guy, six years in motorsports, including Indycar. As fifty gets closer I, like many, seem drawn to revisit what was fun decades before. That's a big part of the reason for turboing a bike that was already near perfection. Anyway, back to the build.

A turbo inlet flange was cut from 3/8 plate. Unfortunately its mild steel so it will need some coating. I didn't want to loose the weekend to get stainless.

The header was extended back towards the turbo.

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This piece will get sectioned later for a slip joint. On a V motor there must be a way to separate the pipes.



Here the tire clearance is being checked with a straight edge. I really cut it close by tucking the turbo in this tight. Its not as bad as looks here though. The straightedge is leaning well forward of the closest point.

It would have been great to get some SE pipes but those didn't fit the budget. Plus, I wanted to try something different.

KTM routed the rear cylinder's pipe down through the swingarm and looped it back up. That makes the pipe lengths more equal, for even cylinder scavenging. For a turbo this scavenging is less important and maintaining high exhaust gas velocity is more important. So, I'm going to build the rear cylinder's pipe shooting straight toward the turbo.

Please, please, please don't be offended by the look of the rusty pipes in the pictures included in this link (I had to use what I had, not what I wished........then rode the thing for 1000's of Km tuning and just enjoying it!), but if you scroll down to pic #3, the upwards pipe to the back cylinder goes into a slip joint, no sealer, no clamps, no leaks.
That's how I did it, might give you some ideas.

http://www.bikeboy.org/daves4r.html


Please continue, enjoying the build very much!

We think alike Modnrod. I plan the same kind of no-clamp slip joint. Turbo charged light aircraft use this set up because its reliable and light. Since the inside pipe runs hotter it expands to make a good seal.

A diametrical clearance of .005" to .008" should seal well when hot but also allow some movement. I measured the pieces from the cut up KTM header and four Ducati mufflers and found pieces that have this clearance.

Fitting the tubes for the aft cylinder was a slow process for a few reasons. There was no fudge factor, a couple of turns were crammed into a tight space, and there was no spare tubing if I screwed up. Worst of all, both tubes were curved at the intersection.

This tube barely misses the cam chain tensioner boss and goes too close to the brake line to leave unprotected. I wish I has an SE around to see how KTM dealt with this.

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Same approach as before, the joints were taped in place as an initial test fit. When things looked good joint was tack welded.



Here a little persuasion is used to adjust the gap for the tack weld.



So far so good.



here is where it gets more challenging. A guess was taken as to the shape of the miter for the Y joint.



After about an hour of gradual trimming the joint looks good from the outside.

Still working on this Y joint. I snapped the tack weld at the cylinder fitting to make a tiny adjustment. That's an example why everything should be tacked together first.



Once everything was fit nicely it was time to mark and cut the hole in the other tube.









All tacked up except for the 90 into the turbo.

Wow.

I wonder if you will have to brace it when you finally weld it solid due to heat distortion? I suppose you could make a mach V to bolt the flanges down to.

Ultra, you're right about the distortion. Half way through welding the Y joint it pulled quite a bit. It's because the Y joint beads are all to one side of the tube. The plan is to weld up the forward end almost completely and then break the tacks by the turbo and re-aim the last section of pipe.

Here is the slip joint. That gap is supposed to be there. It allows the pipes to grow when they get hot. It should also let the pipes move if the subframe flexes down, like from a jump. The proximity of the brake line is clearly a problem that needs to be sorted out.




Formed some tabs for the slip joint by folding some stainless around a #2 phillips screwdriver



Cut tabs to length and smooged as needed




Brazed the tabs on to minimize distortion of the slip joint. Its a really good fit. The bolt may get swapped for a shorter one with a stronger spring, if I can find one in the junk drawer.

Here is an attempt at a bracket to support the tube near the turbo. It's a really 3D part. The tube slopes up and out and has a bend there.



The idea is to support the turbo by the stock KTM exhaust mount up front and by the KTM muffler mount in back. A decision on if this bracket can be used will come after the tubing is welded up more.

Very nice work. The brackets and joints look OEM...
Are you gonna ceramic coat it all when it's done?
The turbo is a long way from the exhaust ports, where efficiency is concerned. A major source of energy for the turbo will be exhaust heat, in addition to flow. The ceramic coating will help to contain the exhaust heat to help aid turbo spoolup. There is a hotter version of ceramic coatings called turbo-kote. It's black, and can even be used on turbine housings and wategates, inside and out.

Swoon! What work! Any interest in a DRZ-SM experiment? I can come over... it is carbed though maybe. A megasquirt setup as well
I am subscribing to this thread.

One of my other lurking zones is Supermoto Junkie and member unclebob did a thread for his DRZ-SM turbo build:
http://www.supermotojunkie.com/showthread.php?23824-DRZ-SM-turbo-project&highlight=unclebob

Here is Turbo 2.0 of unclebob's project:
http://www.thumpertalk.com/forum/archive/index.php/t-683446.html&

Tommy, the slip fit joints are very streamline. I wondered how those made a seal, thanks for the explanation.

Cooooooool

I probably won't go the ceramic coating route, at least not at first. Its hard to do repair/rework with that coating, and it'll probably cost as much as the turbo did. Anyway, I have a couple of special tricks in mind to avoid turbo lag and I hope to get to work on them soon.

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I remember reading every post in Uncle Bob's first thread back in 2006. Honestly, it was probably his project more than anything else that got me spun up to do this one. I'm not sure his project was a 100% success so I can't wait to read the redux thread.

Uncle Bob, if you ever read this I dedicate this thread to you!

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Exhaust pipe clearance to the tire should work out OK. There was insufficient clearance with the mud guard so it needed a little trim on one side. During removal a bolt snapped. Are KTM fasteners made out of cheese? Repaired with a larger fastener.

Installed

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Some more welding was accomplished and a heat shield added. Its actually more camouflage/styling than heat shield. As I said before, I wanted to build a sleeper.

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