My KTM 500 EXC turbo project

Reposting some previous posts that have missing photos

Post #40
Small update in this thread about my turbo conversion:
So far, one can summarize that it works beyond expectations and look forward to the coming winter season!
Among the final rounds last spring began pushing coolant. Realised pretty quickly that I had blown the head gasket. In pic below you can clearly see where it failed. A fairly simple error to fix. Need stronger head studs.


While I still had the head off I wanted to take the opportunity to examine the comp reduction was possible.

Original gasket is more than 1 mm. Washers in the photo is 2 mm, and then the timing chain max tensioned without chain tensioner fitted. This gives the comp ratio 10,05:1. The limitation to raise the head is the timing chain length.

Mounted the head. There were two gaskets. Cylinder head gaskets are comprised of three layers. Had to remove one. Otherwise it would have been too thick and the chain is too short. The chain is stretched with the tensioner in the end position.



This fall I disasembled head, piston and cylinder. Sent them to MotoSpeed in Sweden for correct measurement of volume of the combustion chamber. They ​​work with JE pistons who hopefully make a custom made low comp piston. There are at least 8 weeks delivery time so I'm a little late ... ;-)
Stock comp ration is 11,8:1 and I will run 10:1. This will also require race fuel but do not want to lose too much bottom end. My goal is to safely boost 10-11,5 psi with race gas or 7-8 psi with pump gas.

Measuring squish



to be continued.....
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Post #48
Have been waiting almost 4 months for delivery of the new custom made 10:1 low kompession pistons.
I was about to give up hope but now they're finally here!
Ordered 3 sets, one for my buddy who also building a turbokit and the final one just for spare.

More parts.
APE heavy duty studs.
Didn't find stronger bols with allen keys as the original bots were.
I will use nuts instead.

TCV valve to electronically raise boost pressure from 0.5 to 0.7 bar.
That will give the options to run on two boost levels.
Could be useful if i run out of race gas. Just flick a switch an run on pump gas.

Installation of the stronger studs






The nuts base were a little too big. Machined them down to 19 mm-


Its a close fit but it seems to work.



Here's a pic from my buddys build.
This kit is made with my templates and some minor improvements

Post #51
Will test a new connection of the oil return from the turbo. Previous design was an adapter to the oil filler cap.
Adapter solution has in itself worked well, but as always you want to refine the details ....

New connection is with a banjo connection in the oil drain hole under the engine sprocket.
A neater solution that at the same time provides a greater height difference between outlet of the turbocharger and the inlet to the engine.
Reduces the risk of oil build-up in the return hose if the bike will stand in sharp uphill.

Here's the final solution. Looks like it's gonna work. Welded to a short tube with a bend on the banjo.
I will make a protection shield so that no back spray from the track will damage the connection. A break here leads guaranteed to engine failure because you hardly have time to detect damage or oil leakage.



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Post #52
Fitted the TCV valve under the right side cover. There it's protected from snow and ice. The valve makes it possible to electronically raise the boost pressure from the mechanical setting of 0.5 bar to the desired pressure. Have preset the EFI box so that the valve opens by 30%, which hopefully will raise the a boost pressure to 0.7 bar.

The electronically controlled boost pressure adjusts to different altitudes.
This means that when the atmospheric pressure decreases, it will compensate for this, increasing the boost pressure and maintain the same horsepower at sea level as well as at high altitude.

Connected an on/off switch or to the TCV, a High / lows witch. Low = about 84 hp, high = approx 96 hp.
Low can be useful if I run out of race gas and have to run on pump gas.


The hoses from the TCV valve are connected to the compressor housing and wastegate actuator.

Post #55
Here you see how the low compression piston crown differs from a OEM piston.
It's pretty impressive that you can remove material from such a thin piston to increase the volume of the combustion chamber.

Have now reposted all earlier posts that had missing photos.
Maybe some administrator can put them in right sequense
The bike is still running strong!
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Swedes goes overseas!
Have been on a fantastic roadtrip through California, Arizona and Nevada. When I passed trough Phoenix it seemed obvious to visit KMS performance.
Thank you Kelly for taking your time showing me around your shop!
Always fun to meet people who share the same interest!






Got some advise from Kelly how he equipped Rekluse Clutches for turbocharging. Bought some wedges and springs to the expansion plate. KTM found to have an OEM spring with higher spring pressure. This can be ordered as a OEM part from the KTM spare parts catalog. I will test these parts this upcoming season and see if it holds up....

Brand new KTM 500 SixDays for this season. A lot of work to re-assemble the turbo kit and all other modifications on the new bike.

Here some pictures from recent summer when I built the 2012 bike back to stock.

Since virtually everything was more or less modified, only the frame and left hand radiator was left untouched until I could begin reassembling the bike to oem specs.
The engine was taken out ánd replaced the the piston, studs, clutch and water pump.


Since the bike never been ridden on dirt, it looked like brand new despite its 100 engine hours.





Why do we go for new bikes?
My 2012 KTM 500 a has worked frawlessly turbocharged for three full seasons since new. When I sold it, the engine run smoothly with no signs of abuse.
However, my buddys clone turbo bike suffered from a big end crank bearing failure after only one season and presumably 30 enginehours.
Have always stated that the 2012 has a plain bearing crank. This was completely wrong!!
When we rebuilt my buddys engine, we realized that the 2012-2013 has a roller bearing crank. A bearing design that we think is weak when turbocharging.
We don't know the cause of my buddys bearing failure.
I have always used a high quality Motul engine oil while my buddy used the Castrol of unknown quality.
I claim that my buddy have ridden with some crappy oil, but we do not agree.
It's unclear if the oil quality was the cause of breakdown. Perhaps my buddy was hitting the revlimiter more than me?
We decided to upgrade to the plain bearing engine that the KTM 2014-2016 has. We think plain bearings are a lot stronger.
Of course we can't deny that it's fun to ride with some new stuff ;-)
Posting some photos below from the rebuild of the engine...




Roller crankshaft bearings of the KTM 500 2012-13

2014-2016 has plain bearings

Here C-man are some photos of my 2016 KTM 500 sixdays









I think the look of 2016 graphics is much nicer than the 2015 "Argentina"

Posted my feed in the wrong thread. Deleted it here. I apologize ;-)
Hoping that the moderator Christopher can delete this post....

Have tested running a Rekluse on the turbo bike. I really like the auto clutch feature.
Unfortunately my tests have shown that the Rekluse can't handle this high torque and horsepower.

Modified the Rekluse with the stronger spring and the heaviest avaliable weights.

Already at the second ride, the clutch started to slip.
My first thought was that I have chosen the wrong oil, the yellow-green Motul 300V.
Next ride I switched to the red Motul 7100 and brand new friction discs.
At first it hooked up nicely but after a few hours it began again to slip.
Final test was adding an additional beville spring for even tougher clutch pressure. Pretty soon slippage reappeared
Really frustrating not being able to give full throttle. The whole point of having a powerful engine gets completely lost!

Have now ditched the idea of ​​running Rekluse and will reinstall the OEM clutch with double springs.
That clutch setup has worked flawlessly every year I've run with turbo.

My problems may be due to that the Rekluse has one friction disc less then the OEM clutch.
One other thing could be that the weights are too light and can not engage the clutch hard enough.
In any case, the Rekluse doesn't feel like a reliable option on a turbocharged bike.

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wwillf01 said:

You have to go with heavy weights... Have you asked Rekluse if they have anything special the can send you? Also look at Kms they make a lock out feature for the clutch for turbo applications..

Click to expand...

Check out post #67 in this thread.
Have used RMS 295 weights and a stronger KTM spring.


A lockout clutch is not an auto clutch like a Rekluse.
Lockout clutch is a really nice design but are operated and works like a regular clutch.
They are more like a "power assisted clutch"
The lockout enables you to run a super strong spring and thanks to its design, require less force on the clutch lever.

Starting our next turbo build by measureing the bike's rear wheel power as standard. The measurement was made by MCXpress on their dyno-type "rolling road". Dynoed our first bike on the same dyno 4 years ago, so we already had an aproximate number on the peak power, but we wanted to investigate whether the brand new bike delivers other power numbers. The result shows that the KTM 500 2017 delivers 58 hp at the rear wheel compared to 56 hp on the KTM 500 in 2012. That is 2 hp more, or close to +4% than previos n/a power numbers.
If theory and practice go together, the new bike, with a correctly designed turbo system, will deliver just over 5% more peak power at 0.5 bar (7,25 psi) boost compared to the 2012 KTM500 engine.
The 2017 engine is considerably reworked. We hope that these changes will not lead to problems with boost such like Yamaha Viper 2016 .
KTM500 2014-2016 has to be a proven engine on boost. It remains to see if this works as well. No one remembers a coward guy




This time, the plan is building a low pressure boost turbo kit. By boosting less, no engine modificatons is reqired. We will run standard 11,8:1 compression ratio and 102 octane race fuel. We believe that less is more is the key.
We all look for more power but from our experience, boosting more will require more extensive and pricy engine modifications. You hardly feel any difference between 90 or 96 hp... 90 hp is sufficiant improvement than standard power. Light weight and reliable high power snowbikes is what we all everyday snowbikers look for....


You may think that no intercooler is reqired with such low boost levels. We think by running a standard untouched engine, you're having no room for ending up in engine knocking. Despite low boost and low winter temperatures, an intercooler brings the risk of detonation to a minimum. Have read somewere that for every 0,1 bar of boost, air intake temperature raises by 10 degree C. An intercooler looks to be reqired no matter of boost....

Since the last home built track kit is sprung and moves in relation to the bike, we can't mount the intercooler on this. We will instead have to install the intercooler up underneath the rear fender. With this layout, it has to be quite short in order to fit. We found its hard to find a short cooler element.

Found a 150 mm (6") short fully completed universal intercooler from a swedish turbo parts online retailer, Do88.se. We will not be able to use the caps on this nice unit, so we will be putting the band saw on it right away :-(
Fortunately, we will get aproximately three completed intercoolers out of this unit.
Despite buying a nicely welded and completed intercooler and cut in to pieces, this looks currently to be more affordable than ordering a custom made short intercooler element... As a european, metric measurements you know..

Disassembling the back end to see how the plenum will be designed. The 2017 KTM is a completely new design so previous molds have to be changed slightly. Some attachment points will be changed because the rear frame and fairings are different. In fact, there are better solutions here than the 2012-2016, which will in some way make installation easier and better. Made a simple strut out of steel that replaces the rear shock. Will test the bike on the dyno and this strut will limit the suspension travel as all the turbo installations under the rear fender will not leave any room for suspension compression.



Previous wodden mold of the plenum is redisigned, cut and grinded it at some areas in order to fit the new bike. Electrical relays are located under the battery. Instead of relocating them, we chose to change the shape of the wodden mold to keep them in the original place.


Making cardboard templates out of the wooden mockup. Trying to make bends, radious and so on to limit number of pieces that at the end will require less welding.



All cardboard templates completed. Lets cut all the aluminum pieces and start weld this **** thogether!



Tackwelded most parts of the plenum




The triangular shaped blow off valve base was installed prior assembly.
I had to weld the air outlet from the inside for it to be air tight between the plenum and the BOV-base.