My KTM 500 EXC turbo project

Here is my latest project, turbocharging my 2012 KTM 500 EXC
Today i put it on the dyno.
The result was better than I expected.
Peak power 96,86 hp at 10,1 pounds of boost.
Stock power was 55,6 hp.
Putting up some photos of by build. The dyno charts comes at the end of this post.

Running a rear mount layout. Keeping the exhaust stock. Just replacing the muffler with the turbo. I believe that rearmount is good at smoothing out the powerful exhaust pulses that can be a problem when turbocharging single cylinder engines.


Using a pressure lubricaded non ballbearing turbo. Took a oilfilter cap from a KTM690 which have a threded hole to connect the oil feed line.


One thing that is good with the KTM500 is that it has pressure lubricated big end connecting rod bearing. Most of dirt bikes have roller bearing and a very low oil pressure
Checked the oil presure with a guage, over 46 PSI. Mitsubichi have a recomendation at minimum 37 if I recall.
Now I can be sure that the turbo get the correct lubrication-


The biggest job in the project was designing and building the plenum. Tried to use all the avaliable space to get a very large plenum.
Started with a mockup out of wood then make it in 2 mm aluminum.


The volume of plenum endet at about 4-5 liters.
The triangular thing on the side is a mount for BOV.


Using the MCXpress piggyback fuel injection. A extra fuel injector in plenum delivers extra fuel.


Fuel rail


The injector is placed just at the intake of the throttlebody.


Bigger power reqires a firmer chlutch. KTM using beleville spring. Order another spring and just put in over the stock spring. Now I have double spring force.


A adaptor at the oil fill plug connects the oil return line from turbo


Pressure oil feed from oil filter to turbo



Put isulating wrap around the exhaust.


Not a very good looking mount for the temprary intercooler but it's just for puting it on the dyno. I will later make a smaller and mount it on the tube frame of my snowbike.

Dyno test at MCXpress.
The results looks promising from start. Just over 84 hp at moderate 8 PSI.
Checking with lambda guage to get right air fuel ratio.


Finally the tuning is done. Must say that restults exceeded my expectations! The theoretical power and the final result was pretty spot on. That shows that it's running very good.
Peak power 96,86 hp at 10,1 pounds of boost.
Torque 85 Nm

Thank you guys. :face-icon-small-hap. I'm really excited over the dyno result. This looks promising.

The engine is stock compression ratio 11,5:1.
I wanted to keep the enginge untouched if it would'nt work and I had to ditch the idea of a turbo kit.
Running race fuel for now. 102 octane RON
Not a cheap fuel but hopefully these snowbikes don't consume that much so I think you can handle the extra cost, time will tell.
I will probably end up installing 1,5 mm head chim to lower compresion and run pump gas.

The Mitsubichi turbocharger is from the MCX turbocharged Yamaha Phazer.
It's smaller than the Mitsubishi 16T.

The plenum is really oversize when you compare to other turbocharged multi cylinder engines. I think a big plenum is important on single cylinder engine. Big plenum will smooth out the intake pulses.

The recent test was at 10,1 pounds of boost.
I will lower it to 8-9 pounds so play safe. At that boost it will crank just over 90 horses. At the end of the day it's all about reliability.
The wastegate acuator spring was too firm.
Also the wastegate opening is a bit small to get enough bypass.
Will grind it up a bit to lower the boost.

Not only the horsepower looks good. The tourqe 80 Nm is pretty close to a 600 snowmobile :face-icon-small-hap

We'll have to wait a month to see how it performs in real snowbike conditions. No snow here yet in the north of Sweden:face-icon-small-sad

Judging from how it performed on the dyno was very smooth power delivery over all the prm range.
No splutter or missfiring, almost like a stock bike.

I guarantee to keep you guys informed in how it behaves with both race gas and pump gas.
First I'll run with standard compresion. When I'm broke buing expensive race fuel I will test pump gas configuration.
Not a big deal to put in a shim and see how it performs.

M5- said:

It will likely not behave quite as well if you shim the motor, so maybe its worth it to use the race gas.

M5

Click to expand...

I don't think it will behave much differently.
Top end power will be more like same, maybe a little less. -2 to -4 percent.
The big difference by loweing compression ratio will be low end power/torque.
Big question is how much I have to lower compresion to safely prevent detonation with pump gas.

Early stages in making mounts and tubing for the intercooler.

Intercooler completed.

Thanks Ken
Alot of work after dyno testing.
IC, elecrics, oiling, piping and so on. You'll have to wait for some real testing. Hopefully at the end of december.
Fitting the plastics