Sidewinder – TURBO KITS

The new turbocharged snowmobile Yamaha Sidewinder / Artic Cat ZX 9000  is the most powerful serial produced snowmobile ever build.  And it has great potential to be even stronger.  Yamaha claims the stock power to be about 180 hp. The truth is even better.  When we test in our ASB calibrated and certfied Superflow dyno, we measure 192 to 194 every run.  The stock turbo pressure at sea level is 65 kPa. (=This is 9,4 PSI).  Very impressive for a stock snowmobile.

One of the benefits with turbo is that it’s in these days possible to maitain the power at any altitude.  The ECU gets informed about the barometric pressure and controls a valve (=Turbo Control Valve) so the same total pressure enters the engine.  The baro pressure is about 100 kPa at sea level, and the turbo pressure 65. The total pressure will then be 165 kPa.  At 1000 meter elevation, the baro pressure is 90 kPa. The turbo pressure will then be 75 kPa, so the total pressure will still be 165 kPa.  At 2000 meter, the baro pressure is 80 kPa, and the turbo pressure 85 kPa ,total pressure 165.  Is it actually more relevant to talk about total pressure than turbo pressure, so we will do that in the rest of the text below.  To compare, a natural aspirated engine with 193 hp at sea level, has in best case 0,8 times the power at 2000 meter elevation (=154 hp).

 2017 – 18

225 HP Kit
MSRP – $2069 CAD

The back pressure of the stock muffler is O.K, and still, the power increase by installing a less restrictive muffler is rather much.  Just by a switch to a racing muffler, the power at sea level goes up to 206-208 hp. The total pressure increase up to about 170 kPa due to that the wastegate hole in the turbine housing is a little to small for this setup.  At altitude, the total pressure will drop down to 165 kPa again, and the power will be just over 200 hp.  One problem with just installing a low restrictive racing muffler is that the air/fuel will be leaner.

The MCX Gen 5 EFI-box is specially developed for controlling the total pressure and the opening time of the injector. The best lambda value on a turbo gasoline engine is between 0,80 to 0,85 at full throttle. We prefer to run rather rich to get as much safety limit as possible against detonation, so we aim for lambda 0,80.  If we run richer than 0,80 the power drops rather rapidly, and if we run as rich as  0,73, the engine starts to misfire.  (A natural aspirated engine is normally performing best at lambda 0,90)

We have set the total pressure to just over 180 kPa. The engine delivers 225 hp at this point.  The stock ECU has a boost safety system that cut off the engine if the total pressure rise higher than about 185 kPa.  With our stage one kit, this safety system is still active. This makes it very safe.


250 HP Kit
MSRP – $2689 CAD

The turbo, fuel pump and injectors can handle more power.  And the engine show no sign of detonation with higer boost when using pump gas 98 octane RON.  So with just some more electronics to avoid the boost safety system, we can rise the pressure more.  At just over 200 kPa total pressure, (=15 PSI turbo pressure at sea level) the injectors are fully open at lambda 0,80.  The engine delivers 250 hp at this point.


260 – 340 HP Kit
MSRP – $5699

At higher altitude, the turbo will have to work harder.  The compressor of the turbo will have to pump more the higher up you go if the power shall be the same.  So if you want more power than 250 hp at sea level, or if you want to keep 250 hp or more at high altitude, the stock turbo on the Sidewinder becomes to small.

We have made a lot of tests with the stage 3 Sidewinder turbo.  It works fine up to 340 HP at sea level.  The engine is stock, so Yamaha has done a good job.  The stage 3 kit includes a bigger turbo, for which we use the favorite Mitsubishi 19T.  The new intercooler provides 2.6 times more cooling area than stock.  There is also 3 extra injectors installed in the plenum.

At 2000 meters elevation this turbo can still deliver over 270 HP. (The stock turbo is maxed out at about 220 HP at this elevation).