September 1, 2008
MPI Supercharger Installation
The tech side to making a Yamaha scream
By: Stephen Clark
In the last few years the snowmobile market has really embraced the concept of forced air induction with superchargers and turbochargers. With the exception of a few major players, a few years ago you would have had a hard time finding any company who built a kit for a snowmobile, but now the market is flooded with people building turbo kits.
It seems every time you turn around some other new company is producing a turbo kit. The rapid rise in popularity in forced air induction is not surprising to anyone who has ever ridden a boosted machine. The power is absolutely incredible and puts most naturally-aspirated mod machines to shame.
Yamaha four-stroke sleds respond very well to boost and their excellent build quality becomes a very favorable attribute when you are doubling the horsepower. Mountain Performance has been specializing in Yamaha aftermarket parts for years and since the RX-1 came out it has been concentrating its efforts on supercharger kits for these machines.
Mountain Performance supercharger kits feature a unique Rotrex supercharger from Denmark.
2 All body panels need to be removed to access the engine. Yamaha did us a favor by using dzus fasteners and push-pins to secure all the body work. This means the body work can be removed without tools and the dzus fasteners remain attached to the body work so they cannot be lost. No more searching for fasteners during re-assembly at this stage anyway.
3 Remove front nose cone, bumper, dash panel and headlight assembly.
4 The Nytro really is an engineering marvel. The engine sits low and far back in the chassis, a very much different configuration than the sleds we had a few years ago.
5 Remove the brake caliper from the chaincase and rotor.
6 Disconnect the cables and wires from the steering column. After unbolting, the steering column assembly can be removed in one piece.
7 Remove the lower body panels. These panels are removed much less than the upper body panels so Yamaha secures these with bolts.
8 Remove the exhaust side covers and seat.
9 Remove fuel tank cover.
10 Disconnect all fuel tank connections and remove the fuel tank. Try not to spill gas everywhere.
11 Disconnect the coolant hose from the front heat exchanger (only on mountain models; short tracks do not have a front heat exchanger) and drain the coolant. If you use a clean container to store the coolant it can be re-used later.
12 Remove the radiator assembly from the upper subframe.
13 Remove the large plastic airbox. The area this airbox once filled will be where the supercharger and intercooler will sit.
14 Drain the engine oil reservoir and remove the reservoir from the machine.
15 A pile of Yamaha.
16 Remove the coolant thermostat assembly. The thermostat needs to be modified to make room for the supercharger and intercooler. The temperature sensor is removed and relocated to the supplied billet coolant manifold.
17 Remove the throttle body assembly from the engine.
18 The supercharger will be driven by the engine crank so an extension for the pulley to mount must be installed. Remove the magneto side engine cover and bolt the billet extension to the crankshaft.
19 Some stock electrical components need to be moved as they are mounted where the supercharger drive assembly will be. The bracket is removed and relocated to the stock battery holder.
20 The machine is now ready for the supercharger to be installed. The supercharger will mount on the inside of the Deltabox frame with the pulleys mounted on the outside. A hole needs to be drilled in the Deltabox for the supercharger to mount. MPI supplies a nice template in the kit that takes all the guesswork out of where to drill the hole. The template ensures that a pilot hole is drilled in the exact location. The template is removed and a hole saw used to drill the hole.
21 The kit being installed on this Nytro is a stage 2 featuring the Rotrex C30 supercharger. The C30 comes assembled with a billet pulley adapter assembly that bolts right to the stock frame.
22 With the throttle bodies on a work bench, a billet adapter plate is mounted to the throttle body assembly. This plate will bolt up to the intercooler. MPI has gone to great lengths to ensure that the intercooler is mounted solid to the throttle bodies to prevent the intercooler from blowing off under boost.
23 The Rotrex supercharger uses a self-contained oil system so an oil reservoir, filter and cooler need to be mounted to the machine. The supercharger pumps the oil internally so there is no need for an external oil pump.
24 Install the foam filter and waterproof jacket onto the supercharger inlet.
25 The MPI intercooler fills every last inch of real estate under the Nytro hood; its size and design make it very efficient at cooling the charged air.
26 Install the larger pulley onto the previously installed crankshaft-mounted extension and mount the smaller pulley onto the supercharger. The pulleys are attached using a taperlock with set screws. MPI strongly recommends heating the pulleys and torquing them to spec so that a very tight connection is achieved. It is also crucial that the pulleys are aligned with each other. Taking extra time and making sure this process is done correctly is very important.
27 Install the tensioner pulley.
28 The stock fuel system must be changed so that enough fuel can be injected for the boost. The MPI fuel kit replaces the fuel regulator and adds another fuel line to the tank. After the changes had been made, Abe Carter reinstalled the tank on the machine.
29 All that’s left to do now is install the electronic fuel box. The GEMS module plugs into the stock harness and adjusts the fueling to match the supercharger. MPI supplies base line settings for its kit and the box allows the user to further tune the fueling to match their environment.
The supercharged Nytro is so easy to ride, you can put it almost anywhere you want on the mountain without ever feeling like you are in a sticky situation. The weight disadvantage of the Yamaha is almost completely gone with the added power. There is absolutely no lag and the power is always right there when you need it. If it weren’t for the additional noise from the supercharger you would think that it was just a very powerful, naturally-aspirated engine. The MPI supercharged Nytro is the most fun, maneuverable and capable mountain snowmobile I have ever ridden. The Nytro still starts and runs like stock, only much faster.
For more info on Mountain Performance supercharger systems, check out
www.mountainperformance.com or call
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