2003 Arctic Cat ZR900 Turbocharged with Nitrous Oxide

Hampy Carter from Kim's Garage in Winslow, Maine and Dave Lefebvre from The Starting Line Speed & Custom Shop in Waterville, Maine teamed up to produce a rare high powered severely pressurized two stroke turbo with nitrous snowmobile, that has run 136mph in 1000 feet.

Custom Intercooler and Intake Plenum

A lot of time studying compressor maps and air flow numbers resulted in a nice running engine with very little turbo lag. Several airbox designs were tried. It was difficult designing an ideal box and was complicated by the steering column location. End tanks were fabricated and welded onto an intercooler core to reduce the high boost intake temp. A blow off valve was fitted to the end tank. The carbs were fitted with externally adjustable power jets and the exhaust valves are held full open while the servo is disconnected.

The Fuel System

A large Bosch pump capable of keeping up to 100 psi constant fuel pressure is used. A boost sensitive fuel pressure regulator is necessary to maintain 7 psi of fuel pressure above boost pressure. There is also a blow-off regulator which returns excess fuel from the rail back to the tank. Large feeds, returns and vents were installed into the fuel tank to handle the large volume of fuel needed. All carb vents were attached to a pressure source and the airbox has fittings for the boost gauge as well as the fuel pressure regulator. Power for the fuel pump comes from the sleds stator AC output while using a full wave bridge rectifier and capacitor to change the current to DC.

Liquid and Oil Cooled Turbo

An oil system had to be designed to use this turbo. A rectangular "shoe box" with an oil pan style sump was fabricated from aluminum. It was vented and internally baffled to keep oil where it needed to be when launching. The oil pump used is from an aircraft. The oiling system was first tested on the bench where minimum pressure and gal/min flow could be recorded. An inline oil restrictor was added as well as a Borg Warner pressure switch that trips a dash light if the pressure should fall below minimum allowable. Switches and relays are used to ensure that the sled can not be started unless the oil pump is first running.