Design of the University of Idaho Clean Snowmobile Report uri icon



  • The Clean Snowmobile Challenge is a Society of Automotive Engineers (SAE) student design competition that was first held in March 2000. The competition is designed to give students throughout the US and Canada the opportunity to further snowmobile technology while gaining valuable design experience. Conventional snowmobiles are powered using a two-stroke engine. The two-stroke engine is loud, sometimes in excess of 102 dBA at a distance of 15 m (50 ft) [1], and releases substantially more unburned hydrocarbons and other pollutants than would be released by a comparably powered automobile. The primary goals of the snowmobile design focus on removing these undesirable characteristics from snowmobiles. 

    The goals of the 2001 University of Idaho (UI) Clean Snowmobile Team were to reduce snowmobile exhaust and sound emissions while maximizing fuel efficiency and performance. The competition snowmobile consisted of a four-stroke BMW K75RT motorcycle engine mounted into a 2001 model Arctic Cat SnoPro chassis. A special motor mount was designed to attach the engine to the chassis, and special carriage developed to match the primary clutch to the engine. A custom exhaust system consisting of a single stage catalyst and muffler was designed to control hydrocarbon and noise production. Modified electrical and fuel pumping systems were implemented to maintain the stock fuel injection system. 

    The UI Clean Snowmobile for 2001 finished fifth in its first year of competition. It exceeded the emissions reduction requirements. The competition snowmobile achieved a 59 percent reduction in carbon monoxide, an 84.1 percent reduction in unburned hydrocarbons, and a 39.7 percent reduction in nitrogen oxides. The reduction in the combined unburned hydrocarbons and nitrogen oxides was 83.5 percent. The competition requirements were a 25 percent reduction in carbon monoxide and a 50 percent reduction in the combined unburned hydrocarbons and nitrogen oxides. The results from the fuel economy test showed that the competition snowmobile completed the 162 km (100 mi) course while consuming 19.08 liters (5.04 gallons) of gas, resulting in a fuel economy of 8.43 km/l (19.8 mpg), second best in the competition. The fastest acceleration run for the Idaho competition snowmobile was 8.28 seconds, while the loud side of the snowmobile produced sound emissions of 74.7 dBA at 50 feet. Thus, unfortunately the sound emissions for that side were slightly above the 74.4 dBA requirement. During the cold start test, the competition snowmobile started up within two revolutions of the engine, fastest in the competition. The UI snowmobile placed second in the handling event. The snowmobile also possessed sufficient power to make it to the top of the hill climb. During the competition, the snowmobile had no problems and required no maintenance or repairs. 

    The UI Clean Snowmobile showed reduced emissions well below the competition’s requirements. Fuel economy was doubled, and sound emissions were reduced to a level 0.3 dBA above competition requirements. All of this was done without significantly affecting the snowmobile’s performance or durability. The cost involved in producing this snowmobile is $950 above the cost of the chassis. The UI Clean Snowmobile provides an excellent balance between cost, environmental soundness, and consumer acceptability. 

publication date

  • September 2001



  • recreational vehicles; snowmobile; parks; emissions; competition; education


report identifier

  • Report Budget Number KLK303 
    NIATT Report #N01-16