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The University of Idaho's (UI's) entry into the 2009 SAE Clean Snowmobile Challenge (CSC) was a semi-direct-injection (SDI) two-stroke powered REV-XP snowmobile modified to use flex-fuel. The flex-fuel engine produces stock engine power on any blend of ethanol and gasoline from E10 to E85. The emissions output was reduced using an oxidation catalyst located after the exhaust silencer. Noise from the engine compartment was reduced by custom-carbon fiber hood and side panels, which allowed placement of extra sound absorbing materials. The UICSC design produces 80.5 kW, is lightweight at 238 kg wet, and achieves a fuel economy of 5.65 km/L on E85 fuel. The UI snowmobile achieved Third Place in the competition, while producing the best fuel economy and winning several other awards, including Best Acceleration, Best Value, Best Ride (fueled class) and Best Subjective Handling.

The University of Idaho's (UI's) entry into the 2007 SAE Clean Snowmobile Challenge (CSC) was a third-generation gasoline direct-injection (GDI) two-stroke powered snowmobile. The modulated and battery-less direct-injection system fully met the competition goals of “improved emissions and noise while maintaining or improving the performance characteristics of the original snowmobile.” The students designed and manufactured a new head for a stock two-stroke 600cc snowmobile engine. The head was designed to use direct fuel injection to control fuel quantity and timing to reduce fuel short-circuiting. Performance was refined through the use of precise engine mapping. The emissions output was further reduced by a reduction catalyst located in the exhaust silencer. Noise from the engine compartment was reduced by using sound absorbing materials and a sealed hood. The UICSC team consisted of students from freshmen through graduate students.

Gasoline direct injection (GDI) two-stroke engine technology has been developed for use in snowmobile applications. Applying GDI to a two-stroke engine significantly reduces emissions of unburned hydrocarbons and improves fuel economy by reducing the short circuiting of fuel that occurs in conventional carbureted two-stroke engines. The GDI design allows for two different modes of combustion, stratified and homogeneous. Stratified combustion is typically used during idle and light to moderate loads at low engine speeds while homogeneous combustion is used at moderate to high loads and medium to high engine speeds. This work presents the process and results of determining which mode of combustion provides better fuel economy during cruise point operation, and where the transition from stratified to homogeneous combustion should occur in snowmobile operation.

With the recent advancement in gasoline direct-injection technology for lightweight and high-specific power two-stoke engines, turbocharging a small crank-case scavenged GDI engine promises to be an effective way of increasing engine performance while maintaining the lowered emissions and increased fuel economy of GDI two-stroke engines. Along with increasing the power density, a variable geometry turbocharger should allow for an increase in low engine speed engine performance that will allow the engine to be operated at lower engine speeds providing quieter operation and decreased engine wear. Also presented is a method to increase throttle response and increase low speed torque through the use of a reed valve installed in the intake plenum.

The University of Idaho's entry into the 2006 SAE Clean Snowmobile Challenge (CSC) was a second-generation gasoline direct-injection (GDI) two-stroke powered snowmobile. A modulated and battery-less direct-injection system was used to decrease exhaust emissions and improve fuel economy without reducing the power output of the engine. The team added a reduction catalyst designed for a two-stroke to the exhaust silencer to further reduce exhaust emissions and noise. Under-hood noise was targeted by using sound absorbing materials and a sealed hood. Chassis noise was addressed by using a spray-on rubberized material that absorbs vibrations transferred through the chassis. The snowmobile entered into the 2006 SAE CSC competition was lightweight, easy-to-ride, powerful, fuel efficient, and had reduced exhaust emissions.

The 2001 SAE Clean Snowmobile Challenge entry for the University of Idaho provided proof-of-concept for a clean snowmobile using a four-stroke engine, exhaust aftertreatment, and electronic fuel injection. This combination provided excellent emissions and fuel consumption performance while maintaining acceptable power and nearly acceptable noise production. The 2002 entry built on this design while focusing on improving the overall efficiency of the snowmobile. The BMW engine was tuned for high altitude operation, higher efficiency components reduced chassis losses, and additional sound damping was utilized throughout the chassis.

The goals of the 2001 University of Idaho Clean Snowmobile team were to reduce snowmobile exhaust and sound emissions while maximizing fuel efficiency and performance. The competition snowmobile consists of a four-stroke BMW K75RT motorcycle engine mounted into a 2001 model ArcticCat 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.