Snowmobiles operate in cold weather. Like any internal combustion engine, these
machines like to run rich in the cold, producing high amounts of carbon monoxide.
Cold, stable atmospheric conditions combined with unfavorable topographical
features like mountain valleys can "trap" snowmobile emissions, causing
high atmospheric concentrations of pollution in areas with high snowmobile usage.
Utilize a two-stroke engine.
Are tuned to run "rich" (with excess fuel) for easier starting
and reliable operation. (This results in incomplete combustion and the emission
of high amounts of unburned hydrocarbons and carbon monoxide.)
Have recently been regulated but not required to use exhaust after treatment
(such as catalysts) to reduce emissions.
Two stroke engines:
Feature a high power to weight ratio and good cold-start characteristics.
However, they are inherently "dirty" engines.
Between 20 and 50 percent of the fuel, air, and oil mix can be emitted,
unburned, from a two-stroke engine due to "short-circuiting" of
the fuel-air mixture. (Short circuiting is when both the fuel injection and
exhaust ports are open at the same time. There are no valves on a two-stroke
Partial combustion of traditional two-stroke oils results in visible particulate
Most snowmobile tour operators replace their snowmobile rental fleet annually.
Technical papers from the Society of Automotive
Engineers (SAE) have long been a source for keeping current with advancements
in vehicle technology of all forms. SAE publishes about 2,000 papers each
year which can be purchased online
for a minimal fee. Some SAE publications related to the Clean Snowmobile
Challenge are available free through a special grant arrangement with
Department of Environmental Quality.