Solutions - Four-Stroke Engines

Snowmobile

Overview

The main competitor to the two-cycle spark ignition engine is the older, four-stroke engine, commonly called the Otto Cycle engine.

Major snowmobile manufacturers have begun to introduce new machines powered by four-stroke engines. This appears to be the primary approach to retaining snowmobile access to Yellowstone National Park. The technology for meeting any imaginable requirements for emissions or noise appears easily in hand with conventional, four-stroke engines. Such machines have already been placed in park settings, with plans to expand their use before further restrictions are imposed.

Competing engine technologies include the conventional, piston-type four-stroke Otto engine, and a rotor engine, the Wankel.

The Wankel rotary engine has been employed in vehicles that typically have been powered by two-stroke engines, including about 15,000 engines produced by the Outboard Marine Corporation (OMC).

But the technology has presented several difficulties, including wear and sealing issues. It has also shown lower fuel economy and higher emissions in automotive engines. OMC, which had licensed Wankel patents in the United States and spent considerable effort developing the technology, has filed for bankruptcy. Freedom Motors acquired all of the intellectual property assets for the Wankel, which has developed additional technology for improving emission characteristics of the engine.

Selected Links

Learn More About Four-Stroke Engines

By spring 2002, all four major snowmobile manufacturers,  and smaller companies, Three R Industries (Trail Roamer) and Redline, are touting "environmentally friendly" snow machines powered by four-stroke engines. By July 2002, DEQ teamed up with the National Park Service, and others to evaluate Acrtic Cat and Polaris 4-stoke snowmobiles reported in Laboratory Testing of Snowmobile Engines. Check the links below for news articles and company announcements about these four-stroke snowmobiles:

Arctic Cat
Tahoe.com reports that tests on a four-stroke engine manufactured by Arctic Cat have produced promising results in an article by Emily Aughinbaugh of World News Service titled Industry touts cleaner engines.
Snowmobile World.com writes about the same snowmobile in an undated article titled Arctic Cat Enters New Era of Cleaner, Quieter Snowmobiles – Fifty Environmentally Friendly Snowmobiles Going to Yellowstone National Park.
Polaris
The world's largest snowmobile manufacturer claims it has designed a more environmentally friendly snowmobile. Snowmobile World.com reports about the snowmobile in an article titled Polaris Industries Unveils Cleaner, Quieter Four-Stroke Snowmobile.
Three R Industries
Three R Industries touts its Trail Roamer 2000 as "the most stable, quiet, environmentally friendly snowmobile with the warmest interior, the easiest handling and the most technologically advanced, fuel efficient design available today."
A news story in the February 15, 2000, Billings Gazette titled Clean machines? Snowmobilers plead 'don't squeeze us out' includes a sidebar on the Trail Roamer and its "environmentally friendly" features. 
Redline
On September 11, 1999, Redline Snowmobiles introduced a new model snowmobile called the SP604S. Redline announced that the new model was designed for "economical and eco-friendly travel into our National Park systems."