Abstract
With annual worldwide production of over 100 million units, small off-road engines (SORE) have been recognised as a major source of air pollution. It is estimated that non handheld SORE products in circulation annually produce over 1 million tonnes of HC+NOx and over 50 million tonnes of CO2. These SORE did not have to meet any emissions control legislation until its introduction in the USA in 1995. Since then the gradual implementation of several stages of increasingly more severe legislation has resulted in a decade of intensive emissions control development for utility engines. New carburetted stratified charge 2-stroke engines and catalytic after-treatment are being developed for the handheld products where weight and multi-orientation operation are key requirements. For the non-handheld 4-stroke dominated market, manufacturers are looking at improved fuel system design, improved engine design and the use of after-treatment to meet current and future legislative requirements. The bulk of the total 4-stroke SORE engine market, at around 65%, is taken up by single cylinder 4-stroke gasoline engines of under 6hp or under around 160cc. In this, the largest segment of the market, manufacturers must look to more conventional or new technologies that can be applied without significant add on cost or more preferable with a cost reduction. This paper presents the rational for the proposed EPA / CARB approach to meeting Phase 3 legislation with SORE and considers several possible alternative strategies.
Key Words: Utility Engine, Intake System, Exhaust Emissions