From the Shop: Emissions
1 Feb, 2006 By: Harry Smith Landscape ManagementTechnology continues to meet the emission and efficiency challenges.
Which is better: 2-cycle or 4-cycle engines for small handheld power equipment like blowers, trimmers, edgers, pole trimmers, hedge clippers and hover mowers? The answer is not simple.
Once upon a time there was only one answer, 2-cycle. That's because 2-cycle engines were light in weight, high in horsepower per pound and could operate in all positions. Their drawbacks were relatively high fuel consumption and high emission output.
Stricter regulations
Nothing is permanent, though. In 1998 the California Air Resource Board demanded cleaner off-road engines. The Federal government echoed C.A.R.B.'s standards. Momentarily in the Los Angles (South Coast) basin 2-cycle engines were effectively banned.
This created a mad scramble by lawn maintenance contractors. Suddenly there were generators mounted in every conceivable location on service trucks. Miles of extension cords were purchased and under-powered tools led to frustration and cost.
The engine manufacturers responded with cleaner 2-cycle engines and small, lightweight 4-cycle engines.
New technologies
Was this the end of the story? Definitely not. Emission standards become more stringent each year. Thankfully, 2-cycle engine manufacturers have generally been able to meet the requirements, but a few have decided to put their technological resources elsewhere. Two that have hedged their bets are Stihl and Shindawa. They have designed engines that blend the best of 2- and 4-cycle technology.
Both designs have valves and cam gear like a four stroke but use an oil/gas mix. Several major benefits are derived from this technological marriage. These engines have a more bearable "4-cycle sound," lower emissions and very good lower rpm torque. My students describe them as "gutsy" when they try out one of these engines on a stick edger. They're hard to stall and sound as though they are running at a lower rpm than a comparable 2-cycle engine.
This is not the final answer of course. Technology continues to meet the emission and efficiency challenges.
— The author is turf equipment professor at Lake City Community College, Lake City, FL. Contact him at
smith@lakecitycc.edu.
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