Cleaner, Quieter, Better
Recently there has been a move towards more environmentally sound vehicles for transportation. This includes all small vehicles with small engines that rabidly pollute the air and water. A lot of these small vehicles are powered by noisy, dirty, two-stroke engines. Two-stroke engines are often found on jet-skis, snowmobiles, dirt bikes, chainsaws, lawn care equipment, and many small outboard motors. These engines, although fairly powerful, put out excruciating high emissions. “These high emissions are attributed to the design inefficiency of the two-stroke motor, which has remained essentially unchanged since the 1940's.”(Long). The two-stroke engine is extremely inefficient, due to design flaws that allow some of the gas and oil mix to burn as it flows out of the engine. The emissions are so bad that the Environmental Protection Agency (EPA) plans to eventually phase out the ancient two-stroke engines by 2008 (Phillips). Along with putting out a lot of emissions, and being extremely inefficient, these engines are loud. They scream their distinctive high-pitched whine as they go through the revs, polluting more and more as they go. There is an alternative; the four-stroke engine. These engines are cleaner, quieter, and most importantly, more efficient than the primitive two-stroke engines.
The two stroke engine puts out an extremely high amount of emissions into the air and water as compared to a four-stroke engine. The problem is the two-stroke engine allows anywhere from thirty to fifty percent of its oil and fuel mixture to pass through the engine unburned (Locke). The unburned fuel dumps directly into the air and water, as it has nowhere else to go. In contrast, the four-stroke engine is designed to burn all of its fuel in the engine before it exits the engine, therefore emitting up to 97 percent fewer emissions than conventional two-strokes (Long). Marine two-stroke engines spill 15 times more oil and fuel into U.S. waterways than did the Exxon Valdez (Long). This is a serious problem, as nearly 75 percent of all motorized boats and personal watercraft are powered by two-stroke engines, so the damage is widespread (Long). Two-stroke engines emit 5 times as much oil and fuel into the water as four-stroke engines (Locke). Four stroke engines are the clear way to go, their fuel does not have oil mixed with it, and so it burns strictly gasoline, therefore not dumping oil into the environment. “Petrochemicals released from two-stroke motors float on the surface micro layer and settle within the estuarine and shallow ecosystems of bays, lakes, rivers, and oceans, where marine life is youngest and most vulnerable. These areas are the base of the food chain, inhabited by fish eggs, larvae, algae, crab, lobster, shrimp and zooplankton. Research demonstrates that chromosomal damage, reduced growth and high mortality rates of fish occur at extremely low levels of hydrocarbon pollution.”(Long) Even with a small amount of surface oil on the water, it can have a debilitating effect. Long further explains how such pollution might accumulate and hurt the environment in a very negative manner. 5 parts per billion of harmful hydrocarbons found in oil can kill all zooplankton in a thirty minute controlled test period (Long). “Gas and oil contain more than 100 compounds, many of which are listed as toxic by the EPA.”(Long) Many reservoirs in the U.S. allow boating, so not only is the oil and gas released hurting the environment, it is also hurting ourselves.
As a recreational boater, I am familiar with the toxic plumes of blue smoke that emit out of many two-stroke outboard motors. According to Canada's Environmental Technology Centre (ETC), two stroke engines produce twelve times as many hydrocarbons as four-stroke engines (Locke). The ETC also conducted a test with the same horsepower four-stroke engine, and the identical horsepower four-stroke and two-stroke engine, the two-stroke engine produced 50 percent more carbon dioxide than the four-stroke engine (Locke). “The California Air Quality Board estimates that a personal watercraft used for seven hours will produce more smog-forming emissions than a 1998 passenger car driven for 100,000 miles.” (Locke) So, a weekend at the lake might prove to be more polluting than driving an SUV for a few years. The four-stroke engine is an obvious environmentally-friendly alternative to the dirty two-stroke engines. Also, two-stroke engines put out a considerable amount more hydrocarbons than four-stroke engines. “Four-stroke motors emit less than 4 g/Kwh (grams per kilowatt hour) of hydrocarbons, while two-stroke motors emit more than 150 g/Kwh.” (Long) As you can see, the four-stroke engine emits far less emissions as compared to the two-stroke, a great attribute to the benefits of the four-stroke engine.
Along with the two-stroke engine’s awful track record of polluting, it is also much louder than a four-stroke engine. Almost all two-stroke engines have a very distinctive sound to them, and when they get higher into the revs, they get louder, unlike a much quieter four-stroke engine. Some personal watercrafts, powered by two stroke engines, are loud enough to produce 115 decibels, which means that they can be heard over a mile away (Manoucheri). Four-stroke engines are much quieter. All cars, except diesels, are powered by a four-stroke engine and many don’t consider cars loud. On average, the loudest car might produce only 40 decibels, as compared to the 115 decibel scream many two-stroke engines can produce. This is working as a sales pitch for many small-engine manufactures forced to comply with EPA standards for emissions. “These days for a sales pitch at the Miami Boat Show, Honda keeps a four-stroke running all day at the dock. People strolling by wonder why the motor is spitting cooling water when it isn't running.” This would be impossible with a two-stroke engine, they are simply too loud. Some towns have actually implemented ordnances to keep noise levels down from two-stroke personal watercraft. ”The city council voted Tuesday to limit Jet Ski users with two-stroke engines to ski 1,500 feet away from the Berkeley shoreline and pier, which are the most popular areas of the marina.” (Manoucheri) Many people, myself included, find the sound of whining jet skis zipping around not very pleasing, and would be happy if this ordnance was passed in more places.
Along with being quieter, four stroke engines are much more fuel efficient and cost efficient than two stroke engines. Four stroke engines are substantially more efficient than two stroke engines. Four stroke engines are 30 to 40 percent more fuel-efficient than primitive two-stroke engines (Phillips). Also, by switching to a four stroke engine, it saves the owner the hassle of mixing oil into the fuel, which is something two stroke engine owners must do every time the fill up their tanks. This drives down operating costs of a four stroke engines, you no longer have to buy special two stroke engine oil to mix with your gas. There is one drawback: four stroke engines tend to cost “about 15 to 20 percent more than a comparable two-stroke engine” (Locke). Even so, owners of four stroke engines will save a significant amount on fuel.
Soon, the two-stroke engine will be a thing of the past. Cleaner, quieter, better; four stroke engines are the way to the future, for the environment, and for us.
Locke, Sarah. “Four-stroke engines kinder to the environment”. yourYukon: Four-stroke
Engines kinder to the environment. 2003. 12/09/04. http://www.taiga.net/yourYukon/col330.html
Long, Russel. “2-stroke engines pollute 2-much”. ET 8/97: 2-stroke engines pollute 2- much. August, 1997. 12/09/04. http://www.sdearthtimes.com/et0897/et0897s2.html
Manoucheri, Elnaz. “City Limits on Watercraft Intended To Curb Noise, Pollution in Marina”. City Limits on Watercraft Intended To Curb Noise, Pollution in Marina – The Daily Californian. 7/13/01. 12/09/04. http://www.dailycal.org/article.php?id=5774
Phillips, Angus. “Cleaner, Quieter, but at a Price: New Engines Do Old Ones Two Strokes Better” The Washington Post. March 10, 2002. 12/09/04. http://proquest.umi.com/pqdweb?RQT=309&VInst=PROD&VName=PQD&VType=PQD&sid=2&index=4&SrchMode=1&Fmt=3&did=000000110332075&clientId=20795