27 November 2013
Four-stroke vehicle engines are dominating the streets of the 21st century, but why has the engine been so successful? Since its introduction in the year 1876 (Bellis), the four stroke engine has been modified to be incredibly efficient, reliable, and easy to maintain. Complicated to look at, the engine is actually a pretty simple mechanism consisting of a metal compartment where the fuel mixture is drawn into the engine’s cylinder, compressed, ignited and combusted in a total of four steps or strokes. Not many people know that there are rivals to the four-stroke engine including the two-stroke and the rotary engine. The four-stroke engine remains the preferred choice among machines in almost every vehicle, and it continues to dominate the automobile and motorcycle markets despite attempts by manufacturers to develop alternative machines. When vehicles became a common necessity, four-stroke engines were built around the world to meet consumer demands and were modified to achieve greater performance. Changes have been minor, but the four-stroke engine is now the leading vehicle engine in motorcycle and automobile markets. The motor is inexpensive, reliable, easy-to maintain and to refuel making it the perfect choice to purchase. If aftermarket parts are added like a turbo charger, the horsepower increases to incredible rates while being more efficient. In recent years, the motor has been increasing in speed and fuel efficiency. The Suzuki Hayabusa four-stroke liquid cooled motorcycle, for example, is fitted with a 1340cc four-stroke engine. It can easily reach a top speed of 248mph (Top 10 Fastest Bikes in the World).
While speeds have improved, maintaining and fueling the four-stroke engine is easier than other types of engines. A four-stroke engine only requires periodic oil changes, replacing oil and air filters, checking the spark plugs and checking the engine valve clearances every 15 hours of riding (Griswold). In today’s economy, gas is very expensive and four-strokes have excellent gas mileage and don’t require mixing the fuel with oil like the two-stroke engine competitors. Looking inside a four-stroke engine will reveal sparks, combustions and pistons in motion delivering power efficiently to the drive train of the vehicle. “The four strokes of the cycle are intake, compression, power, and exhaust” (Keveney). These four steps can be shown in an animation or video online. When the motor intakes gas into the chamber it then compresses the gas using the piston that is already in motion, meanwhile a spark ignites the gas expanding the chamber making the piston take its third stroke. The final stroke involves the release of the gas emission into the exhaust system completing the four-stroke cycle. All of this occurs in a matter of a second with high efficiency. “The crankshaft in the engine at five thousand rpm will rotate eighty three times per second while the piston will travel up and down one hundred and sixty six times” (Mercurymarine2011). The work produced at the end of the process helps propel the vehicle using unleaded fuel in an engine design that has evolved and has been improved beyond the design of its competitors. Even though the four-stroke has been the leader of the engines there are still other types of motors out there on the market including the two-stroke and the rotary engine. These engines involve the same concept, but they go about it in a different shape or compression chamber. The two-stroke engine takes only two steps to complete the cycle using a gas mixture with oil and air because the chamber is shaped to where the combustion is released while the gas is injected creating only two-strokes of the piston. Because of the resulting air pollution, certain two-stroke engines have been banned in California. “A carbureted two-stroke engine can emit up to 25-30 percent of its fuel unburned into the water or…