The internal combustion engines used in automotive vehicles are mainly of two basic ypes: two-stroke-cycle and four-stroke-cycle. Either may be water-cooled or air-cooled However, most automobile engines operate on the four-stroke-cycle This type of engine is known as Otto cycle, after the name of its inventor, Nikolaus Otto. Each cylinder of the four-stroke-cycle engine has a piston, which reciprocates (move back and forth) within the cylinder. Each piston is connected to the crankshaft by means of a link known as a connecting rod The power production cycle consists of four strokes of the piston in a reciprocating engine. The first stroke draws the combustible mixture. The second stroke compresses the mixture. The third stroke creates the power of combustion. The final stroke forces burned gases out of the cylinder. The operating sequence of a four-cycle eng ine can specifically be described as follow In the first place, as the piston moves downward to the bottom Dead Center, a vacuum is created in the cylinder. The intake valve opens and air fuel mixture enters the cylinder Next, the air-fuel mixture is compressed as the piston moves upward. The spark plug is fired to ignite the air-fuel mixture prior to the piston being at the Top Dead Center. Note that both valves are closed. Then, the air-fuel mixture explodes, which forces the piston downward. Note that both valves are closed Finally, as the piston starts to move upward the exhaust valve is opened. The piston moving up forces the exhaust gases out of the cylinder. This four-stroke-cycle of piston within the cylinder is repeated time and again to push the vehicle forward Although many advanced technologies have been applied to the improvement of automobile engines, scientists have still been making efforts to concentrate the future development of engines on the three targets: reducing fuel consumption, lowering exhaust emissions, and reducing engine noise. The three targets are actually interrelated For example, reduced fuel consumption can reduce carbon dioxide emission, which a long period of time, may cause problems with the earth's climate. So, the fut developments must endeavor to achieve the three targets simultaneouslyThe internal combustion engines used in automotive vehicles are mainly of two basic types: two-stroke-cycle and four-stroke-cycle. Either may be water-cooled or air-cooled. However, most automobile engines operate on the four-stroke-cycle. This type of engine is known as Otto cycle, after the name of its inventor, Nikolaus Otto. Each cylinder of the four-stroke-cycle engine has a piston, which reciprocates (move back and forth) within the cylinder. Each piston is connected to the crankshaft by means of a link known as a connecting rod. The power production cycle consists of four strokes of the piston in a reciprocating engine. The first stroke draws the combustible mixture. The second stroke compresses the mixture. The third stroke creates the power of combustion. The final stroke forces burned gases out of the cylinder. The operating sequence of a four-cycle engine can specifically be described as follow: In the first place, as the piston moves downward to the Bottom Dead Center, a vacuum is created in the cylinder. The intake valve opens and air-fuel mixture enters the cylinder. Next, the air-fuel mixture is compressed as the piston moves upward. The spark plug is fired to ignite the air-fuel mixture prior to the piston being at the Top Dead Center. Note that both valves are closed. Then, the air-fuel mixture explodes, which forces the piston downward. Note that both valves are closed. Finally, as the piston starts to move upward, the exhaust valve is opened. The piston moving up forces the exhaust gases out of the cylinder. This four-stroke-cycle of piston within the cylinder is repeated time and again to push the vehicle forward. Although many advanced technologies have been applied to the improvement of automobile engines, scientists have still been making efforts to concentrate the future development of engines on the three targets: reducing fuel consumption, lowering exhaust emissions, and reducing engine noise. The three targets are actually interrelated. For example, reduced fuel consumption can reduce carbon dioxide emission, which, over a long period of time, may cause problems with the earth's climate. So, the future developments must endeavor to achieve the three targets simultaneously