Engine Contrast

Matt

Ingles

English 100

13 February 2006

Engine Contrast

The engines in most cars today use what is called a four-stroke combustion cycle to convert gasoline into motion. The four-stroke combustion cycle was invented in 1867 by a man named Nikolaus Otto. In the end of the 19th century, gasoline engines were not very efficient. A man named Rudolf Diesel set out to develop an engine with a high efficiency. Rudolf Diesel came up with the idea of the diesel engine, and in 1892 he patented his idea in Germany. Diesel engines also use the four-stroke combustion cycle. Gasoline engines and diesel engines differ in several ways such as efficiency, the fuel systems and how they function.

One difference between gasoline engines and diesel engines is the efficiency. Gasoline engines tend to be made from relatively light weight parts which mean they tend to wear out faster or break easier. In order to produce more horsepower, gasoline engines have to turn higher RPM (revolutions per minute). Higher RPMs mean parts tend to wear out faster. Since gasoline engines have fuel mixed with the air in the cylinder, they will only have a compression ratio from between 8:1 to 12:1. If the compression ratio gets too high, the engine gets an uncontrolled combustion, otherwise known as preignition. Diesel engines, on the other hand, tend to be made from heavy parts that do not wear out as fast. Diesel engines also turn a lower RPM to produce horsepower. Most diesel engines operate at a compression ratio from between 14:1 to 25:1. Diesel engines can operate at such a high ratio because they only compress air.

Another difference between gasoline engines and diesel engines is the fuel systems. Gasoline engines generally use either a carburetor or port fuel injection. With a carburetor, the air and gasoline are mixed long before they enter the cylinder. In a port fuel injected engine, the right amount of fuel is injected into each individual cylinder right above the intake valve. Gasoline engines cannot use direct fuel injection. However, diesel engines cannot use a carburetor or port fuel injection. Diesel engines can only use a direct fuel injection. Direct fuel injection is when fuel is injected directly into the cylinder, not outside it.

The final difference between gasoline engines and diesel engines is how they function. In a gasoline engine, the piston starts at the top of the cylinder. As the crankshaft turns, the intake valve opens and the piston moves down to let the cylinder fill with a mix of gas and air. This is known as the intake stroke. Then, the piston moves back up the cylinder to compress the mixture (compression makes the explosion more powerful). This is known as the compression stroke. As soon as the piston reaches the top, a spark plug makes a spark which ignites the mixture causing