Gasoline engine because fuel viscosity is small, fast evaporation, and the air outside the cylinder can form a uniform

mixture, and then the mixture sucked into the cylinder, fuel injection system or fuel injected into the cylinder, the gas

expansion work done. From the beginning of 1886 the first car, the gasoline engine in the car, especially on the extensive

use of small cars, has not changed.
The disadvantage of gasoline is lower than the thermal efficiency of diesel engines, fuel consumption higher than the engine

ignition system complexity, reliability and ease of maintenance is not as diesel engines. [1] gasoline engine works: a

working cycle includes four piston stroke (so-called piston stroke means the piston from the TDC to BDC the distance between

the process): the intake stroke, compression stroke, expansion stroke ( power stroke) and the exhaust stroke.
 Gasoline engine compression stroke

To sucked into the cylinder of the combustible mixture can rapidly burn in order to have a greater pressure, so that the

larger issue of the engine power, must be burning combustible mixture before compression, to reduce the volume, density,

increased temperature, the need for compression. In this process, the intake and exhaust valve fully closed, push the piston

crank up only by the next point to move a trip point that compression stroke. At this point the mixture pressure will

increase to 0.6-1.2MPa, temperature up to 600-700K.

In this trip there is a very important concept, that is, the compression ratio. The so-called compression ratio, the gas

cylinder before compression is the maximum volume and minimum volume compression ratio. Compression ratio is generally

greater in the compressed mixture of the end of the higher pressure and temperature, the faster the burn, thus the greater

the power the engine issue, the better the economy. General car between the compression ratio in the 8-10, but now the latest

listing of Polo reached a high 10.5 compression ratio, so it's relatively good performance of torque. But the compression

ratio is too large, not only can not further improve the combustion, but there will be violence and surface ignition fuel

combustion, which are not normal phenomenon (the impact of fuel quality is also occupies a relatively important position,

which we will explain in more detail later).
Deflagration is due to gas pressure and temperature in the combustion chamber than the distance from the center of the end

ignited combustible mixture ignition caused by an abnormal combustion. diesel water pump deflagration to a very high rate when the flame to

spread, even in the case of expansion of the gas too late, sharp rise in temperature and pressure to form a pressure wave,

the speed of sound to move forward. When this pressure wave hit the combustion chamber wall is a sharp knock on the issue of

sound. At the same time, will cause engine overheating, power down, fuel consumption increases and a series of adverse

consequences. Severe storms can cause burning or burned valves, broken bearings, spark plug insulators and other parts

damaged by breakdown phenomena.
Gasoline engine fuel in addition to violence, high compression ratio engines may also face another problem: the surface

ignition. This is because the tank at the hot surface and hot (such as the exhaust valve head, spark plug electrodes, carbon

deposition at) ignite the mixture produced by another abnormal combustion (also known as hot as early as ignition or fuel).

Surface ignition occurs, is also accompanied by a strong Knocking sound (more boring), the resulting high pressure causes the

engine load increases, gasoline water pump shortened life expectancy.