Understand. What is the compression ratio?

Every engine regardless of the amount, type of fuel, power and torque has a number of technical characteristics that do not change over time. For example, if you wear the engine develops less power than the new torque. In addition, it increases fuel consumption. But there are others, such as piston diameter, stroke, displacement. So, among these variables it is possible to meet the compression ratio. Is estimated value.

So, you want to know what is the compression ratio. The ratio of displacement of one engine cylinder to the volume of the combustion chamber. Therefore, if the car owner wants to increase the compression, there are two ways to reduce the second (i.e. the combustion chamber) or to increase the first (that is, the volume of the cylinder). The second path is much harder, so the tuners prefer to perform all sorts of operations with the cylinder head. This is done by grinding the plate, since the head is molded, and a method of filling here is not suitable. In addition, in most engines the calculated distribution of the combustible mixture in the cylinder, so the violation of the intrinsic geometry is fraught with consequences.

The compression ratio of the engine affects many of its characteristics in daily use. First of all, it has torque, since the higher the pressure above the piston, the more energy it receives in the process of the stroke. As a result, increases the pressure on the neck of the crankshaft, and thus, increases the time to abuse the engine.

Another characteristic, which directly affects the degree of compression – is the fuel consumption, and this dependence is inversely proportional, i.e. the higher the first, the less the second. But not all fuel is able to be used in high compression. For example, if the degree exceeds 9,0, gasoline must be with an octane number not below 92 (AI-92). The fact that the low octane number of gasoline tells about his instability to detonation, i.e., premature ignition from pressure and temperature. This leads to increased wear of the connecting rod and piston, since the explosion of the mixture occurs before the moment the piston reaches top dead center. This reduces the engine power. In addition, the increased temperature, which is fraught with other, more dire consequences like burning rings to the cylinders.

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In conclusion, it should again be recalled that such a degree of compression. This is a characteristic of the engine, which does not change throughout the time of operation, since the dimensions remain the same. Many people are confused compression ratio with compression in the engine. We will not go into details, what is the compression, just to say that this pressure, which is measured with the pressure gauge. Our compression ratio can only be calculated. In order to do this, you must measure the combustion chamber volume. This is done by pouring liquids from beakers with divisions of 1 ml.