# We understand. What is the compression ratio?

Cars

Each engine, regardless of volume, typefuel, power and torque has a number of technical characteristics that do not change over time. For example, when worn, the engine develops less power than the new torque. In addition, fuel consumption also increases. But there are others, such as the diameter of the piston, stroke, working volume. So, among such quantities it is possible to meet the degree of compression. This is the calculated value.

So, you want to know what is the degreecompression. This is the ratio of the working volume of one cylinder of the engine to the volume of the combustion chamber. Therefore, if the car owner wants to increase the compression ratio, there are two ways for this: to reduce the second (that is, the combustion chamber) or to increase the first (that is, the cylinder volume). The second way is much more complicated, therefore tuners prefer to perform all sorts of operations with the cylinder head. This is done by grinding the plate, since the head is solid-cast, and the filling method is not suitable here. In addition, in most engines, the distribution of the combustible mixture along the cylinder is calculated, so the violation of internal geometry is fraught with consequences.

The compression ratio of the engine affects a lot of itcharacteristics in daily operation. First of all, this is its torque, because the higher the pressure above the piston, the more energy it receives during the working stroke. As a result, the pressure on the crankshaft's neck increases, which means that the engine's torque also increases.

Another characteristic directly affectedthe degree of compression is the fuel consumption, and this dependence is inversely proportional, that is, the larger the first, the smaller the second. But not all fuels can be used with a high compression ratio. For example, if the degree exceeds 9.0, then gasoline should be with an octane rating of at least 92 (AI-92). The fact is that the low octane number of gasoline indicates its instability to detonation, that is, premature ignition of pressure and temperature.

This leads to increased wear and tearpiston-piston group, because the explosion of the mixture occurs even before the piston reaches the top dead center. This reduces engine power. In addition, the temperature regime increases, which is fraught with other, even more terrible consequences, such as sticking rings to the cylinders.

The compression ratio of the diesel engine is much higher,sometimes even twice. It reaches 16, since ignition of the combustible mixture occurs not from the spark of ignition, but from the pressure in the combustion chamber. Pistons here have special sleeves in the bottom, which serve to direct the mechanism straight down.

In conclusion, it is worth recalling again thatcompression ratio. This is the characteristic of the engine, which does not change during the entire operation time, as the dimensions remain the same. Many confuse the compression ratio with the compression in the engine. Let's not go into details about what a compression is, let's just say that it's pressure, which is measured using a manometer. Our compression ratio can only be calculated. In order to do this, you need to measure the volume of the combustion chamber. This is done by topping up the liquid from the beaker with a division of 1 ml.