# Understood. What is the compression ratio?

Each engine, regardless of size, type of fuel, 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 piston diameter, stroke, displacement. So, among these values you can find the degree of compression. This is a calculated value.

So, you need to know what the compression ratio is. 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 to do this: reduce the second (that is, the combustion chamber) or increase the first (that is, the volume of the cylinder). The second way is much more difficult, so tuners prefer to perform all sorts of operations with the cylinder head. This is done by grinding the plate, since the head is one-piece, and the filling method is not suitable here. In addition, in most engines, the distribution of the combustible mixture over the cylinder is calculated, so a violation of the internal geometry is fraught with consequences.

Engine compression ratio affectsmany of its characteristics in everyday use. First of all, this is its torque, since the higher the pressure above the piston, the more energy it receives during the power stroke. As a result, the pressure on the crankshaft journal increases, which means that the torque of the engine also increases.

Another characteristic that is directly affected by the compression ratio is fuel consumption, and this dependence is inversely proportional, that is, the more the first, the less the second. But not every fuel can be used at a high compression ratio. For example, if the degree exceeds 9.0, then gasoline must 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, pre-ignition from pressure and temperature.