Engine Compression

Compression in the engine provides an increase in the useful energy from the combustion of the fuel mixture. The very concept originated from the Latin word "compressio" (compression). Compression is the compression of a gas under the influence of forces from the outside. This leads to a decrease in its volume. As an external influence may be an increased temperature or pressure. In the engine (internal combustion engine) also there is a compression of the engine. In this case, the fuel mixture is compressed.

In many designs of modern cars are installed four-stroke ICE. Compression of the engine is detected, first of all, in the combustion chamber, in the zone between the walls of the chamber, the compression ring and the piston bottom. It occurs at the moment when the pressure reaches a maximum when the piston almost reached the mark of the top dead center, before the ignition of the combustible mixture.

Compression of the engine, without taking into account the deformation and acceleration of the motor, is considered a relative indicator for the state of the cylinder-piston system of ICE and a number of other units. Piston, rings, valves (exhaust and inlet), gaskets in the head of the motor block and a number of other parts ensure the quality of compression.

In the chamber there is a load that can reach fifteen atmospheres in a gasoline engine. Compression of the diesel engine is formed at a pressure reaching thirty atmospheres. In this regard, all the details involved in the process must be able to withstand such a load constantly.

When the piston moves from the created pressure, gases enter the gap between the groove and the ring. The gases are pressed against the surface of the ring cylinder as a result.

Constant loading on the cylinder-piston system, gas distribution mechanism due to constant high pressure adversely affect the state of the parts. This, in turn, worsens the power and economy of the engine. It should be noted that the compression of the engine (the same) can be completely different. This is due to different conditions of measurement: the temperature, the frequency of rotation of the crankshaft, the amount of incoming air in the cylinder.

So, for example, oil, having a greater density, viscosity, increases the compression, accumulating on the walls of the cylinder, sealing in the mating details gaps. Excess fuel, which falls into the cylinder, flushes this oil film, resulting in the compression is reduced.

When measuring the compression ratios in the cylinders, it becomes possible to determine the reasons for the reduction in engine power or "bad" start-up. Thus, for example, in machines with a mileage of more than one hundred and fifty thousand kilometers, a high compression can be caused by the formation of a significant layer of deposit on the walls of the combustion chamber. This, in turn, reduces the volume of the cavity. Because of this, accordingly, the compression also increases.

The compression level can be measured in many ways.

When the throttle is open, the maximum possible air flow in the motor is realized. The results may be affected by leakage from the air cylinders when the rings wear, in the presence of burn-throughs, cracks, scratches on the walls of the piston and cylinder, hanging valves and other things.

With the throttle closed, you can get a fairly accurate indication of the level of compression. In this case, a small amount of air comes in. In this case, it is possible to calculate the leakage caused by deformation of the rod or the wear of the valve seat.

If the motor is difficult to start, it is recommended that it be measured on a cooled engine. In this case, the compression is less than when measured on a warmed-up engine. As a rule, it should be measured with a hot engine at a temperature of about 80-90 degrees. This is due to a reduction in the viscosity of the oil and a reduction in the gaps between the moving parts.