Compression in the engine cylinders is one of the most important factors of its work. It denotes the maximum pressure during idly scrolling the motor. Separately taken models of power units involve various indicators of the level of compression. About this further in the article.

Engine compression that is

Compression among motorists is considered a diagnostic factor to estimate the state of the piston group and the operability of the car engine. Compression is the greatest pressure in the cylinder, which is created by the piston at the end of the compression tact. The engine compression can be measured in different units, but the greatest popularity gained measurement in the atmosphere.

Compression is an important point when diagnosing a car engine

High compression protects the crankcase from excessive gas ingress, as a result of which the gases are sent to performing useful work. This entails a decrease in fuel and oil consumption, therefore, the power of the power unit and its efficiency increases. Under conditions of low compression, the motor power drops, the car dynamics deteriorates and the consumption of fuel and lubricants increases.

The degree of compression that it

Not very experienced car owners sometimes confuse the concept of "compression ratio" with the concept of "compression", but in reality these are different things. The degree of compression is the ratio of the volume of the cylinder of the power unit to the volume of the combustion chamber.

The degree of compression and compression than their dependence is determined

Unlike compression, the compression ratio is a constant value that is indicated by the manufacturer in technical documentation. It is not measured in units, therefore it makes no sense to compare it with compressions. Also, this parameter directly affects the power of the motor. What it is more, the pressure above the piston is higher, and, therefore, above the torque.

The compression is influenced by the time of time as a result of gradual wear of the components of the piston group and, as a result, reducing the pressure in the cylinder. It is worth noting that compression in the engine directly depends on the degree of compression, this connection of values \u200b\u200bis displayed in the calculated parameters for each type of power unit.

Compression table from gasoline cars

Compression indicators in VAZ cars, provided that all systems and aggregates are working:

• VAZ 2106-2107 - compression 11 kg / cm2 . 
• VAZ 2109 - compression of 11 kg / cm2.
• VAZ 2110 is a compression of 12 kg / cm2.
• VAZ 2112 - compression 12.6 kg / cm2.

Compression in gasoline engines of some other models of transport of different manufacturers:

How to calculate the compression of the car

To determine compression, use the following formula:

Compression \u003d coefficient x x to compression ratio

The indicator of compression can be found in engine technical documents, while each car model has its own degree of compression. As for the coefficient X, it is also separately defined for each group of motors, for example, four-stroke gasoline power units with a spark ignition system have a coefficient 1.2-1.3.

What is the compression of diesel engines

The compression indicator in diesel engines is significantly higher than in gasoline, since the ignition of the fuel mixture in diesel units does not occur from the spark, but from compression under strong pressure. To the ignition temperature, the fuel is heated at a pressure of about 35 kg / cm2. Naturally, the final pressure indicator, which is sufficient to ignite the diesel fuel, also depends on certain conditions like the state of the motor itself or the ambient temperature. However, it can be concluded that in the process of reducing compression as a result of wear of the piston, the car with diesel is becoming more difficult to start.

Experts determined the value of the compression of the diesel engine, sufficient for its start in conditions of different external temperature:

• 40 - power unit starts at temperatures up to -35 degrees.
• 36 - the vehicle becomes at temperatures up to -30 degrees.
• 32 - starts after a long parking at temperatures up to -25 degrees.
• 28 - fuel flashes after a long parking at -15 degrees.
• 25 - Motor without problems starts after a long parking in a warm environment at -15 degrees.
• 22-23 - not cooled by a power unit starts immediately, a long parking is possible only in the garage at the positive temperatures.
• less than 18 - even a preheated engine under any conditions will not start.

Diesel Cars Compression Table Normally

The values \u200b\u200bbelow will be reliable when starting serviceable motors, in transport, where all systems work. In the presence of faults, these indicators are capable of not true.

The value of the compression of diesel engines of some car models:

• KAMAZ Euro-0 - compression 29-35 kg / cm2.
• KAMAZ Euro-1 - compression 29-35 kg / cm2.
• KAMAZ Euro-2 - compression 29-35 kg / cm2.
• KAMAZ Euro-3 is a compression of 32-37 kg / cm2.
• KAMAZ Euro-4 is a compression of 32-39 kg / cm2.
• YAMZ 236 - Compression 33-38 kg / cm2.
• YAMZ 236 turbo - compression 33-38 kg / cm2.
• YAMZ 238 - Compression 33-38 kg / cm2.
• YAMZ 238 turbo - compression 33-38 kg / cm2.
• YAMZ 240 - compression 33-38 kg / cm2.
• YAMZ 240 turbo - compression 33-38 kg / cm2.
• D240-245 (MTZ80-82) - compression 24-32 kg / cm2.
• MAN F90 / 2000 - Compression 30-38 kg / cm2.

How to make a measure of the engine compression correctly:

The technical condition of the power unit and the conditions under which measurements are carried out are affected by the compression indicator, therefore, the compression should always be measured and in the same mode.

conditions for measuring compression

Measurements are usually carried out in such conditions:

1. Good starter.
2. Charged battery.
3. Disconnected fuel hose.
4. From coils disconnected low-voltage wires.
5. In all cylinders, candles are twisted.
6. Shot air filter.
7. Open throttle.
8. Preheated to the required temperature of the power unit.

measurement of compression using a compressometer and a candle wrench

The procedure for measuring compression is carried out using a candlestone and compressometer. The compressometer should be inserted into the hole from the twisted candle at one time with the start of the power unit at idle and hold until the testimony on the scale will stop growing. Such manipulations need to be carried out with all motor cylinders.

Why the data obtained may differ from passport data

The information obtained when measuring compression, as a rule, differs from the numbers declared by the manufacturer of the car in the technical documents. The discrepancy in the values \u200b\u200bis due to the wear of the piston group arising from the regular operation of the vehicle. With increasing wear of elements, compression in the cylinders of the power unit decreases.

Undoubtedly, with low deviations from the figures declared by the manufacturer, the car owner can continue to use the vehicle, without repairing the piston group. Permissible is the discrepancy of up to ten percent. With an increase in the rupture of indicators, the components of the motor are considered strongly worn.

Causes of decline in compression

1. The appearance of Nagara due to the wear of the oil-challenge caps.
2. Defect camshaft camshaft.
3. The mark or deformation of the valve.
4. Piston squeezing.
5. The crack in the piston jumper.
6. Piston rings sat down in the piston grooves - the most common cause of compression reduction.

What threatens the car when working with reduced compression

As a rule, with these reasons, the decrease in compression occurs only in one cylinder, so the motor overhaul is not required. In this case, it is sufficient to clean the combustion chamber from Nagara and replace the details.

If the compression decreased in all cylinders at the same time, most likely, the tightness of the combustion chamber was disturbed, which could lead to overhaul of the motor. If the tightness of the combustion chamber is broken, the gaps are needed, as well as the gas distribution mechanism.

In diesel power units, the cause of the decrease in compression is the wear of cylinders mirror. A sign of a decrease in compression in diesel engines - the appearance of blue smoke from the exhaust pipe as a result of the incomplete combustion of the diesel fuel in conditions of not high temperatures.

Sometimes the fault of the third-party elements can lead to a decrease in the pressure in the cylinders, for example, poor spraying of fuel as a result of a nozzle fault.

How to raise compression

To eliminate the problem of low compression of the power unit, it is necessary to replace or repair the damaged parts and the aggregates, after which the engine power will increase again.

Tips Pros: Additive for engine compression, enjoy or not

Undoubtedly, special additives are capable of increasing the compression of the power unit, since they have a lot of positive complex properties. However, you need to understand that you should not expect a substantial effect from additives if the engine is very worn. By the way, among the car owners there are a number of negative feedback after use. In any case, the choice is yours.