Compression in engine cylinders. Compression check in the cylinder of the car engine

As you know, the engine is the heart of the car. A lot depends on its serviceability. An important factor determining its condition is compression in the engine cylinders. This parameter is different on diesel and gasoline vehicles. What is engine compression, how to measure it and what are the normal parameters? You will learn all this from our today's article.

Characteristic

So, what is the compression in the engine cylinders? This is a parameter that indicates the pressure that is created in the cylinders at the end of the compression stroke. The technical condition of the engine depends on the value of this figure. Therefore, the compression test in the car's engine cylinders is taken as a diagnostic factor, which makes it possible to evaluate the serviceability of the power unit.

What is the norm?

If we talk about gasoline engines, this parameter is on average 11 to 12 kilograms per square centimeter. This compression on most cars brand "Daewoo", "Ford", "Kia", "Toyota" and others. The highest - in the "Mazda" of the sixth series. So, the manufacturer allocates a standard of 16 kilograms per square centimeter. But there are also engines, where the norm is 7-7.5. As a rule, these are old, deformed motors with a low compression ratio. A vivid example can serve as the engine ZIL-130 or from GAZ-3307. The compression ratio in the cylinders of these trucks is 7 kilograms per centimeter square. This is done for the purpose of moving the engine to a lower-octane gasoline. As practice shows, such engines easily "digest" the 76th and 72nd gasoline, even the most dubious origin. Now let's move on to diesel engines. Here the average is in the area of 25-30. A critical indicator for diesel engines is the pressure of 20 kilograms per square centimeter. In this case, the engine may not even start.

Can we take a run for the testimony?

It should be noted that the compression in the cylinders of the engine should be not only high, but even. If in one cylinder this indicator is 12.8 kgf, and in the other - 10, this is not good. The manufacturer allows a take-off run of not more than one kilogram per square centimeter. A strong drop can signal a malfunction. As for diesel engines, the error here can be 3 atmospheres, but not more.

Metering conditions

The most important conditions for checking the compression in the engine cylinders are the warmed-up motor and the open throttle. Measurement is performed with the candles unscrewed and on a working battery.

About compressometers

It is this device that measures this parameter. There are many models of compressometers, but they differ only in their design. So, this device consists of a tip (it is installed in a candle hole), a manometer and a check valve. Elements are connected together by a thick hose or metal tube. Experts advise buying the first option, since the part of the device can rest against other hanging elements because of the rigid rod. Also there are compressometers that are screwed into the candle hole or just pressed against it.

Checking engine compression - useful recommendations and work stages

So, first warm up the engine to operating temperatures. Then muffle it, open the hood and unscrew the candles. Next, install the tip of the compressor in the hole (screw it into the thread or just press it) and call the assistant. It will be on your team to spin a starter. Rotate it for about two to three seconds. It is no longer necessary - the compression will not be higher, but the battery will be discharged substantially. Then we fix the readings of the manometer and write them down in a notebook. Then go to the second cylinder. The procedure is repeated in a similar way. It is not necessary to screw the candle onto the cylinder - only after the end of all measuring procedures (otherwise the motor will start and will touch). After completing the measurements, set back the candles and analyze the result.

Measurements on the diesel engine

Earlier we considered the procedure for measuring the compression in the cylinders of the petrol engine. But in diesel spark plugs there is no - the mixture ignites from compression. How on such motors to measure compression? It's simple. First, you need to prepare a specialized compressometer with a scale of up to 60 atmospheres. It must go with an adapter in the form of an injector. Then turn off the fuel supply. To do this, de-energize the solenoid valve. It is worth noting that the compression in the cylinders of the diesel engine can be measured only with one nozzle removed. So, start the starter and twirl it for two or three seconds. During this time the shooter should rise to 25-30 (and possibly more) atmospheres. Then the nozzle is put in place and the next one is rolled on the next cylinder. All data should be recorded in a notebook or photographed.

What can cause a low compression?

If this parameter is significantly different from the factory one in the lower side, this is a very bad sign. Perhaps the engine will require major repairs. And the causes of low compression may be:

• Scuffs on the walls of the cylinders. They are formed due to the metal chips that occur inside the cylinders during the operation of the ICE. Shavings signal a significant production - perhaps, the motor experienced oil starvation or lay rings.
• Blasting the head of the block. As a result, the "valve-piston-cylinder" system is not sealed.
• A crack in the block. This phenomenon is due to engine overheating.
• Leakage of valves. It can be caused by burnout or incorrect adjustment. Also note that the valve clearance is violated even if there are hydraulic compensators. Over time, their oil holes are clogged. Elements are no longer able to compensate for the necessary clearance, and the valves are not working properly (they do not close fully, which is why the pressure at the end of the compression stroke drops significantly).
• Corking of piston rings. The problem can be caused by the use of poor-quality fuel or by the late replacement of oil.
• Natural wear. Over time, the clearance between the walls of the cylinders and the piston increases. Because of this, the chamber does not generate the required pressure for the working process. Usually this happens after 300-400 thousand kilometers.

Is it possible to delay this problem? In order not to experience problems with low compression, just change the oil, filters and candles in time (if you have a gasoline engine). This is the only way to extend the life of your engine.

Conclusion

So, we found out what compression is in the engine cylinders and for what reasons it can change. If this parameter is below the factory one, it is necessary to take immediate measures to repair the engine. The exact reason can be established already by the minder. But usually these are rings or burnt out valves.