Make a compression gauge with your own hands
If until recently the engine of your car worked like clockwork - it started well, fuel and oil consumption was normal, there were no dips in traction - but then everything changed dramatically exactly the opposite, then one of the reasons for this deterioration may be a drop in compression - the pressure developed in the cylinders.
To make sure that your assumptions are correct, a simple tool like a compression tester will help you. A compression gauge is one of the types of pressure gauges, its feature is the presence of a check valve. This valve is installed so that when the crankshaft is turned, there is no pressure release, that is, the compression gauge will record the maximum pressure on the compression stroke.
How to measure compression?
We already wrote about what compression and compression ratio are on our portal Vodi.su. This is one of the basic characteristics of the engine, and the octane number of gasoline depends on what pressure is reached in the cylinders at the peak of the compression stroke.
It is clear that if the compression drops, the fuel-air mixture does not completely burn out and fuel consumption increases.
Using a compression tester is quite simple:
- warm up the engine to operating temperature;
- turn off the fuel supply (gasoline pump), remove the terminal from the ignition coil (otherwise it may burn out);
- remove all spark plugs.
This is the preparatory stage. Then it would be nice if you have a partner who will press all the way on the gas pedal so that the throttle is open. But first you need to install the compression gauge hose into the spark plug wells - the hose comes with several types of nozzles that fit the sizes and threads of different types of spark plugs - European or regular.
Then you will need to crank the crankshaft with a starter so that it makes a few turns. Two or three seconds is enough. You record the indicators and compare them with the data from the table.
You may also need an engine oil syringe. By pouring a little oil into the cylinder, you will understand why the compression is reduced - due to wear on the piston rings (after oil injection, the compression level will return to normal), or due to problems with valves, timing mechanism or cylinder head (after oil injection the level will still be lower than necessary).
As you can see, nothing complicated. But there is one problem - there are budget compression meters on sale that do not give accurate readings, the error can be very large, which is not acceptable with accurate measurements.
Good devices are expensive - about a hundred dollars. And some drivers generally prefer not to bother with such questions and go to the service station in order to give a few hundred rubles for such a simple operation.
We make a compression gauge with our own hands
It is not so difficult to assemble this measuring device; all the necessary elements can be found in the garage of experienced motorists or in auto parts bazaars.
What you need:
- manometer;
- a valve from a camera for a truck (popularly called a "nipple");
- spool (nipple);
- brass adapters of the required diameter and threaded;
- hose (high pressure hydraulic hose).
The valve from the chamber must be in good condition, not bent, without cracks. The valve diameter is usually 8 millimeters, and it can be curved. You need to align it and cut it off from the side that was welded into the chamber, and the threaded part where the spool is screwed in must be left as it is.
Using a soldering iron, from the cut side, solder the nut into which the pressure gauge will be screwed. We twist the spool into the resulting tube and put a 18x6 rubber hose on it. We sharpen the end of the hose under a cone so that it enters the candle hole. Basically, that's all.
Using such a device is quite simple: insert the end of the hose into the hole in the cylinder block, measure the pressure.
The spool acts as a bypass valve, that is, the peak pressure that occurs at top dead center on the compression stroke will be recorded on the pressure gauge. To reset the readings, you just need to press the spool.
Of course, this is a very simple option. The hose must fit exactly the size of the tube. For reliability, small diameter metal clamps can be used. True, they will need to be removed each time in order to get to the spool and reset the readings.
You can also pick up brass adapters of the same diameter and with the same thread pitch as the candles at the end of the hose. By screwing such an adapter into the hole, you will be sure that the compression will be measured accurately.
Please note that the results obtained cannot be considered one hundred percent correct - the compression level changes in different engine operating modes.
If the discrepancy between the cylinders is minimal, this does not indicate any serious problems. If you see that the indicators really seriously deviate from the norm (the standard value is indicated in the instructions), then this indicates a number of problems that remain to be clarified.
Also, compression can be measured in different units - pascals, atmospheres, kilograms per square centimeter, and so on. Therefore, you need to select a pressure gauge with the same units of measurement that the manufacturer indicated, so that later you do not have to suffer with deciphering the results and transferring them from one scale to another.
Video on how to measure compression in a cylinder without a compression gauge.
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