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How to do a compression test : Nissan Skyline R34 GT-R Vspec

The compression test gives an indication of the condition of your engine's valves, its valve seats, and piston rings and whether these parts are wearing evenly.
First we will show you the steps to take to perform a compression test on the RB26DETT, and then we will explain more about the results.
The first step is to warm up the engine.
Then the fuel pump and fuel injection fuses must be disconnected. The goal is to remove gasoline from the engine. When the engine dies, we always crank up the engine three times to make sure that no more gasoline is left. Remaining gasoline could set the engine bay in fire.
The next step is to remove all spark plugs
Now it is time for the test, we screw in the first cylinder the compression test adapter with the compression gauge.
Then crank the engine at least 4 times while pushing the gas pedal.

Take note of the result and the cylinder you are testing. After that we proceed on the next cylinder in order.

After all cylinders are tested, put back the spark plugs and reconnect the fuel pump and fuel injection fuses.
Now let’s interpret the results !
In Japan, we are measured in kg/cm2 instead of PSI.
Here is a quick conversion for you :
100 PSI = 7.03 kg/cm2
110 PSI = 7.73 kg/cm2
125 PSI = 8.78 kg/cm2
150 PSI = 10.54 kg/cm2
175 PSI = 12.30 kg/cm2
180 PSI = 12.65 kg/cm2
185 PSI = 13.00 kg/cm2

The compression test result for this Skyline R34 GT-R Vspec with 159,000 km are the following:
No1 12.7 kg/cm2 // 180.63 PSI
No2 12.5 kg/cm2 // 177.79 PSI
No3 12.6 kg/cm2 // 179.21 PSI
No4 12.9 kg/cm2 // 183.48 PSI
No5 13.0 kg/cm2 // 184.90 PSI
No6 13.0 kg/cm2 // 184.90 PSI
First the compression should be between 8.7 kg/cm2 // 125 PSI and 12.3 kg/cm2 // 175 PSI on an average condition engine.
But having high compression is not the only factor, it is also important to have less than 10% difference between the highest and lowest compression cylinder.

In our case the minimum is 12.5 kg/cm2 and the maximum is 13.0 kg/cm2. We have here 4% difference between the highest and lowest cylinder. So we can conclude that the engine is healthy.
In the case the compression is too low or there are more than 10% difference between the cylinders. Redo the test with a stronger battery and check that the timing belt is not  worn out.
If the compression test result is still not good, there are many reasons why.
Pistons, valves, head gasket, piston rings, camshaft, camshaft lobe and timing belt could cause a low compression test result.

In conclusion, the compression test standard would be different for each engine type. We will talk more about the rotary engine in the next topics.
Moreover, the compression test is a good indicator about the car condition, but a bad result can be caused by many factors.
When you buy or store a car with Toprank, you can ask for compression test and additional maintenance on your car. 
Toprank has experience selling import export JDM cars worldwide for Nissan Skyline R32 GTR, Skyline R33 GTR, Skyline R34 GTR Vspec, Nissan Silvia S13, S14, S15 Spec R, Honda Integra Type R, Civic Type R, Nissan Stagea 260RS, Toyota JZX100 Chaser Tourer V.
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