Compression test: warm or cold engine?

Hello everyone!

Is the compression test typically performed on a cold or a warm engine?

The context of my question is as follows: This week, I performed a bounce test with my A3 AGR and my wife's G4 ALH at the same location.
The only difference was the operating temperature of the engines, because my AGR was already warmed up, while the ALH was still almost cold.
The differences were dramatically large .
In my AGR system, a fluctuation lasted approximately 5.5 seconds, with all cylinders being practically equal (maximum variation of +/- 0.2 seconds). The ALH had values below 3 seconds per jerk under the same boundary conditions. There were practically no noticeable differences between the individual cylinders, however, I find the absolute value compared to the AGR to be quite shocking.
The ALH engine might be experiencing cold start problems due to its low compression ratio.

I still hope that the difference can be explained by the different engine temperatures, as the piston seals less effectively in a cold engine because its operating clearance is still too large. Now, please don't tell me anything that contradicts that!

You also need to consider that the second... The gear ratio of the DQY transmission is slightly longer than that of the CZL transmission, but this does not explain the significant difference.

How do you assess the situation?

Regards,
Alex.

Just warm up the golf cart and run the test again. That way, you'll have the same conditions. Compression tests are usually performed on warm engines.
Best regards, Harri.

Hello,

Under normal operation, the motor does not require 3 seconds per half revolution (10 RPM).
The test, in my opinion, only allows for a comparison between the cylinders, and that comparison looks good. If the engine isn't visibly blowing smoke out of the oil filler cap, I wouldn't worry.

Sincerely,
Christian