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| Compression test results. Normal? | |
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| Tweet Topic Started: Dec 3 2016, 08:22 PM (250 Views) | |
| ohiohouston | Dec 3 2016, 08:22 PM Post #1 |
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Did a compression test yesterday just to see what I got, and cylinders 1, 2, and 3 were all around 155+/-5 but cylinder 4 was 180. What would cause the one cylinder to be so much higher? Test was done hot |
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| myredvert | Dec 3 2016, 08:46 PM Post #2 |
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myredvert
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Since 180 is close to average compression, while your 155 numbers are pretty much right at the minimum end of the range, and the difference is notably higher than the specified maximum, a more appropriate question would be "what would cause the other two cylinders to be low." ![]() Compression can be low for quite a few reasons - cylinder wear, valve issues, improper rebuild/installation issues resulting in uneven compression, improperly done compression test, etc. Since you are close to Sea Level, and your weather conditions over the last day or so have included lower than Standard temperatures and lower than standard barometric pressures, these two conditions would be approximately a wash and there would be little to no correction to your values for density altitude. If your test was done in accordance with the Factory specifications for the test, then the results can be considered reliable. Also, if the test was done by following the factory specifications, there would have also been clues observed that the factory instructions specify that could possibly point towards valves or cylinder issues, e.g., did the compression raise quickly and evenly to the factory specified values. In addition to verifying the test was done correctly, if any of the values are near or below the minimum for any cylinder or near or above the maximum for individual compression differences, or the compression rise for any cylinder did not behave normally during the test, a wet test would be appropriate. |
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| ohiohouston | Dec 4 2016, 01:24 AM Post #3 |
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Thank you very much! I will dive a little deeper to figure out what's going on |
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| Stubby79 | Dec 4 2016, 02:39 AM Post #4 |
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Throttle wide open? I always forget that one important step.
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| Woodie | Dec 4 2016, 07:50 AM Post #5 |
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One is not worn out, the other three are. |
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| 1 user reading this topic (1 Guest and 0 Anonymous) | |
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