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Old 10-11-2018, 04:02 PM
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PerfTech PerfTech is offline
Join Date: Sep 2010
Location: Redlands, Ca.
Posts: 1,369
Default Food for thought!

We build, modify and test a lot of engines at our facility, and thought our
testing procedures could be of interest to some reading this thread. The leak
down test, that is commonly referred to as a compression test in the aviation
community, really doesn't provide much of the true picture of cylinder health.
Firstly it only addresses what is happening at the very top of the stroke, and
then only the compression ring. Its very possible that one or two inches down
the bore a completely different scenario exists. Cylinder taper, galling, pin
button damage Etc. can be happening and the leak down numbers can be
perfect. After performing the standard test, while the top plugs are out get an
automotive type compression tester and do a cranking compression test as well.
This will or can expose some possible other problems, and you can't have
too much information. High oil consumption can many times be attributed
to a stuck or broken oil ring or wiper ring, that will not show up on either of
the compression tests. Always do a cranking test as well. It only takes a couple
of minutes and can provide considerably more information. Thanks, Allan...
Allan Nimmo
Innovative Aircraft Safety
Products, Tools & Services
Southern California (KREI)
RV-9A / Edge-540
(909) 824-1020
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