Alan Maurer Posted February 14, 2021 Report Posted February 14, 2021 Flying an M20R ,2008 model with around 800 hours total time. Last annual six months ago noted low compression on cylinder #4. Was not told this was a big problem and boroscope check was OK , but have noted that EGT for that cylinder is usually 50 hotter that the others. Pressure was 45/80. Can easily recheck this but have thought this cylinder may have ?? and exhaust leak. Glad to have some thoughts :-) Thanks Alan Maurer N913ND
carusoam Posted February 14, 2021 Report Posted February 14, 2021 Hey Alan! Are you able to send your engine monitor data to Savvy, push the share button, copy the link, and post it here? This would allow us to review your engine data along with you, to see what may be going on... Got any of the boroscope pics you can share? We are pretty good at discussing heat signatures on exhaust valves... As always... IO550 / Continental compression data isn’t very helpful compared to other engines...Too Often, the rings align in time to run a funny compression test... Expect the most popular cause for an EGT to go high... is a deposit inside a fuel injector... The usual next step is to do a flow test of the injection system (baby food jar test) or go right to cleaning the fuel injector... Always try to capture what washes out of the fuel injector... if it is a solid part... you want to know where it came from... If you have JPI data, this is easy... go for it! PP thoughts only, not a mechanic... Best regards, -a-
GeeBee Posted February 14, 2021 Report Posted February 14, 2021 https://resources.savvyaviation.com/wp-content/uploads/articles_eaa/EAA_2013-07_compression-in-context.pdf 1
V1VRV2 Posted February 14, 2021 Report Posted February 14, 2021 Need to know the master orifice number recorded that day for cylinder compression relevance. What were the other cylinder compressions? Could be a ring not expanding correctly due to carbon buildup. Could be a leaking valve. Leak down test will help you find the culprit. 1
PT20J Posted February 15, 2021 Report Posted February 15, 2021 45/80 is pretty low and I would want to investigate that. You can tell where the air is escaping by listening at various points: Tail pipe for exhaust valve; air inlet for intake valve, oil filler for rings. At the museum, when we get one with low compression, if the filter is clean, we run it up to temp and then check it again. But, it's usually a valve or a ring. Skip 1
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