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I am in the midst of an assisted annual on my Tiger.. The compression measured cold were 70/80, 72/80, 71/80, 48/80 in cyl 1, 2, 3 4. There was air coming out the exhaust. Looking in the engine log, compression at last annual was in the mid to high 70s in all cylinders, likely after the engine was ran.
Is it normal that one cylinder could drop that much?
I’ve had the Tiger now ~9months, and have put ~40hrs.. Except for the trip home where we fire walled it, flying at ~9500′(approx 6 hrs), I generally turned 2350 in cruise.. For leaning during cruise, it was lean till rough, then enrich until smooth.. The temp gauge generally showed ~180 (unfortunately don’t have an engine monitor for CHT / EGT)
Monday, We plan to run the engine, then test hot, and later cold again..
Any thought on [1] is this for real? [2] what could have caused it? [3] any suggestions on next steps before the drastic step of removing the cylinder assembly for overhaul?Thanks in advance..
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Matt had #3 at 18/80, all others fine. So just one can go just like that.
FYI
Roscoe
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Ran the engine today and measured hot.. #4 was at 58/80.
The engine ran like it always has.. it did not seem any weaker than before.. So wondering if #4 has been weak all along..
I am in the Chicago area, and my static rpm at full throttle generally was 2150-2200.. (sensenich prop) Does this indicate a weak cylinder?Plan is to remove the cylinder assembly and have it inspected and repaired.
My immediate question was could this have been prevented?
A number of friends at my airport suggest 100LL can cause this kind of failure (earlier we had determined the cylinder was leaking through the exhaust valve).. We did see balls of lead inside the plugs, and spatters inside the cylinder..
They also suggest switching to 91 octane gas
Others have recommended adding Marvel Mystery Oil at fillups to negate the effects of lead.Switching to 91 octane makes a lot of sense.. Can it harm the airplane? Anyone on the forum burning 91 octane?
Thoughts on the Marvel mystery oil fuel additive?thanks!
-tony
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