I'm finding that at about 100F LOP I sense that the engine is starting to not like it – like it doesn't seem to be entirely smooth; maybe an occasional miss here and there. Am I right that some of you guys run as much as 200 LOP; or is it my imagination – in both cases.
Would timing setting have much of anything to do with running LOP?
Just past by the 100 hr mark on the engine near the end of a 500 mile trip on Monday. I plan to leave next Monday on a round trip of over 2000 nm over the following week. That'll rack up a few hours.
Al
In olden times, if your engineer didn't dial up well lean of peak on all 4 engines
you would be landing in the water well short of Gatwick.
Now, instead of thousands of pilots knowing about lean of peak operation, we have that number badmouthing LOP because they saw in the Lycoming manual that it hurts the engine. Why this institutional ignorance would be carried forward is a mystery to me.
George Braley in Ada Oklahoma has run the flat engines for thousands of hours on the dyno to see for sure what is what. He sells kits of injectors for flat engines using the Bendix dribble injection system, so that each cylinder can be tuned to hit peak EGT at the same time while leaning. You need EGT probes on each cylinder of course. A recording system of some sort is a big help.
So you install the GAMMI injectors and run the test at several altitudes and send in the results with however many GAMMIs need changed. He sends back the leaner or richer injectors for each cylinder, and you test again.
Once you finish, you may have 6 different flow rates in 6 cylinders. Since the fuel delivery is based on airflow and a look at the itake system shows 6 differing lengths of tubing, 6 different injectors seems like the right answere.
Once you have this finished, you can hammer from Columbus Ohio to Zephyrhills (the place to park when going to Sun&Fun) at the top of the yellow arc and at 12 GPH. In a 1960 M model with a fresh 550 and super simitar 3 blade prop. Engine is smooth as silk. Low cylinder head temps, low oil temps, no metal in the reports.
It should work just fine in a rotary, so long as fuel flow in both housings is about the same. The troubled engine feel is when one housing is performing less well than the other. So when leaning one housing has peaked before or after the other, or has reached well lean of peak before the other.
The leaner mixture is a bit harder to light, and burns a bit slower than a richer mixture. This is a benifit in big piston engines as it replicates a higher octane fuel, resisting detonation along the way.
So a slight increase in ignition advance might be a help. Also the balance of the injectors may be off slightly, and there are companies who can balance stock injectors, or just test and tag a bunch of them so you can pic two pair that are very close in performance.
Nobody races a rotary without a multi spark ignition system. The performance you are trying to achieve is at the upper edge of Kettering system performance. So, timing adjustments and split changes might be helpful.
Fresh plugs gapped tight. Throttle wide open.
Lynn E. Hanover
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