It takes me just an hour or so to break in an Enya Iron P/L engine.
Enya Engines with Iron Piston and Liner (not other types) has a reputation for taking too long to fully break in, and that is true If the break-in is done just letting the engine run rich as you normally do with other engines.
Iron Enya engines has very good metallurgy that is hard to wear out and they come with very tight fittings from Factory. That is why Enya engines are hard to start in the beginning and without proper break in they can quit when it gets hot. Iron piston gets bigger than the liner when it gets hotter, exactly the opposite of ABC engines. When the piston expands it creates so much friction that the engine quits, but as soon as you flip the prop it is back to normal, and there is absolutely no harm to the engine when this happens (if you use mostly castor oil fuel).
A special breaking is required so when the engine gets hot the piston will smoothly match with the liner with minimum friction.
I have been getting great results with this break in method that takes just one hour or so on the bench.
First Phase – Thermal Treating
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I do 10 short runs of 1min with the needle set so the engine is breaking to 2 in short bursts, letting the engine totally cool down between runs. Then 8 short runs of 2 min and then 6 of 3min (perhaps the 6x3min is not necessary but I do it anyway)
Second Phase - Unleashing the Power!
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3 to 5 runs of 6 minutes with the same needle setting as in Phase 1. Depending on how tight the engine is, it may require more or less runs. In this phase I pinch the fuel line with care, leaning the mixture to the absolutely highest rpm I can get and keep it there for 10 seconds, release the fuel line, wait for about 25s and repeat the process till the end of the 6 minutes.
It is important to understand that you need to get the engine to the max rpm possible, not just higher rpms, that is key in this process, otherwise it will take a lot more time to break in.
The top rpm will improve significantly in this stage. We do want the engine to get very hot for the piston to grow, this will cause the P/L to lose the excess particles to match with each other perfectly. The engine will end up with strong compression and will start cold or hot very easily.
USE ONLY CASTOR OIL FUEL IN THIS PROCESS!!! Absolutely no Synthetic oil!
Then go flying and after about 50 flights using all castor fuel, it will be ok to start using Blend Fuel with Synthetic oil because the engine should be running cooler by now with less friction between P/L. I have been using Byron 10/20 with castor added to 23% total oil and after many many flights with this fuel my Enya SS30 is just perfect!
Martin
p.s. do at your own risk! A friend of mine did 2nd Phase only from the start and saved a lot of time! Unfortunately he went to RC and died a few year later, so I am not sure what happened with that engine in the long run, but the Enya SS25 worked quite well on his Ringmaster at Brodaks 2008.