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-   -   CPI timing optimization ? (https://vansairforce.net/community/showthread.php?t=179933)

DanH 03-08-2020 08:53 AM

Quote:

Originally Posted by rwtalbot (Post 1413009)
Yes its interesting. The "standard" approach, common across most of the vendors I have looked at seems to be to start at about 25-24 inches MP and advance 2 degrees over base engine timing for every inch of MP reduction until they reach 14-18 degrees.

The same basic approach was suggested by Nigel Speedy in his May 17 KITPLANES article.

Note Nigel's suggestion that essentially the same cruise performance at less CHT is available by sticking with less advance and simply climbing a few thousand feet higher. The interesting thing about the approach is the ease of climbing higher...due to not fighting CHT in climb.

Quote:

I don't know, but I suspect no one has really run an engine on a dyno to optimize too much.
It will be interesting to see the Lycoming-derived advance schedules in the Lyc-branded version of the Surefly.

Toobuilder 03-08-2020 09:59 AM

My 540 is going to spend some time on the Ly-Con dyno in the near future and I hope to be able to play with the timing. In my case, I'm looking to quantify the 100% power figure and see how it compares to my in situ flight testing.

As for development of a high altitude curve - that's pretty tough to do unless your dyno room is also an altitude chamber. Short of an altitude compensated test cell, the in situ testing is the way to go. Fortunately, the SDS product architecture makes that drop dead simple.

rwtalbot 03-08-2020 11:26 PM

Quote:

Originally Posted by DanH (Post 1413040)
Note Nigel's suggestion that essentially the same cruise performance at less CHT is available by sticking with less advance and simply climbing a few thousand feet higher. The interesting thing about the approach is the ease of climbing higher...due to not fighting CHT in climb.

Climbing higher is a good option if operational issues don't prevent that.

My ECI engine has cam squirts, a cold air (hot oil) induction and super corrosion resistant (extra blow by, too hard for mere mortals to hone) barrels. I have never really had an issue with CHT. Oil temps ...

Quote:

It will be interesting to see the Lycoming-derived advance schedules in the Lyc-branded version of the Surefly.
It would be great if Lycoming actually publish those curves. I am not sure we really need them as there are not a lot of aircraft suffering engine damage. It does seem the older platforms are not sufficiently open to really facilitate a lot of experimentation.

The more I learn about it the more I'm not overly comfortable installing an ignition with "special sauce" inside. 10+ years of operational history has had me chasing around fixing things which were most likely the result of sub optimal components supported by excellent marketing. Just my opinion...


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