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Old Oct 26, 2012, 06:00 PM
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Joined Feb 2012
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Originally Posted by Brutus1967 View Post
I have fiddled around a bit with all needles, but they ended up pretty much the same as they were.
Main needle is maybe one or two clicks richer now, just in an attempt to get the temperature down when WOT, the rest is more or less unchanged.

It has never been a power house anyway....

Brgds, Bert
If you have not leaned the mixture out you are probably running pretty rich & not making peak power. That is why you are not observing the usual power increase & improved fuel economy.

It would be to your advantage to get your mentality out of the glow ignition mindset. Leaning out the mixture for peak power W/CDI will not raise temperatures as much as it would W/glow ignition.

Also, your ignition timing is now "fixed" by the spark timing. It is not altered by mixture or engine temperature.

The engine will run hotter W/CDI compared to GI, but the engine temperture will not result in volitile ignition timing issues as W/GI for the reasons stated above.

If there was a way for you to mount the engine on a test stand, you could put a large prop on it to load the engine down to the expected RPM operating range.

Blocking some of the the prop wash from cooling the engine to simulate conditions in the heli would allow you to do some real world testing of timing, mixture, engine cylinder head temperature relationships under load.

It is going to be very difficult for you to tune your engine on the heli.

High performance water cooled automotive 4-stroke engines typically make peak HP @ the top of the RPM ranges W/around 36* BTDC ignition timing on unleaded pump gasoline.

W/methanol in a small aircooled 4-stroke, the peak HP should be developed @ similar ignition advance. On gasoline, that timing advance needs to be backed of to about 28* BTDC unless the compression ratio has been reduced to prevent detonation..
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