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Date: Tue, 03 Jul 2007 09:51:59 -0400
From: Ernest Christley <echristley@nc.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] FW: Phase 1 completion
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Al Gietzen wrote:
>
> The other is that there is something strange about the timing. At low 
> power things appear fine; switching off leading ignition has more 
> effect than switching off trailing, as expected. At operating power 
> levels, however; switching off leading has almost no noticeable 
> effect; whereas switching off trailing drops the rpm by 400+ rpm – 
> which suggests that the timing is very late. Yet advancing the timing 
> via mode 8 does not make any improvement. What is wrong with this 
> picture? It is possible that the added filters caused a delay in the 
> timing, although analysis suggests the effect would be small. Why 
> doesn’t advancing the timing improve the power? Is there a timing 
> change to one set of coils associated with disabling the other? We are 
> removing the filtering capacitors from the ignition circuits as a test 
> to see what the effect is.
>
Just a shot in the dark, but is it possible that you are too far 
advanced and are reaching peak pressure to soon? Just a slight alignment 
or measurement error could mess you up, and the rotary's resistance to 
detonation would mask the problem. A test would be to retard the 
ignition 1 degree, then disable the leading and trailing to compare the 
numbers to what you have now.