Mailing List flyrotary@lancaironline.net Message #38193
From: Ernest Christley <echristley@nc.rr.com>
Subject: Re: [FlyRotary] FW: Phase 1 completion
Date: Tue, 03 Jul 2007 09:51:59 -0400
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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.
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