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Date: Wed, 22 Feb 2012 16:52:58 -0500
From: Ernest Christley <echristley@att.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Throttle Back Bobble
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Chris Barber wrote:
> Hmmm? I have become pretty comfortable with most of my EC2, but before I screw up what I consider mostly a good thing, would you explain how ya did this?
> 

I'm not using an EC2.  The Megasquirt has tables for mixture and spark advance with RPM on the horizontal axis and
manifold pressure along the vertical.  You can change the values on each axis, so that the values can range (for
instance) from 400 to 4000 RPM or from 700 to 8000 RPM.  Each row and column is individually editable, so that you can
get more resolution where you want it.  You then specify the spark advance or AFR for each box on the graph.  If the
actual RPM and MP false between buckets, as it usually does, it will take a weighted average of the four closest.

When tuning, the program displays a bouncing ball that shows you where the computer thinks the engine RPM and MP is at,
and highlights the cells with varying amounts of yellow indicating how heavily weighted each one is. On one trial run, I
throttled back hard from a high-RPM/high-MP situation, and while I watched the tracer drop almost straight down and then
tack to the left (down to low MP then left toward zero RPM) I listened to the engine going bwap-bwap-bwap.  I shift the
AFR to way lean...something like 17:1, and shifted the advance up to around 35*.  A quick test run verified a smooth
deceleration without the popping and bwapping.