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Date: Wed, 16 May 2012 11:56:25 -0500
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Subject: Re: [FlyRotary] With great power comes...the ability to muck things up
From: Mark Steitle <msteitle@gmail.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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Ernest,

Great diagnostics there.  Let us know how the MegaSquirt works out.

Mark

On 5/16/12, Ernest Christley <echristley@att.net> wrote:
> I cleaned the plugs, but they just kept getting flooded, and despite the
> modifications I made to the intake manifold, I
> was still getting fuel pooled in there.
>
> I moved on to checking the spark.  The timing light was only flashing
> occasionally, and I noticed that my VR sensor was
> mounted so that it was almost in front of the toothed wheel.  I have some
> new tools I didn't have when I originally cast
> the mount, so I cleaned it up, and trued it.  Timing light was still
> sporadic.  Plugged the wire into a scrap spark plug
> and sat it on the engine while I cranked.  Nice, consistent blue-white
> spark.  May have been there all along, but at
> least my VR sensor mount looks nicer.
>
> I've got new fuel, good compression, and good spark.  Deep breath, back up,
> and compare what I have now to what I had
> when it was running back in November.  I consult TunerStudio (the user
> interface I'm using to my engine controller).
> The only thing significantly different is that I converted from using
> Speed-Density to Alpha-N.
>
> Background:  MegaSquirt has several, user-configurable ways to determine how
> long to have the fuel injectors spray. One
> way is to measure the manifold pressure and combine that with the RPM.
> Another is to look at where the throttle is and
> combine that with RPM.  Both are just secondary measurements of how much air
> the engine is swallowing, and have a whole
> slew of corrections and modifications for various conditions.  Tuning
> involves filling numbers into a table.  Across the
> bottom is the RPM.  Up the side is either the throttle position, or the
> manifold pressure.  For each cell you specify a
> volumetric efficiency as a percentage.  You've already specified how long
> the injectors would spray for a 100% VE cycle,
> so the cells essentially become a percentage of that value.  By switching
> modes, my table no longer resembled reality.
> Instead of picking up the value of 43 from the table while cranking, it was
> picking up a different cell that had 93.
> More than double the required fuel.
>
> I switched the setting back, and gave it a try this morning.  It took about
> 30 seconds of spinning while it was
> obviously trying to kick off before it caught up and ran smooth at 1500 RPM.
>  It has taken two weeks since I got
> everything painted and tried start taxi testing, but I'm now back in the
> game.
>
> --
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