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Date: Sun, 29 Jun 2008 14:25:19 -0600
From: Bob White <bob@bob-white.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] SAG
Message-Id: <20080629142519.6ad9f73d.bob@bob-white.com>
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Tracy's system doesn't charge the coil primary.  Both the Mazda and the
LS-1 coils have built in circuitry that only needs a 12V logic signal
from the EC2.  It should work fine as a trigger for the MSD.

I still have the unexplained power loss on my last flight.  For now I'm
calling it SAG but I'm not sure that's the answer.  Full power returned
when I hit the primary injector disable switch.  Like SAG, the engine
was running smoothly, but with a power loss. Unlike SAG, it didn't
start at full power but at cruise, and I didn't have enough power to
maintain level flight.  If it had happened on take-off, I would have
gone down.  I would assume an injector problem except for the engine
running smoothly.  I would like to try replacing the LS-1 coils with an
MSD system as well.

I hope to do some more diagnostics when I get the engine running
again.  I still have the same plugs installed but I did pump a lot of
oil into the rotor housing when I stored the engine.

Bob W. 


On Sun, 29 Jun 2008 11:37:33 -0400
"Lynn Hanover" <lehanover@gmail.com> wrote:

> While the SAG thing might get you heart rate up there with a cross country
> runner, it is not fatal. It is a warning that plug fouling is ocurring, and
> action of some sort is required. Usually lead salts from aviation low lead
> fuel building up on the porcelain. This is the same as a low value resistor
> shunting the plug gap. So energy in the gap is reduced in increasing amounts
> until there is not adequate energy left to jump the gap. Starting with a
> small gap takes away the warning that SAG really is. The plug might be
> dreadfully fouled by the time it starts to miss fire, and then there is no
> quick fix to get home on. (if you forgot the box of new plugs and a plug
> wrench).  With a CD or MSD system the plug will fire with a giant blob of
> crap building up on it. On the one hand you could say this is a great thing.
> But eventually you need to check the plugs as part of some maintanance
> program. Should the plug load up completely, the CD or MSD is not going to
> help you, and that plug is finished. So now the fact that it ran great and
> sounded good right up to the instant it quit running is not a help.
> 
> I would run an MSD on the leading plugs in any case. Let the trailing
> plugs show you the SAG when it develops. If you are not screaming the
> engine, there is no need for the super small plug gaps. Then with the gaps
> reccomended by Mazda, SAG give you an easy fix for more hours of power if
> you just tighten the gaps to go home. Or better yet put in the new plugs.
> 
> Tracy's system might need a load of some sort or a signal transformer to
> prevent damage while triggering another system instead of charging a coil
> primary.
> 
> 
> 
> Lynn E. Hanover
> 
> 


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