I agree with Lynn regarding SAG.
Having experience SAG a number of times
running on 100LL (Get an average of about 25-30 hour before SAG starts).
While it certain gets your heart beat accelerated – the engine continues
to run. Treat it as simply a good warning about your plug’s deteriorating
condition. The “good” thing about SAG is that it normally
comes on gradually but continues to get worst in that the frequency of occurrence
increases and the duration lengthens. The “bad” thing is it
does affect power. A rotor in full SAG will drop 300F on the EGT and rpm
will drop off as well (I’ll hazard a guess at about 150-200 rpm).
If both rotors go into SAG at the same time, it can really get your attention
as you could lose around 300 rpm. I had that happen once on take off with
a full load of fuel on a hot day, but even with both rotors in SAG, heavy
aircraft and Hot day, I still managed 500 fpm on climbout, I was breathing hard
(or hardly breathing) until I recalled, that if I got 500 fpm on a hot day
while flying a Cessna 150, I thought I was doing great. So I relaxed,
climbed to Altitude while circling the airport and once at altitude and pulled
back on the power, the SAG went away {:>) (for a while).
On one LOOOONG trip from Louisiana
to North Carolina
(with the plugs well over-due for change), I had SAG become a consistent plague
– like every few minutes. I did discover that if I killed the spark
to the Lead plugs for approx 30 sec using Tracy’s EC2 ignition check
switch (can only do this with controller B selected on the EC2), that the EGT
would go way up but when I released the switch the SAG was gone for
considerably longer. I have no clear answer as to why this would be the
case, but thought I would pass it on.
SAG has a bad habit of showing its face
when you least want to see it. Like at full power settings – SAG on
take off is not my idea of fun time, so if it’s not your idea of fun,
then pay heed when your spark plugs are talking to you. Spark Plugs are
cheap.
Also folks not using 100LL get a much
larger number of hours between needing plug changes. Tracy, I know, gets over 100 hours and I
think the last I heard it was closer to 200 hours.
Ed
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Lynn Hanover
Sent: Sunday, June 29, 2008 11:38
AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] SAG
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
So would a smaller
gap plug reduce or eliminate SAG (sparkplug attention getter)? Would a CD
or MSD system eliminate it altogether? Can either work with Tracy's EC-2?
Bill B