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Hard to say, John. I have had surges both
ways but they were mainly due to the fact my fuel map is somewhat
uneven. So changes in rpm or manifold pressure change the operational area
to a point in the map where it either gets an enrichment (more power) or a
leaning (less power). Also, when an SAG event clears up you certainly get
a surge as the rotors starts producing normal power again.
If you hit a "rich" spot in the fuel map, it would
cause an increase in power, an increase in RPM, but not certain why it would
cause a drop in manifold pressure - unless the higher rpms happened quickly
enough (sucked the manifold pressure down) before the turbine wheel and
compressor caught up. However, If you are using the EM2 to tailor
your EC2 Fuel map then less likelihood of unevenness in the fuel
map.
But, if it were a sparkplug "clearing up" I would
think the event would be longer term. I don't know what the
symptoms would be with SAG underboost but if my speculation about the cause of
SAG is correct, it should be worst and last longer. Based on what I
observed with oil and coolant temps while under SAG, I would think yours would
be quite elevated. If they are not - then doubtful you encountered SAG
(yet).
So really don't have a better SWAG about what you
may have encountered, but can understand you wanting to find that "sweet" spot
again {:>)
Ed A
----- Original Message -----
Sent: Monday, March 14, 2005 10:19
PM
Subject: [FlyRotary] Re: SAG Report
Speaking of SAG, I had a strange
experience during today's flight which might be the opposite of SAG.
Everything seemed normal. I was boosting about 38 MAP
at 4500 rpm and 5000'. I was gently adding a little throttle to increase speed
for another ASI calibration when I felt a surge of acceleration way beyond
what I'd expect for the minor throttle adjustment I'd made. This
was literally a shove in the back.
It lasted maybe 2 seconds, then the engine carried on at the new power
level. RPM jumped up a couple of hundred.
I glanced down at the MAP. It had dropped to 34. My best guess is that
I'd been running with a gummed up plug which suddenly cleared and gave me
added power.
I'd appreciate any opinions on
this.
Now
if I could just make it happen again - and again.....
John
(getting relaxed enough to test the
airframe)
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