The CHT data is not any good for diagnostic purposes in this
scenario. If you had fuel flow info as someone asked about, that would
be good. You didn't mention EGT. Got any? How about manifold
pressure? Not likely to have this on a Lyc, but mixture info from O2
sensor would be even better. I won't leave home without it after
getting used to it.
Can't answer for Kevin, but I have Fuel
Flow and MAP (which were both consistant with the power I was getting -
2100-2200 rpm). All 4 CHTs were pretty normal. EGTs were more
scattered, sometimes a little erratic (I speculated they were
consistent with running 300 rpm LOP). Fuel pressure was not available
then, but is now (haven't flown since I limped home). Main thing about
is that electric boost pump works, which my only viable theory said it
wasn't. I have to get the airplane annualed before I can fly again,
but am open to ideas. The mechanics at IJX would make a declaration of
what the problem was and then bend the laws of physics as necessary to
support their conclusion.
Now for my mystery of the day. Was doing more tests on coil /
alternator cooling & wingtip testing today and got around to stall
tests. I was pleasantly surprised to find that my clean stall speed
was down a full 5 MPH. That is HUGE, especially from such a simple
mod. Repeated the test multiple times, accelerated, power on, idle, 1
mph/ 10 second deceleration, the works. The change was real. Then I
tested 1/2 & full flap stall expecting that I would see the usual
4-5 mph drop in stall speed. Absolutely no difference. Stall was the
same clean or dirty.
Anyone care to take a stab at this?
Tracy (still not happy with coil temps)
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Original Message -----
Sent:
Saturday, July 23, 2005 4:33 PM
Subject:
[FlyRotary] Lycoming debugging test - -HELP!
I realize that this isn't
exactly the right forum, but you guys seem to have excellent debugging
skills. my local RV group is totally worthless ("I find the carnauba
wax doesn't show fingerprints as much as the....")(except Mike!) the
on-field mechanics are sick of me coming by.
my O-320 RV-6A is
having RAG (rpm attention getter) problems. it runs fine until about
300' on take-off, then the rpm's drop to like 1700 (from 2200).
switching mags to electronic ignition(Rose) makes no difference.
mixture no diff. pulling the throttle it will seem to run fine at
1700rpm. I have 4 new cyls that I am attempting to break in. ground
run ups can only go like 2 minutes before CHT's exceed 400 degrees. I
discovered I can get the rpm drop on the ground if I run it a minute or
so full power. cht's will typically approach 415 degrees when the drop
takes place. I don't know if the temp is significant or not, it does
seem that way. I have a brand new slick left mag. rose checked the
electronic ignition and could find nothing wrong, even put it in an
oven to test. I installed a new carb since the old one showed signs of
leakage (and I'm at whits end). no change. my fuel pressure has been
showing 8psi this last year, up from 6 psi when originally
installed.(no idea why) I installed a pressure regulator in-line which
works like a charm. I can dial whatever pressure I like. 2 psi makes
no difference. I bypassed the mechanical fuel pump and ran it just on
the facet electric. 2 psi, no difference. I discovered that you can
run the carb for maybe 30 secs with no fuel pressure while it burns off
the bowl gas. premier engines suggested induction leak making the
engine run lean. no leaks detected cold or hot engine. (pressurized
intake with vacuum, sprayed soapy water)
if the engine didn't
run right to start with then many explanations would hold. but it runs
fine for several minutes. it runs the same under mag or electronic
ignition both before and after the problem kicks in. everyone really
wants to blame the rose ignition, but I'm not seeing any connection.
with such a quick run-up my oil temp barely registers, so I doubt parts
are seizing. I have new mineral oil in it for breakin right now.
there is a bit of MMO in the fuel too I believe, left over from a
mechanics "what the hell" attempt from way back. my cyls are all new,
rebuilts, so no valve problems. I checked the push rod lengths when I
reinstalled them. the engine isn't missing when the problems occurs,
it simply won't run faster and it seems to prefer the throttle pulled
back to match the rpm it is putting out. I can't figure out any more
lean mixture scenarios to try. the new carb runs just like the old one
did. I recently replaced the mag harness with a much newer, used one.
I tested it and it was fine. the plugs are all new, but again, no diff
between mag and elec ignition. if I flip the ignition to R and shut
off the elect ig then the engine quits as would be expected, no wiring
problems.
fuel, spark, air,
timing, that's all there is. this damn lycoming lawn mower has me
stumped. my engine has been running fine up until this (hey, we all
have "cracked" cylinders, get out your microscope and look!). you guys
have any ideas?
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Original