Interject
when you figure out my
underlying issue.??
Please!
It started
about a year ago.?? I
was putting a lot of
hours on N4VY (Turbo
rotary RV-6) commuting
for work.?? One day I
flew to Ramona to meet
up with my formation
flying buddies.?? After
the brief we went to
start our planes but
mine wouldn't start and
I had to bow out of the
flight.?? It would crank
and almost catch, but I
wore out my battery
trying.?? After
recharging for a couple
hours it started up
normally.?? I flew home
and wrote it off as some
sort of start procedure
SNAFU.?? I use Tracys
EC2.
But that
was the start of a long
succession of difficult
starts when pre-warmed,
starting fine when
cold.?? Sometimes
leaving me stranded at a
gas stop until the
engine cooled.?? While
in a safe place I tested
air starts and there
seemed to be no issue
there just turning the
fuel pumps back on with
the prop spinning.
Then it
started doing something
else strange.?? After
starting it would run
really rough?? whenever
the alternator output
got above 55amps or
so.?? By rough I mean
sputtering and resisting
advancing the throttle
by sagging and
occasionally backfire.??
If I had been cranking
for a long period it
could take a minute for
the amps to drop and the
engine to run normally.
I started
by checking for loose
wires and replacing the
spark plugs. (No
improveement)
So then I
replaced the battery, it
still seemed strong but
maybe the voltage was
dropping with cranking
or somethng.?? I got
interested in Li Ion
batteries and splurged
on the Big one.?? It
increased my total
enerrgy storage, CCAs,
and decreased weight by
over 10#.?? Expensive
but worth it considering
they are also supposed
to last longer.
But it
turns out the old
battery was fine
after.?? Not only did it
not solve the problem,
but because the Li Ion
battery can take a much
faster charge, it would
max out the alternator
at least briefly on
EVERY start, making the
problem worse.
Next was
fuel filter and spark
plug wires, no
improvement.
The
condition continued to
slowly worsen despite
trying richer mixtures
of 2-stroke oil and or
MMO.?? So I finally
grounded it.
My thought
at this point was that
the compression had
finally deggraded to the
point where compression
was not enough for
combustion unless
turning really fast.??
Perhaps the extra drag
from full output of the
alternator made the
condition worse.?? And
when it was hot the
rotor housings expanded
just enough to really
kill the compression.??
The side iron plates in
that engine had the
better part of 1000
flight hours plus
unknown time in an
RX7.?? Compression
measured mid 20s on both
rotors, for what thats
worth.?? Time for a
rebuild.
I went all
out.?? All new rotor and
side housings, seals,
springs, o-rings and the
necessary aircraft mods
to those parts.??
(fittings, etc..., EGR
passages pluged)?? I
also replaced the LS1
coils and the coil
harness.
And???
Nothing.?? Fuel flow and
injector gross function
verified.?? All sparks
verified during cranking
with a timing light.??
Tried a different CAS
just for kicks.?? The
engine is a little tight
because it is new,
compression is not
spectacular cause the
seals have not set,
perhaps the apex seal
little bits are still
glued on..
Jump in
here anytime.
You know?
You are right, I just
need to disconnect the
alternator and keep
cranking until it
finally catches and gets
a little bit of a
break-in.????
This talk
has been really helpful
for me.
Dave
Leonard
(the
forever optimist)
Also going
to switch to full
synthetic 2-stroke oil
without MMO.?? The new
engine will never know
how good it has it.??