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.??