----- Original Message -----
Sent: Wednesday, February 09, 2005 10:55
AM
Subject: [FlyRotary] Re: Microtech EFI
and Tuning, was Re: [FlyRotary] Re: Bad day at the airport
I got up to 5100 rpms static, and most
people told me that the prop would most likely unload in flight. How can
I obtain more than 5100 rpm's unless I fly it?
Hi Paul,
I asked Tracy that same question when I was first tuning
my EC-2. The answer (for his unit) was that it didn't matter. The
system bases it's fuel injection pulse width on MAP, which will be nearly
the same in static runs as it is in normal climb speeds.
When your prop unloads in flight, you run higher rpms, but that doesn't change
the pulse width requirement for each intake cycle at a given MAP. It
just means you need more pulses, because you have more intake
cycles.
It's VERY important to realize that everything I just
said was based on Tracy's EC-2. There's a very real chance that the
MicroTech DOES care what the rpm is. I know that the Power FC
computer in my FD had a fuel injection and timing table that was based on RPM
and MAP. This gives you more power to tune, but as they say, with power
comes responsibility :-)
FWIW, I really do like the MicroTech unit, and I
thought really hard about getting a couple for the single rotor project, but
eventually went with what I know, which is Tracy's EC-2. Part of
that decision was based on having a backup controller if I ever suspected a
problem, though it sure would be nice if someone would include the
ability to save and restore tuning parameters (between
slathering foam and fiberglass on a clapped out travel trailer)
:-) I also like the built in backup (which would have ruled
out an EFI tuning issue for you), and don't quite know how you'd wire two
MicroTech's together. I also like the mixture knob, which is
powerful enough to overcome almost any tuning mistake. I also felt it
was safer for me to have only one unit to try to remember.
Hang in there Paul. Give this
some thorough consideration before doing anything drastic. I seem
to recall you giving me some similar advice not long
ago.
Cheers,
Rusty
Hi, Rusty....stealing your red
color....Yes, you program the MicroTech unit according to rpm's. At
every 500 rpm, you can set it up for that rpm....ie...3000 rpm, 3500, 4000,
4500, etc. I had it set up for 5000, but could not really properly set
it up for 5500 or 6000 until I reach that rpm and do the fine tuning. I just
set the 5500 and 6000 the same as the 5000 rpm settings, figuring that would
be close enough to at least continue running so that I could fine tune it in
the air.
I have not
been able to get to the computer for a couple of days, so I have 324 messages
to look at, so if I say something in this post that is out of date, I
appologize.
I went to the
airport yesterday and pulled the spark plugs and inspected them. They looked
brand new. No soot, no sign of overheating or porcelain damgae.
I fired the engine up
and of course it ran like a fine swiss watch. Good idle, good midrange, and
5300 rpm's static instead of the usual 5200 rpm's. I have been
doing a lot of thinking (dangerous territory, I know) about my incident.
I'm 99.95% sure it was vapor lock/fuel delivery problems, not the MicroTech
unit or it's settings. On the day of the incident, I had run the engine
up with the larger prop until the temps got too hot. (pusher, no prop blast to
help cool it), then I immediately swapped props (installed the smaller prop to
get more rpm's), which only took about 10 minutes with my brother's help, then
fired it up, lined up on the runway and tried to do some more tuning for max
rpm's. Now, the temps were above 220 and climbing. I needed to get
it airborne ASAP, as my cooling system will cool the engine even in a
climb. Unfortunately, I suspect that by the time I rotated, the temps
were probably around 230 or 240, with the engine at WOT. Pretty good
scenario for hot cowling temps and vapor lock.
The
one thing that I failed to do, and probably should have done was to turn on
the aux fuel pump. I have a Facet fuel pump that was originally intended
to supply 6 psi to the sump tank. Never needed it, but it certaintly
wouldn't have hurt anything to turn it on. It would only pressurize the sump
tank, and that may or may not have had any effect, as the sump tank is always
full because it gets fuel from both the tanks as well as the return fuel from
the fuel pressure regulator.
Looking at
my fuel system closer led me to a couple of observations/improvements that
might solve the problem. Number one would be to install firesleeve over
the stainless steel braided fuel supply line that goes from the fuel pumps to
the fuel rail, as it is close to the engine, and attached to the engine with
adel clamps.
Second might be
to move the two high pressure fuel pumps to the cold side of the firewall, or
install a small duct to allow cooling air to the pumps. In rethinking
this, the duct would not supply any air unless the plane was moving, and I
believe the pumps get plenty of moving air as is in flight.
Third....avoid
long max throttle runups just prior to takeoff. I think this is the biggest
"helpful hint" of all. Yesterday, when I ran the engine up until
the water temp hit 240, the surge tank overflow was spitting out antifreeze
about 3 feet. It just did it for a moment, then I put a 100 volt fan
under the NACA duct to supply cooling air. After 10 minutes, the water
temp still read 230, so I started the engine, and as the water circulated at
idle, the temps immediately came back down to around 180.
Hope I didn't
bore everyone to death with this long post. Just trying to keep everyone
informed. Paul Conner
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