Ed and Mike,
Tracy would be the one to comment on this,
if he was available, but it is my understanding that both the A and B
controllers are running all the time. The A/B switch operates a relay
that just changes which controller’s outputs are connected to the rest of
the plane. When the injector relay changes contacts there is the
possibility for arcing between the contacts depending on whether or not the
injectors were turned on at that time. Tracy said once that he had
trouble with corruption of the controllers probably due to this arcing and that
was the reason for the transient suppression diodes in the injector driver
circuitry. Changing to the snubber circuitry, possibly increased the chance
for the arcing problem but helped with injector response time. A
compromise like everything else. Moving the A/B switch shouldn’t
cause a problem unless this has changed the relay response time and caused an
arcing problem. I don’t know if the PCM has any circuitry involved
with this other than the switch itself. If it does, it’s not
obvious. Is there any chance that any of Mike’s injectors are
drawing more current than intended? Wiring for saturated when one
or more of them is peak and hold or otherwise damaged? That could cause
arcing and corruption problems.
How’s that for speculation?
Steve Boese
-----Original Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Ed Anderson
Sent: Thursday, July 02, 2009 5:18
AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Narrowing in
on Cause? [FlyRotary] Re: frustrating couple of days
I think you may be
narrowing in on the cause of your problem, Mike.
Remoting the cold start
and/or controller selection switch might have unintended effects. IF this were
the cause, my bet would be on the controller select switch. I don’t
know what all that switch does – but it clearly transfers control of the
ignition and injectors to the B controller (when so switched). So several
High Power circuits are being turned on (or switched over) to the B controller
by a switch that is no longer co-located on the program Controller PCB.
Again, IF this remoting of the switches could cause this, the question is HOW?
Not certain of what
de-bounce routine Tracy uses – whether software or hardware – but
if you turned on the switch to B controller, I would presume the B controller
immediately loads the MAP into its working memory. I would assume the Map
(as well as other data such as staging) would normally reside in EEPROM
and upon activation one of the first things the B controller would do is to load
this MAP and data. Now, lets say a second voltage spike from the
un-debounced switch were sent to the B controller during the time it was
loading the fuel Map, it could cause the chip to do a reset during this
interval. That could result in part of the MAP or other data stored in
EEPROM getting corrupted. I don’t know the internal coding for moving
data from EEPROM to working memory inside the EC2, I do know that for the
Serial data its code is in MIDI format.
Using the MIDI format
means if only one bit is corrupted out of the 256 bytes used to transmit the
Map over the serial link – then all data after that point is
corrupted. That is one of the reasons I had to give the Rs232 USART comm.
Module in my EFISM chip top priority during interrupts. I can lose any number
of injector pulses and it not affect its accuracy enough to display – but
corruption of the most significant bit of the High byte MIDI pair during the
MAP serial transmission and the remaining bytes are hopelessly corrupted.
I was pretty
confident the problem was not caused by the EFISM as it has no way to talk to
the B controller, but glad to have it confirmed. The only way I can see
the EFISM affecting the B controller is rather round about. You
would have to 1st make the change to the A MAP using the EFISM and
then use the EC2 to copy the A MAP to the B MAP. Even then you can not
change the staging point using the EFISM only the Map and ignition.
A second thought is
whether any “ground currents” could be in play. You have
probably already done this, but try connecting an alligator clamp (or your
favorite attachment device) to the ground of your controller switch and hook
the other end to the grounding stud on the EC2. If a ground circuit
current/voltage was playing a role this might eliminate it.
Good luck on your trouble
shooting. Don’t give up – I think you may be on the right
track.
From: Rotary
motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mike Wills
Sent: Thursday, July 02, 2009
12:37 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re:
frustrating couple of days
So I vented to you guys, lost some
sleep last night pondering this, wasted more time today thinking about it, and
then went back to the airport to check things out.
I had previously made all of the
changes Tracy recommended in case there was an issue with ground or supply
noise. I didnt believe that was the problem before, but with no better ideas
went ahead and made the changes. I'm now pretty sure that the electrical system
is solid.
Another possibility was that there
was something about the EFISM installation that caused this problem. Not sure
how this could be the case but the EFISM does have the capability to write to
the MCT, so maybe something was getting scrambled in the process?
I disconnected the EFISM. And the
EFISM was disconnected yesterday when this latest problem occured, so its not
the cause. Yesterday just before I quit in disgust I reconnected the EFISM and
captured the MCT to make sure it hadnt been corrupted. It looked fine and thats
why it was so puzzling.
Today when I started the engine it
was clearly still screwed up. I put the EFISM in EC2 monitor mode and
immediately saw the problem. This latest problem was due to the fact that my A
controller injector staging point had been corrupted and set to 12" MAP.
The engine sure wont idle on 4 injectors! I reset the staging point to where it
belongs and the engine is back to running as it should.
I now have 5 known episodes of
spontaneous changes to the EC2 (possibly more). The first time the staging
point was erased and the secondaries wouldnt come on. The next 3 cases (twice
in the past couple of days) the B controller lost its program (since I dont
have a way to view the B MCT I dont actually know whats happening here, just
that the engine immediately dies when I flip to B). And then this last episode
with the staging point resetting to 12". I say there may have actually
been more cases because my engine has never really ran well on the B controller
after doing an A to B copy. But it does run - usually.
So Ed asks is there an action or
sequence of actions that may be related? Well the common thread here is
switching to B. I ran this engine for about 20 hours of ground testing before I
noted the first instance of this occuring. And this coincides with when I
started actually flying the airplane - and routinely switching to B as part of
my pre takeoff checklist. Then I stopped flying about 4 months ago to make all
of these changes and further tune the engine. During this time I dont think I
ever switched to B and noted no problems. This past weekend I started prepping
to fly and went through my typical pre takeoff prep and once again problems.
Started troubleshooting by routinely checking the B controller and once again
corrupted the EC2, this time the staging point.
Since my most consistent indicator
of a change is corruption of the B MCT its hard to say for sure, but if i can
force the staging point screw up a few times by switching to B I'll be
convinced. I should note that my install is not standard for the EC2 PCM. I removed
the A/B switch, Cold Start switch, and Coil Test switch from the PCM and
remoted them to my instrument panel. Tracy noted this as an optional way to do
things in my EC2 manual. I dont recall how Tracy implements these switches, but
I assume they are SPST to a pullup resistor on the EC2. I dont know if he has
any circuitry to de-bounce or noise filter the switch input? I dont even know
for sure that this is the cause but seems to be the most reasonable explanation
at this point. Stay tuned.
----- Original Message -----
Sent: Wednesday,
July 01, 2009 6:15 AM
Subject: [FlyRotary]
Re: frustrating couple of days
Mike, its got to be
frustrating to have it run well for a couple of months and just when you have
convinced yourself the problem is gone, it comes back.
I presume there is
nothing (no action, sequence of actions) that you can think of having taken
recently - any different than you have done during the months the engine ran
well that you can think of. Nothing different perhaps in getting ready
for another flight?
Since the fuel map is
stored in non-volute memory, it’s hard to figure out how it is being
re-written or destroyed. Normally (as you know) access to EEPROM on a
chip is a rather non-trivial process. Since the A and B controller
are two different chips, I suppose there could be a problem with the B chip
– but, while that does happen, it’s pretty rare. Have not had
one myself (yet).
You are able to copy over
the A MAP to the B MAP and it apparently does the copy, but then something
causes it to be re-written with garbage. You do not have Auto tune and I
presume you do not attempt to change the B MAP – but it changes on its
own. It sounds as it the changes to B happen whether you have selected B
controller or not – is that correct. Or does it only happen when
you are using the B controller or can you tell.
Ed
From: Rotary
motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mike Wills
Sent: Wednesday, July 01, 2009
12:10 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] frustrating
couple of days
I havent flown my RV since a couple
of cases of lost data in the EC2 back in february. Spent the last few months
making a bunch of mods, some suggested by Tracy, others were things that I
thought might increase long term reliability. Also had to fix leaking fuel
tanks in the ensuing period.
Been working up toward renewing
flight testing. Engine has been running really well for the last few months.
Thought that the problem was cured, though not clear how. Then on saturday
found that once again my B controller had lost all data. Engine wouldnt run at
any throttle setting on B. Restored the B controller by copying A > B.
Last night after work ground ran the
engine for about 30 minutes at various throttle settings and it ran as good as
always. Also ran fine on the B controller.
Tonight after work I fired it up.
Ran fine initially. After about 15 minutes noted some minor surging at a couple
of throttle settings below 2000 RPM. Also noticed that in this RPM range where
the mixture had previously been fine, my mixture monitor is off the scale
lean. Slowly got worse, to the point that it wouldnt idle at what was
previously a solid 1350RPM. Couldnt get it to run at all below 1500, everything
between 1500 and about 3000 RPM pretty rough. Everything over 3000 is fine. No
idea what caused this change. I put the airplane away and walked away in
disgust. I'm back to where I was a year ago and I'm just about fed up with this
thing.
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