Below is an email that I just sent to the AeroElectric
list, but as many of you on this list also use the EM2 but may
not be on that list, I thought I would send it along here too.
Charlie, I know you are on both lists, and are a frequent
contributor on the AE list, I figure your insight to the EM2
could be invaluable along with anything Electric Bob can add.
But I welcome any advice from anyone who may have also
encountered this issue. I have sent an email to Tracy, but as
he seems to be offline up in Colorado, I'm hoping to be able
to solve it without bothering him too much.
Thanks, Todd
I have an issue with my engine monitor display where the
display will scramble leaving me with a meaningless display as
can be seen in the attached picture
The engine Monitor is from Real World Solutions and is the
very early first edition EM2 (serial #003). I also have an
early edition EC2 (engine ignition and injection controller).
RWS was Tracy Crooks company before he retired, and he
still provides some support when he can, however he also is
enjoying his retirement offline so is often hard to get a hold
of,
so I thought I would pose the question here while awaiting
a response so maybe I won't even have to bother him.
So here are the details of the problem. The engine
monitor has 36? different parameters that it displays on 8
screens. There are 24 different sensors (pressure,
temperature, level) with the remaining being provided through
a serial data link from the EC2 along with an EFI sense which
is connected to the #1 primary injector output from the EC2.
I've determined that it's this last wire that is causing my
grief.
This EFI sense is measured for it's pulse width in order to
calculate a surprisingly accurate fuel flow, RPM, HP, fuel
remaining, MPG (for efficiency). But the noise on this line
seems to be the cause of the data scrambling on the display.
Simply pressing the cancel button (there are 4 user buttons to
control display) will rest and clear the issue.
But here's the weird part. It seems to be related to
relative humidity. During hot dry, summer weather this display
will rarely scramble, sometimes going up to an hour without an
issue. But on cooler humid days I would have to reset it every
few minutes which gets a little annoying. However right now as
we are not enjoying the cold November rains before winter will
arrive with cold dry weather, I'm finding that it is
scrambling almost immediately after a reset. This makes no
sense to me, but I've observed this pattern enough to be sort
of certain that it is not a coincidence... but I could be
wrong.
In any event, it matters not whether it is or isn't
triggered more by the humidity, but what it did allow me to do
is determine where the issue is coming from as before it was
too random to allow easy troubleshooting but now as it is more
consistent it was quite quick to narrow it down.
I've cut this line (which is shielded with only one end
of the shield grounded) and installed a connector. With it
disconnected, the EM2 display is rock steady (up to a 10
minute ground run) but with no RPM or any fuel, power, or
efficiency data. Connect the line and it immediately will
scramble. I estimate that the frequency of the injector pulse
on this line would only be at max about 100Hz at 6000 RPM.
I've considered that a simple low pass RF filter to ground may
work as the frequency that I'm trying to measure is well below
what the filter would remove, but would it still have an
effect on the pulse width? which would be undesirable as that
would effect the signal driving the #1 primary injector.
I'm hoping that someone can suggest an easy fix so that I
can implement it when I get back up to the airport this
weekend, other wise if more data is needed to help find a
solution I will take a scope up there and try to get some more
detailed data.
Right now our days are getting pretty short up north here
so it's dark by the time I get off work, so I'm restricted to
weekends only. Thanks for any help that can be provided.
Todd Bartrim
RV9 13Bturbo