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