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Message
ED, George, Steve,
A strong contributor to this may lie in the
fundamental design of the EC2. It's output control is sinking rather than
sourcing. If it were sourcing the positive EMF would be switched and the
other side of the could would always be grounded, leaving a place for the
coil breakdown current to go. Well the controller is what it is, so the
question become what can we do to work around the problem? Encoders are
used often in industrial applications, these are generally connected in a
sinking fashion just as the EC2. In high frequency (encoder
pulses) applications the impedance of the input electronics is often to
slow to bleed of the leading edge of the encoder on voltage before the next
pulse cycle. End result is that the input does not detect tithe state
change. The solution is very simple for the described situation is very
simple. Installing a pull down resistor between the sensor signal line and
ground. This technique is used with standard input electronics with pulse
trains up to 50kHz, which translates to a cycle period of 20µS.
How does this translate to our application?
If we were to add a pull down resistor in injector signal line, which may
very well be a simple method to reducing the off delay time. This would of
course add a small increase in the current for the injector circuits, but that
increase would likely be minimal. The value of the resistor would
certainly need to be determined using factors such as Injector turn on voltage,
turn off voltage, device current, etc. IMO this may be a simple
solution to the delay issue.
In the end I defer final recommendations to Tracy,
who certainly knows the characteristics of his controller system better than
I.
Joe
----- Original Message -----
Sent: Saturday, March 10, 2007 11:44
PM
Subject: [FlyRotary] Re: The truth??? /
Injector flow rate mystery solved
Ed and
George,
In my plane, at
least, injector open times need to be less than 2 ms at idle and just above
the staging point. This is not
possible with a minimum open time of 2 ms due to the delay on closing. You can program the EC2 for less than
2 ms but the hardware is unable to do this. That means that the problem can’t be
fixed with software or programming different values in the map table. A shorter close delay time is required
unless you lower the flow rate of the injectors by changing the injector
itself or lower the fuel pressure.
The injector open time is at least 2 ms or it doesn’t open at
all.
Steve Boese
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