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Sounds like a reasonable approach to me
Joe. A pull-down resistor would be relatively easy for me
to install - I have the resistor pack required for the peak-hold type
injectors. So I could easily place four additional resistors in
that box.
If I understand you (please correct me if I don't), the
pull down resistor should go between the injector and the EC2 sinking
terminals. That way the current induced when the intended pulse terminates
and the magnetic field collapses will have a path to ground rather than being
opposed by the diode in the Ec2.
The value of said resistor could be around 100 ohms.
Since the induced voltage could reach from 50 - 100+ volts an 100 ohm resistor
could flow from
0.5 - 1 Amp (for a very short duration). As far as
affecting the 12 Volt signal it would only draw 12/100 = 0.12 amp or 120
milliamps. That would be pulled through the injectors at all times.
The injector resistance is probably (peak and hold case) around 3
ohms. So the injector would draw 12/3 = 4 amps (DC case - its undoubtedly
less due to the A/C impedance of the coil). It make take some
experimenting - but 100 ohm looks like a good place to start.
The wattage should probably be around 5 - 10 watts just to
be on the safe side.
So certainly looks like a suggestion that would work,
Joe.
Ed
----- Original Message -----
Sent: Sunday, March 11, 2007 10:54
AM
Subject: [FlyRotary] Re: The truth??? /
Injector flow rate mystery solved
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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