As Al said, yes, these diodes are necessary. I'm still studying this situation and determining what the best configuration is for the 20B version. I have been hampered by a number of problems encountered on my 20B installation (too many to mention here but I'll talk about a few in a minute).
Here is what is certain so far. There needs to be an isolation diode in series with EACH of the 6 injectors, not just the two power feeds to the primary and secondary banks. There are more important reasons than the power isolation issue that Joe mentioned. In addition to these diodes, there should be a diode (regular, not schottky) from the junction of the secondary injector power feeds to ground. I am also changing the spec on the 20B staging relay to a solid state type. Attached is the preliminary schematic for this configuration but it is still under study until I can verify everything on my engine. This is the Renesis crank sensor version of 20B controller but the same changes apply to the standard crank sensor as well.
One delay I had was due to my oil cooler springing a leak. As you may recall, I made one out of an AC evaporator core. Thought the core had failed like Rusty's had but it turned out to be the way I installed the fittings on the modified core so I was able to fix it. The leak was hard to see as it was hidden and did not show up anywhere on the cooler itself. I thought it was the gear drive and tore that down to replace the rear oil seal (didn't help of course). Then I thought I had another mysterious engine problem that caused it to run rough at random times so chased my tail for awhile until I found out that the throttle body was inhaling the oil spraying from the oil cooler. It went on like this for quite a while. Just now getting back to checking out the diode and relay changes I mentioned. BTW, this cooler (and associated duct) is working incredibly well. I can run the engine at power settings high enough to maintain level flight (as determined by fuel flow readings) while static on the ground at 90 degrees F and oil temps stay in the green (~185 F). Water temps are almost as good (~200 degrees). This makes me confident enough to not bother putting the spray bar cooling for initial flight testing (if I ever get there).
Also been out of contact with the list for awhile due to Wildblue satellite Internet problems.
Tracy (Back on dial-up, Arghh.......)
On 10/14/07, Al Gietzen <ALVentures@cox.net> wrote:
Joe;
You are right. We discovered this crossfeed issue some time back. Is applies only to the 20B version as the 13B has separate drivers for each set. Install Schottky diodes in the circuits for each injector.
Tracy
is aware of this, and has installed the diodes in his as well.
Al
-----Original Message-----
From: Rotary motors in aircraft [mailto:
flyrotary@lancaironline.net] On Behalf Of Joe Ewen
Sent: Sunday, October 14, 2007 3:20 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] EC2 20B Injector Power Circuits
I have been testing my wiring harness from the EC2. I found a behavior that I did not expect. The manual drawing (EC2 manual) show a single injector supply that splits at the Injector primary and secondary disable switches. On my installation, I have 2 separate feeder circuits, supply Primary comes from battery 1, and supply Secondary comes from battery 2. I did this for redundancy. If I had a failure such as a short to ground in either circuit, its related overload should trip, but the other circuit should remain active.
While testing the injector circuits, I noticed what I would term an abnormality. With both injector disable switches in the enable position, I turned on the power for the primary circuit (I have LED indicators on all circuits that annunciate power present) and the secondary circuit also showed power present even though the power switch for the secondary circuit was off. The same is true when the secondary circuit is engaged and the primary is off.
Initially this led me to think I had miss wired something in the circuit. After checking out the wiring, I found no issues. So I took a closer look at the wiring diagram in the manual. It turns out the power was being back feed through the injectors to the opposite circuit. On the 20B version of the EC2, the injector control lines for each rotors injectors are junctioned going into the EC2. For example the Rotor 1 Primary and Secondary control lines are junctioned into a single input point at the EC2.
I can see several situations where this may lead to undesirable operation. For example, if the Primary circuit had a hard short to ground, it would take out the primary circuit's overload (CB or Fuse.) Since the primary and secondary circuits are electrically connected on the control line, the other circuit would also trip. Another situation that could occur is a medium to high resistance short. Current would then flow uncontrolled through the unaffected circuit's injector to the affected circuit's injector then to the resistance short. This could keep both injectors on 100%. While this situation is unlikely, it seems possible.
I believe the 13B version uses separate control lines for each injector, so this in not likely to be an issue on the 13B version.
It appears that isolation diodes are needed to prevent these possible problems. Before making any changes I have to look the circuit over more closely, as well as a call to Tracy on the next service day. My question to the group, especially anyone with a 20B, is am I looking at this wrong?
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