Ed,
I tested the engine on the stand with variable resistors across each CAS yesterday. With the engine idling at about 1500 RPM, less than 100 ohms resistance across either CAS would cause the engine to quit completely. Resistances this low must decrease the voltage generated by the CAS to a value too low for the controller to use. The engine would not start with 200 ohm across one CAS and 1K ohm across the other. It didn't matter which CAS had the lower resistance. The engine would start with 300 ohm across one CAS and 1K ohm across the other. This makes sense since the CAS cannot generate a very strong signal at cranking speed.
What doesn't make sense to me:
Starting with 1K resistance across each CAS, if the resistance on one CAS was increased to 69K, the engine would still run fine at 1500 RPM. If the resistance was increased to 69K on the other CAS, the engine would only run on one rotor. It didn't matter which CAS resistance was increased first.
With 1K resistance across one CAS, changing the resistance of the other CAS from 69K back to 1K by connecting a wire would sometimes cause the engine would miss what seemed to be one firing event. Again, there was no difference in the behavior of either CAS in this regard.
The conclusion seems to be that adding the 1K resistor to each CAS seems to be beneficial and the value of 1K is not critical or on the threshold of causing other problems.
Steve
From: Rotary motors in aircraft [flyrotary@lancaironline.net] on behalf of Ed Anderson [eanderson@carolina.rr.com]
Sent: Thursday, November 08, 2012 6:38 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Renesis CAS & EC-2 upgrade?
Seeing as how both the ignition and injector pulse drop out in that band - it would seem to me that the problem must lie in the circuit common to both which is the CAS signal processing circuit. If only one pulse train, either the ignition or the injector pulses only dropped out, then of course you would suspect the respective circuit - but, this is common to both.
On the other hand, rotor 1 continues to run - but, as you noted - the pulse duration for even rotor 1 in this rpm range does not appear normal in that range.
I suspect that since your 1K ohm resistor (which brings the peak voltage down to 6 volts) where it appears to run ok at that point, that for some reason the input circuitry has a problem handling the +13 volt peak in the 660-1400 rpm range. Since this would fall in normal TTY signal range (used by the microprocessor), I suspect that perhaps due to some bandpass filter effect of the components in the input circuit that the +13 volt peaks are overdriving the input circuit within that rpm range. Adding the resistor changes the bandpass frequency and puts it someplace (probably lower) out side your operating rpm range.
But, again without knowledge of the input circuit and seeing what is really going on inside the EC its difficult to say.