The attached plot is of EC2 primary and secondary injector and CAS signals for 13B (not Renisis CAS) showing the primary injector sometimes at max pulse width and sometimes saturated and then at the right beginning to use both the primary and secondary injectors when
the MAP exceeded the staging threshold. The voltage had been divided by about 3.5 when the signals were captured.
The fuel flow from the primary injector will increase by about 15% when it saturates.
With equal sized primary and secondary injectors, mode 6 at default, and a staging change, the total fuel flow from the primary and secondary injectors will decrease by about 12% compared to the fuel flow from the primary injector at max pulse
width. So a staging transition from a saturated primary injector to using both the primary and secondary injectors results in a fuel flow decrease of over 25%.
An instrument monitoring injector pulses to determine RPM will cease to function when that injector is receiving a saturated signal.
Steve Boese
From: Rotary motors in aircraft <flyrotary@lancaironline.net> on behalf of Bobby J. Hughes <flyrotary@lancaironline.net>
Sent: Saturday, August 6, 2016 8:43 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Finding the gremlin
Steve
I would limit running the engine to a minimum at or above the problem rpm point. I don't think it's good for the gearbox and may create torque reversals.
The CAS voltage clamp is installed outside the EC2. Tracy may have added the final 1K fix internal at some point during upgrades. It's an easy test if the CAS wiring has slack and in accessible location. Cut the 2 wires for the CAS and twist in a 1K
per Tracy or test the zener circuit. If it corrects the problem clean up the wiring. My circuit was installed about 8" from the EC2 connector. Mark Steitle adapted a renesis CAS to his 20B and experienced the same symptoms that started in the low 5k rpm
range. During testing we spliced in a long section of CAS wire through a breakout block. The breakout block allowed us to monitor peak to peak voltage that increases with rpm and easily jumper in and test higher resistor values. The long wire allowed us
to run the engine outside the hanger and not disturb the test bench setup and o-scope. As we increased the resister value it would push the problem area to a higher rpm point. Please note that this was done before Tracy identified and recommend the 1k fix.
Does the rpm display problem and engine stumble happen at or near the same rpm point? I'm not sure how the injector signal would look when fully saturated. Temporally crank up the fuel pressure and see if the problem point moves to a higher rpm. Temporally
lower the staging point. Use mixture knob to control with no tuning changes.
Are the injector and coil trigger wires ran separately from their power sources?
Back to the coffee pot. Bobby