Mailing List flyrotary@lancaironline.net Message #59199
From: Bobby J. Hughes <bhughes@qnsi.net>
Subject: Re: [FlyRotary] Re: Renesis CAS & EC-2 upgrade?
Date: Tue, 6 Nov 2012 19:11:47 -0600
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Floating ground? 

Sent from my iPad

On Nov 6, 2012, at 6:52 PM, "Steven W. Boese" <SBoese@uwyo.edu> wrote:

A follow-up on the attempt to use Renesis CAS with an EC2 controller set up for '86 stock Mazda CAS

 

There appeared to be a correlation between loosing the rotor 2 controller signals with crossing the staging threshold on startup.  This was tested by starting the engine with the throttle open sufficiently that the manifold pressure should not drop to less than the staging threshold.  The result was that the engine still ran only on rotor 1 until RPM reached at least 1400 RPM.  It just didn't take as long to reach this RPM as before.  This behavior and examination of controller signals recorded during the startup disproved the appearance of a correlation between loosing rotor 2 controller signals and staging.

 

1K ohm resistors were then added between each Renesis CAS signal and ground.  With these resistors installed, the engine started easily and ran normally at all throttle settings.  Since the engine was operated with this setup for only a few minutes, it is unknown if this is a reliable solution.  If it isn't, it is certainly a step in the right direction.  Plots of the CAS signals with and without the 1K ohm resistors are attached.  The voltage scales on the two plots are the same, but voltages read from the plots must be multiplied by a factor of 3 to give absolute values in volts.  Higher resolution plots of the CAS signals are available on request.  Any feedback on why adding the resistors is effective would be welcome.

 

Steve Boese
RV6A, 1986 13B NA, RD1A, EC2

 

  


From: Steven W. Boese
Sent: Monday, November 05, 2012 1:50 PM
To: Rotary motors in aircraft
Subject: Renesis CAS & EC-2 upgrade?

I have the 2011 Renesis engine running on my test stand...sort of.  On startup, when the manifold pressure drops below the staging threshold, both ignition signals and the primary injector signal from the EC2 are missing on rotor 2 on the next cycle after the dropping of the secondary injector signals on rotors 1 and 2.  This occurs at about 870 RPM.  The engine then runs on just rotor 1 until the RPM reaches the range from 1420 to 1750 at which time the rotor 2 coil signals and primary injector signal return.   The engine runs normally up to 5350 RPM which is as fast as the prop load will allow.  If the engine is idled into the rpm range less than around 1700, it goes back to running only on rotor 1 with the rotor 2 primary injector and coil signals missing. 

 

The CAS for this engine is set up as 2 Renesis CAS units, one triggered from a eccentric shaft mounted 12 tooth wheel and the second CAS triggered from a single pin on the side of the 12 tooth wheel. The 12 teeth are the same size and shape as those on the stock Renesis wheel.  It was hoped that this would allow use of the same EC2 controllers that were used on the '86 engine with the stock CAS with the 24 and 2 tooth pickups.

 

Searching the archives indicates that trying a 1K ohm resistor from each Renesis CAS to ground and/or limiting the CAS voltage with the circuit suggested by Bobby Hughes might be worth trying.  Traces of the Renesis CAS and the stock '86 CAS are attached.  The recording uses a factor of 3 divider so the voltage scale for each trace must be multiplied by 3 to give actual volts.  The white trace is of the 1 tooth Renesis or the 2 tooth "86 CAS while the colored trace is of the 12 tooth Renesis or 24 tooth "86 CAS.  The amber vertical and horizontal lines are software generated cursors, not EC2 signals.  One thing of note may be that the Renesis 1 tooth signal crosses zero between triggers whereas the 2 tooth '86 signal remains above zero between triggers.  There is no discernable change in the Renesis CAS signals when the transition to missing the Rotor 2 signals takes place.  There is also no discernable noise on the CAS signals under the measurement conditions of 3000 samples per second.

 

Any suggestions for investigating this issue would be appreciated.

 

Steve Boese

RV6A, 1986 13B NA, RD1A, EC2
<Renesis CAS with and without 1k resistor C.jpg>
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