If you are using the Oz M&W capacitor discharge ignition for the
 rotary make sure your voltage regulator is set for at least 13.5
 volts.

 I suspect we found this out on the TTC the hard way because we do not
 have an alternator or voltage regulator. Consequently the battery
 voltage can fall well below 12 volts at high RPM and that probably
 causes the M&W to mis fire. The higher the RPM the higher the current
 drain with CD systems. No voltage regulator and alternator causes the
 battery voltage to drop off.

 When we were running it on the ground at full power we had the
 battery fully charged and no problem. When Dan flew it at full power
 it started missing. The vapor out of the blow off valve indicates
 full power on the ground run video.

 Here is the M&W installation instructions. They recommend 16 or 18
 volts.

 We can use 3 of these Uausa batteries wired in series to generate 18
 Volts.

 https://www.summitracing.com/parts/ysa-6n4-2a-4?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-yuasa-batteries&gclid=EAIaIQobChMIqZyS4drJ1QIVAZN-Ch3lxgxSEAQYASABEgLkh_D_BwE





 The weight is 1.9 pounds for each battery and the dimensions are
 each bat  is 3.5 inches long 2.75 inches wide and 4 inches high.

 The new battery box will be 8.25 inches wide and 3.5 inches deep.

 Thanks to Nills Castillo for the advise.

 All else fails read the instructions :-)

 -----------------------------------------------------------------------------------

 We are going to fix the problem by putting in a second 18 volt
 battery just to power the M&W ignition. 18 volts may be too much on
 the Motec and the electric boost fuel pump for starting and the
 electric pump for manifold water injection.

 Two separate electrical systems. One 12 volts and one 18 volts.

 The aircraft has now flown four times. Including one short cross
 country flight.

 I also upped the boost to about 80 inches of Hg  (I think).

 We are getting closer to making the TTC record attempt.

 Paul Lamar

 Dan discovered this 18 volt battery so we will use this to power the
 M&W ignition only. Nothing else.

 Not needed of course if you are using an alternator with voltage
 regulator.

 Paul Lamar

I am using a M&W CDI on my single rotor and it does fire down to 10V at
crank. Never had a problem.

FWIW.

Richard Sohn

Thanks Richard for the info.

Are you running 8,000 RPM?
The higher the RPM the more current drain. In our case the
voltage may have gone below 10 Volts.

10 Volts is more or less the industry standard lower limit  for
12 to 300 volt DC converter power supplies. That is what is inside most CD ignition
systems. The capacitor is charged with 300 to 400 volts  DC and
then dumped through the ignition coil primary.


Paul Lamar


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