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Q-talk 85 - Revmaster Electronic Ignition

Electronic Ignition

"Ya gotta love it"
Jerry Marstall, Asheville, NC.
N222RR 145Hrs

REVMASTER/POSA — You either love that combination or you hate it. I happen to be one who has experienced both emotions. Up until recently we have periodically had a mutual mistrust of one an- other. It seems that in order to get it to run well at the high-end the carburetor had to be adjusted such that it would not idle smoothly. It was a little disconcerting on final, at idle, to hear it choking in its own fuel. The rich setting also tended to foul the plugs on the ground.

Right now, I am very much in the amorous state. This change in affection has been due to the recent installation of dual electronic ignition systems (EIS). Now its as smooth as a Singer sewing machine and can even do a double-stitch and zigzag without fouling the plugs. The difficulty associated with POSA adjustment seemed to have disappeared. It’s the first time that I can actually read my vacuum gage at idle - it doesn’t shake anymore.

I made the decision to replace the mags with EIS because I was fed up with the rough running and having to pull the engine to check the mags on each annual. There is a very strong tendency NOT to pull the engine and wait until something goes awry. As we all know, Revmaster uses the dual mags in one case. That eliminates any possibility of retaining one mag and installing one EIS. Since I wanted to replace both mags, it wasn’t a problem with me except for the added expense (sizeable) associated with another EIS. It also complicates the installation somewhat.

I chose Electroair’s EIS. I had talked with Jeff Rose several times on the phone and at Sun N’ Fun last year. I also learned that several of the 0-200 guys use his unit along with a mag.

To my surprise, dual EIS’s are practically the same weight as the two mags. Therefore, I didn’t gain anything weight savings there. Since the EIS’s are dependent on electrical supply from the battery, I thought it good advice to follow Bob Nuckoll’s recommendation and bought an auxiliary battery identical to the 17 ah main battery. Bob’s procedure is to swap the older battery out every annual and be assured of having two good power sources at all times should the alternator fail. In a failure situation, there should be more ampere hours available than hours of fuel, thus getting me safely to a suitable airport.

Previously the main battery was mounted in the luggage area. Since I was operating in the rear half of the CG range, I decided to move it to the front and locate it on the left side, on the canard, next to the fuselage. The second battery I located in the same place on the right side. This brought my CG up to where I wanted it. It made for much shorter battery leads, which has helped on those cold days.

Since the Revmaster turns in the opposite direction of real airplane engines, Jeff had to make a special timing gear that comes in two pieces that you fit around the prop shaft and screw together. Jeff furnishes a pickup” mounting for one sensor, but nothing that holds dual sensors. Therefore, I fabricated my own as shown in the photos. Jeff s installation instructions are good. However, he doesn’t supply any assistance in wiring dual EIS’s to your electrical system. Being extremely electrically challenged, I struggled through the design of the otherwise simplistic wiring diagram. Because of my mental encumbrance, I don’t warrant this application. As crude as it may appear, it seems to work. It possesses complete redundancy. It allows me to operate either or both ignitions off of either battery and I can charge the secondary battery from the main battery. I am aware that it would be better to have a diode so that the main battery can’t discharge the secondary battery. At this time I control that with the “Battery Connector Switch”. The absence of a diode does allow me to use the secondary battery to energize the main buss if the main battery goes low. (If someone sees any inherently stupid problems with this design, for my sake, let me know). By each battery being attached to the voltmeter, with a controlling switch I can continually check the charge of either battery.

Its imperative that you take your power source for each EIS directly from the battery, not the bus. If you hook it to your main bus and for some reason (electrical fire) you have to turn the bus off your engine will do likewise.

The EIS also has altitude compensation. It advances the timing automatically as you climb to altitude, producing more power. This is coordinated off of manifold vacuum. There are provisions to attach a multimeter so that you can monitor the timing at all times. I used the cheapest Radio Shack digital multimeter they have. I did discover that you have to ground the multimeter back to one of the EIS unit’s case. Using the A/C ground resulted in spurious readings.

Results? Other than having to turn the mixture needle in two turns to smooth it out (saving gas), the fact that it idles like a Swiss watch and is more throttle responsive at all rpms, I’m not sure. Its been so cold I haven’t had an opportunity to leave the pattern to test fuel consumption, speed, or altitude. I do know that the plugs sure look a lot cleaner. No more fouling. This should save me from having to pull the bottom plugs so frequently. As the weather improves and I get some data, I ‘11 update you. Over all, it feels so smooooooooooooth. I LOVE IT!!

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