Electroair Rough Running
 

Hi,

I'm encountering a problem with my electronic ignition that I'd
appreciate further opinion on. My RV6 has an O-320 with a Slik
magneto on the left drive and Electroair EIS on the right drive. The
EIS is an older model with the DIU and coils mounted together, and has been
successfully operated for 480 hours.

The problem is that each time I go to take off the engine misfires
when full power is applied. I am getting 2180 rpm static, and as the
plane accelerates at full power, after 10-15 seconds the engine
starts to misfire. The misfires occur at roughly 1-2 seconds
frequency and last for 200-700 milliseconds. There is never any
backfiring.

I've conducted one flight, and found that as soon as I eased the
climb and reduced power, the problem went away. I was able to fly at
2,600 rpm with no problems, and could not re-create the misfire
whilst airborne. Because there is no backfiring, I initially assumed
a problem with fuel supply. This has been eliminated, and I have been
testing the ignition system whilst static on the ground.

I connected an oscilloscope input to an ignition lead and the trace
gave large spikes at every 1/2 engine revolution as expected.
However, intermediate lower amplitude spikes were also observed at
2/3 to 3/4 of the main spike period. This occurrs throughout the full
rev range, including clean running.

I also tested the signal output from the magneto timing housing. It
was found to have irregular modulation and an irregular gap.

I don't know what signal the processsor unit can tolerate, but I
think that the irregular signal from the timing sensor may be the
issue. However, the manufacturer still suggests that the charge is
arcing out through either the leads or plugs.

One significant point is that when I turn off the EIS, the engine
runs perfectly on the single magneto. When the EIS is turned back on
and the misfire occurs, I would expect the magneto to continue firing
as normal. I think it probably is, but possibly there's no fuel left to burn
and the misfiring is caused by wrongly timed sparks from the EIS
igniting fuel in the cylinders before the mixture is compressed and
ignited by the magneto.

Am I missing something? Any thoughts would be much appreciated

Regards, James
RV6 G-JSRV

Welcome to VAF

Sounds like you have figured out the problem, now you just have to replace it with another Slick. I've removed 2 electronic ignitions in the last 12 months to find very smooth running engines. The EI's were causing the problems. It just seems to me that the EI's are prone to problems and failure for far too many reasons. They seem to work fine for a while then fade as vibration, heat, and time take their toll. Nothing lasts forever and you got 500 hours out if it.

JMHO

Have you verified timing? At low RPM, and high MP (like on takeoff with a FP prop), you're much closer to detonation margin. If you accidentally mis-timed your EI, or if the housing slipped in the mag hole, the timing might be off by quite a few degrees.

You have a bad pickup sensor. You can get a new one from Electroair or from the original manufacturer, which is Electromotive.

http://www.electromotive-inc.com/sensors.html

part # 250-72212

I carry a spare with me in my tool bag.

Electroair Rough Running
 

Guys, many thanks for your replies.

Bob, I think you are right, as the evidence that I picked up on the scope suggests a faulty magnetic sensor. The signal amplitude varies by as much as 50%, and I can't get an answer from Electroair as to what signal the DIU expects to recieve or how much variance it can tolerate.

I'll keep you posted.

Thanks, James

James, I bought my -6 with the same set-up as you, Slick mag on the left and older model Electroair (Jeff Rose) on the right. Everything fine until about 450 hours total time, when the Electroair began dropping off line intermittently. When it worked it ran smooth - it just didn't work all the time.

Replaced the pickup unit, as others have mentioned, and all was well until about 800 hours total time. Then the same problem returned. This time I had the Electroair replaced with another Slick mag.

I think my airplane actually runs smoother now, but fuel flow has increased slightly, maybe half a gallon per hour. I don't miss the electronic ignition. I like the assurance of knowing that if a mag fails, I can get it replaced anywhere, unlike with the Electroair.

I know some like to bash magnetos as being obsolete. Maybe they're right. Or maybe another word for "obsolete" is "proven."

I totally agree.

I've removed 3 different electronic ignition systems over the past 2 years. All were giving me some level of problems. For as little number of hours flown in a year I will gladly pull the throttle back another 1/2" of manifold pressure to make up for the fuel flow to get the increased security of Slick reliability and serviceability in the field.

Larry,

My experience has been different from yours. I have the Jeff Rose Electroair system installed for the last 9 years in my 6A with over 800 hours of use. I never have had a problem.

However with the Slick magneto I have had to have it OH at 500 hours and again it is showing signs of weakness.

Probably you are one of the few people who have been unlucky with your electronic ignition system, it happens. Are you aware of the recent SBs on Slick magnetos?

There are 1000s of airplanes now flying with different makes of electronic ignition and the vast majority of people seem satisfied.

Barry

Rose
 

Almost 1200 hours on a dual Rose system. in that time, one pickup sensor replaced when a bit of gravel somehow made it behind the flywheel and between the teeth of the timing wheel. Offers a lot of advantages for high altitude operation and helps with LOP operations. I would definitely do it again.

Ross,

I hear what you say, and have fitted a Slik magneto on the right hand side. I was intending to prove that whatever the fault was, it was with the electronic ignition system. However, I am getting exactly the same rough running at max rpm with both mags. Oddly, when I turn off the right mag, again the problem goes away. This is strange to say the least, and I have a few tests to run before I can reach any conclusion. Any ideas?

Cheers, James