Ignition check oddity?

[2High2Fast]

Hello, all.

When I run-up to 2000 rpm and check my ignitions for independent operation, I get about 150 rpm drop when operating the mag, and about 50 or so when running the electronic alone. But when I switch from the Lightspeed back to both, I get a pronounced stutter with accompanying airframe shudder (torque). It may be a backfire, but I can’t hear it. It’s very consistent, (every time, exactly the same), but this is my first operation with electronic ignition in a Lycoming engine, so I’m not sure what’s up.

Thoughts?

[Kent Ashton]

More clues, Dr. Watson.   Impulse mag or non-?  Using a key switch or toggles? Tried leaning the mixture?  What sort of LSE triggers are you using?  How do you start up and how does it work after starting?    How's the engine run when switching ignitions in idle.  How about when going from idle to higher RPM on only one ignition?  I think you would hear a backfire.

Edited August 3, 2020 by Kent Ashton

[2High2Fast]

17 hours ago, Kent Ashton said:

More clues, Dr. Watson.   Impulse mag or non-?  Using a key switch or toggles? Tried leaning the mixture?  What sort of LSE triggers are you using?  How do you start up and how does it work after starting?    How's the engine run when switching ignitions in idle.  How about when going from idle to higher RPM on only one ignition?  I think you would hear a backfire.

Not sure if impulse or non (I’ll try starting with the LSE ignition off), key switch, leaning makes no difference, triggers?, start with key - starts easily, idles well, haven’t tried at idle

[Kent Ashton]

An impulse mag will snap or click as the spring winds up and trips the pawl(?) inside.  It is possible to time them wrong.  See  https://vansairforce.com/community/showthread.php?t=159907    It's not good to start on a non-impulse mag because it fires before TDC and can backfire and ruin you starter.   Lightspeed recommends toggles because key switches are subject to miswiring.   Lightspeed uses on of three kinds of triggers:  The Mini-sensor, or the green plastic ring or the Hall Effect mag-hole trigger.  http://lightspeed-aero.com/

I can't tell what you have wrong but I suspect it is the mag or timing.  However some of the LSE Plasma boxes have had a problem with broken solder joints inside and had to be repaired.  I imagine you can call them with your serial number and they can advise.

[2High2Fast]

Ah- just didn’t recognize the term trigger. I think this has the HEDs, but I’ll have to look again.

thanks

[macleodm3]

Like Kent mentioned... if its a non-impulse magneto then don’t start it on that mag.  The plane should be wired so it can’t start with that mag operational.  

[2High2Fast]

On 8/5/2020 at 6:51 PM, macleodm3 said:

Like Kent mentioned... if its a non-impulse magneto then don’t start it on that mag.  The plane should be wired so it can’t start with that mag operational.  

Understood.