Lightspeed Plasma III problem
 

I have an RV-10 with a Mattituck Red/Gold IO-540 that has a Lightspeed Engineering Plasma III on one set of plugs and a traditional magneto on the other set.

I recently noticed an abnormal drop in the RPMs when I switch to just the Plasma. I checked the EGT and it showed that cylinders 3 and 4 are not firing when only the Plasma III is on. When I switch back to the mag or both, those cylinders immediately come back up to the appropriate temperature.

Cylinders 3 and 4 are driven by the same coil in the LSE design so I suspect that the coil has gone bad.

I am planning to order another one tomorrow. I have downed the airplane while waiting for the part.

I am wondering how the reliability of the LSE has been for other people. This one has been problem free for 18 months so I am not particularly upset. A coil costs $79 so it seems that having an extra one might be a good idea.

Does my diagnosis sound right? Any thoughts or guidance from engine experts?

Thanks

The only things left seem to be the connectors at the coil, the connector at the controller, and the wire inbetween.

Before you invest in a new coil, why not swap the two coils and make sure it is not the bain box or the connections?

The LSE Plasma 111 is not as reliable as the Plasma 11. The longer spark duration places higher stresses on the ignition coils.

But builders continue to buy the Plasma 111 because of the "Spinal tap theory"......a higher number must be better.

That's a new one to me; I hope you're wrong. I have trouble understanding how a coil can fail, anyway - it's just a bunch of windings of wire. Unless heat destroys the insulation...

Flew 400 hrs on my last plane with a II and no problems; this plane has a III and no problems yet either. Most of the issues I've heard of are either poor cooling or bad connectors.

If cooling is the issue, perhaps mounting them in or near the inlets would be a good idea?

AFAIK, the Plasma III is the only one offered by Mattituck
 

I agree that most people (including me) assume the higher number means a better (or at least newer) product.

In this case though, I think the Plasma II is not available as an option on the Mattituck Red/Gold.

Verify the wire connections on that coil. Also unplug and reseat the connectors into the box. I had a problem once not unlike yours (best recollection) and swapping out things did not result in a failed unit.

My guess is that corrosion on the connectors was cleaned by the removal and reseating of the connectors.

Can you defend that first statement with facts? Not just anecdotes gleaned from the internet. As for the second statement, those are pretty harsh words.

plasma III
 

There is one major functional difference with the III that I am aware of. The sensors are mounted differently on the III than they are on the II. They are mounted in such a way that they are easier to adjust. This is one of the primary differences that has convinced me to go with the III instead of the II.

It was at one time
 

My Mattituck IO-360 came with a Plasma II. This link still has them listed towards the bottom.

http://www.mattituck.com/tmx%20brochure.pdf