Lightspeed Plasma III problem

[Walt]

Don't really want to get invloved in this "debate" but I've been running both an LSII for about 900 hrs and a III for about 500 hrs, I've had one or two issues with the II and my buddy had an issue with his II that I helped him with (box problems in all cases) but the III has been trouble free to date.

I believe MTBF is more dependent on design, build and component quality than the measure of output power alone. Not much to go wrong with coils unless they can't take the heat/stress, wires and plugs are normal maintenance items that should be replaced every so often prior to "failure" so they don't count.

I've have also talked to Klaus quite a bit both on the phone and at Osh about II vs III & the problems I've seen with the II, he indicated that there was absolutely no evidence that one was more reliable than the other and he was adament that the III was the better unit. When I installed the III and dumped the second mag I was looking for maximum reliability and I could find no evidence to support that the II was more reliable than the III other than the II has been around longer.

Just my 2c for what it's worth

[Scott Hersha]

I have a III (and a mag) and when I decided to use it, my decision was based on advice from Klaus. Reliability wasn't discussed because I didn't realize there was a difference. Klaus told me that with a carburetor a Plasma III may be slightly better in terms of fuel economy and leaning because of the inherrant uneveness of fuel/air distribution between cylinders (with a carb). The longer duration spark would help the slightly richer cylinders burn their extra fuel and in a way help balance things out a little - 'least that's what I think he said in general. I only have a little over 80 hours so reliability is not an issue yet. I plan on buying new spark plugs for the EI every 100 hours or so if they look a little worn. They're cheap enough.

Scott
RV-8 FB

[Captain Avgas]

Originally Posted by Walt

Don't really want to get invloved in this "debate" but I've been running both an LSII for about 900 hrs and a III for about 500 hrs, I've had one or two issues with the II and my buddy had an issue with his II that I helped him with (box problems in all cases) but the III has been trouble free to date.

I believe MTBF is more dependent on design, build and component quality than the measure of output power alone. Not much to go wrong with coils unless they can't take the heat/stress, wires and plugs are normal maintenance items that should be replaced every so often prior to "failure" so they don't count.

I've have also talked to Klaus quite a bit both on the phone and at Osh about II vs III & the problems I've seen with the II, he indicated that there was absolutely no evidence that one was more reliable than the other and he was adament that the III was the better unit. When I installed the III and dumped the second mag I was looking for maximum reliability and I could find no evidence to support that the II was more reliable than the III other than the II has been around longer.

Just my 2c for what it's worth

Walt, I always respect your opinions. However this is what Klaus said to me in writing and I quote him verbatim:

"Only the output section is different in the two Plasma CDI versions. The power supply and all logic is the same. I don't see many failures in the output configuration. One could say that the longer spark erodes the spark plugs faster and stresses the high tension wires and coils more on the Plasma 111".

Unless I am mistaken I think this is the manufacturer stating quite clearly that the coil failure rate is higher on the Plasma 111 (which is what you would expect with a longer duration spark).

Additionally, I think that individual reports of failures (or successes) are interesting but I must admit I'm influenced more by the comments of a major engine builder who has installed hundreds of both units and is therefore in a position to have the sort of feedback that would provide a bigger picture.

Incidentally, now that you have been running both systems side by side for a longer period of time do you have any further data that would suggest that the Plasma 111 provides you with any improved performance whatsoever (smoothness of running, increased engine power, fuel savings, etc) over the Plasma 11 when you switch from one side to the other.

I note that back in 2007 when asked the same question on VansAirforce you stated: "Well after careful evalution between the LSE II/III I've concluded I can't really tell the difference".

Now I must admit that because you were the only person I knew with a Plasma 11 on one side and a Plasma 111 on the other side (and therefore in a unique position to draw a direct comparison) I was VERY influenced by that information.

[Ron Lee]

On this subject is there a recommended replacement interval for the coils and wires on a Plasma III ? I don't recall ever reading anything on this.

[Walt]

Originally Posted by Captain Avgas

Walt, I always respect your opinions. However this is what Klaus said to me in writing and I quote him verbatim:

"Only the output section is different in the two Plasma CDI versions. The power supply and all logic is the same. I don't see many failures in the output configuration. One could say that the longer spark erodes the spark plugs faster and stresses the high tension wires and coils more on the Plasma 111".

Unless I am mistaken I think this is the manufacturer stating quite clearly that the coil failure rate is higher on the Plasma 111 (which is what you would expect with a longer duration spark).

Additionally, I think that individual reports of failures (or successes) are interesting but I must admit I'm influenced more by the comments of a major engine builder who has installed hundreds of both units and is therefore in a position to have the sort of feedback that would provide a bigger picture.

Incidentally, now that you have been running both systems side by side for a longer period of time do you have any further data that would suggest that the Plasma 111 provides you with any improved performance whatsoever (smoothness of running, increased engine power, fuel savings, etc) over the Plasma 11 when you switch from one side to the other.

I note that back in 2007 when asked the same question on VansAirforce you stated: "Well after careful evalution between the LSE II/III I've concluded I can't really tell the difference".

Now I must admit that because you were the only person I knew with a Plasma 11 on one side and a Plasma 111 on the other side (and therefore in a unique position to draw a direct comparison) I was VERY influenced by that information.

Well after 2 more years of very careful very non-scientific evalution I can definately say "I still can't tell the difference". That doesn't mean there isn't one just that I have not been able to tell (or do I care enough to do any further testing) any difference between the II and III. If I was doing it again I would just go with 2 LSI II's purely from a maintenance standpoint so you could swap boxes easier for troubleshooting.

I will say now that I have switched to AFP FI the motor is smoother than ever. I always run LOP now which is especially nice in this heat (95+). Just today cruising at 2350/20" at 6gph cht's were 280, egt's around 1330 (70 lop on the richest) oil temp at 180.

I do run Iridium plugs all around, I feel like they do run better (smoother) than the std plugs plus they are holding up very well and not eroding near as fast as std plugs.

[Walt]

Originally Posted by Ron Lee

On this subject is there a recommended replacement interval for the coils and wires on a Plasma III ? I don't recall ever reading anything on this.

Yes there is a recommended replacement time for the wires but not the coils.

LSE recommends high tension lead replacement every 500 hours or every three years whichever comes first, independent of the ignition source

[Captain Avgas]

Originally Posted by Walt

Well after 2 more years of very careful very non-scientific evalution I can definately say "I still can't tell the difference". That doesn't mean there isn't one just that I have not been able to tell (or do I care enough to do any further testing) any difference between the II and III. If I was doing it again I would just go with 2 LSI II's purely from a maintenance standpoint so you could swap boxes easier for troubleshooting.

Walt, that's very interesting information but maybe not really all that surprising. LightSpeed makes lots of claims for the Plasma 111 with its longer spark duration but they have never provided any empirical test data (at least not that I can find on their website) that proves the Plasma 111 generates any real performance gains over the Plasma 11.

Quite often technologies that provide greater efficiencies in car engines running at higher RPM, higher cylinder pressures, and at extreme mixtures, fail to provide similar benefits in a Lycoming engine which chugs along at a very slow RPM in a very narrow RPM range. Multiple valves are a typical example. Judging from your observations and from the lack of any real data to the contrary it may well be that the longer duration spark is one of those technologies.

All that is known at the moment with any certainty is that the longer duration spark tends to chew through ignition leads and coils at a faster rate (and that the system costs more, and weighs more).

It may well be that after the Plasma 11 has produced 10 degrees of high energy spark the fire is well and truly lit in a Lycoming (if the fire is going to light at all)....the additional 10 degrees of spark produced by a Plasma 111 may do nothing. I'll continue to wonder about that until some-one produces some real comparative data compiled in a scientifically controlled way on a Lycoming. Until that time your observations and testing are probably as good as any going at the moment.

[airguy]

Originally Posted by Captain Avgas

The failure rate on the Plasma 111 units, including failed ignition coils, is higher than on the Plasma 11 units. LightSpeed themselves acknowledge this fact (if you bother to ask them...which I did).

I also had extensive discussions on this specific subject with one of the most respected (and largest) Experimental engine builders in the market place (a company that has installed literally hundreds of these units) and they confirmed the same information.

I do believe I specifically mentioned the exception of additional resistance heating overcoming passive heat rejection to be a failure cause. Did you get any information during your discussions with either Lightspeed or the engine builder as to what was the specific cause of the coil failures? These coils already operate in a hot environment, and are heat stressed from the word go. Additional spark dwell will certainly increase electrical heating in the coil and could conceivably push them into the thermal danger zone. Personally, I would be a little surprised if they were operating that close the edge, but we've seen it before, it is possible.

[RVadmirer]

Speaking of "heat soaked coils", has anyone mounted them somehwhere cooler than on top of the engine in probably the hottest place possible, as suggested by the manufacturer? (!)
Has this resulted in a better life span?

[w1curtis]

Originally Posted by RVadmirer

.. on top of the engine in probably the hottest place possible, as suggested by the manufacturer? (!)

This is the hottest location ONLY after shutdown when engine is NOT running. When the engine is running, temperature at that location should be around ambient as airflow is downward.