Rick6a

Rick6a

Well Known Member
Guys,

Make this easy on me. I am out of my depth in such matters and dazzling me with arcane trivia will only serve to confuse. I've seen this type of question go way off on a tangent with wordy responses that lose me after the second paragraph.

As background, I am a recreational VFR pilot and cross country accounts for roughly 20% of my flying. I posed this question to Van's support several days ago and have yet to receive a response.

Item: I am going to install a Van's ordered XIO-360MIB and want to install a Lightspeed ignition system to replace one magneto. Van's offers two Lightspeed options, the Plasma II and the Plasma III and the price differential is around $275. Is the extra cost of the Plasma III really worth the premium or would I be perfectly happy ordering the Plasma II and save some serious money in the bargain?
 
Pick the best

I chose the III because of the improved spark IIRC. If in doubt, call them and talk to Klaus.
 
Rick,

I also chose the PIII unit for my 9a. The PIII unit has a longer duration spark than the PII and LS says this contributes to better fuel efficiency or higher hp.


Cheers,

db
 
Plasma III

I have the Plasma III with the front-mounted direct crank sensor. The timing will ALWAYS be correct. The direct crank sensor, the ring gear comes with two magnets permanently installed in it at the precise timing location needed.

And yes, the fuel economy is better. I cruise up high with an ECI 160 HP O-320-D1A equivalent engine. I get 160 MPH true air speed with a Hartzell CS prop at 12,000~13,000 feet, burning around 5.5 to 6 gallons per hour of 100LL fuel.

Jerry K. Thorne
East Ridge, TN
RV-9A, N2PZ
 
I spoke to Klaus and crew at OSH about this very issue, and he said exactly what you've already been told above, but added that the spark advance is different between the two.

This came from the FAQs on Lightspeed's web site.

What is the difference between the Plasma II Plus and the Plasma III system?
  • All Plasma systems are high energy Capacitor Discharge type systems. They are more accurate due to their faster voltage rise time and provide a hotter spark from a smaller and lighter coil when compared to the typical inductive type ignition system.

    The Plasma II series is a single spark system which has a fixed spark duration at all rpm.

    The Plasma III has a dual output stage which provides a continuous spark for about 20 degrees of crankshaft rotation at all rpm. Extensive flight testing with cockpit variable spark duration showed maximum performance gain with an un-interrupted 20 degree spark.    ​
BTW... I'm fairly certain I am going to go with the III. Good luck!
 
OK Rick, I'll give you the plain vanilla facts and you can read the following thread as well which has lots of info. http://www.vansairforce.com/community/showthread.php?t=16721

1. In THEORY the Plasma III SHOULD give slightly better engine performance than the Plasma II, particularly when running Lean of Peak when a longer duration spark would be beneficial to ignite the more stubborn mixture.

2. In REALITY no-one has been able to discern a quantifiable difference in favour of the Plasma III under real flight conditions. Walt Aronow is the only person I know who has the LS Plasma II on one side and the LS Plasma III on the other side. In the above thread he reports that with Iridium fine wire plugs all around he finds he gets smoother engine running on the Plasma II than the Plasma III when he switches backwards and forwards between the two systems in flight (and that's a pretty definitive and practical test).

3. The downside of the Plasma III (apart from price) is that the longer duration spark erodes the plugs faster and stresses the high tension wires and coils more. Thus reliability is reduced. Very few purchasers of the Plasma III understand that.

4. The crank sensor has less failures than the Hall Effect sensor, but is a bit more trouble to instal.


So the bottom line is this. No-one who has been able to compare both systems directly has been able to report any performance improvement with the LS Plasma III (in fact the opposite has been true). And the Plasma III is DEFINITELY not as reliable as the Plasma II.

If you prize engine reliability above all, then the Plasma II would be the choice. It has been around for a long time and is a very mature product with an excellent history. The panel is still out on the Plasma III.

In the meanwhile builders continue to buy the Plasma III model due to what might be called the 'Spinal Tap' theory ie. a bigger number must be better. You might remember in Spinal Tap that the guy was raving on about his amp being the best because the volume knob went up to eleven. :)
 
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You might remember in Spinal Tap that the guy was raving on about his amp being the best because the volume knob went up to eleven. :)
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Thanks guys for all the insights. My DNA tend towards the Spinal Tap theory when making purchases. I've learned the hard way that sometimes less is more. Bob....your explanation was particularily concise, easily understandable and compelling. Thanks to all for helping me make a decision.
 
Rick6a said:
Thanks to all for helping me make a decision.
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Glad to be of help Rick. I spoke face to face with both Klaus Savier of LightSpeed and Bart Lalonde of Aerosport and had in-depth discussions with both of them on this very subject before I ordered my engine with the Plasma II on one side and an impulse coupled mag on the other.

It's the Experimental category but I am reluctant to be too "experimental" when it comes to FWF matters. I fly IFR (occasionally at night) so I view the engine as a life support system. For that reason I won't opt for anything FWF that don't have a proven track record over MANY years. That was the reason I also crossed the EMAG off my list. I love all the latest and greatest gadgets coming onto the market...but when it comes to FWF I am not inclined to be a beta tester.

Cheers Bob
 
Captain Avgas said:
Glad to be of help Rick. I spoke face to face with both Klaus Savier of LightSpeed and Bart Lalonde of Aerosport and had in-depth discussions with both of them on this very subject before I ordered my engine with the Plasma II on one side and an impulse coupled mag on the other.

It's the Experimental category but I am reluctant to be too "experimental" when it comes to FWF matters. I fly IFR (occasionally at night) so I view the engine as a life support system. For that reason I won't opt for anything FWF that don't have a proven track record over MANY years. That was the reason I also crossed the EMAG off my list. I love all the latest and greatest gadgets coming onto the market...but when it comes to FWF I am not inclined to be a beta tester.

Cheers Bob
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Interesting. I look at LSE (or EI in general) as a way of providing dissimilar redundancy for the engine. We all know that mags normally sit there and work just fine, but when they fail, it's sometimes without warning. Mags and EI have different methods of failure, different MTBF, etc. I like dissimilar reliability and, for that reason, really don't want two EI of the same type.

Most of the LSE failures that I have heard of are from the Hall Effect sensor failing. Going with the crank sensor seems like a PITA, but if it's more reliable, then I'll take it.

I think EI has a pretty good track record in general (use mine every day to drive to work), and the LSE systems' failure modes are pretty well understood. EMAG/PMAG are well conceived systems, but have had some teething problems with their software. I like LSE because of the lack of software / hard-coded spark advance map. Perhaps not as flexible as LSE, but it seems to be more reliable at the moment. However, it does not have the level of redundancy that a PMAG has.

TODR
 
I need to do some more testing....

I must admit I haven't really taken the time to conclude one way or the other which system does better. I think I'll try to go up today and do some better tests to see if I can determine if there really is a difference between the II and the III. I usually run lean of peak at about 65% power or less and with a carb when I turn one system off it does get rough so I tend not to want to run there other to do a some quick checks. Today I'll try at some higher powers and keep it around the 100 f on the rich side so roughness won't be a factor. I can watch GPS grd spd, egt's/cht's etc, anything else specific you want I should watch for?
 
If anybody has any qualms about going with the Plasma II versus the spinal tap philosophy, don't. The Plasma II works absolutely wonderfully. Coming up on 1400 hours on it and it really kicks butt. My RV-8 will most likely have dual Plasma IIs (if not, it will have one Plasma II and one Slick 4371).
 
I finally received a response from Van's about the virtues of installing either Lightspeed. Because they have not done any testing, they were non-commital on the subject but added this rather significant note.

In a sense, it really does not matter which Lightspeed you fit to a factory new Lycoming engine ordered thru Van's because either one will void the engine warranty and suggested it would be best to wait until the warranty expired before installing one. :eek:
 
Rick6a said:
(snip.....) In a sense, it really does not matter which Lightspeed you fit to a factory new Lycoming engine ordered thru Van's because either one will void the engine warranty and suggested it would be best to wait until the warranty expired before installing one. :eek:
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Hmmm. One more reason to buy an engine from Mattituck etc., with the Lightspeed installed and a full warranty.
 
Guy Prevost said:
Hmmm. One more reason to buy an engine from Mattituck etc., with the Lightspeed installed and a full warranty.
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Yup. My AeroSport Power engine came with the LSE Plasma II installed and had their normal warranty. No biggie.
 
Walt; Tested LSE II & III yet?

Walt,

I've been reading the discussion about the differences between the LS II & III. I was wondering if you had come to any conclusions about their performances. On your dual LSE ignition, you mentioned that when you switched the II off, that the III seemed to run a little rougher than visa versa. Also mentioned in another post, you mentioned that the III plugs were on the bottom & the II were on top. Did you switch them around to see if that in itself was the difference. Here's a quote from LSE's instruction manual:
"If your mag fires top and bottom plugs, reroute the cables to fire either all on top or all on the bottom spark plugs. The PLASMA CDI can fire either the top or the bottom plugs. If you use one magneto, your engine runs a little better with the advanced spark on the top plugs."
This, of course, is for the common one mag + one LSE setup.

Anyway, good info in this thread...just checking to see if any new info was available.

Thanks,
 
Your experience?

Hi Darrell,

You said, "You live and learn!" :confused:

What has been your experience with the LS II & III?

Thanks,
 
LSE II/III

Well after careful evalution between the LSE II/III I've concluded I can't really tell the difference :D The III is hooked to the bottom plugs and when switching between one or the other system the difference looks and feels about the same (I do have 4 cyl egt/cht). Now if what has been said about the top being the preffered location makes a difference than switching the III to the top may change things, but I'm not going to go throught the effort. I will say that if I was to do it again I would go with either both II's or III's so that they are physically interchangeable. I continue to be very satisfied with the performance of this system. I always run around the same power during cruise (21/2350) and run lean of peak with smooth operation (with a carb mind you, for ref EGT peak at this power setting is around 1360 and I lean to approx 1320, CHT around 300d).
 
Walt said:
"...for ref EGT peak at this power setting is around 1360 and I lean to approx 1320, CHT around 300d).
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Do you really like running the engine that cool. As I understand it, the cylinders have quite a bit of choke with the upper end about 0.006" less in diameter, so that when the cylinder head heats up to the 350F to 400F region, the cylinder head will have expanded to make the cylinder straight up and down. If this is the case, running that cold would cause the rings to expand and contract more with each cycle. I shoot for 370F to 390F. Comments?
 
elippse said:
... I shoot for 370F to 390F. Comments?
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How do you do this? How do you maintain such a high CHT at altitude when you are below 75% power?

I guess my only thought would be that while Lycoming recommends keeping CHTs below 400 for engine longevity, the don't really specify a minimum. At cruise ALL my cylinders are usually below 350 and I like it that way. Aircraft reciprocating engines have considerable looser tolerances than say auto engines because they are air cooled and though I don't think it is measurable, I would think operating at 390 would cause more damage than operating at 350.
 
At cruise ALL my cylinders are usually below 350 and I like it that way. Aircraft reciprocating engines have considerable looser tolerances than say auto engines because they are air cooled and though I don't think it is measurable, I would think operating at 390 would cause more damage than operating at 350.

Several places in the "Lycoming Flyer Key Reprints" it says to keep the cylinder head temperature AT or below 400F. They are not going to recommend that you operate it where it will sustain damage.

"... I shoot for 370F to 390F."
"How do you do this? How do you maintain such a high CHT at altitude when you are below 75% power?"

I have variable apertures on my combined cooling-exhaust ducts from my special augmenters which allow me to control the flow. I used to overhaul my Cadillac engines, which spec'ed .0005" to .0015" piston clearance. When I first saw the .018" to .022" Lycoming spec for piston clearance, I thought I was seeing a mis-placed decimal point. But no, they need lots of cold clearance due to the high CHTs. That's why running the engine too cold has the piston banging around with lots of slop, which can lead to the piston getting cocked and breaking the skirt. 'Tis funny, lots of people subscribe to the "If one is good and two is better, let's make it four." philosophy. For me, I usually stick with the manufacturer's recommendations. Consider: a forty-year old plane owner who flies 50 hours/year wants his new engine to go to a 2000 hour TBO. He'll be 80 then! Is he really going to keep that plane all that time? I'm not recommending abusing the engine, just don't try to go the engine maker one better unless you really know and understand everything about the engine. Don't baby it! I know lots of people who won't operate their engines over 2400 rpm. Why? That engine is certified to operate all day long at 100% power at rated rpm. That red line at 2700 rpm doesn't mean that if you exceed it your engine will implode! If you are really concerned about fuel economy, operate your plane at the best range point, which is considerably slower than normal 75% cruise. I operate an airplane because I want to get places fast. My Lancair 235 gives me 198 mph TAS at 14,500' dalt at 5.6 gph for about 35 mpg. I could fly it at 150 mph TAS and flow 3 gph for 50 mpg, but forget that; it would take me over 6.6 hours instead of 5 hours to get somewhere! I want to get their as fast as I can!
 
Well for me personally most of the time getting there is half the fun so rather that run 75% pwr or more I run 55% or under. Less fuel, easier on the engine and more time to enjoy the ride is my motto!

I've been around cars/airplanes for the last 30 years wrenching, have raced, built race motors and all that good stuff. Nobody can tell me that running a motor hard all the time will make it last longer! IMO if you treat your equipment nicely (lower power levels) it will last longer than one that is run hard. Also high temps are hard on valves which is probably a weak point in most Lyc top ends, cool cht's mean cool valves which will help them last longer.

Add lots of oil changes and proper leaning and that should make for a long and healthy engine life :D

PS: I would like to have adjustable inlets to be able to control temps better but until I figure out how to do that I'll just have to live with the OAT having the last word on temps.
 
Walt said:
Nobody can tell me that running a motor hard all the time will make it last longer! IMO if you treat your equipment nicely (lower power levels) it will last longer than one that is run hard. Also high temps are hard on valves which is probably a weak point in most Lyc top ends, cool cht's mean cool valves which will help them last longer.

Don't do that for break-in, or you will glaze the cylinder walls! What constitutes running an engine hard? I had a 1976 Rabbit that I drove round-trip 94 miles/day, and it was running close to wide-open most of the time, at least 75% or better. At 196,000 miles the head gasket started to leak. Imagine my surprise when I looked at the cylinders and they still had the cross-hatch hone marks and there was NO ridge in the top of the cylinder. NONE, ZERO, NADA! I even had a friend run his finger-nails up the cylinder to see if he could find one, and he couldn't. 'Course, I used Mobil 1 most of the time!
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