J

jcbarnes1

Active Member
Hi Folks,

ANYBODY running high compression and a Lightspeed please share your knowledge.

Just got an overhauled engine w 10-1 pistons, hot cam etc. Now re-installing my Plasma III. Engine mag is set to 25 btdc on the MAG from respected builder who says that is best timing for max HP.

Lightspeed manual says for engines set to 25 btdc, set crank to TDC #1, turn hall effect until light comes on/off, your done. Simple enough.

But Lightspeed manual says 25btdc is usually for "standard" engines, and 20btdc is usually for compressions 8.7:1 or higher.

I call Klaus. He's in shop getting ready AVC 2012: says he cant read me the manual, that why he wrote it. Ok. I mention the 25 btdc timing on the mag side although engine is 10:1 compression, he indicated that wasn't wise, but didn't elaborate. I was too intimidated to press for a better explanation - this being my first time on Klaus' dont-suffer-fools-side and all.

I confirmed 25BTDC with respected builder - assures me that's where I want it for max HP, but couldn't comment on how to set a Lightspeed.

Thanks

Jeff Barnes, RV6 O360, Slick and Plasma III
 
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This thread may help. With 10:1 pistons I think you would need to retard the LS by the recommended 5 degrees. Mahlon (Mattituck) seems to indicate that for 9:1 compression ratio the mag can be at 25 degrees but suggests 20 degrees "if you had significant compression increase".

I have an 0-320 with 9:1 pistons with dual Plasma III retarded by 5 degrees as per LS instructions.I also have the digital display that shows ignition timing. For most of my flying the LS is usually advanced at least about 25 degrees. I would have to be down low and at high power for the LS to advance below 25 degrees. If I was doing a sea level takeoff the LS would only advance to around 20 degrees but at sea level the engine makes heaps of power anyway so I don't really need the extra 5 degrees advance.

Some data points (from memory- I will check on my next flight):
My home base is at about 4000ft AMSL and I typically see about 25 degrees advance on a full throttle and 2,700 rpm takeoff.
At my normal cruise power settings of about 22" to 22.5" and 2,250 rpm the LS advances to about 27/28 degrees.

Fin
9A
 
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Mag and LSE Plasma III

I Have 9.2-1 pistons IO 360 and set the mag at 20 deg same with the IGN, seems to be what I hear frequently for High Compression set ups
Peter
 
We operate a number of certified and non certified Lyc powered aircraft. Our 10/1 angle valve Lyc 540 clearly requires 20 degrees of timing. It makes less power with more timing. And, believe it or not, the in flight detonation is so loud, it's easy to discern.

Our 8.7 to 1 angle valve produces slightly more HP with 25 degrees. However, it can also be run at 20 degrees without significant penalty. I think the difference is less than 3HP (or about 1%) About the only thing I can say is that it "seems" smoother at 25 deg.

Remember, aircraft engines with 2 opposed spark plugs need far less timing advance than single plug conventional engines. The "advance" situation is not the same as typical car engines.
 
cujet said:
Remember, aircraft engines with 2 opposed spark plugs need far less timing advance than single plug conventional engines. The "advance" situation is not the same as typical car engines.
Click to expand...

True, plus there is the RPM range of aircraft vs car engines that factors in there also.
 
Jeff I think you must have figured it out

Race Record (RR)# Race Date Class Aircraft Type Pilot Speed Kts Speed MPH
1357 AirVenture Cup 2012 7/22/12 RV Blue RV-6 Barnes, Jeff 196.51 226.14
1358 AirVenture Cup 2012 7/22/12 RV Blue RV-6A Axsom, Bob 195.26 224.70
 
We operate a number of certified and non certified Lyc powered aircraft. Our 10/1 angle valve Lyc 540 clearly requires 20 degrees of timing. It makes less power with more timing. And, believe it or not, the in flight detonation is so loud, it's easy to discern.

Our 8.7 to 1 angle valve produces slightly more HP with 25 degrees. However, it can also be run at 20 degrees without significant penalty. I think the difference is less than 3HP (or about 1%) About the only thing I can say is that it "seems" smoother at 25 deg.

Remember, aircraft engines with 2 opposed spark plugs need far less timing advance than single plug conventional engines. The "advance" situation is not the same as typical car engines.
Click to expand...

An excellent post indeed!!!!

Many folk fail to understand the importance of Theta PP and how torque is produced. A lower PP at a greater Theta (from less spark BTDC) generates more delivered torque. Advancing the timing just moves the PP closer to TDC and the only thing that gets more of anything is the rods crank and heads!

:)
 
Sounds like Greek to me

RV10inOz said:
An excellent post indeed!!!!

Many folk fail to understand the importance of Theta PP and how torque is produced. A lower PP at a greater Theta (from less spark BTDC) generates more delivered torque. Advancing the timing just moves the PP closer to TDC and the only thing that gets more of anything is the rods crank and heads!

:)
Click to expand...

Theta PP = ?
PP = ?
Unit of measure = ?

I have signed up for the Lycoming school again - standby for now and firm in the January class if I don't get in earlier, because I need to increase the thrust to stay competitive in the cross country air races of SARL and I intend to focus on the power side of things next season. However, it is not too soon to start. I make some assumptions because they are not anything more than jargon to me in this apparently knowledgeable post. I assume Theta is use to represent some angle and PP is a power pulse. You say that people fail to understand the importance of Theta PP and how torque is produced. You do mention BTDC which possibly is intended to bring in a angular reference. I assume that when you talk about Theta PP you are talking about the actual power pulse angle relative to top dead center and NOT the spark that we all worry about so much when we set the timing. I seems intuitive that the power pulse occurs after the spark and it can be measured in time or in an angle. The angle measure can be related to the spark angle or TDC. From your post the convention must be to reference the angle to TDC. And you last statement reinforces that with the assertion that the piston it still moving up in the cylinder and the power pulse occurring before TDC is opposing the direction the crank is turning, applying force to the heads, etc. and is not producing useful work until the crank rotates past the TDC point and the piston can be driven down and apply force to the crank in a way that boosts its rotation force rather than impeding it. I'm sure this is all correct BUT I do not for one minute believe it is all that simple. I can imagine an optimum power pulse angle is not a constant over the full range of operational parameters or even from one engine to another of the exact same type. Your post is thought provoking and God knows I need to think about this more as I am getting beaten rather regularly of late.

Bob Axsom
 
Gooday Bob,

I sit here on the lounge after a 28 hour trip home, and been awake all day, so I must apologies for not explaining the abbreviations which I must say you have worked out anyway.

PP as Mike explains is the peak pressure, and Theta PP is the angle from TDC at which the pulse peak occurs.

Once again this is not something you can learn from posts on a forum, so do not expect a magic bullet here, but you have summed it up pretty darned well yourself.

I get hammered when I suggest the best source of education for piston pilots is in your own backyard, well in Oklahoma at least. This and much much more is well covered, and seeing it on the dyno in front of your own eyes is worth a million posts on VAF.

On that note, over 12 years, the guys do not recall one RV flying in to Ada to attend. Unless they attended in disguise ;) Myself excluded, as it is a bit tough to fly the -10 from here! :D So maybe there is a reason for this. :cool:

All the best with your racing, and my suggestion is chase drag more so than HP. And weight, including the pilot :eek:
 
Thanks for confirming - you have me going now

This is unabashed thread drift but I think Jeff has his feedback and ... well I can't help myself.

As far as drag reduction is concerned I am about at the end of my options. There are a few possibilities left - aileron mounts for example - but otherwise the potential is so small that I don't think the effect could be measured by my test method. I will be removing the tip tanks that I gambled on for the AirVenture Cup race on July 22. That will give me back 2.2 kts in top speed.

Weight reduction - The rule of thumb I picked up at a race years ago was 1 kt per 100 lbs in cruise. I should lose 15 pounds so according to that rule I could pick up 0.15 kt that would be good in more ways than one. In the recent AirVenture Cup Race a long climb was involved and excess weight alone could have cost me a position. There is a race in Indianapolis in less than two weeks and I can ... wow that was bad, I almost let part of my plan slip out.

I have stayed away from the power (thrust) side of the speed equation but I can't ignore it any more. I have not won a race in nine attempts this year and I haven't been close. Competition that I routinely beat in the past has increased their power and the situation has reversed. That and the big ignorance discomfort thing is nagging at me. I also have a unique opportunity after the season ends to deal with it in a very special way. I hate putting myself in a young man's classroom environment again but the Lycoming school has got to help as well.

Now, if I can just pass my medical examination at the end of the season.

Thanks for your response.

Bob Axsom
 
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Programmability of EFII ignitions

For you guys who want to play with your timing curves relative to RPM as well as engine load (MAP). Our ignitions are fully programmable with respect to both those parameters.

Robert Paisley
 
jcbarnes1 said:
Hi Folks,

ANYBODY running high compression and a Lightspeed please share your knowledge.

Just got an overhauled engine w 10-1 pistons, hot cam etc. Now re-installing my Plasma III. Engine mag is set to 25 btdc on the MAG from respected builder who says that is best timing for max HP.

Lightspeed manual says for engines set to 25 btdc, set crank to TDC #1, turn hall effect until light comes on/off, your done. Simple enough.

But Lightspeed manual says 25btdc is usually for "standard" engines, and 20btdc is usually for compressions 8.7:1 or higher.

I call Klaus. He's in shop getting ready AVC 2012: says he cant read me the manual, that why he wrote it. Ok. I mention the 25 btdc timing on the mag side although engine is 10:1 compression, he indicated that wasn't wise, but didn't elaborate. I was too intimidated to press for a better explanation - this being my first time on Klaus' dont-suffer-fools-side and all.

I confirmed 25BTDC with respected builder - assures me that's where I want it for max HP, but couldn't comment on how to set a Lightspeed.

Thanks

Jeff Barnes, RV6 O360, Slick and Plasma III
Click to expand...

So customer service seems a bit lacking at Lightspeed? With a $30k engine hanging in the balance, I don't think it's outside the normal customer service range to ask a question of the electronic ignition supplier (which also is not inexpensive) and expect a reasonable answer rather than being dressed down. That's unusual to hear when discussing vendors in the RV world, as most are more than happy to chat. Unless they are working voodoo that nobody else is, wouldn't one be best to steer clear of Lightspeed for that reason alone? I have a few minutes before I have to make the EI decision, but I'm leaning towards dual Pmags.
 
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My experience:
I have six years on my EVO rocket now, 600 hours. Last year I had an intermittent miss that was eventually found to be a cracked distributor cap on my one bendix mag. My other ignition is a Lightspeed plasma III. I have 10 to 1 pistons.
Originally, as mentioned in the lightspeed manual for high compression pistons I set my mag at 20 degrees BTDC. During my search for the miss issue we advanced the mag to 25 degrees as was suggested by a few experts in the field. This matched what was written on the data plate of the engine. However the old data plate did NOT reflect the HC pistons.
The take off power was noticeably increased and engine temperatures were also higher by a significant amount. Although I liked the additional power I just did not like how the engine "felt" and sounded during low level full power climbs. I have a display that shows what the electronic ignition is doing and it was reading 20 degrees BTDC at full power. Thus the mag was doing most of the work in this situation, and up to a few thousand feet at which time the electronic ignition advanced more then 25 degrees.
I changed the mag timing back to the previous 20 BTDC and the engine felt normal again. Based on my experience I would suggest following what the lightspeed manual suggests.
To me this points out that two electronic ignitions would be preferable except I do hate that battery dependence. A proven six cylinder emag will be welcome. The ability to adjust mag timing in the air is interesting and could add to the power and fuel efficiency but how exactly does one know if you have it advanced too far at full power? I believe, based on my experience, that 25 degrees in not the place to be for full power at low levels and that 20 is conservative and safe. If you are not a really serious racer then I would leave things as Klaus suggests in his manual.
 
ColoRv said:
So customer service seems a bit lacking at Lightspeed? With a $30k engine hanging in the balance, I don't think it's outside the normal customer service range to ask a question of the electronic ignition supplier (which also is not inexpensive) and expect a reasonable answer rather than being dressed down. That's unusual to hear when discussing vendors in the RV world, as most are more than happy to chat. Unless they are working voodoo that nobody else is, wouldn't one be best to steer clear of Lightspeed for that reason alone? I have a few minutes before I have to make the EI decision, but I'm leaning towards dual Pmags.
Click to expand...
Hello Bill,
Enjoyed spending time at OSH with you and John. Hope things are going good with your build.

I have the Plasma III on my airplane. I have had occasion to talk with Klaus when I was building. He most definitely is a character. The times I talked with him he was fairly pleasant to talk with. My conversations with him were related to problems I was having on initial engine runs. Ultimately, my issues turned out to be installation errors (I had a good long talk with that fella who installed the engine and components, once I found out what he had done). I did not get the "in your face" behavior from Klaus that many others have posted about. I am sure I was just lucky. I did get a sense of impatience somewhat though once I informed him of my installation error. As far as the product goes though, I believe it is a very good EI. I have had zero problems with it since day one. I have no problems recommending the product. You just have to know that if you ever have to deal with Klaus be prepared.

I have not used the P-Mag but I have had several talks with the owner both online and in person at their manufacturing facility. They really are a hands on small shop. I think the product is a good one and would be interested in using the P-Mag if given the need to replace my current setup.
 
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