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Surefly electronic ignition

Adjust it a little?

So, if a feller wanted to limit his Surefly to 36.5 degrees max advance, then all he needs to do is install it at 1.5 degrees BTDC? That setting may aid in the starter kickback syndrome some folks experience at startup. I?ve got my PMags set a whole 5 degrees BTDC to aid in preventing kickback and also limit max advance.

To be more precise for a standard Lycoming, it appears to be 36.5 degrees at 2700 rpm

https://docs.wixstatic.com/ugd/712b87_19a81ce5b1eb45f3b07af440a99b37e8.pdf
 
Sounds like you guys have it all figured out. I look forward to the development of your product and its introduction to the market. I?m sure it will be perfect and there will be no criticism on this forum as a result of all your hard work. I can?t imagine someone undermining your success with strong opinions or speculation. Good luck!

Not sure why you seem to be taking this so personally, but I can assure you that it is not my intent to attack. However, we do have a "new" product that seems to have a few skeletons in the closet. On a technical basis, that deserves debate. So here we are.
 
So, if a feller wanted to limit his Surefly to 36.5 degrees max advance, then all he needs to do is install it at 1.5 degrees BTDC? That setting may aid in the starter kickback syndrome some folks experience at startup. I?ve got my PMags set a whole 5 degrees BTDC to aid in preventing kickback and also limit max advance.

I think you meant to say AFTER TDC...
 
So, if a feller wanted to limit his Surefly to 36.5 degrees max advance, then all he needs to do is install it at 1.5 degrees BTDC? That setting may aid in the starter kickback syndrome some folks experience at startup. I?ve got my PMags set a whole 5 degrees BTDC to aid in preventing kickback and also limit max advance.

No, just limit your RPM to the Lycoming recommended 2700 rpm...
 
I am about to replace one of my Slicks with electronic ignition and do appreciate you all sharing your viewpoints. It's an education and will allow me to make a better informed choice.

Thank you!
 
If you want to replace your Slicks with some electronic ignition system, I think you should consider empirical data from either the experts that designed it, or 3rd party experts with no interest in the system one way or the other - not from the ?experts? on this forum. Pretty much everyone here is opinionated - me included. I would, in fact I have, asked myself a few basic questions:

1. Is this system reliable (more reliable than your Slicks)
2. How much does it cost.
3. How hard is it to install on my engine.
4. How much ongoing maintenance is required.
5. Will this company be around in 10 years.

Almost all of the popular electronic ignition choices are better than traditional mechanical mags, in terms of efficiency and maintenance. All of them gain their efficiency by variable timing. Improved maintenance is due to solid state electronics and a more robust system for dealing with the hot and harsh engine environment. Some EI systems boast a ?hotter spark?. Big deal. Once the fire is lit, the job is done. If you are the kind of person that wants to tweak your engine timing on a regular basis, then the Surefly and Emags are probably not for you. There are different levels of redundancy. Some require a secondary aircraft system architecture that will need to be addressed. All of this has been done - successfully. Keep in mind, you have two mags, or two EI?s. One of them will keep you going. You need to keep at least one of them going all the time if you are going to ditch both of your Slicks.
 
If you want to replace your Slicks with some electronic ignition system, I think you should consider empirical data from either the experts that designed it, or 3rd party experts with no interest in the system one way or the other - not from the ?experts? on this forum.

Scott, can I be a third party with no interest in the system one way or the other? After all, I'm not flying any of the store-bought aircraft EIs, or even a mag. My interest is keeping the BS to a minimum.

Pretty much everyone here is opinionated - me included.

Pretty much everyone everywhere is opinionated. Nothing wrong there. The question is "Does the opinion have a basis in fact?"

Allow an example. Mike's opinion is that custom, optimizing timing is the way to go. His opinion has a factual basis. I've said the Surefly's fixed timing option is a practical choice for many users. That opinion also has a factual basis. We have debated the matter, but no one is wrong.

Here the spit hits the fan because Mike's choice can't be implemented with a Surefly, and I've said the canned advance is too aggressive for an angle valve engine. Those too are facts, but they are not condemnations. I can't speak for Mike, but personally I really like the Surefly package. It's a great choice for many. It won't be the best choice for all. Honest discussion, messy as it may be, is how potential users determine if it's the best choice for their particular set of needs and interests.
 
Almost all of the popular electronic ignition choices are better than traditional mechanical mags, in terms of efficiency and maintenance. All of them gain their efficiency by variable timing. Improved maintenance is due to solid state electronics and a more robust system for dealing with the hot and harsh engine environment.

Not sure I agree with the above. One of the more popular units requires removal every year to inspect, does this qualify as "improved maintenance?
I'd also contend that bolting electronics to the engine makes for about the worst possible environment imaginable for electronics.
Do higher CHT's lead to longer engine life?
What happens when one of these EI's fails away from home?
You can do quite a few 500 hrs insp on mags (every 5-6 yrs for most folks) for the price a most of these systems.

I do like some things about EI's (fuel saving when cruising at altitude) but there's no free lunch.
 
So to be clear, Dan. Are you implying that the timing advance curve on the Surefly is currently too aggressive for a 200hp angle valve IO-360? I am ready to pull the trigger on a Surefly unit for the non-impulse mag in my Aviat Husky with the IO-360 angle valve engine with counterbalanced crank. I now find myself taking pause.

Jim
P.S. I have a PV IO-360 at Barrett Precision for a TDI with dual Pmags for my RV-8. And an RV-3B with a set of Bendix on a 160hp O-320. Maybe a set of good old CMI mags is the way to go on the Husky. This is all a brave new World that I may not be prepared to deal with.
 
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So to be clear, Dan. Are you implying that the timing advance curve on the Surefly is currently too aggressive for a 200hp angle valve IO-360? I am ready to pull the trigger on a Surefly unit for the non-impulse mag in my Aviat Husky with the IO-360 angle valve engine with counterbalanced crank. I now find myself taking pause.

Jim
P.S. I have a PV IO-360 at Barrett Precision for a TDI with dual Pmags for my RV-8. And an RV-3B with a set of Bendix on a 160hp O-320. Maybe a set of good old CMI mags is the way to go on the Husky. This is all a brave new World that I may not be prepared to deal with.

Been quietly following this thread. I am not going answer on behalf of Dan, but let me point out his previous post, one worth everyone taking note of.

Your observation matches mine, and Marvin McGraw's; sweet spot about 28 degrees.

The angle valve requires less advance. Given all the 390's going into 14's these days, it is why I object to canned advance maps based on parallel valve observations.

For example, the Surefly max is 38 BTDC at low manifold pressure. I've flown my IO-390 with advance pushed to 35 BTDC at 16,500, and found it wrong as a soup sandwich, slow and hot. 38 would be serious abuse.

I would also go as far as to say the canned approach on parallels is much the same. Sub optimal.

To reinforce Dans comments, EI's will fire the spark plugs about 2 degrees earlier than the original design spec. They do it in varying amounts engine to engine mag system to mag system. The Chieftan is even more retarded. But thats another animal. Unless you have the dyno gear to measure this, you would never know.

At full power ROP you really want something less than factory spec, maybe 1-2 degrees less, but LOP you want a few more. A fixed mag is a compromise. So the ideal setup is a EI that fire at around 2 degrees later, say 23 or 18 depending, and when at LOP/up high, (MP 22" or less) around 28 degrees, and no more.

This is not my spitballing. This is from doing this stuff on the GAMI dyno with George Braly.

Dan's advice is sound from an engineering perspective, (same as Ross's) but outside that, well its your plane!

PS: If any system has the ability to adjust the trigger position or set the timing like a Mag, you can always dial out a couple of degrees by going past TDC or wherever the trigger point is. If it has way past 5 degrees extra advance that becomes another issue.The SDS system from Ross is goo for this.
 
Another data point

Very informative discussion. One extreme of the circumstances discussed is my 7.2:1 (150 HP) parallel 0320 with two Pmags. I use pump 91 mogas and Pmags installed per instructions. CHTs run around 300 in T.O. climb and 280 in low alt cruise. EI commander shows cruise timing at least 35BTC.
Also, I did not pull the Pmags ( with all SB's confirmed) at last inspection cause I only flew abut 50 hr. I will remove this year.

My point is there are a lot of serious technical issues to be aware of and YMMV. Thank so much for VAF !
 
So to be clear, Dan. Are you implying that the timing advance curve on the Surefly is currently too aggressive for a 200hp angle valve IO-360? I am ready to pull the trigger on a Surefly unit for the non-impulse mag in my Aviat Husky with the IO-360 angle valve engine with counterbalanced crank. I now find myself taking pause.

I previously wrote "Honest discussion, messy as it may be, is how potential users determine if it's the best choice for their particular set of needs and interests." Your Husky application is an excellent case in point. Your needs are not the same as they might be given an RV application.

The Surefly offers both fixed and variable advance, with user choice of base timing.

The base timing for your angle valve IO-360 is generally accepted to be 20 BTDC. Some folks set 25, an option for some certified installations with fixed timing magnetos, as it will slightly improve altitude performance (think Mooney) in return for higher CHT. The best fixed timing compromise appears to be 23, based on personal experience and dyno work by a now deceased friend.

The Surefly's fixed timing option allows the user to select a setting between 18 and 30, with 20, 22, 24, or 25 being the choices suitable for a normally aspirated angle valve.

Begin by asking yourself what you most want from an EI. If the answer is (for example) "easy hot starting", then a Surefly installed with fixed timing is a fine choice. It will definitely start easier, it will run further lean of peak than you can with a mag (assuming you increase the spark plug gaps), it's easy to install and time, and you ditch the required overhaul period. It will otherwise act just like the mag it replaced. So, there is no reason for pause. If you like the product, do it. The issue is how you set it, not the product itself.

It's a Husky. STOL performance at higher elevations is probably on your list of "must do well" items. That means best power mixture, 100 to 175 F rich of peak. Operating rich of peak, there is no significant compromise with any fixed timing in the low 20's.

As previously noted, you'll be able to pull very lean for those times when fuel conservation is critical. Optimized LOP timing (more advanced than the fixed values noted above) generates a notable speed increase with (for example) a 6-cyl Rocket a higher altitudes. A Husky is at the far other end of the drag scale. Optimized LOP timing would offer very little return, because more power doesn't make a draggy airframe go a heck of a lot faster.

Let's look at variable advance. Here is the Surefly advance schedule. I've added some notes, specifically a pressure schedule for standard atmosphere, a scale for advance, and two RPM lines. The manifold pressure values Surefly has posted on the right margin are kinda fuzzy (23 to 25 inches, for example), so it's hard to know exactly what timing value results from a particular MP and RPM. A block schedule would be more accurate, but we'll go with what we have.

Advance%20Schedule.jpg


Bumping around at less than 5000 feet will keep timing at 25 BTDC or less. CHT's will rise some with rising advance. CHT considerations must get greater emphasis in the Husky application, as lower airspeed means lower available dynamic pressure. That said, I don't see a significant problem here, ROP or LOP.

With increased altitude, the schedule moves progressively toward one suitable for a parallel valve engine run high, fast, and lean. Assume 2400 RPM for cruise, and by 8000 feet the system has advanced past the 28~29 range we're finding optimum for an angle valve run LOP. Max advance for 2400 appears to be 31.5, not unreasonable for LOP but way past optimum for ROP. It's not a horror story, in that it should not break the engine. However, it is pointless given that it will come with a performance decrease, and a higher cooling load.

Let's return to STOL fun, 2700 RPM at best power mixture. Given a strip at higher altitudes, 2700 RPM has the system advanced to as much as 36.5 degrees, well beyond desirable timing for best power mixture. CHT will be high, a combination of lower air density (less cooling mass), lower airspeed (less dynamic pressure to drive the cooling mass), and peak cylinder pressure moved closer to TDC. I think it would be a very poor choice for a Husky, but again, it's the setting, not the product itself. The product gives you a choice.
 
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great illustration Dan - thanks

I was just doing the same, but with pen to paper print of the timing advance schedule - yours is much more sophisticated. I think this really helps us get to where many are looking for this discussion to go - how does using this EI impact the operation, efficiency and longevity of my engine?

It seems that the advance curve and upper limit may not be optimal for operating an angle valve O-360. The fixed timing may be a better option for the Surefly in this application.

How about the parallel valve O-360 with 8.5-1 compression? Better?

If, for instance, I'm not comfortable with the high end advance at 38*, what impact would setting base timing for the EI to 23* rather than 25* have? If the EI thinks its at 25* when its at 23*, would that effectively limit advance to 36* max? What would you be giving up on the low end (high MP/RPM) operation?
 
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How about the parallel valve O-360 with 8.5-1 compression? Better?

Yes.

Like any of the available systems with a pre-set map (notably Electroair, P-mag, and Lightspeed), the pre-set tends toward LOP cruise, which is typically still too advanced to be optimum for ROP climb. The resulting CHT rise is manageable for most users. Sometimes it requires work. Spin back to Jimmy's post #5 for an example.

The best parallel valve timing data available is from Nigel Speedy, published in Kitplanes. Nigel is a professional test pilot, and he put a lot of time and effort into the report.

With the author's permission: https://www.danhorton.net/Misc/Nigel Speedy - Ignition Advance .pdf

If, for instance, I'm not comfortable with the high end advance at 38*....

As others have noted, the system reaches 38 only at 2800 RPM. The 2700 RPM max appears to be 36.5 degrees.

...what impact would setting base timing for the EI to 23* rather than 25* have? If the EI thinks its at 25* when its at 23*, would that effectively limit advance to 36* max? What would you be giving up on the low end (high MP/RPM) operation?

The DIP switches allow the user to pick base timing of 18, 20, 22, 24, 25, 26, 28, or 30, fixed or variable. If I understand correctly, these settings have no effect on the advance schedule or maximum advance. In reality, they define the minimum running advance.
 
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timing set to limit advance

I'll have to run down a copy of Nigel's article! Very curious where his data leads on parallel valve timing.

For the sake of discussion, assuming 25* timing (minimum running advance) set for advance on the Surefly, if you set it up with the crank 2* past TDC (instead of 0*) would that give you an actual timing/minimum running advance of 23* and max advance of 34.5* at 2700 rpm?

Assuming there's no reason you wouldn't want your timing set to 23* (and there may be a myriad of them), would this be a reasonable way to limit the advance and some of the negative consequences of high advance referenced by others earlier in the thread?

May be chasing unicorns here.
 
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Dan. You and RV10nOz are Jedis. Excellent explanation. Excellent objective and technically sound posting. Hot starting is an issue. So it will be fixed timing for the angle-valve Husky. My field elevation is at or above 8,000' density altitude for most of the Summer so that clinches the deal on the fixed timing.

Slightly off topic, my parallel valve IO-360 with new 9:1 compression ratio cylinders/pistons and dual PMags is on the test stand at Barrett today. Rhonda Barrett suggests jumpering my PMags to the "A" curve which I think is less aggressive. And I like the sound of that too.

Thanks again to you and VAF forums for great information.

Jim
 
I'll have to run down a copy of Nigel's article! Very curious where his data leads on parallel valve timing.

Free download for Kitplanes subscribers: www.kitplanes.com May 2017 issue if I recall correctly.

For the sake of discussion, assuming 25* timing (minimum running advance) set for advance on the Surefly, if you set it up with the crank 2* past TDC (instead of 0*) would that give you an actual timing/minimum running advance of 23* and max advance of 34.5* at 2700 rpm?

Yes. Clocking the installation is common with a P-mag, same thing here. No unicorn.
 
Surefly

Maybe someone mentioned it already but could a backup source of electrical power be a standby geared aleternator dedicated to the Surefly in the case of a main battery problem?

From the Surefly website

?Where do I connect the SIM to aircraft electrical power?
​SureFly requires you to connect the SIM directly to the aircraft?s primary battery. You may connect the SIM power wire directly to the battery?s positive terminal or to the battery input terminal of the master solenoid.?
 
Maybe someone mentioned it already but could a backup source of electrical power be a standby geared aleternator dedicated to the Surefly in the case of a main battery problem?

From the Surefly website

?Where do I connect the SIM to aircraft electrical power?
​SureFly requires you to connect the SIM directly to the aircraft?s primary battery. You may connect the SIM power wire directly to the battery?s positive terminal or to the battery input terminal of the master solenoid.?

The short answer is no.

There are many practical options to support dual ship power dependent ignitions, this is not one of them.

Carl
 
Why Carl?

The short answer is no.

There are many practical options to support dual ship power dependent ignitions, this is not one of them.

Carl

Hey Carl....would you care to expound on the rational for your statement? Electrical components care not where the juice comes from and I know you have background in electrical engineering (I believe) and would love to learn the "why" of your statement above.

Thanks.......Bob
 
Let's not launch into power supply in this thread. Important subject, but not specific to the Surefly. I'm just sayin'...
 
I will be mounting a SureFly on my angle-valve Aviat Husky today. Going with fixed timing of 24 degrees (data plate says 25). With fixed timing no manifold pressure line hookup is required so that port on the SureFly is plugged. My SureFly is replacing the non-impulse Slick on the right side so I will remove the grounding jumper from the ignition switch to allow firing both the magneto and SureFly on start.

Jim
 
Hey Carl....would you care to expound on the rational for your statement? Electrical components care not where the juice comes from and I know you have background in electrical engineering (I believe) and would love to learn the "why" of your statement above.

Thanks.......Bob

I don?t recommend running any alternator without a battery. Happy do provide some detail if you PM me your email address.

Sorry Dan for the thread drift - just answering Oly?s question.
Carl
 
I've now replaced both of my Slick Mags with Surefly SIM's on my RV-6, and I love it. I have a Lycon, high compression IO-360. Engine starts MUCH easier, hot or cold. Smoother. I can easily run LOP. It's just happier overall.

I'm working on a small battery backup in the unlikely event that the alternator and the battery suddenly die at the same time. I say unlikely because the SIM's will supply ignition down to 8.5V. If I were to miss my alternator failure warnings, my avionics would shut down well before the SIM. The SIM only uses 600mA at 2700 RPM, so I should have plenty of time to find a place to land. A small 12V backup battery would give me a lot of time at only 600mA.

I've read where users are adjusting their base timing away from the data plate timing on the engine. I would highly discourage this practice as Surefly, in conjunction with Lycoming, has exhaustively developed a proprietary ignition curve which depends on the user setting the base timing at the engine spec. Anything different is at your own risk. Note that the curve that has been referenced on this thread is dated 2016, version 1.0.

If you want to experiment with your ignition curves, I'd suggest you go with one of the alternative EAB ignition systems. Good people, good products. If you want a simple magneto replacement that gives you reliable ignition with advance timing, consider the Surefly. Lycoming did!
 
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Gents, I have been following this thread for awhile and I thought I would throw my experience in here. I am flying a Maule with an O-360 and I have about 40 hours on the SIM4N and Slick combination. I was using the timing advance and what I noticed was my takeoff power and climb capability seemed to be very diminished on high DA days here in Colorado as compared to how it performed with two Slicks. It was very noticeable once DA got above about 8500ft, while around 6000ft DA the plane performed significantly better. I called Surefly and given my conditions on a 8500ft DA, at 2700RPM and 21" of MP the Surefly was running at the full 38 degrees of advance. Their rep suggested that it was perhaps not correctly timed, so I verified the timing and ended up switching it back to 24 degrees fixed timing. The plane appears to have the power back, shorter takeoff rolls and the climb rate was back as well. I don't have a ton of data other than just rate of climb, but given the same conditions, weight, etc, advanced timing gave me a 400-500fpm climb out vrs 700fpm at 8800-9000ft DA.

The Surefly reps say that this is all backwards and it should have more power given that 38 advance and they suggested that maybe I need to open up my spark plug gaps since they are all brand new and came gapped to the .016" give or take that tempest plugs come with.
 
The Surefly reps say that this is all backwards and it should have more power given that 38 advance and they suggested that maybe I need to open up my spark plug gaps since they are all brand new and came gapped to the .016" give or take that tempest plugs come with.

Perhaps I'm not understanding here but I hope Surefly isn't saying that best power is made at 38 BTDC?

This flies in the face of plenty of dyno and flight data saying that isn't so. 38 will give you way less power, high CHTs and detonation almost for sure.
 
Gents, I have been following this thread for awhile and I thought I would throw my experience in here. I am flying a Maule with an O-360 and I have about 40 hours on the SIM4N and Slick combination. I was using the timing advance and what I noticed was my takeoff power and climb capability seemed to be very diminished on high DA days here in Colorado as compared to how it performed with two Slicks. It was very noticeable once DA got above about 8500ft, while around 6000ft DA the plane performed significantly better. I called Surefly and given my conditions on a 8500ft DA, at 2700RPM and 21" of MP the Surefly was running at the full 38 degrees of advance. Their rep suggested that it was perhaps not correctly timed, so I verified the timing and ended up switching it back to 24 degrees fixed timing. The plane appears to have the power back, shorter takeoff rolls and the climb rate was back as well. I don't have a ton of data other than just rate of climb, but given the same conditions, weight, etc, advanced timing gave me a 400-500fpm climb out vrs 700fpm at 8800-9000ft DA.

The Surefly reps say that this is all backwards and it should have more power given that 38 advance and they suggested that maybe I need to open up my spark plug gaps since they are all brand new and came gapped to the .016" give or take that tempest plugs come with.

Herein lies the problem with canned timing curves. 38* at 8500' when LOP with one traditional mag (25*) doesn't seem that high. I run just a few degrees less than that in LOP cruise, with one mag. However, at t/o power, full rich with two EI's, both at 38*, I am not surprised you are seeing a significant fall off in power. Even with one mag @ 25*, this is still way too much timing for best power / ROP operations.

Larry
 
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Agree with Ross and Larry, and will double down on the hope that the Surelfy rep didn't think 38 degrees at TO power is a good thing.
 
On my SureFly I opted for fixed timing (25*) rather than hooking up the manifold vacuum line. I have an agle-valve IO-360 and everything I reasearched and found answers to on VAF led me to go with fixed timing. My objective with SureFly (and P-Mags for that matter) was easy starting and smooth running. On my P-Mags I would choose fixed timing if it were an option like SureFly. So I just use the least aggressive curve on the P-Mags.

And I have to say I am very pleased with both systems. In my Husky with the angle valve fuel injection the airplane starts super easy, hot or cold. That was transformational on that bird. I would recommend SureFly as a cure to injected hot starts without a lot of mixture and throttle fuss. The P-Mags came on my inected RV-8 and I am satisfied with the timing jumper connected. Then again I am super happy with my old Bendix mags on my RV-3. It starts and runs great and Bendix are solid mags compared to Slick. If they ever act up I would lean towards a EI solution.
 
Here's our Surefly experience so far:

I'd decided to replace some of the slick mags on our club's 172s with Surefly.

The install is easy although we did have to install mp, fuel flow, pressure etc etc to get the full benefit but it was bangin' from day one. You can just keep leaning and leaning. Saved us at least 1 gph on our O320-D2J. As stated before it does highlight inefficiencies. Needed aluminum tape to block about 15% of our oil cooler duct as it was stealing air from cylinder #3, replace some baffle rubber, etc

It didnt turn out all roses (yet) though. We wound up having to send it back to Surefly to go through a service cycle as we were having problems of momentary engine stutter (~.5-1sec).

Full story: A pilot squawked that there was a very short but noticeable engine stutter that'd happen every 20 minutes or so. I test flew her for an hour, same altitude, relatively same conditions and experienced nothing of course. Our club mechanic and I went through and replaced pretty much everything we could think from the plugs back to the switch including at Surefly's behest switching to the mag harness they recommend.

We switched back to two slicks and hadn't had an issue while waiting for the surefly to come back.

As an aside: The mag check was interesting as when you went from right (slick) to left (surefly) we saw a half second stutter as the surefly came alive... or at least that's what we're thinking it is. Has anyone else experienced that?
 
As an aside: The mag check was interesting as when you went from right (slick) to left (surefly) we saw a half second stutter as the surefly came alive... or at least that's what we're thinking it is. Has anyone else experienced that?

Yes, and from what I've read that's completely normal. I think the SureFly is programed to make two revolutions to determine direction of rotation before it resumes firing.
 
For me the main advantage of pMags is the advanced timing (jumper in). Over the years I find they provide superb service for my primary mission, high efficiency LOP cruise.

In other words, for me fixing the timing at 25 degrees (or whatever) for an EI takes away the primary reason for having it.

One note on leaving off the manifold pressure sense line. If this is all you do, you still get timing advance as you go up in altitude. Consider a typical cruise at 8000?, WOT. The manifold pressure will very close to atmospheric pressure - and your EI timing will advance per it?s programmed curve.

I know of one Lancair builder that does just this. He spends 99% of his time high, WOT and LOP. He just left off the manifold line as he did not what to add another firewall penetration.

Carl
 
Perhaps I'm not understanding here but I hope Surefly isn't saying that best power is made at 38 BTDC?

This flies in the face of plenty of dyno and flight data saying that isn't so. 38 will give you way less power, high CHTs and detonation almost for sure.


They are still mulling over the data before they give me an answer, but their immediate thought was it should only give you more power, so in essence, yes. I asked if they had any test data for high DA and that info wasn't available.

Just to be clear my setup is one Slick and one Surefly. I think for me its fairly clear to me that their advance is probably terrible for us people trying to get off the ground in Colorado. The plane sure starts nicely though!
 
Let me see if I understand this:

A canned timing curve that looks at MAP and RPM has no knowledge of mixture and therefore flame speed. So a best power mixture at 8500 DA may need less advance than a best economy mixture.

Is this why Ross at SDS has an LOP switch that advances timing for economy operation?

Vern
 
Let me see if I understand this:

A canned timing curve that looks at MAP and RPM has no knowledge of mixture and therefore flame speed. So a best power mixture at 8500 DA may need less advance than a best economy mixture.

Is this why Ross at SDS has an LOP switch that advances timing for economy operation?

Vern


Yes.

Except that best power mixture WILL (not may) need less advance than best economy mixture. There is no merit to debate on this - it's fact. If a canned advance curve is optimized for LOP, then best power will suffer. Conversely, if the canned curve is optimized for best power, LOP will suffer. They are two very different requirements, and you need two curves to satisfy both conditions.
 
Let me see if I understand this:
A canned timing curve that looks at MAP and RPM has no knowledge of mixture and therefore flame speed. So a best power mixture at 8500 DA may need less advance than a best economy mixture. Is this why Ross at SDS has an LOP switch that advances timing for economy operation?
Vern

Yes again.

If I may add to Mike's illustration...

If your EI choice is not switchable between best power and best economy ignition advance schedules, install a best power schedule.

Yes, that advice flies in the face of claims made repeatedly. Humor me a moment.

Many EI users conflate two separate EI factors. One is the ability to light less-than-optimum mixtures, a function of spark duration, energy, and wide gap. The other is the incorporation of variable advance. A user will install an EI, and then gush about his new lower fuel burn, easier starting, etc, while silently pondering his new higher CHTs. He often fails to understand that most of what he loves about his new EI is due to the spark, and much of what he dislikes is due to the timing of that spark.

Two weekends ago I found myself flying side by side with another RV-8. The nice young man was a relatively new owner, with a limited grasp of things in-cowl. Beautiful airplane...with very high CHTs. Before we went flying, I took a look under the cowl at his request. Yep, it had all the usual baffle seal errors, and lots of leaky spots, and a blast tube, and even two totally empty holes in the rear wall. I explained the needed corrections and stuck some aluminum tape on the worst spots, just so he could observe a difference when we went aloft for a visit to another airport.

The ignition? One Slick, and a P-Mag, with no jumper, which means an advance schedule beginning around 28 and maxing at 38 degrees BTDC. I suggested at least installing the jumper to subtract 5 degrees or so, and offered to do so, but the owner said no, not without consulting his own expert, who had apparently blessed the whole setup at least once before. Hey, no problem here...just don't forget.

So, we're cruising about 3500 and 150 knots TAS, the hot CHT airplane leading because he doesn't want to push CHTs. He was throttled, so MAP was low, so the P-Mag was advancing. The numbers? 11 GPH and 360-380F for a 360 parallel valve, vs 7.5 and ~315F for my 390 with an EI at a fixed 23 degrees. He was flying at 3500 because climbing got things too hot too quickly, and slow and full rich to keep cruise CHT below 400.

Sorry, that's just dumb as dirt.

Yes, I can hear keyboards warming right now. Yes, I'm sure you enjoy wonderful efficiency with your highly advanced EI after slowly climbing to some rarified altitude. However, before going further, consider this question: Have you ever flown back to back tests with your EI fixed on a standard 25 BTDC (parallel valve), vs highly advanced?

Well, some of us have, and here's the bottom line. Optimized best power and best economy require two different advance schedules. If optimized operation is your cup of tea, your dual map EI choices are currently limited to SDS and EDIS/Megajolt.

If only one is available, install the less advanced best power timing, as any speed lost to insufficient advance at best economy can be recaptured simply by flying higher...and when there is no climb cooling problem, it is easy to get there quickly. It's also easier on the engine; lower peak cylinder pressures, lower temperatures.
 
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Excellent post Dan.

Have done a lot of flight testing now on a PV 540 and see no gains in power ROP WOT at over 25 BTDC. 50-75 LOP up high WOT, MPG peaks with around 30 BTDC. Some other folks have reported best MPG at 30-33BTDC LOP. Maybe so, but I haven't seen needing more than 30.

You'd simply never want to run 38 under ANY circumstances on a PV Lycoming and especially so WOT, ROP and down low. CHTs will be through the roof, power will drop off noticeably and you seriously risk detonation damage.

I know for a fact that one EI manufacturer relies on Beta testers to supply them with optimal timing figures rather than doing their own flight testing. Not such a good plan in my view. Others want the curve kept secret. Again, why?

Surefly had the resources to get this right before any product was sold to customers but it seems from at least one post that they also don't have a clue about appropriate timing values. I hope that one post was in error.

Blunty, anyone advocating 38 BTDC ROP and at high MAP, is no expert and should bear responsibility for engine damage if that's what they are advocating with their EIs.

Proper ignition timing is important stuff for your engine to perform well and last a long time. Use science here, not guesses. The information has been out there for some time now.
 
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After all these years of debate on ignitions, the light bulb has gone on. operation at high DA/ROP, An electronic ignition optimized for LOP Operations may provide less HP than one optimized for ROP operations.

This explains a lot. Time to reinstall my arduino based variable timing controller for my Electroair. I've already seen TAS improvements with more advance when LOP. I can try best power mixture and less advance to see if TAS improves in that regime.

If this indeed the case, then it makes a lot more sense to use an integrated controller that controls both fuel and timing together. Automotive folks figured this out years ago. So have a few suppliers who advertise here.

V
 
Excellent post Dan.

Have done a lot of flight testing now on a PV 540 and see no gains in power ROP WOT at over 25 BTDC. 50-75 LOP up high WOT, MPG peaks with around 30 BTDC. Some other folks have reported best MPG at 30-33BTDC LOP. Maybe so, but I haven't seen needing more than 30.

You'd simply never want to run 38 under ANY circumstances on a PV Lycoming and especially so WOT, ROP and down low. CHTs will be through the roof, power will drop off noticeably and you seriously risk detonation damage.

I know for a fact that one EI manufacturer relies on Beta testers to supply them with optimal timing figures rather than doing their own flight testing. Not such a good plan in my view. Others want the curve kept secret. Again, why?

Surefly had the resources to get this right before any product was sold to customers but it seems from at least one post that they also don't have a clue about appropriate timing values. I hope that one post was in error.

Blunty, anyone advocating 38 BTDC ROP and at high MAP, is no expert and should bear responsibility for engine damage if that's what they are advocating with their EIs.

Proper ignition timing is important stuff for your engine to perform well and last a long time. Use science here, not guesses. The information has been out there for some time now.

My experience is similar with the new 540. I have my base curve set to give me around 32* at 21" of MAP. My megasquirt setup has both a second advance table that I use to up the timing 2* at lower MAPs and also have a 4* retard from the base table. I can set each of the two ignitions interdependently (important as total timing is a composite of the two spark events). As I play with the settings at cruise, I am only seeing only about a 2 knot variance as I play with timing in the 30-35* range. Not enough time and testing yet to correlate all of the variables to determine a best advance, but my gut is that it is right around 32* when LOP at 8000'. That said, we all fly at different levels of LOP and that will give us some variability in optimum advance.

I have my advance (both tables) set at 23* above 27" and have been playing with the 4* retard beyond that to experiment with CHTs. At 55 hours, I still haven't seen 400* CHTs (max that I have observed is 375) and that includes break in. Though that was done in ambients below 40*. That said, I did use a more agressive advance to raise my CHTs during the break in, as I was struggling to get CHTs above 340 and felt it was impeding my break in.

I had never given a lot of thought to these crazy canned timing curves, but after this thread, I really feel for the users taking off from high DA airport's. I just can't imagine someone stuck with a 38* advance at full rich. In my 6, I had some heat issues in the climb as the MAP came down (timing was still well less than 38) and the answer there was to use a 5* retard in order to accomodate ROP climbs.

We all know that the fixed timing of the mags is a limitation, but we need to recognize that many of the modern EIs are also fixed to a large degree, as they don't include enough variables to be optimal across our engines operating envelop. Kudos to SDS for creating options to real world requirements. I would never consider and EI that didn't have at least two discrete, user selected advance tables.

Larry
 
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After all these years of debate on ignitions, the light bulb has gone on. operation at high DA/ROP, An electronic ignition optimized for LOP Operations may provide less HP than one optimized for ROP operations.

This explains a lot. Time to reinstall my arduino based variable timing controller for my Electroair. I've already seen TAS improvements with more advance when LOP. I can try best power mixture and less advance to see if TAS improves in that regime.

If this indeed the case, then it makes a lot more sense to use an integrated controller that controls both fuel and timing together. Automotive folks figured this out years ago. So have a few suppliers who advertise here.

V

anxious to hear more about this. You should be able to incorporate fuel flow into the list of variables and this should be enough to set an appropriate timing level. That additional data point should allow you to determine an optimal timing level, when used in conjunction with MAP and RPM, assuming you have config details related to displacement and compression ratio. ambient temp input should also be incorporated, as IAT / MAT (derived from ambient) should drive a retard at certain levels to increase detonation margin.

Larry
 
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anxious to hear more about this. You should be able to incorporate fuel flow into the list of variables and this should be enough to set an appropriate timing level. That additional data point should allow you to determine an optimal timing level, when used in conjunction with MAP and RPM, assuming you have config details related to displacement and compression ratio. ambient temp input should also be incorporated, as IAT / MAT (derived from ambient) should drive a retard at certain levels to increase detonation margin.

Larry

Turns out I have all the data I need in the serial stream from the SkyView, including timing advance, MAP, RPM, Altitudes, Fuel Flow, Leaning state and cylinder temps. I also have the pins I need on my OnSpeed display module to turn it into a control head for ignition timing. What I do is modify the MAP sensor output to force the Electroair timing advance.

I read the raw MAP sensor voltage, then add or subtract a bit to change the timing. Right now I do this manually, but with the proper testing, I can make it automatic. I need to gather a bunch of data and try not to blow up my engine.

#42 on my list of things to do. I should be done Tuesday.

V
 
I wonder if an electronics whiz will engineer a LOP/ROP switch that we see in other systems for the Surefly to control the timing schedule that is done when installing the SIM.
 
Surefly had the resources to get this right before any product was sold to customers but it seems from at least one post that they also don't have a clue about appropriate timing values. I hope that one post was in error.

Let's assume that data point was an outlier, a case of one misinformed individual, or a communication error. And arguably, every P-Mag owner flying without a jumper got the same instructions.

In Surefly's defense, remember the standard EAB versions allow the installer to easily set one of eight fixed timing choices, or one of eight more variable schedules. No laptop or expensive accessory needed, just set the switches. Put another way, if it doesn't get installed with reasonable timing, it's not really Surefly's fault. The installer has easy options.
 
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Just a side note, the new six cylinder pMag has a switch that locks the timing at 25 degrees (or whatever you set it at) or in the timing advance position (you set the max timing advance on install). The switch is operable at anytime - as in you can select in flight.

I?m told this was a requirement from the FAA for them to get this ignition approved for certified aircraft.

Carl
 
After all these years of debate on ignitions, the light bulb has gone on. operation at high DA/ROP, An electronic ignition optimized for LOP Operations may provide less HP than one optimized for ROP operations...

Absolutely spot on.

And to ask Dan for clarity - with your RV-8 side by side comparison, was the other ship an angle valve like yours? I just flew the RV cross country yesterday with the SDS system replacing the Pmags and can attest that the AV engine responds very differently than the PV (Rocket) I'm used to. My data is limited, but all indications point to the fact that aside from the name on the data plate, the PV and AV engines are very different breeds. If nothing else, the "one size fits all" approach of certain EI suppliers is incorrect and borderline irresponsible.
 
Absolutely spot on.

And to ask Dan for clarity - with your RV-8 side by side comparison, was the other ship an angle valve like yours? I just flew the RV cross country yesterday with the SDS system replacing the Pmags and can attest that the AV engine responds very differently than the PV (Rocket) I'm used to. My data is limited, but all indications point to the fact that aside from the name on the data plate, the PV and AV engines are very different breeds. If nothing else, the "one size fits all" approach of certain EI suppliers is incorrect and borderline irresponsible.

Not surprising. Don’t know much about AV engines, but do know that the shape of the cylinder head chamber and piston head can greatly impact the optimal timing required.

Larry
 
Let's assume that data point was an outlier, a case of one misinformed individual, or a communication error. And arguably, every P-Mag owner flying without a jumper got the same instructions.

In Surefly's defense, remember the standard EAB versions allow the installer to easily set one of eight fixed timing choices, or one of eight more variable schedules. No laptop or expensive accessory needed, just set the switches. Put another way, if it doesn't get installed with reasonable timing, it's not really Surefly's fault. The installer has easy options.

I hope your first sentence turns out to be the case.

With regards to the 2nd paragraph, hopefully Surefly gives sound advice on making the timing options safe for their customers.
 
The DIP switches in my SureFly are set for 25* fixed timing, the same as the Slick mag it replaced. SureFly recommends fixed timing for any engine that may use auto gas and I wanted to have that option. My mission profile is primarily short low-altitude flights so the greater economy that advanced timing might yield at higher altitudes and longer flights is not a priority for me. I also don't know how the advance curve is configured and have no desire or reason to explore it.

The SureFly so far is an excellent alternative for the impulse mag it replaced and was a quick and low-stress plug-n-play. I suspect this device was intended primarily as a mag replacement. Other more 'experimental' ignitions may be a better choice for those who wish to explore the corners of the ignition envelope. But maybe SureFly will be forthcoming in the future with more details about the advance curves.
 
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