PMAGS or SDS

[M McGraw]

…The P-MAG, not to be understated is self powered. No other EI does this. Contrarian's counter OH YEAH...my EI has double batteries, back up alternator and switches on the panel for main, avionics, backup, emergency buses. Great, but it comes at cost of weight and complexity…. …Even Ross at SDS had an off field landing in his Subaru powered RV6 due to ignition. We butt heads on automotive engines as well…

I really do not understand your goal. I deleted out all the other stuff where you say your not really interested in an EI war. On that we agree. The part quoted above is not the first time you have stated as fact the P-mag is the ONLY system that is self powered. There was a respectful attempt to lead you towards the CPI-2 design in post #40. Others caught the reference. The CPI-2 on a Lycoming 4 cylinder at 2500RPM requires 3.2AMPS. I believe that gives a man all the info needed to size an ignition battery for a desired flight time. All the statements about double batteries, back up alternators, switches, and emergency buses simply indicate you are unaware of the design or passionately attempting to win an unnecessary argument. You really like a particular product, GREAT! It is a good company and Brad has truly great customer service. Why not use your knowledge to help the casual reader understand his/her options?

I have absolutely no doubt you know and understand the Ross event you reference was not the CPI-2 product and Ross changed his electrical system as a result, that story is available at SDSEFI.com.

 

[2theskyy]

I honestly glazed over most posts. So, all the data in the world does not matter if you cannot get the system/parts. That goes for any industry. I was told I’d get certain parts first of October so I could continue build or integrate certain items into my build. Nothing and no communication. If you don’t care to sell then I don’t care to buy.

 

[airguy]

Great.

Ya'll woke George up again, and got him on a tear. Guess I can safely ignore this thread for a while.

 

[Bavafa]

There is a compromise setup. Use the SDS CPI-2 and stay with your mechanical fuel injection. The CPI-2 does not require a robust electrical system because it includes a battery large enough to run out of fuel. With that said, I have been running a full SDS EM-5F system for 1000 hours over the last 5 years.

Have you or anyone has tested the failure scenarios and observed the behavior? If not, I will encourage those with any EI that is dependent on the ship's power to test ALL components that feeds their EI. I personally know of two aircraft with electrically dependent EI (Lightspeed) that one had an engine out at 300' AGL and miraculously landed on the taxiway and one who had an engine out on the run up area right before take off. Both have had multiple source of power and the latter is a Stein designed electrical system, multiple battery and two alternators.

I suppose a simple test would be to flip your master to OFF or something similar to that effect to see if the engine will still run. Do this for your own sanity and protection and not necessarily to prove your system is better than your friend's system.

 

[Bavafa]

Patrick,

The short answer is SDS (or other EFII) does not change the laws of thermodynamics. In other words “there is no free lunch”.

Consider typical RV cruise conditions (typically 90% of my flying). 2400-2500 RPM, WOT (above 6K’ or so), perhaps 20 degree LOP to gain fuel efficiency. It took me three iterations and swap out of 2 of 4 injectors in the RV-8, 4 of 6 injectors in the RV-10 to have a GAMI spread of 0.0-0.1GPH. At $26 per injector (from AirFlow Performance) this is about the best bang for your buck that you can get. Timing advance of no more than 9 degrees (pMag with jumper in, or six cylinder pMag set up) provides the most gain in cruise fuel efficiency as possible (any more advance and you just get higher CHTs). At this point you have achieved the best gain that an EFII system can provide.

Keep in mind your engine at full power will be ~25 degrees BTDC (mag or pMag) if that is what you set it at. I assume any EFII system would mirror this.

I have never seen any EFII advertisement that promises an increase in power. The one (or two) lever aspect may attract you, it does not me.

As I already stated, I consider the main advantage of EFII is the increase in fuel line pressure to mitigate vapor lock when using Mogas. This does not eliminate whatever timing change you need to do gain detonation margin for high compression engines (greater than 8.5:1). I do it the old fashion way, all my engines are 8.5:1, parallel valve.

Carl

Just to add to Carl's experience, I have also done a fair amount of testing changing my advance shift with my PMAGs which I can do in the air similar to SDS and found no appreciable improvement/efficiency over the default shift so I fly with the default curve A 99.9% of the time now, not worth the changing of the shift and remembering to change it back as you start descending lower. I have gained much more by focusing on the nuzzles and bringing my spread to the lowest.

 

[M McGraw]

Have you or anyone has tested the failure scenarios and observed the behavior? If not, I will encourage those with any EI that is dependent on the ship's power to test ALL components that feeds their EI. I personally know of two aircraft with electrically dependent EI (Lightspeed) that one had an engine out at 300' AGL and miraculously landed on the taxiway and one who had an engine out on the run up area right before take off. Both have had multiple source of power and the latter is a Stein designed electrical system, multiple battery and two alternators.

I suppose a simple test would be to flip your master to OFF or something similar to that effect to see if the engine will still run. Do this for your own sanity and protection and not necessarily to prove your system is better than your friend's system.

Yes, why ask me? I have not recommenced the OP use the system I have. I recommended there was a system that better compared to the P-mag the OP may consider before going with the system I have.

 

[lr172]

McQueen, I know of at least two other magneto replacements with an internal generator.

Barrett's system for the M14 replaces the Russian M-9 magneto.

The upcoming Kotuku is a self-powered EFI and EI. I declined an generous offer to beta test becasue the electronics did not have the appropriate AEC Q200 Grade 0 (150C) or minimal Grade 1 (125C) temperature rating for a device bolted directly to an engine. P-Mags suffer the same issue.

It's not a radical requirement. Pretty sure Lycoming EIS (Surefly) meets the Grade 1 standard. All our cars meet it, or higher.

Of course, the temperature concern (and associated crap like blast tubes) goes away when the system design doesn't mount electronic components on the engine. Mine is all behind the firewall.

same here. WHat I really like about my system is that the only three components FWF are the hall effect sensors (automotive grade, rated for 125C), the coils and the plugs, all of which are designed and rated for the heat they see. SDS is similar, PMAG is not, which is why they put heat sensor tape on it; So they can blame you when it stops working due to heat outside of your control. It is clear that they can only handle a limited amount of heat and that limit is pretty close to what we see on most summer heat soaks. Just like the highway adage - speed kills; For electronics it is Heat kills. Absolutely no way I put a CPU thay my life depends upon under the cowl.

Larry

 

[Toobuilder]

….changing my advance shift with my PMAGs which I can do in the air similar to SDS and found no appreciable improvement/efficiency over the default shift…

This right here illustrates that people will just not understand until they see it for themselves (Myself included). You can not change your advance curve “similar” to SDS with your Pmag. You may be able to shift the whole curve up or down, but you can’t edit the curve itself. And that is the important element of “variable” timing. It’s the “product discriminator” for the SDS product.

Pmag owners need to mechanically spoof the timing to soften the harsh initial curve to keep from over advancing and keep CHT’s under control. You also have to make sure the jumper configuration is right for the same reason. And of course this is especially important if you have an Angle Valve. This is a well known and well advertised “fix” for the Pmag owners. The heck of it is, once you hobble the canned curve like that, you don’t have ENOUGH advance left when you go LOP.

SDS accommodates any compression ratio, head configuration, displacement or fuel type. Set it up and forget about it. Pmags are “fine”… SDS gets you all the way to “right”. That’s the difference.

 

[sportflyer]

McQueen, I know of at least two other magneto replacements with an internal generator.

Barrett's system for the M14 replaces the Russian M-9 magneto.

The upcoming Kotuku is a self-powered EFI and EI. I declined an generous offer to beta test becasue the electronics did not have the appropriate AEC Q200 Grade 0 (150C) or minimal Grade 1 (125C) temperature rating for a device bolted directly to an engine. P-Mags suffer the same issue.

It's not a radical requirement. Pretty sure Lycoming EIS (Surefly) meets the Grade 1 standard. All our cars meet it, or higher.

Of course, the temperature concern (and associated crap like blast tubes) goes away when the system design doesn't mount electronic components on the engine. Mine is all behind the firewall.

Thanks Dan, I can confirm that the Kotuku EFII now meets Grade 1 (125C), the EIS is rated to 105C, same as the Lycoming engine core. We don't ever see temps in the EFII that exceed oil-temp + 5 degrees.

 

[DanH]

Thanks Dan, I can confirm that the Kotuku EFII now meets Grade 1 (125C),

Excellent!

 

[Bavafa]

This right here illustrates that people will just not understand until they see it for themselves (Myself included). You can not change your advance curve “similar” to SDS with your Pmag. You may be able to shift the whole curve up or down, but you can’t edit the curve itself. And that is the important element of “variable” timing. It’s the “product discriminator” for the SDS product.

So my interest, can you describe how the SDS advance curve is done and what kind of knowledge, level of testing is required to achieve that?

Pmag owners need to mechanically spoof the timing to soften the harsh initial curve to keep from over advancing and keep CHT’s under control. You also have to make sure the jumper configuration is right for the same reason.

This indicates that you either did not read my post well or speaking in general terms. I did say it that I can change it in the air, right, I would say It would be really hard to do this mechanically in the air, right?

 

[Toobuilder]

So my interest, can you describe how the SDS advance curve is done and what kind of knowledge, level of testing is required to achieve that?

This indicates that you either did not read my post well or speaking in general terms. I did say it that I can change it in the air, right, I would say It would be really hard to do this mechanically in the air, right?

The SDS products allow you to set a discrete timing value for each 100 RPM increment and each 3/10 of an inch of MP. My particular curve has a big retard while cranking to eliminate kickback, a big advance at idle, another big retard at TO power to eliminate the possibility of detonation, a moderate slope in the mid power ranges for CHT management, an “optimized” ROP advance at altitude , and finally, a separate additional “optimal” advance when I’m LOP. Not hard to learn, and easy to set on the fly where you can monitor results in real time. With all the people willing to share their experience, it’s a lot easier than transitioning from a 172 to an RV, learning how to manage a C/S prop or establish basic aircraft performance during phase 1.

And yes, I am aware that you did not mechanically move the unit in flight. But it is because of the limitations of the Pmag programming (even with the 3rd party controllers) that the conventional wisdom is to clock the mechanical timing to make the “as delivered” curve more suitable for many people. It’s hard to say why you did not see much of an improvement when manipulating the timing, but I certainly have done a bunch of testing and have seen, documented, and reported real gains in LOP cruise speed. Speaking generally, if you have a PV engine and the Pmag is “optimized” when LOP, then it is definitely over advanced when you are ROP, and almost certainly over advanced in the climb. On the other hand, If you follow the conventional wisdom of this forum and “spoof” the timing mechanically to address the over advance (and resulting high CHT’s) in climb, then you are likely not going to have enough advance to “optimize“ your LOP condition. The simple fact is that the Pmag curve is limited by design and as a result the operational envelope is not as wide or versatile as SDS.

 

[Bavafa]

The SDS products allow you to set a discrete timing value for each 100 RPM increment and each 3/10 of an inch of MP. My particular curve has a big retard while cranking to eliminate kickback, a big advance at idle, another big retard at TO power to eliminate the possibility of detonation, a moderate slope in the mid power ranges for CHT management, an “optimized” ROP advance at altitude , and finally, a separate additional “optimal” advance when I’m LOP. Not hard to learn, and easy to set on the fly where you can monitor results in real time. With all the people willing to share their experience, it’s a lot easier than transitioning from a 172 to an RV, learning how to manage a C/S prop or establish basic aircraft performance during phase 1.

And yes, I am aware that you did not mechanically move the unit in flight. But it is because of the limitations of the Pmag programming (even with the 3rd party controllers) that the conventional wisdom is to clock the mechanical timing to make the “as delivered” curve more suitable for many people. It’s hard to say why you did not see much of an improvement when manipulating the timing, but I certainly have done a bunch of testing and have seen, documented, and reported real gains in LOP cruise speed. Speaking generally, if you have a PV engine and the Pmag is “optimized” when LOP, then it is definitely over advanced when you are ROP, and almost certainly over advanced in the climb. On the other hand, If you follow the conventional wisdom of this forum and “spoof” the timing mechanically to address the over advance (and resulting high CHT’s) in climb, then you are likely not going to have enough advance to “optimize“ your LOP condition. The simple fact is that the Pmag curve is limited by design and as a result the operational envelope is not as wide or versatile as SDS.

I can see that the ability to set your own curve is much more advanced and capable with SDS as with PMAG I can only change the number of degree advanced for different phase of the trip. But also I know my technical ability is nowhere near enough to be able to identify the best curve or possibly worth the amount of gas that I need to burn to create one that also gives me confidence.
At the end of the day, there are some trade offs with each system and we all select what we believe suites us best. I am happy that you are so satisfied with your system and I have nothing bad to say about it, but the complexity and lack of self supporting has moved me towards what I have become comfortable to fly with.

 

[Toobuilder]

….but the complexity and lack of self supporting has moved me towards what I have become comfortable to fly with….

At the end of the day, the “complexity” (if you are referring to the setup) is the same. The SDS system is programmed and will fly very well right out of the box. It is the “ability” for the user to make changes that discriminates the product (and this thread IS a comparison after all). If an SDS owner wants to create a custom curve, replicate the Pmag curve or lock it out to fixed timing like a magneto, that action is only a few keystrokes away. We don’t shy away from the EFIS that features an advanced autopilot, the EIS that has more engine monitoring parameters, or IFR navigators because they have a touchscreen and moving map do we? No, we generally embrace the added features and learn how to use them. So why is more control of the ignition a “bad” thing - especially when that feature rich product comes at a LOWER cost than the competition? If one is looking to buy or build an RV and has the choice between full glass panel, fuel injection, and a C/S prop vs. steam, carb and FP for the same price - how many would shy away from the additional features because they did not want to learn how to use the more feature rich version? Not many, I suspect. And let’s not gloss over the fact that the curve required for a PV is quite different than an AV, yet the Pmag curve is the same. Throw in different compression ratio, FP or CS props, exhaust and induction, and you quickly run into the limitations of the Pmag architecture. And THAT is why the current logic among the community is to mechanically shift the unit to trick the timing into something that works. How can one knock the “added complexity” of the more feature rich SDS while defending the band aid fixes required of the Pmag?

And to your final point - both the Pmag and SDS will power the ignition independently of the ships electrical system long enough to outlast the fuel supply on board, so from a practical perspective, that’s a wash.

And I respect your choice, but this thread is not about your or my ultimate decisions, it’s about providing cold, hard comparison to the OP.

 

[2theskyy]

So, to that point, the op would want to consider fuel return choices. Must do something with SDS. Possible duplex fuel selector with building a return line system into each tank to balance fuel usage/return or a variety of other choices. Not necessarily a bad thing, just an added complexity.

 

[Toobuilder]

So, to that point, the op would want to consider fuel return choices. Must do something with SDS. Possible duplex fuel selector with building a return line system into each tank to balance fuel usage/return or a variety of other choices. Not necessarily a bad thing, just an added complexity.

If I understand post #1 correctly, The OP is asking about ignition products, with the option to then upgrade to EFI at some point if the SDS ignition turns out to be his choice. so far my responses have been in that light.

 

[Toobuilder]

…But also I know my technical ability is nowhere near enough to be able to identify the best curve or possibly worth the amount of gas that I need to burn to create one that also gives me confidence…

This sentiment is exactly what I have been trying to overcome since I started using the SDS ignition product and “saw the light”… It is NOT hard to establish a curve. It CAN be done while flying on your next cross country. It’s not much harder and about the same level of risk as fiddling with the red knob for best LOP performance or switching fuel tanks in flight. To try help, I started a “CPI Tricks” thread (now a sticky in this section) to try pass on the info. Please check it out and see if you still have questions.

 

[2theskyy]

If I understand post #1 correctly, The OP is asking about ignition products, with the option to then upgrade to EFI at some point if the SDS ignition turns out to be his choice. so far my responses have been in that light.

I believe just asking for pros and cons. The fuel system is a con or at least extra work for anyone that doesn’t realize how it must be constructed. It is different enough to deter at certain stages or at least plan ahead to get all the pieces in hand. I’m an SDS fan but went with Pmags and plan to go SDS at some point down the road.

 

[Toobuilder]

I believe just asking for pros and cons. The fuel system is a con or at least extra work for anyone that doesn’t realize how it must be constructed. It is different enough to deter at certain stages or at least plan ahead to get all the pieces in hand. I’m an SDS fan but went with Pmags and plan to go SDS at some point down the road.

Perhaps the OP will chime in here but I understand the “pros and cons” was limited to the ignition products. The reference to the eventual EFI upgrade was anecdotal.

 

[DanH]

It’s about providing cold, hard comparison to the OP.

I'm going faintly off topic here, but cold hard comparison has merit.

For the last 700 hours or so I've been flying a system based on a Ford EDIS module. It receives instructions from an external controller, and defaults to 10 BTDC if no instructions. There are many, many millions of them worldwide.

The controller gets its crankshaft position information from a simple magnetic reluctor, exactly like an Electroair. My reluctors are mounted in the mag holes. They can also be at the flywheel end.

The Ford module is a sealed brick. They're $100 or less used everywhere. Been a few years, but I bought new ones for $99 on eBay. The current Megajolt/e MkII controllers are about $200 each (Mk1 controllers in the photo below, since upgraded). They're mounted behind the firewall.



Coils are $30 to $100 depending on source. The p-mag uses a second generation Ford EDIS coil. I use a 1st gen because it includes positive plug wire retention.



The controller is temporarily connected to a laptop via USB for setup and entering advance maps. It holds two maps, switchable in flight with a simple toggle. I keep one map set for fixed 23 BTDC, and experiment with the other. Here's the current advancing schedule. I've not changed it in quite a while.



Data entry is just fill-in-the-blanks on the laptop, manifold pressure increments on the left (inches of mercury and kPa), RPM increments across the top, timing in the grid. The controller extrapolates between points. The 10 kPa line is set at 23 across all RPMs so a MAP sensor failure cannot cause a timing advance at any throttle position. Max advance is 29 BTDC, based on flight test. Remember, this a 390 angle valve. The angle valve does not respond to advance like a parallel valve.

How do I know? I can switch from 23 fixed to an experimental schedule, observe the results, and go right back to 23 at any time.

Cruising at peak EGT and 2400~2450, there is no practical difference between a typical 28~29 per the above, and fixed 23 timing. The advanced schedule is used to run significantly LOP, but I rarely do so. Yes, I know the arguments, but running 8 knots slower to save less than 3 gallons on a three hour tour just doesn't float my Minnow.

Power is direct connection to the main PC925 and a 3 AH backup. To be forced to the backup would require losing both the alternator and connection to the PC925. Then I could only fly about two more hours. I have flown from the Knoxville area to 08A on main battery alone, with everything running, including the autopilot.

I originally assembled these systems for less than $400 each. It would cost more now, but not a lot more. They've been bulletproof. The only moving parts are the re-machined Bendix mag shafts in the reluctor assemblies. Forgive me, but I don't see much value in self-generation when it comes with engine mounted electronics, lousy connectors, blast tubes, and canned advance, at nearly $4000.

True story. A few years ago Bill Kervaski brought some friends down from Birmingham and we all flew over to Falcon. One of the friends was a nice kid with a new-to-him 390 powered RV-8, pro-built as I recall. P-mags, no jumpers, no clocking. We literally flew side by side, and he was burning twice the fuel (full rich for "cooling") with 50F higher CHTs. Even if you like p-mags, the settings were wrong as a soup sandwich. Don't be that kid.

 

[Carl Froehlich]

This sentiment is exactly what I have been trying to overcome since I started using the SDS ignition product and “saw the light”… It is NOT hard to establish a curve. It CAN be done while flying on your next cross country. It’s not much harder and about the same level of risk as fiddling with the red knob for best LOP performance or switching fuel tanks in flight. To try help, I started a “CPI Tricks” thread (now a sticky in this section) to try pass on the info.

I note with interest no data on before and after engine efficiency (as in miles per gallon) with SDS. Who will want to offer this up?

I did post in 2020 about before and after engine performace when installing a single six cylinder pMag on my old RV-10 (still flying, pushing 800 hours on the pMag).

Six cylinder pMag - flying

All, I installed the final production verson of the six cylinder pMag on my old RV-10. I had installed a beta version, it is now replaced with this standard version that is being shipped out to customers. Installation was very simple. On install you set the timing to whatever you want. For...

vansairforce.net

My point, I would expect this or similar gain on any EI install that provides some timing advance. So back to the original OPs question on SDS or pMags:
- Add up the costs.
- Decide if you want to build a far better backup electrical system than offered in the install guidance. Keep in mind having reserve electrical capacity is much different than having that capacity delivered to the components that need it. Considering what I see in the field there are a few builders (or buyers) that have no clue how their electrical system works.
- Carefully review what you need to do to install SDS or other EFII.
- I say again the single practical gain for EFII is higher fuel pressure to reduce the risk of vapor lock. I’ve run 93 octane ethanol free gas in my RV-8A and RV-8 with no such problems with a standard fuel system install (AFP fuel injection and dual pMags).
- The “arguous” annual requirement for checking pMags is trivial. Of note this is a relatively new recommendation as there were a small number of fire breathing engines (as in very high compression and competitive use) that reported a problem. I ran dual pMags for 15+ years before this recommendation came out. When I did the check I found no problem.

I read all the pMag bashing about “suboptimal” timing curves and such. I suspect the same can be said for anything we put in the plane. The question is, so what? Is there data that to indicate this as an issue?

Side note. I did a dual Lightspeed Plasma II+ install on my first build (first flight 2001). It had the timing bias controls and digital timing readout in the cockpit. I found this to be more of a distraction than any practical gain. I ended up running timing in the as delivered setting as I never got much from any tweaking when flying. Both of these ignitions were replace with pMags at 300 hours after experiencing multiple problems. The pMags have been flawless.

Side note #2. I developed a redundant electrical system to support the Lightspeed Ignitions (I found the install instructions for a backup battery to be not acceptable to my engineering eye). All you guys running SDS/EFII, or any ship power dependent EI might find this design of value. Send me your email address and I‘ll provide. I still run the same system in all four builds, but I do this for IFR flight risk mitigation, not to keep the engine running.

Carl

 

[2theskyy]

Perhaps the OP will chime in here but I understand the “pros and cons” was limited to the ignition products. The reference to the eventual EFI upgrade was anecdotal.

Fair point. I enjoy the posts of different opinions. At least we are past the ole shower of sparks systems? Boy, I loved stepping up into the new slicks.

 

[Toobuilder]

I read all the pMag bashing about “suboptimal” timing curves and such. I suspect the same can be said for anything we put in the plane. The question is, so what? Is there data that to indicate this as an issue?

There are literally decades and hundreds/thousands of posts concerning the issue. How many “my CHT’s are too hot” threads are traced back to the Pmag curve ON THIS FORUM ALONE? How many “fixes” are offered up to correct the “one size fits all, sub optimal” curve, including 3rd party controllers, mechanically resetting the Pmag housing to correct kickback, and finally clocking the engine off TDC to spoof the curve. This isn’t “bashing” brother, it‘s fact. The Pmag was designed 30 years ago and we have learned a lot since then. The fact that the product remains fixed in the ’90’s is a choice made by the manufacturer.

 

[DanH]

I note with interest no data on before and after engine efficiency (as in miles per gallon) with SDS. Who will want to offer this up?

My point, I would expect this or similar gain on any EI install that provides some timing advance.

Largely true. Spark is spark, despite all the silly advertising claims.

As for timing, do keep the angle valve vs parallel valve differences in mind. Way back when, the fleet was almost entirely parallel. Now 390's are becoming common, so blanket pronouncements may not be appropriate.

I like speed with economy. If I seriously wished to make max MPG the #1 priority, I'd be flying the -8 about 140 knots. Actually, I do, if I'm just out on a Sunday evening patrol.

 

[Toobuilder]

Decide if you want to build a far better backup electrical system than offered in the install guidance.

Do we really have to repeat this yet again? The SDS product under discussion has a self contained electrical system Right out of the box. It will continue to run with a completely dead ship system - no modification needed by the buyer.

 

[Toobuilder]

I note with interest no data on before and after engine efficiency (as in miles per gallon) with SDS. Who will want to offer this up?

“Engine efficiency” manifests in many forms. One of those is increased speed at the same fuel flow. I have offered THAT data point many times on this forum. It is available for the reading if you will take the time to do a search.

But to your point, there is no “magic spark“ resident in the SDS product. If your particular engine needs, say, 32 degrees LOP to be optimum, I would expect the speed and FF of the airplane to be the same regardless of the ignition source that provides that spark at 32 degrees (including a mag, if you could twist the housing in flight). The discriminator is the curve that gets you there. The Magneto can’t get there at all, and the Pmag may get you there (32 degrees), but at the expense of the other points on the way (high CHT in climb anyone?)…. SDS gets you 32, and can do it “correctly” at every RPM and MAP point all the way back to engine start. Pmag CAN NOT do that. Period.

Anyone is free to discount or minimize the limitations in the Pmag curve as unimportant to them, but it is a fact that the SDS product offers more options for less price. That’s a valid differentiator in any market survey - and that’s exactly what this thread is.

 

[Toobuilder]

True story. A few years ago Bill Kervaski brought some friends down from Birmingham and we all flew over to Falcon. One of the friends was a nice kid with a new-to-him 390 powered RV-8, pro-built as I recall. P-mags, no jumpers, no clocking. We literally flew side by side, and he was burning twice the fuel (full rich for "cooling") with 50F higher CHTs. Even if you like p-mags, the settings were wrong as a soup sandwich. Don't be that kid.

Testify Brother Horton!

I flew an AV RV-8 for years with Pmags. This experience pre dated my SDS experience and I too flew without jumpers and attributed the higher CHT to “more power”…. As soon as I started flying the Rocket with the CPI ignition I got an education real quick and pulled the cowl on the -8, installed jumpers and spoofed the base timing to take some of the edge off the sharp (and wrong) curve. Of course the CHT’s improved immediately and so did the utility of the airplane. Eventually I pulled the trigger and dumped the Pmags for dual CPI and then started the same flight test routine I did on the Rocket. I was SHOCKED at the difference in ignition advance behavior between the PV and AV. Like you, I was shown very conclusively that the AV needs much less of an advance AND it is relatively insensitive from a performance perspective. Temps sure go up with too much advance, but the “peak” in speed that is so easy to spot in the PV engine is pretty flat in the AV. Main takeaway for me was the realization that as wrong as the out of the box Pmag curve is for a PV, it’s is indeed a “soup sandwich” for the AV.

 

[2theskyy]

All this SDS talk has convinced me to get the system. Where do I get one?

 

[Mike S]

All this SDS talk has convinced me to get the system. Where do I get one?

SDS EM-6: Aircraft

 

[2theskyy]

SDS EM-6: Aircraft

What’s the old saying. A bird in the hand is worth 2 in the bush. Pmag is in my hand. SDS has been on order for awhile. Sometimes we run what we got instead of hope to get someday.

 

[kentlik]

Very informative thread. I am installing the SDS system currently and is all good information! Thank you!

 

[M McGraw]

I'm going faintly off topic here, but cold hard comparison has merit.

For the last 700 hours or so I've been flying a system based on a Ford EDIS module. It receives instructions from an external controller, and defaults to 10 BTDC if no instructions. There are many, many millions of them worldwide.

The controller gets its crankshaft position information from a simple magnetic reluctor, exactly like an Electroair. My reluctors are mounted in the mag holes. They can also be at the flywheel end.

The Ford module is a sealed brick. They're $100 or less used everywhere. Been a few years, but I bought new ones for $99 on eBay. The current Megajolt/e MkII controllers are about $200 each (Mk1 controllers in the photo below, since upgraded). They're mounted behind the firewall.

View attachment 54563

Coils are $30 to $100 depending on source. The p-mag uses a second generation Ford EDIS coil. I use a 1st gen because it includes positive plug wire retention.

View attachment 54564

The controller is temporarily connected to a laptop via USB for setup and entering advance maps. It holds two maps, switchable in flight with a simple toggle. I keep one map set for fixed 23 BTDC, and experiment with the other. Here's the current advancing schedule. I've not changed it in quite a while.

View attachment 54565

Data entry is just fill-in-the-blanks on the laptop, manifold pressure increments on the left (inches of mercury and kPa), RPM increments across the top, timing in the grid. The controller extrapolates between points. The 10 kPa line is set at 23 across all RPMs so a MAP sensor failure cannot cause a timing advance at any throttle position. Max advance is 29 BTDC, based on flight test. Remember, this a 390 angle valve. The angle valve does not respond to advance like a parallel valve.

How do I know? I can switch from 23 fixed to an experimental schedule, observe the results, and go right back to 23 at any time.

Cruising at peak EGT and 2400~2450, there is no practical difference between a typical 28~29 per the above, and fixed 23 timing. The advanced schedule is used to run significantly LOP, but I rarely do so. Yes, I know the arguments, but running 8 knots slower to save less than 3 gallons on a three hour tour just doesn't float my Minnow.

Power is direct connection to the main PC925 and a 3 AH backup. To be forced to the backup would require losing both the alternator and connection to the PC925. Then I could only fly about two more hours. I have flown from the Knoxville area to 08A on main battery alone, with everything running, including the autopilot.

I originally assembled these systems for less than $400 each. It would cost more now, but not a lot more. They've been bulletproof. The only moving parts are the re-machined Bendix mag shafts in the reluctor assemblies. Forgive me, but I don't see much value in self-generation when it comes with engine mounted electronics, lousy connectors, blast tubes, and canned advance, at nearly $4000.

True story. A few years ago Bill Kervaski brought some friends down from Birmingham and we all flew over to Falcon. One of the friends was a nice kid with a new-to-him 390 powered RV-8, pro-built as I recall. P-mags, no jumpers, no clocking. We literally flew side by side, and he was burning twice the fuel (full rich for "cooling") with 50F higher CHTs. Even if you like p-mags, the settings were wrong as a soup sandwich. Don't be that kid.

This is very similar to the curve I developed. When I built my -14, first time builder, my interest was the educational part of EAB. At the time I had no background in ignition advance so I did what many in this community do, I asked questions and tested. I did about two hundred hours of flight testing and loved every minute of it, I’m still learning!

The two most important things I learned is that to truly take advantage of a variable timing ignition, in an airplane, one needs a minimum of two curves. My personal choices will be defined below. With one curve there is a compromise either ROP or LOP at the owners discretion. The second thing I learned is a parallel valve (PV) and an angle valve (AV) engine are noticeably different. A PV advance curve will generate unnecessary CHT temps on an AV engine.

What I learned after two hundred hours of joyful testing is that I could have copied DanH and gotten VERY similar results. Somehow, I have the curve that toobuilder uses. I don’t know if it was posted here or we communicated privately, I do know I have never met him.

Here is what I tell people when they ask about my experience FOR AN ANGLE VALVE Lycoming.

ATDC = After Top Dead Center
BTDC = Before Top Dead Center

Curve 1: Rich of Peak (ROP)
500RPM and below (starting). 5 ATDC or slightly more
750 and 1000RPM 15 BTDC
1100-1700RPM a linear climb from 15 to 23 BTDC (linear is simply easier on the engine)
1800-2700RPM 23 BTDC

Curve 1 is my takeoff and normal climb ROP flight condition. The difference between that curve and DanH is two-fold :

(1) My low power settings simply allow the engine to run a bit smoother on the ground; has no bearing on efficiency, but the capability is there so I took advantage.

(2) for any Manifold AIr Pressure (MAP) at and above 25.1 I decrease the advance by 3 degrees. In other words, my takeoff, initial climb, and balked landing/ go around are automatically set to the Lycoming value of 20. Again a personal choice that was available so I used it. I believe Toobuilder is even more conservative at 17 BTDC?

Curve 2 is what I use for Lean of Peak (LOP)

LOP can be a bit tricky, I found minimal advantage to shifting the curve unless I am leaner than 25LOP. Therefore, when I fly at PEAK I use Curve 1. At 50LOP I advance to 28 BTDC, at 100LOP I advance to 30 BTDC on the exceedingly rare occasions I fly at 150 to 175LOP I advance to 32 BTDC. At that point the airplane is burning insanely little fuel and also going slower than any reasonable RV owner would choose. Beyond 175LOP I get roughness.

Last point: The manufacturer of my system has an automatic program that in the event I am flying on Curve 2 and exceed 25MAP the ignition reverts to Curve 1 value at 25.1MAP. In my system that would mean the Lycoming value of 20 BTDC.

If I were using a P-mag on an AV engine, I would prefer jumper in and clocking 3 to 5 degrees. Another possibility would be to purchase the controller from Bill R.

All the data above was shared with DanH years ago and he programmed his system to verify my results. He even had data from Monty Barrett that was similar. For the purposes of learning about ignition systems all the conversations about electrical redundancy and fuel systems are irrelevant. The EI system I have been discussing simply is self powered. All the ignition data I have tested would not matter if the fuel delivery were a carb, mechanical injection, or EFI with the exception of how lean they can operate.

For those that have an interest in how I came to the conclusions above the data is on this forum. I have posted everything. The learning process was non-linear, I made mistakes. My goal in this thread was merely to add to the overall knowledge,
Respectfully,
Marvin

 

[bertschb]

I'm interested in going with SDS but as a new builder with no prior experience with EI, the SDS website just makes me dizzy. 95% of it is photos of race winning airplanes, cars, installs, etc. Very little information to help somebody like me choose their product over "traditional" ignition systems.

PMags would be simple for me to install. If I could install the SDS system with some kind of factory "default" settings for a 390 that I could tweak later as I learn more, I'd be interested. As it is, SDS is voodoo science from my perspective. I'm a techie-nerd so I'm not afraid of working with tuning software. I am afraid of blowing up my new engine the first time I start it because of my total lack of understanding EI.

 

[IowaRV9Dreamer]

The controller gets its crankshaft position information from a simple magnetic reluctor, exactly like an Electroair. My reluctors are mounted in the mag holes. They can also be at the flywheel end.

Dan do you have a picture of this setup, especially the inside of the engine portion? I looked at the Megasquirt page and it talked about gears with missing teeth. Is that how yours works? Thanks for this post BTW - I found it very informational.

 

[Toobuilder]

…If I could install the SDS system with some kind of factory "default" settings for a 390 that I could tweak later as I learn more, I'd be interested…

That is how SDS works. The unit will be loaded with a very safe curve right out of the box. Bolt it on and go.

 

[M McGraw]

I'm interested in going with SDS but as a new builder with no prior experience with EI, the SDS website just makes me dizzy. 95% of it is photos of race winning airplanes, cars, installs, etc. Couldn't car less about that. Very little information to help somebody like me choose their product over "traditional" ignition systems.

PMags would be simple for me to install. If I could install the SDS system with some kind of factory "default" settings for a 390 that I could tweak later as I learn more, I'd be interested. As it is, SDS is voodoo science from my perspective. I'm a techie-nerd so I'm not afraid of working with tuning software. I am afraid of blowing up my new engine the first time I start it because of my total lack of understanding EI.

When I installed mine, I changed the factory defaults to the Lycoming dataplate value, 20BTDC, at all settings. That allowed me to break in the engine and get good baseline fuel flow, EGTs, and CHTs. After I was convinced of the engine baseline numbers I started playing with the curve. You could easily follow that path or simply start with the factory supplied curve.

 

[dmattmul]

I'm interested in going with SDS but as a new builder with no prior experience with EI, the SDS website just makes me dizzy. 95% of it is photos of race winning airplanes, cars, installs, etc. Couldn't car less about that. Very little information to help somebody like me choose their product over "traditional" ignition systems.

PMags would be simple for me to install. If I could install the SDS system with some kind of factory "default" settings for a 390 that I could tweak later as I learn more, I'd be interested. As it is, SDS is voodoo science from my perspective. I'm a techie-nerd so I'm not afraid of working with tuning software. I am afraid of blowing up my new engine the first time I start it because of my total lack of understanding EI.

SDS is a good system and Ross does some very nice CNC work. Take a look at EFII also (FLYEFII.Com). After 500+ hrs. in my 14A with a 390 very satisfied. The as supplied curves the engine ran within one or 2 blades after start-up. I actually thought the starter was still engaged it was so smooth. 10 mins later after fine tuning the MAP curves was good to go. Installing EFII on my 540 as we speak. I've heard nothing but good reports from both EFI systems. Don't be intimidated by the technology, worth the effort.

 

[skelrad]

I'm interested in going with SDS but as a new builder with no prior experience with EI, the SDS website just makes me dizzy. 95% of it is photos of race winning airplanes, cars, installs, etc. Very little information to help somebody like me choose their product over "traditional" ignition systems.

PMags would be simple for me to install. If I could install the SDS system with some kind of factory "default" settings for a 390 that I could tweak later as I learn more, I'd be interested. As it is, SDS is voodoo science from my perspective. I'm a techie-nerd so I'm not afraid of working with tuning software. I am afraid of blowing up my new engine the first time I start it because of my total lack of understanding EI.

I'm in the same boat. PMags just SEEM simpler, largely because of the SDS website, which doesn't really lay things out all that well for a novice. I have the stock fuel injection setup with AFP electric fuel pump. What changes to plumbing and overall setup does SDS require?

 

[Mike S]

What changes to plumbing and overall setup does SDS require?

The SDS uses a return line to the tank, and for RVs you need a selector for the return line. There are two pumps in a single module, filters before and after the pumps. The pump output goes to the fuel distribution block, individual lines to each injector, and then a pressure regulator returns excess to the tank. The pressure regulator uses manifold pressure as a reference to keep the fuel pressure at the right value above ambient.

Both pumps on for T/O and landing. One pump for normal cruise ops.

 

[DanH]

Dan do you have a picture of this setup, especially the inside of the engine portion? I looked at the Megasquirt page and it talked about gears with missing teeth. Is that how yours works? Thanks for this post BTW - I found it very informational.

Not Megasquirt. Controller is a Megajolt/e, from Autosport Labs.

There are no custom components inside the engine. The reluctor wheel is driven with a standard magneto drive gear on a re-machined Bendix shaft. That end is identical to a non-impulse mag.





The reluctor wheel is indeed an off-the-shelf 36 tooth gear with one tooth removed. The pickup is a common ND unit.



Nothing new really. Here's an Electroair mag hole trigger, tubular pickup, 60 less one tooth rather than 36 less one.

 

[Toobuilder]

What changes to plumbing and overall setup does SDS require?

In the context of this thread which is ignition only, you do not need any changes to your fuel system to run the SDS ignition. If you are going to EFI, follow Mike’s guidance.

 

[Walt]

Still loving my dual Bendix mags, no interest in running LOP. Simple, reliable, proven.

 

[kearney]

Perhaps a different perspective.....

There is a lot one can do with the SDS system in terms of tweaking and tuning. Some may view this as complexity but in fact it could also be viewed as simplicity. Once the engine maps are tuned, there is no longer a great need to do anything else. The system just works in much the same way as the ECU in your car just works. To me this is true simplicity.

There is an upfront price to paid in terms of learning how to tuned the maps but it is not hard but it does require a bit of study. This is no different from any other aspect of building. We learn how to build, learn how to wire, learn how to install an engine. People do a lot of things that seem to be magic to the uninitiated but once you know how is quite simple. Think of visitors who see you building a plane and how they react.

So the real question is,what system will allow operation of the engine efficiently, effectively and simply,

i can’t speak to PMAGS but my SDS system minimizes my use If the mixture knob, LOP happens with a flip of a switch. Mixture is automatically adjusted for takeoff power settings, Extra spark advance offsets some of the power loss when LOP. My plugs are very clean and my engine runs very, very smooth. Once the maps were tuned, even my need for the programmer display was largely gone.

The SDS system by design allows for fine tuning. Compare this to “spoofing” PMAGS reported by others.

 

[aturner]

FWIW the SDS CPI-2 is currently unavailable (according to the SDS website) and has been so for some time.

 

[Toobuilder]

Still loving my dual Bendix mags, no interest in running LOP. Simple, reliable, proven.

yep. Settling for the mediocre is certainly an option too. Not really relevant to this thread though.

 

[gasman]

All this SDS talk has convinced me to get the system. Where do I get one?

This will get you right to the ignition section..... http://www.sdsefi.com/cpi2.htm

 

[gasman]

I'm interested in going with SDS but as a new builder with no prior experience with EI, the SDS website just makes me dizzy. 95% of it is photos of race winning airplanes, cars, installs, etc. Very little information to help somebody like me choose their product over "traditional" ignition systems.

PMags would be simple for me to install. If I could install the SDS system with some kind of factory "default" settings for a 390 that I could tweak later as I learn more, I'd be interested. As it is, SDS is voodoo science from my perspective. I'm a techie-nerd so I'm not afraid of working with tuning software. I am afraid of blowing up my new engine the first time I start it because of my total lack of understanding EI.

The website is not user friendly, but the product is solid.

Scroll up from the bottom of this page to find many links about installation and use of the SDS ignition.... http://www.sdsefi.com/aircraft.html
Here is the basic ignition.... http://www.sdsefi.com/cpi.htm Best to call for current prices.... Sales phone number 403-671-4015

 

[DanH]

Still loving my dual Bendix mags, no interest in running LOP. Simple, reliable, proven.

yep. Settling for the mediocre is certainly an option too.

Not necessarily true. Remember, spark source and timing are two different things. And this ain't Walt's first rodeo.

Walt, which Bendix mags? 1200's? 200's with SoS?

 

[DanH]

FWIW the SDS CPI-2 is currently unavailable (according to the SDS website) and has been so for some time.

Call Ross to confirm. As of January 2023 (one year ago) the CPI2 was sold out, and Ross said he wasn't producing any more until he got ahead of the EM-6 backlog.

 

[Walt]

yep. Settling for the mediocre is certainly an option too. Not really relevant to this thread though.

Not necessarily true. Remember, spark source and timing are two different things. And this ain't Walt's first rodeo.

Walt, which Bendix mags? 1200's? 200's with SoS?

Dan, I run the S-20 series (new version of the S-200 I believe).

"Toolbuilder": I find many of your comments to be a bit rude and sarcastic, I really don't need attitude.
I have had, and installed, every type of EI out there, so I don't need a lecture from you either!

I think folks need to understand that "old technology" is not necessarily a bad thing in the aviation world. I've had a number of customers over the years call me having been stranded with an EI failure and wondering what to do/how to get home. I've been in this game a long time, one thing I value over everything is reliability, and if something does go wrong (which it will), can you repair it in the field or are you at the mercy of a single source supplier. Every shop/mechanic in the world can help you with a mag problem, with an EI/EFII systems you most definitely are on your own. All those $$ spent on fancy systems don't make you go any faster and could buy a lot of gas, and personally, I could care less about saving a gal/hr in the name of "efficiency".

Folks start reading these forums and think they have to install all this fancy stuff otherwise they somehow will be left behind, which is absolutely not true.
Mags are not "mediocre", what they do represent is a proven ignition system with many millions of hours of documented reliability.
And just a point of interest, I do like the CPI ignition for its flexibility, but you don't really "need" it.