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SDS CDI vs Pmag

FLY6

Well Known Member
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I currently am flying behind two magnetos with a carburetor and am starting to investigate electronic ignitions. I have tried to keep up on any post regarding this subject. I am trying to determine the difference between SDS CDI and Pmag or if there are any significant differences as I would like to eventually change one mag to EI.

Any comments from people with either experience or knowledge in this field would be greatly appreciated.
 
This is a good place to start:

http://www.vansairforce.com/community/showthread.php?t=140263

I started out with Pmags and they provided good service. They did exactly as promised. However, I gave the CPI a shot on my latest airplane and soon discovered just how limited the advance curve was on the Pmags. For my mission, the ability to tune the advance curve is the discriminator which strongly favors the CPI.
 
Chart Correction

Thanks for directing me to the chart.
I believe date in A&B 22 should be yes. From reading SDS's site, it states they are weather proof
 
Like Michael my original Pmag has worked exactly as advertised. I am currently in the process of installing a second one.

That being said, if I were not already in bed with the Pmag, I may have gone a different direction if I were starting out fresh today.

The SDS CPI would be very high on my list....

Pros: Complete monitoring and control of the ignition from cockpit (without any 3rd party add on box) including completely customizable and user selectable curves, no moving parts, electronics out of the heat and vibration, great quality components etc. are what would push me that way. Bonus are they are less expensive as well.

Cons: They are harder to install and the user must provide some sort of backup power scheme.

This list is not complete, just what would be important to me at this time.
 
Like Michael my original Pmag has worked exactly as advertised. I am currently in the process of installing a second one.

That being said, if I were not already in bed with the Pmag, I may have gone a different direction if I were starting out fresh today.

The SDS CPI would be very high on my list....


The Pmag is almost plug and play, no doubt. However, after doing several installations of each type, I dont find the CPI is much harder. The flywheel magnets are really the only items which require a bit of consideration.

I'm completely "pregnant" with dual Pmags on the -8 and I'm probably going to switch to CPI before too long.
 
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Minor note...the OP wrote "SDS CDI", and of course that should be "SDS CPI".

Capacitive Discharge Ignition (CDI) would describe a Lightspeed system. Very different operating principle.
 
Al - if buying Canadian means anything to you then SDS is the only choice! :)

I have a P-Mag and a Slick impulse-coupled mag. The engine starts and runs very nicely on the P-Mag alone. Installation is easy. For me the discriminating factor was the self-powered aspect of the P-Mag. If I were to replace the Slick I would give serious consideration to using the CPI system, powering it from the Essential bus which has its own backup battery.

Ross Farnham has proven himself to be a real stand up guy and his products are well tested. The installation kit appears to provide top-quality components. I just wish the CPI controller wasn't quite so gaudy in its colour scheme... LoL
 
CPI, Correct

Dan is correct, I did mean CPI. Is my thinking correct to see the only big difference in the two unit would be that the SDS can be programmed for more advanced curves? If I am of the school where I lean using my tach as an indicator, would either unit be an advantage? If I am just putting one EI on, would I still need to put a separate power source for the SDS or would I count on my mag with an impulse coupler to start the engine?

As stated earlier, I am in the beginning stage of research so forgive me if some of the answers to my questions are simple.
 
Preliminary design work on the next gen CPI will begin on Sept. 1 after we finish some additional engine running on our test stand this week.

All I can say so far is that it will be completely repackaged to take up about 1/4 the panel space of two of the current CPIs and there will be a single head to access optional dual boards, all integral. Also, the much hated green will be gone.

Pretty much all the proven software and basic hardware will remain as is.

Planned release is early 2018 but that's dependent on how busy we are with filling our regular orders and how long it takes to get it all developed and properly tested.

Looking for customer feedback on any additional features people might want.

We'll offer 4, 6 and 8 cylinder systems as we do now. They will all be released simultaneously so no waiting for a 6 cylinder system...
 
I still think it funny how Ross's poor green color gets maligned on multiple boards.

Good luck on the next release.

Tim
 
Ross - I'll chime in as a very basic user... I want automation rather than having to forever fiddle with ignition. That's one of the reasons my first EI is a P-Mag. I know the CPI controller allows an incredible amount of control over the ignition. I haven't read the user's manual recently, but my hope would be for a couple of quick button pushes to set the CPI into some default auto mode where the ignition provides as much advance as is needed to ensure good power, good economy and good protection of the engine. Not all of us are engine tuners, nor do we want to be. Ideally I'd like to mess with the CPI controller once at installation and then tuck it up behind the panel, never to be touched again. "Easy Mode" for me, please!
 
Ross - I'll chime in as a very basic user... I want automation rather than having to forever fiddle with ignition. That's one of the reasons my first EI is a P-Mag. I know the CPI controller allows an incredible amount of control over the ignition. I haven't read the user's manual recently, but my hope would be for a couple of quick button pushes to set the CPI into some default auto mode where the ignition provides as much advance as is needed to ensure good power, good economy and good protection of the engine. Not all of us are engine tuners, nor do we want to be. Ideally I'd like to mess with the CPI controller once at installation and then tuck it up behind the panel, never to be touched again. "Easy Mode" for me, please!

We'll still offer the original CPI to those who want to blind mount behind the panel as the new design won't be suited to that.

We send out all of our ignitions with a base map duplicating what a basic mag does- say 24 degrees total advance above 1400 rpm and no MAP advance. We'll custom tailor your curve depending on CR and fuel used (91 or 100LL)

The LOP switch allows the user to add whatever amount of advance you program in on top of that. We feel this gives the widest detonation margins and avoids excessive advance as some of the other EIs plainly have. We also disable the LOP switch input above about 25 inches as further protection in case you forget the switch position.

We understand that all users are not timing/ engine savvy and many just want a basic ignition. People should also understand that pre-set proprietary curves put out by some of the other EI makers may not suit different engines with CR changes or operating on different octane fuels but since people can't easily see what they have or do anything about it, they blindly operate them, hoping all will be ok. We prefer to give people the info and choice to change curves easily without any add-on devices if they want. Our philosophy differs from the others in the field.

We're going to try to keep the price of the new system below the other big players in the market and give you higher reliability, less maintenance and more features for less money.
 
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Preliminary design work on the next gen CPI will begin on Sept. 1 after we finish some additional engine running on our test stand this week.

All I can say so far is that it will be completely repackaged to take up about 1/4 the panel space of two of the current CPIs and there will be a single head to access optional dual boards, all integral. Also, the much hated green will be gone.

Pretty much all the proven software and basic hardware will remain as is.

Planned release is early 2018 but that's dependent on how busy we are with filling our regular orders and how long it takes to get it all developed and properly tested.

Looking for customer feedback on any additional features people might want.

We'll offer 4, 6 and 8 cylinder systems as we do now. They will all be released simultaneously so no waiting for a 6 cylinder system...

This is great news!

Will the next Gen CPI be a plug and play replacement for the current much hated green CPI's?

Any plans to change the EM-5 LCD Controller/display?

Thanks
 
feedback

I have your controller and it is tough to read as the display is quite small and so only can show limited data with each screen. What would be nice is an serial interface with my GRT EFIS display, perhaps as an option screen on the engine pages. Allow me to see a lot more data at once. Maybe control settings from there as well.
I like having my Trig transponder controlled like that quite a bit.
Just a thought.

John Koonce
RV 10
N78MU
 
This is great news!

Will the next Gen CPI be a plug and play replacement for the current much hated green CPI's?

Any plans to change the EM-5 LCD Controller/display?

Thanks

The Gen 2 will likely have a different connector with more pins so the harnesses will be slightly different. All the FF bits will be the same. So, with minimal harness changes, the Gen 2 could be substituted for a Gen 1.

No plans to change the EM-5 programmer display. We just spent a lot of money on new boards last week to use the wider temp spec LCD and offer the dimming and contrast adjustment. We also have a lot of expensive keypads on the shelf...
 
I have your controller and it is tough to read as the display is quite small and so only can show limited data with each screen. What would be nice is an serial interface with my GRT EFIS display, perhaps as an option screen on the engine pages. Allow me to see a lot more data at once. Maybe control settings from there as well.
I like having my Trig transponder controlled like that quite a bit.
Just a thought.

John Koonce
RV 10
N78MU

The Gen 2 CPI will have a larger display.

It would take too long to develop an interface with other engine monitors at this time but that's something we've considered so we'll have serial output capability on this device to be able to possibly add features like this when we have time to write and validate software to communicate with other devices.
 
Is my thinking correct to see the only big difference in the two unit would be that the SDS can be programmed for more advanced curves?

Much less advanced curves.

Get a copy of Nigel Speedy's recent Kitplanes article titled "The Effects of Ignition Advance on Cylinder Head Temperature, Speed, and Efficiency" (June 2017). Nigel is a professional test pilot, who put a lot of time and money into finding his optimum ignition timing for both best power and best economy mixture settings. It turns out that best power, as you might use for climb, requires little or no advance beyond the fixed setting specified by Lycoming, Superior, Titan, etc. The data says the pre-programmed ignition systems are wrong; when you try to use the expensive horsepower you bought, all they do is increase CHT. They advance when advance is not wanted or needed.

There is benefit to significant ignition advance when mixture is set LOP, up high. Even so, Nigel notes that running fixed timing and simply climbing to a higher altitude can result in near equal efficiency....with lower CHT. Higher altitudes are easy when you don't fight CHT in climb.

Mike Robinson has done a fair bit of ignition test flying also, and can tell how closely his data compares with Nigel's. If I ever find time to return to experiments, I intend to gather a similar data set for an angle valve.

There are only two systems which allow programming dual ignition maps (one for best power and one for LOP), and changing between them in flight with a single switch flip, SDS and Ford/MegajoltE. Only the SDS is self-programming; the EDIS/MegajoltE requires a laptop. And as noted, the SDS system now switches to the ROP map automatically above 25".

Nice one Ross.
 
Article

Thanks Dan I will look for the articles you mentioned. Thanks everyone for your input, I obviously have a lot more reading in front of me.
 
I'd add that the Gen 2 is designed with aviation 100% in mind rather than a spin-off adapted from automotive as the original CPI was. It will have some of the new features recently introduced on the EM-5 as well.

The advantage of several product lines- once we write new software for one, that code can be carried over to other products at little additional cost outside validating it.

In case some new people are following this thread and are unfamiliar with what the CPI offers, here's a quick rundown:

Timing adjustable in logical 1 degree increments at 500, 750, 1000 rpm and then every 100 rpm above that

Timing adjustable with MAP- retard or advance which is subtracted/ added to the basic rpm programmed timing. 1 degree increments

Adjustable coil charge time

Adjustable cranking retard

LOP switch adds a programmable amount of advance to the base RPM/ MAP curves

Adjustable rev limiter

Integral coil test function without engine running plus error LED for quick diagnostics

12V tach signal output

Runup mode for testing coil packs (single module driving both plug sets)

Integral MAP sensor

Hall triggered off the flywheel, Conformal coated PCBs, no blast tubes required, no maintenance required outside of annual spark plug checks.

Easy to understand programming
 
Dumb questions from newbie, does the sds system require a mixture knob? Does it require fuel return lines? What type of cockpit switches/controls are needed? What is the recommended electical system for this setup (I assume dual batteries)?
 
Hi Ross I have a dual cpi setup on my RV6A and it has performed flawlessly. I'm not familiar with the adjustable coil charge time? I don't recall seeing that in my setup?


Thanks
Bill

About the 5th one under the hidden settings.
These can be accessed by holding down the left arrow button when powering up the CPi unit.

From manual page 12:
Adjusts the charge time or dwell of the coils in milliseconds. Default is 3.5mS. Increasing may help spark if running high boost on turbo/supercharged engines. Increasing dwell will increase current draw of the coil pack, and could cause the coil pack/ignition fuse to blow at high rpm. If experimenting with larger coiltime settings, rev the engine in neutral and monitor ignition current. One way to monitor current is to pull the coil pack fuse out and substitute your ammeter leads into the fuse socket. Fuse should be at least 30% greater amperage capacity than what you observe on the meter at redline.
 
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"We also disable the LOP switch input above about 25 inches as further protection in case you forget the switch position."

Ross is this new? I purchased a system in January, is that included in my system?
Thanks, Tim Andres
 
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Dumb questions from newbie, does the sds system require a mixture knob? Does it require fuel return lines? What type of cockpit switches/controls are needed? What is the recommended electical system for this setup (I assume dual batteries)?

This thread is really about P Mag and the SDS CPI. The SDS EFI is a different product doing fuel and spark. I'll PM you answers to your questions here. :)
 
Hi Ross I have a dual cpi setup on my RV6A and it has performed flawlessly. I'm not familiar with the adjustable coil charge time? I don't recall seeing that in my setup?


Thanks
Bill

This feature is in the setup mode as it's not something most folks need to play with. It allows max coil saturation when using different coil types.
 
"We also disable the LOP switch input above about 25 inches as further protection in case you forget the switch position."

Ross is this new? I purchased a system in January, is that included in my system?
Thanks, Tim Andres

That feature has been in there for some time. What version of software do you have? (displays on bootup)
 
I don't mind the green :D (doesn't look nearly as terrible as the GRT engine monitor!) If I knew during the build what I know now, however, I probably would have hidden both of them somewhere out of sight and left that panel space for something else (DVD player for passengers??? :))
Been running 1 impulse coupled slick and the SDS for about 6 months now without a hiccup.

KzeBl6Bl.jpg
 
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Should we keep the green then? :D

No. Please no.

Can you identify and explain the differences in function between the EM-5 using the round LCD for electronic Ignition only vs going with SDS gen 2 CPI.

For example, will the new gen 2 CPI be smaller then the EM-5 round LCD controller?

I sincerely appreciate that SDS is continually improving and updating their products.
 
No. Please no.

Can you identify and explain the differences in function between the EM-5 using the round LCD for electronic Ignition only vs going with SDS gen 2 CPI.

For example, will the new gen 2 CPI be smaller then the EM-5 round LCD controller?

I sincerely appreciate that SDS is continually improving and updating their products.

There is not much difference in function between having the full EM-5 ECU control ignition and the CPI. Cost is roughly $800 more with the dual EM-5 setup off the top of my head. The EM-5 way would give you a future upgrade path to EFI if you were interested in going that direction, the CPI does not give you that choice.

Yes, the CPI2 face will be a bit smaller than the current 3 1/8 round EM-5 programmer.

The market is asking for these improvements and re-packaging. If we keep making the same old stuff, we'll be left behind in this field or lose market share. I think our key to success is to give the people what they want. Too many other companies don't listen and give you what they think you should have and continue to offer 5 or even 10 year old products with few or any useful improvements.
 
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Too many other companies don't listen and give you what they think you should have and continue to offer 5 or even 10 year old products with few or any useful improvements.

I think Ross' active participation in this discussion form is a strong indictor of how closely SDS listens to its customers. Add to that Ross' ability to respond to questions via email, often within minutes, and a potential customer gets the feeling that he's dealing with a company that actually cares. We are very fortunate in this little corner of the aviation industry to have access to a supplier of such high caliber. (I say this without yet being a customer - years of Ross' posts here reveal he is as straight a shooter as they come.)
 
Thanks Ross.

I really like the EM-5/LCD controller solution as it would allow me to start out with SDS EI and one mag and progress from there to a full SDS compliment of 2 SDS EI's and FI.

I know I'm getting off topic on the FI speak so I'll stop there.

Thanks again !
 
I think Ross' active participation in this discussion form is a strong indictor of how closely SDS listens to its customers. Add to that Ross' ability to respond to questions via email, often within minutes, and a potential customer gets the feeling that he's dealing with a company that actually cares. We are very fortunate in this little corner of the aviation industry to have access to a supplier of such high caliber. (I say this without yet being a customer - years of Ross' posts here reveal he is as straight a shooter as they come.)

I agree, I am also not a customer. However Ross has explained multiple ignition items for me, in way even a dumb programmer can follow.

Tim
 
Automotive pedigree showing

"If experimenting with larger coiltime settings, rev the engine in neutral and monitor ignition current. "

Can I leave the plane in gear and just hold the clutch in? :D:D:D
 
"If experimenting with larger coiltime settings, rev the engine in neutral and monitor ignition current. "

Can I leave the plane in gear and just hold the clutch in? :D:D:D

It's not good to experiment seat of the pants with coil charging times. For normal aircraft systems we charge to get them within about 95% saturation to minimize heat in the coil. This is plenty for the low specific outputs present here. We typically only use two coil types on aircraft engines but if we had to use an unusual coil in the future, we're all set to later alter the charge times.

For the Reno guys, we push the charge time out to get 100% since they are short duration races. Some folks may be pushing to 90 inches this year in Sport Class and that requires every joule of coil energy to light off such dense mixtures.
 
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Preliminary design work on the next gen CPI will begin on Sept. 1

Looking for customer feedback on any additional features people might want.

One thing I'm interested in (when contemplating dual electronic ignition) is robust protection against any common cause taking out both of them. My RV-8A was hit by lightning a few years back. The dual Lightspeeds ignition units were unscathed (the voltage regulator for the alternator was fried). Any idea how the SDS CPI would handle a lightning strike?

Another thing on my radar is new battery technology like EarthX. The weight savings are tempting and doubtless they are the way of the future, but all of their self-monitoring features introduce possible failure modes that a simple lead acid battery doesn't have (such as shutting itself off due to perceived internal fault, overvoltage, etc). If the battery disconnects itself while the alternator is running then everything on the bus gets hit with a pretty good surge, which some electronic devices can handle and others cannot depending on how robust their design is.

Good electrical system design mitigates most of my concerns but it would still add some peace of mind knowing that my electronic ignition units have been designed/tested to handle potential anomalies within reason. Reference DO-160 standards which most certified equipment are developed to meet...I have seen several documented cases of lightning strikes and overvoltage conditions taking out the 'experimental' stuff in the panel while leaving the TSO'd radios/GPS/transponder unscathed.

Oh and +1 for the more aesthetically pleasing user interface that will look nice with the G3X panel in my -14.
 
We finished some engine testing on the stand yesterday which decided some of the design layout of the CPI2. This should speed things along as we won't have to add the extra components now.

The case here about the lithium battery shutting itself off a month or so ago due to alternator overvoltage and then frying some expensive electronics as a result of even higher surge voltage leads us to recommend having electronic crowbar protection when using these batteries with our electronics. We will look at doing some sort of internal voltage limiting to protect the device from serious OV and have it reboot after the OV condition is removed.

We are a small company and the testing required to pass DO 160/178 standards would probably quadruple/ quintuple the product cost in the end due to the small production volumes. It would add many months to the release date as well. This would in turn reduce sales to nil making the whole process a waste of time. Fine for companies with the financial resources to do this and sell to the certified market, but not for us. Most Experimental folks are already flying around with a panel full of equipment which has not been tested to these standards.

We do our usual over voltage tests, low and high temperature tests and vibration is no concern with our components. I suppose we could try some crude "lightning tests" with an ignition coil arcing to the CPI case. Would be interesting to see if the system would reset and keep going or not.

We do have some new test equipment now which we didn't have a couple years ago. This will aid in testing the software and hardware faster and better than before.

All good food for thought. Thanks for your comments.
 
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Ross in the new model put a 9v back up battery.
Bob

This is a good idea. Powering the CPI with it is no problem with the .1 amp current draw. Powering the ignition coil would be challenging though. I'm interested enough to do some testing though. Perhaps an up sized AGM battery would give you 15 minutes or so in case of a complete electrical failure. We may have room on top of the unit for such a backup.

Appreciate the comment. We'll look into that.:)
 
A sized up battery is something many of us using glass are familiar and comfortable with. It's become, for lack of better words, the experimental industry standard. Examples include the newly released G5 which has an optional battery that can be added.

Plus one on this idea.
 
Ross,

What about selling a super capacitor option for both the coil and the CPI?
The super capacitor could be sized to provide anything from a few seconds to minute of capacity. It would give constant current and voltage, and should buffer and voltage spikes.
FYI, this is way beyond my knowledge, except we used one on a printed circuit board we had designed about eight years ago. The board was designed to run in a super dirty power environment.

Tim
 
Ross,

What about selling a super capacitor option for both the coil and the CPI?
The super capacitor could be sized to provide anything from a few seconds to minute of capacity. It would give constant current and voltage, and should buffer and voltage spikes.
FYI, this is way beyond my knowledge, except we used one on a printed circuit board we had designed about eight years ago. The board was designed to run in a super dirty power environment.

Tim

I know nothing about these but I'll do some reading tonight. Thanks.
 
Looks like a super capacitor would not be suitable for what we have in mind- to run the coil and CPI for 30-45 minutes and get you back over an airport. We've already looked at an AGM battery which weighs about 1 pound and would do the job. Considered some automatic health monitoring and switching already.
 
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Looks like a super capacitor would not be suitable for what we have in mind- to run the coil and CPI for 30-45 minutes and get you back over an airport. We've already looked at an AGM battery which weighs about 1 pound and would do the job. Considered some automatic health monitoring and switching already.

Correct, not to run the system for long. There were concerns about transient voltage issues taking out the CPI system. Which implied could end up with the engine stumbling and which would affect the alternator which would....

The goal is to have a UPS for the ignition and injection system for some period of time. Most wanting 30-45 minutes. LiPo batteries are very well suited to the sustained power draw requirements, however, they are susceptible to power issues when used for a UPS because they are not tolerant of voltage variations (current is often mitigated also by the battery controller), either high or low. There are a couple of ways to handle this voltage variations, you can either use a MOV or similar device to handle the over voltage, and then drain the battery some on the low voltage side.
The problem with this is the the number of cycles on the battery. Now if the battery is lead/acid it is not much of an issue; but it can be a problem for LiPo. So one viable solution is to buffer the transient dirty power with super capacitors. I would guess you only need about 15-30 seconds of power in the super capacitor. This would practically eliminate the draw down of the LiPo except in an actual emergency.
The advantage of this is you can then select a LiPo battery for maximum energy density and minimal cycles. (balanced with cost of course.)

Tim


Tim
 
While the LiPO battery would be light, I see too many potential issues with them in this application. For the CPI, we're looking at a Powersonic PS-1212 AGM battery.

We're not too worried about transients, it will function from 7.3V to at least 18 (we'll test how high eventually). If voltage falls below 7.3, the CPI auto resets as soon as voltage returns, takes about .2 seconds.
 
While the LiPO battery would be light, I see too many potential issues with them in this application. For the CPI, we're looking at a Powersonic PS-1212 AGM battery.

We're not too worried about transients, it will function from 7.3V to at least 18 (we'll test how high eventually). If voltage falls below 7.3, the CPI auto resets as soon as voltage returns, takes about .2 seconds.

I have had one of these Powersonic PS 5ah on my bench for over 5 years and has maintained an 90% charge for a 12 month standby period. It gets charged once a year.
 
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