PMAGS or SDS

[Retooferab]

I’m interested in pmags and sds.
Pros, cons, and why?
If I was to go sds I’d use their fuel injection too.
Just wanting the pros and cons of both systems.

 

[KRviator]

I have dual PMags and a Rotec TBI. If I were doing it again, I would go the full SDS route. There's nothing wrong with my PMags, I just have the benefit of 6 years experience to better judge what would work. The reason for that is the Rotec doesn't like Mogas in summer, whereas with SDS you could run it continuously. SDS also offers more flexibility in trimming fuel to individual cylinders, datalogging and more that you won't get with just PMags. Pricier, of course, but each to their own.

 

[Darin Watson]

I have dual PMags and a Rotec TBI. If I were doing it again, I would go the full SDS route. There's nothing wrong with my PMags, I just have the benefit of 6 years experience to better judge what would work. The reason for that is the Rotec doesn't like Mogas in summer, whereas with SDS you could run it continuously. SDS also offers more flexibility in trimming fuel to individual cylinders, datalogging and more that you won't get with just PMags. Pricier, of course, but each to their own.

Agree with the above, however, depends on what you want to do with your fuel system. You should also recognize that if you want minimal change P-MAG is a drop in for a regular mag, whereas SDS will require significant redesign of your electrical system and the requisite redundancies. That’s not to say that SDS is not a great system, because it is, but if not done from day 1 it is a much more involved retrofit.

 

[Dan 57]

SDS for a new built, P-Mags for an upgrade, easy choice

 

[Toobuilder]

The slightly added installation complexity of the SDS ignition is more than offset by the lifetime of maintenance free flying you will enjoy AFTER that first installation. The Pmag is “easier” to install initially, but you will remove, inspect, reinstall and time your Pmags every year you own them. SDS is install and forget.

 

[2theskyy]

I would have gone SDS but can’t get any parts of the system nor duplex fuel selector( everything has been on order). I had to make certain decisions to build on and needed parts to do so. So I ordered Pmags and fuel system to coincide. They came within days of ordering. If or when I get the SDS, I’ll have it to install someday. Both great systems in their own right.

 

[M McGraw]

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.

 

[Bavafa]

I wonder, folks who have installed SDS, do you consider the hall sensor as a single point of failure of the system. Afterall, it is one device, one magnet and one set of wires that run both sides.

 

[Ron77]

I wonder, folks who have installed SDS, do you consider the haul sensor as a single point of failure of the system. Afterall, it is one device, one magnet and one set of wires that run both sides.

No. I have one set of magnets, two hall sensors with two sets of wires. Hall sensors are shielded from wayward alternator belt.
Ron B.

 

[Ralph Inkster]

I wonder, folks who have installed SDS, do you consider the haul sensor as a single point of failure of the system. Afterall, it is one device, one magnet and one set of wires that run both sides.

If you have a single Cpi2 ignition, you have the single crank sensor, true.
But you could still have a second mag or ignition (it’s own sensor if needed) for redundancy.
If you have dual CPi2 ignitions, you would have a dual crank sensor setup.
I have never (talking with my buddy Ross) have heard of a crank sensor failure other than installer error in wiring it.
The popular Dual SDS EFI/EI systems all have the dual crank sensor setup.

 

[airguy]

SDS is the way to go - with dual boards.

 

[Carl Froehlich]

The CPI-2 does not require a robust electrical system because it includes a battery large enough to run out of fuel.

I again caution that a robust electrical system is required anytime you are flying behind a ship’s power dependent engine. While a well maintained battery is very reliable, having a power distribution design that is tolerant to faults is critical to have some confident the power from this battery gets to where you want it to go.

If you cannot fail any single switch, relay, solenoid, alternator, battery, ground or other connection and still have electrical power to the engine you should sharpen your pencil and try again. While this may sound hard, if you bite the bullet to design using two identical ship batteries you have options to move foward. The good news is such a robust electrical power distribution solves the issues with getting power to the panel for continued IFR flight as well as keeping the engine running when these “low probability but high impact” faults happen.

I offer that any EFII system does not provide more power or better engine efficiency compared to a well balanced mechanical injected engine with dual pMags. I will point out the one big advantage of EFII, the higher fuel pressure provides good margin to vapor lock when running mogas. The builder will need to decide if this is worth the EFII price and complexity.

Carl

 

[Pdp7427]

Carl, I am genuinely interested in your opinion and input about thoughts on no improvement in power or efficiency in a fully electronic injection and ignition system. My understanding is that a tuned SDS system will be highly efficient at all MAP and RPM settings with the ability to adjust both fuel injection parameters as well as specific timing advance. How does this not result in better efficiency over a tradition fuel and ignition system? Having a limited amount of ignition advance will certainly help on a traditional system, and balanced injectors is a good thing for temps and efficiency. I guess I need a better education on this topic.

I know that my personal preference for deciding to install an SDS system was operational simplicity: two-lever engine operation (basically), ease of starting under all conditions, flexibility on fuel choice looking down the road.

How does a traditional system match the ability of an SDS or similar style system from setting fuel injection values and timing advance for every possible RPM setting and MAP value?

Thanks for the opportunity to learn more, not looking for any “which is better” battle!

Best,

Patrick

 

[Retooferab]

I have one mag and a Light Speed ignition now. I’m just looking at options. The easiest would be to keep what I have, but I want to get rid of the magneto and have full electronic ignition. That’s why I’m exploring all options. I like the idea of SDS, but dual PMags would be a lot easier install, or switch to dual Light Speed ignition.

 

[Mike S]

Had the dual CPI in the RV 10, installed after the Lasar system failed-----I wanted Pmags, but they were still vaporware at that time.

Based on my experience there, and with watching all of the Reno racers with SDS systems, I decided to go SDS on the new plane.

Very pleased with the system, as well as the support from Ross.

 

[RV10inOz]

I have experience with all of them, multiples of all of them, with customers aircraft. You can take my comments as you like.

I have two slicks, 2200 hours and soon a rebuild will mean a decision as the slicks are at the point of not viable for overhaul again (due at around 2650 hours). I will do the hard yards and go SDS.

So far SDS has proven to be the most reliable. It can be easily set up conservatively and is far less likely to have weird or spectacular failures, of which I have seen several from all the others including the more recent certified units.

SDS is a bit more work to install, and you must get your head around it (and lousy instructions) but the end result is way better and no ongoing maintenance every 100/500 or whatever hours.

Last comment. No matter which EI you go for, remember this: Magnetos on the engines we use have a 2-3 degree lag or latency in them. So a 25 degree engine fires the plugs at 22-23 degrees, not 26 or more like the EI will. Some you cannot easy offset this (LS with sensors) where as say a PMAG you set 2-3 past TDC and then tell it is at TDC (run the less aggressive setting). SDS you just program it 2-3 degrees less than the data plate and with the LOP function set that around 4 degrees above base. Note the angle valves are 20 degrees so same offsets required. High compressions also. Look at the Lyc spec and adjust accordingly. Anyone using mogas you probably need a bit more retarding.

Hope this helps.

 

[kearney]

Reliability Data

A while back I collected some SDS reliability data from Ross in order to help a builder get LAA approval for this system in an RV10.

The data can be found here : https://rv10.ca/sds-efi-ei-reliability-data/

It speaks for itself. I have about 400 hours on SDS systems - it has been flawless. One thing I did do was to adjust the fuel map so at above 2500 RPM (takeoff power) the mixture is automatically adjusted. While I do have to tweak the mixture on very hot days, I mostly can ignore the mixture in all flight configurations. Also, to keep things simple, I only fly LOP in cruise when power is <65%.

 

[Bavafa]

If you have a single Cpi2 ignition, you have the single crank sensor, true.
But you could still have a second mag or ignition (it’s own sensor if needed) for redundancy.
If you have dual CPi2 ignitions, you would have a dual crank sensor setup.
I have never (talking with my buddy Ross) have heard of a crank sensor failure other than installer error in wiring it.
The popular Dual SDS EFI/EI systems all have the dual crank sensor setup.

So, a dual CPi2 has two separate crank sensor and two separate sets of wires? I know the magnet itself is probably a single one but that I would imagine can be excluded. If the wiring run together, a broken belt could take both of them out.

 

[Richard Connell]

So, a dual CPi2 has two separate crank sensor and two separate sets of wires? I know the magnet itself is probably a single one but that I would imagine can be excluded. If the wiring run together, a broken belt could take both of them out.

https://www.atsb.gov.au/sites/default/files/media/5341498/AO-2013-221%20Final.pdf

While I do believe this failure mode has been thought about and mitigated mostly, youll never know until the belt breaks and tests it.

I’m on the fence about going to SDS at mag overhaul time. Mainly because of the considerable work required on a flying aircraft tho. Not the crank pickup

 

[gmcjetpilot]

Oh no... not this. Ha ha. Use search and spend hours reading. I have dual P-mags. They are the EI on the market that are self powered. That is #1 reason. I have used no other EI to compare.

#2 Customer service from Texas, USA, E-Mag. The best.

They both work and produce hotter spark than Magneto. They both advance timing based on RPM and MAP.... I have P-Mags. No regrets. They bolt in, min wiring and no need for redundant electrical sysyem.

 

[Carl Froehlich]

Carl, I am genuinely interested in your opinion and input about thoughts on no improvement in power or efficiency in a fully electronic injection and ignition system. My understanding is that a tuned SDS system will be highly efficient at all MAP and RPM settings with the ability to adjust both fuel injection parameters as well as specific timing advance. How does this not result in better efficiency over a tradition fuel and ignition system? Having a limited amount of ignition advance will certainly help on a traditional system, and balanced injectors is a good thing for temps and efficiency. I guess I need a better education on this topic.

I know that my personal preference for deciding to install an SDS system was operational simplicity: two-lever engine operation (basically), ease of starting under all conditions, flexibility on fuel choice looking down the road.

How does a traditional system match the ability of an SDS or similar style system from setting fuel injection values and timing advance for every possible RPM setting and MAP value?

Thanks for the opportunity to learn more, not looking for any “which is better” battle!

Best,

Patrick

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

 

[gmcjetpilot]

Patrick,

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

Carl well said. There is only so much you can do with fuel and ignition. Yes electronics help at a cost of some Cons, i.e., no free lunch.

Mechanical injection works and gasp carburetors work as well. But LOP fuel injection is best, especially with balanced injectors as you did.

Electronic Ignitions are so full of claims. They all do similar things providing a hot spark and advance timing with RPM and MAP.... There may be slight differences in performance but the gain is going from Mag to EI. Between EI's not much. I'd have to see test to belive any noticeable gain between EI brands. Some are better for tinkering, may be racing.

Depending on operations Mags and a Carb works well. High Alt WOT sub 75% power by all means FI & LOP and EI advanced timing, adds 4% to 6% efficiency over Mags and a Carb. Will fuel savings pay for electronics? Over time if you fly enough. People who fly little gain little.

 

[airguy]

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

Largely true - but SDS/EFII can also allow you to run autofuel without vapor lock due to the electric fuel pumps and higher pressure fuel rail. I bought 125 gallons this morning for my private strip at $3/gal.

I started with a Bendix FI system, made lots of changes/mods, and after 600 hours just went to SDS to get all the advantages it offers for my particular flying style. 1000 hours later, still loving it and it will go on the 10 I'm building.

 

[DanH]

They both work and produce hotter spark than Magneto.

Can anyone provide a link to data supporting a claim of hotter spark with an EI? I'm speaking of "hotter" in a strict sense, specifically "higher temperature". To be fair, let's stick with cruise RPM. (Note; I fly two EI's.)

 

[Chkaharyer99]

I’m interested in pmags and sds.
Pros, cons, and why?
If I was to go sds I’d use their fuel injection too.
Just wanting the pros and cons of both systems.

I have the SDS CPI2 with two boards.

Taken directly from the SDS website, I consider all of these items to be “Pros”

Advanced Features​

• CPI-2 gives you complete, user programmable timing control with rpm (100 rpm increments on direct drive engines) as well as manifold pressure (boost retard and vacuum advance)
• Logical, 1 degree programming increments for all parameters
• Small size of panel programmer- 2.8 X 2.8 X 1.2 inches deep
• Integral MAP sensor
• Rev limiting
• Backlit LCD has gauge mode to display rpm, manifold pressure and actual ignition timing
• 12V tach output
• Programmable dwell time and cranking retard values
• Single CPI-2 module can drive two coil packs for twin plug, 4 cylinder engines (Continental, Lycoming, Jabiru 2200, Rotax 912/914 etc.)
• Based on proven SDS EM-5 and CPI software over 20 years experience and thousands of systems in service worldwide
• Low current draw/ long spark duration. 4 cylinder coil pack and controller draw about 1.2 amps at 2500 rpm.
• CPI-2 has a button to alter advance with mixture strength for best LOP cruise economy or swiching between mogas and 100LL.
• Magnet alignment screen for fast crank sensor setup, error warning for missed magnets/ alignment issues
• Coil test mode
• Runup test for twin plug aviation installations
• Simple wiring hookup, wiring harness included made from Mil Spec Tefzel wire.
• Hall Effect triggered. Flying magnets (supplied) can be mounted to crank pulley or flywheel
• Magnets are crankshaft mounted so timing is precise, no worries about magneto gears, drives, bearings, oil seals wearing or failing as on some other EIs
• Never any "Lost Timing" scenarios as with other EI brands
• No chance of engine kickback and broken starters when cranking as with some other EI brands
• No electronics mounted inside hot engine parts like many other aircraft EI systems
• No cooling blast tubes required like some other aircraft EI systems
• No periodic inspections on mag gears, cotter pins, bearings, shafts, seals, PCBs like P-mag. Just check spark plugs during annual
• All components firewall forward are waterproof unlike some other aircraft EIs
• Our circuit boards are conformal coated in key areas to resist humidity, condensation and oxidation unlike some EIs which have bare boards
• Coil packs are engine mountable
• Bolt on kits for Experimental Lycoming 4 and 6 cylinder, Continental O-200, IO-550, Jabiru 2200/ 3300, Rotax 912/914 engines
• Variety of coil pack mounts available for Lycoming engines- (top case, mag hole and firewall)
• Backup battery option with automatic switchover and charging circuit
• Over voltage protection
• Ability to data log to a Windows device
• Aural warning output
• Automatic timing advance protection with MAP when LOP is engaged
• Power saving options when operating on backup power
• Adjustable display dimming and contrast
• Status and warning LEDs plus screen messages tell you how the system is operating

Now for the cons:

-Removing the slick mags and installing the SDS CPI2 was time consuming but not difficult.

-I change out the backup battery annually. Not completely maintenance free. It’s easy and gives me peace of mind knowing a have a fresh backup battery in case I need it.

I’ve never owned or used PMAGS.

 

[Toobuilder]

I wonder, folks who have installed SDS, do you consider the hall sensor as a single point of failure of the system. Afterall, it is one device, one magnet and one set of wires that run both sides.

I consider the single set of magnets that triggers my SDS dual element hall sensor better than or equal to the single 5/16 bolt that holds the accessory drive gear to the crankshaft.

 

[Toobuilder]

I offer that any EFII system does not provide more power or better engine efficiency compared to a well balanced mechanical injected engine with dual pMags.

This statement should be taken in context. After years of data reporting on this site and others, we KNOW the Pmag curve is “sub optimal” except for some possible very rare engine configurations. We also know that the curve is the most important part of the efficiency equation, and the relative “heat” of the Ford automotive ignition coil used in the Pmag is no substantial difference from the automotive based coils of any other ignition manufacturer (including Slick and Bendix). Yes, if you can find that lucky sweet spot where your particular engine is happiest with the canned curve the Pmag forces you to run, you will not see any improvement compared to any other “well maintained” ignition. Good luck being the rare configuration and use case where the Pmag curve is actually correct though. For most of the rest of us, we turn to the ignition that allows us to make those choices on the fly, set it, and then forget it. That’s the ignition side.

for the injection, yep, a well set up Bendix at cruise is hard to beat. And since that’s where the engine spends the majority of the time, that’s where you are going to draw your efficiency data from. Nobody pulls efficiency data from the time at idle, but EFI is a VAST improvement in performance there. Same at extremely low fuel flows when really high and really LOP. The atomization and spray pattern of the EFI injector is based largely upon constant rail pressure so the GPM flow has little effect. It is exactly the “improved efficiency” (also known as emissions performance) in all aspects of the operating envelope that drove EFI to be the universal standard for automobiles in the first place.

All that to say that if one is going head to head on a dyno, I don’t think that EFI is going to move the needle much compared to a “properly set up” magneto and mechanical FI at one RPM point, but unlike the traditional hardware, the EFI will remain strong everywhere else and be far easier to tune.

 

[akschu]

I again caution that a robust electrical system is required anytime you are flying behind a ship’s power dependent engine. While a well maintained battery is very reliable, having a power distribution design that is tolerant to faults is critical to have some confident the power from this battery gets to where you want it to go.

If you cannot fail any single switch, relay, solenoid, alternator, battery, ground or other connection and still have electrical power to the engine you should sharpen your pencil and try again. While this may sound hard, if you bite the bullet to design using two identical ship batteries you have options to move foward. The good news is such a robust electrical power distribution solves the issues with getting power to the panel for continued IFR flight as well as keeping the engine running when these “low probability but high impact” faults happen.

I offer that any EFII system does not provide more power or better engine efficiency compared to a well balanced mechanical injected engine with dual pMags. I will point out the one big advantage of EFII, the higher fuel pressure provides good margin to vapor lock when running mogas. The builder will need to decide if this is worth the EFII price and complexity.

Carl

Carl,

I think you are confused about the CPI-2 that Marvin mentions. The CPI2 does not require a robust electrical system because it connects to and maintains a small battery that is completely isolated and only used for ignition. The wires go from the CPI2 though a fuse to the battery.

With a single install you can fail anything an run on a mag, with a dual install you can loose one of the crank triggers, a switch, a master contractor, an alternator, a coil pack, or short to ground and it just swings to its own dedicated battery then lights up a fault light to tell you what it did.

I like this system better than a p-mag because it solves the electrical problems with a dead simple backup circuit and doesn’t involve electronics bolted to a hot vibrating thing and eliminates the mechanical points of failure because there is nothing to wear out.

I agree that full EFI demands a lot of thought about electrical system (and fuel system) but if someone wanted simple and almost no mx, a CPI-2 with airflow performance seems to be a good setup.

 

[rv8ch]

I have AFP FI and dual pmags, and like them. They were the right thing for me at the time, since I was in "get 'er done" mode. If I were to build another aircraft, or needed to completely swap out my ignitions, I'd go full SDS. We're very fortunate to have multiple excellent suppliers for our ignitions - having dealt with both Ross and Brad, they are both top guys.

 

[gmcjetpilot]

Can anyone provide a link to data supporting a claim of hotter spark with an EI? I'm speaking of "hotter" in a strict sense, specifically "higher temperature". To be fair, let's stick with cruise RPM. (Note; I fly two EI's.)

BTW, this thing uses magnetos and constant flow injection to make 10,000 HP. I'm just sayin...

View attachment 54329

That is a great question. NO DATA FOR YOU. NEXT. Ha ha. My short answer is they are all good enough.

You can review a old EAA Cafe Foundation test of EI's on a Mooney. It mostly was EI (original Jeff Rose design) and Mags. Most of the current crop of EI's did not exist at the time. However it is interesting and shows improved fuel economy. Did they measure spark energy or temperature? Don't recall, but proof is in the pudding, measurable performance. It's not a quantum leap from Mag to EI. From memory one EI + one Mag was 4%. A second EI, dual EI's only added 1% or 2%. So 6% better than Mag in low power. High power all EI's use fixed timing, same as Mags, and the advantage is not as great.

My opinion head up difference between different EI's will be small. No one has ever tested this. The issue is not temperature but size of spark (gap) and duration.

As far as spark energy you need enough to jump a larger gap of an automotive plug. That makes a bigger spark for better more complete combustion. That is why EI's don't use aircraft massive electrodes. Gap is smaller in AC plugs, and reduces advantages of the higher energy EI over Mag. I don't have qualitative numbers. Mags are no slouch to be sure in "temperature" but size of spark smaller. Mags woukd struggle to spark larger gaps under compression. Duration I don't know. Mags were not about squeezing every ounce of power and efficiency out of the engine, but reliability. Ei did not exist in late 1800's when Magnetos were invented.

All EI's use inductive coils from off the shelf automotive applications. Physical size, windings, number of number of coils per plug will clue you into spark energy. P-Mags have 2 coils for 4 plugs. This is called wasted spark method. The coil is from a Fird EI system.

Somw EI manufacture will make claims about volts or energy they make. Others do not and recognize it's not important as long as you have energy for a strong spark across gap. One claims to have the most spark energy of any EI. My question how much energy do you need. All inductive ignotion coils are engineered for this. At some point it's diminished returns. Bigger the coil the more room and weight.

I can tell you Mags use small spark plug gaps because of limited energy. However it is more than adequate to fire the gas air mixture at 2700 rpm and 9 5 to 1 CR with 100LL @ 25 BTDC. It is pretty mild compared to an automobile race engne intentionally. Reliability is more important.

These aircraft EI's are all based on car inductive discharge except Lightspeed II, which is CDI. They all are going to provide adequate spark, just as Mags do.

As important or more is EI's do their best work at lower power by advancing timing. Mags are fixed at 25 degrees BTDC. That is fine at 75% to 100% power. At 55% power; say flying at 12,000 feet you need way more advanced timing. The flame front is so slow you have to kick it off sooner. If timing is too advanced at high power you will damage engine. 25 degrees is the base line compromise timing for Mags on Lycoming typically. So spark energy is not everything, timing is key as well.

Some EI's give you a little more flexibility in messing with the timing advance. That is great but can get you in trouble. P-Mag gives you a choice of fixed and base Adv curve. They really do not want customization. It can be changed but not easily. Some EI's put a controller on your panel to mess with in flight. P-Mags design philosophy is not about tinkering in flight, but flying. P-MAG does have a fairly aggressive stock Advance curve and total advance to safely get great performance with out risking detonation on a STOCK ENGINE. If you have a hot high CR Lyc you will want to time the P-Mag back to limit total Adv. These race applications I would say is where other EI systems may be better, with more controls.

CDI however can provide not only high energy can provide longer duration multi sparks. CDI recovers faster and suitable for high revving engines and two stokes, which sparks every Rev verses every other crank rotation in 4-srrokes. I don't think CDI's claim to fame is hotter spark, but longer duration spark and faster recovery for higher Rev'g engines. Most cars are Inductive discharge ignitions, which is most common and works well, even if it's a single spark. If it's a big gap and timing is right all is good with one spark.

Some EI's use wasted spark as I said, meaning one coil works for two plugs on two cylinder pairs, 360 degrees out of phase, saving complexity. The dwell time of coil is shorter. In theory this could reduce spark energy. I did the math. Lycoming apication it's no issue. The coil saturation is Bueno. RPMs are low l, so dwell is not an issue by wide margins Remember old V8's had one coil and a distributor for 8 cylinders? That is a spark every 90 degrees of crank rotation. On a Lyc with wasted spark we have 369 degree rotation per spark and low RPM compared to an automobile engine.

We are not talking 19,000 RPM formula 1 race car. I am pretty sure they use CDI. High performance street cars use inductive ignition, but use separate coils for each cylinder and plug. My two cylinder BMW motorcycle has 4 plugs and 4 coils.

How much energy or plug Temperature do you need? Plug temperature is controlled by heat range of the plug, not ignition.

Lycoming low compression normally aperated engine, timing advance is the big gain over fixed timing Mags at low power. However to use this Adv timing requires lower power. Advanced timing on a Lycoming at high power will cause detonation.

LIGHTSPEED CDI capacitive discharge promises to be in theory the best design? Again we are talking fairly low RPM and low compression aircraft engines. However if racing may be this is better. Can you measure the difference? My opinion may be and it would be small for normal Lycoming operations. A high revving race car or 2-stroke (which fires every crank revolution) would benifit from CDI ignition. Another benifit of CDI which would benifit any engine including a Lycoming is longer duration. It does this by spitting our multiple sparks making longer duration. Inductive ignition is one spark.

Most important is customer service. Second reliability, cost, form, fit and function. All EI's spark is more than adequate to fire a wide gap automotive spark plug in Lycomings. I think the other factors are as important or more important. P-Mag may not be sexy but is better than a Mag performance wise and is still self powered, the only EI to be self powered.

However back to Mags. They are also self powered and adequate for general local flying at 75% power or greater. Even if you fly at high altitudes and lower power 6% loss in efficiency may not be enough to pay for EI, if you already have Mags. If starting from scratch and given a choice EI is good. If up grading you only need one EI to get most bang for buck (pun intended).

 

[gasman]

Well, that did it.... now I do need sleep.

 

[Freemasm]

Carl,

I think you are confused about the CPI-2 that Marvin mentions. The CPI2 does not require a robust electrical system because it connects to and maintains a small battery that is completely isolated and only used for ignition. The wires go from the CPI2 though a fuse to the battery.

With a single install you can fail anything an run on a mag, with a dual install you can loose one of the crank triggers, a switch, a master contractor, an alternator, a coil pack, or short to ground and it just swings to its own dedicated battery then lights up a fault light to tell you what it did.

I like this system better than a p-mag because it solves the electrical problems with a dead simple backup circuit and doesn’t involve electronics bolted to a hot vibrating thing and eliminates the mechanical points of failure because there is nothing to wear out.

I agree that full EFI demands a lot of thought about electrical system (and fuel system) but if someone wanted simple and almost no mx, a CPI-2 with airflow performance seems to be a good setup.

The EFI fuel delivery systems require electrical redundancy; more than a small BU battery can provide. Looks quite possible that you two had different configurations in mind. The good thing about a well designed, dual/redundant electrical system = the deletion of any dedicated back-up batteries for either systems or avionics; a nice periodic (and costly for Garmin stuff) expense that goes away. There's good points to any related configuration' otherwise, they would all look the same. Now I get to go relax and go lead a combustion/emissions class here at work.

 

[M McGraw]

Some may be confusing the CPI-2 with EI/EFI. The CPI-2 is ignition (EI) ONLY. In the catagory of Pmag, Surefly, and all other EI only systems. Every system has an advantage/disadvantage. My reference to the CPI-2 was that it includes an independent power source. The following link will describe the system. Consider the CPI-2 to be the EI side of the EM-5F EI/EFI with a built in battery (removable) and charging capability. I consider the battery backup a PRO and the OP did request PRO and CON opinions. SDS EI/EFI is not the same category as Pmag; however, CPI-2 and Pmag are the same catagory. I offered it as a more accurate comparison.

SDS EM-5: Aircraft

 

[DanH]

Let's not conflate (a) how the spark was made and its characteristics with (b) when it is delivered. They are very different subjects.

CDI is typically provides a rapid rise time, but very short duration. The rapid rise time offers resistance to fouling. Multi-spark CDIs were developed to provide duration comparable to inductive systems while retaining the fouling benefit.

Generalizations about magnetos are silly. The familiar Slick, a 1200 Bendix, and an MSD 44 are all magnetos. Consider a Cub, an RV, and a Mustang. They share the same general operating principles, but performance is quite different.

Returning to the OP's question (warning: opinion), I'll take the SDS as the more reliable choice, even factoring the requirement for a good supporting electrical system.

 

[Toobuilder]

I have never seen any EFII advertisement that promises an increase in power...

One of the EFI vendors used to make some fairly wild claims about an “increase in power” in bold letters on their home page.

…and then there is the EFI vendor that has “No BS” right on their home page. I’ll let you research who is who.

 

[climberrn]

Been running P-Mags for over 800 hours on 2 different IO-360's. They have worked flawless. In the first year flying the -7, I had an alternator failure that caused an over voltage incident. It wiped out most electronic devices in the plane including the LEMO powered headsets, EMS, AP, both Dynon Skyview screens. The P-Mags worked normal, providing full power, allowing me to make a precautionary landing at the nearest airport. There was an internal "Fuse" in the P-Mag that was blown which protected them according to Brad. They needed to be sent back for an overhaul after that, but they did their job, kept the fan running.

After that, I added some redundancy to the electrical system and changed to a B&C alternator. I doubt the OV incident could happen again, but I am not willing to give up the self sufficiency of the P-Mag for some (Possible) efficiency. There are some awesome electrical layouts out there, but I wouldn't bet everything on that.

 

[Toobuilder]

Been running P-Mags for over 800 hours…

In the context of this discussion, it seems like the OP is willing to do the full Monty and become electrically dependent. That fact alone erases the single remaining useful feature of the Pmag. And since the CPI-2 product is ALSO redundant, independent and auto switching in the case of the ships power failing, all that is left is the tunability and reliability features. And Pmag is demonstrably deficient in both areas when compared to the SDS product.

 

[[email protected]]

So, a dual CPi2 has two separate crank sensor and two separate sets of wires? I know the magnet itself is probably a single one but that I would imagine can be excluded. If the wiring run together, a broken belt could take both of them out.

Not really true, As a competent builder/installer will make and and install a protective shield over the wires and sensor block. It's going to take a hammer and serious work to damage mine unless the broken belt has a chainsaw effect
My luck varies Fixit

 

[gmcjetpilot]

This statement should be taken in context. After years of data reporting on this site and others, we KNOW the Pmag curve is “sub optimal” except for some possible very rare engine configurations. We also know that the curve is the most important part of the efficiency equation, and the relative “heat” of the Ford automotive ignition coil used in the Pmag is no substantial difference from the automotive based coils of any other ignition manufacturer (including Slick and Bendix). Yes, if you can find that lucky sweet spot where your particular engine is happiest with the canned curve the Pmag forces you to run, you will not see any improvement compared to any other “well maintained” ignition. Good luck being the rare configuration and use case where the Pmag curve is actually correct though. For most of the rest of us, we turn to the ignition that allows us to make those choices on the fly, set it, and then forget it. That’s the ignition side.

Who is "we KNOW". Ha ha, "sub optimal"? Again "we know" the importance of the "curve" for efficiency? Then Ford automotive ignition coils are bad why? Then a claim of similarity of the P-Mag coil to a magneto coil? Most of all you claim P-Mag is no better than a magneto? Oh my. That is redonkulous, no disrespect.

1) Logical fallacy appeal to authority "we know". Who is "we" and what do you "know"? You need to back your comment with facts my friend. Not going to explain how a P-Mag works. See two links below. P-Mag has start advance, base advance, A and B curve, AND optional you can customize the timing advance curve, if you must, with a 3rd Party EI Commander. Your point is moot. Two links

E/Pmag timing advance explained

Engine Update: EI Commander​

2) The difference between a P-Mag (a distributor-less inductive electronic ignition) and a Magneto are miles apart. Do you know how a Magneto works? ALL EI's are inductive ignitions (except LightSpeed II which is CDI) and distributor less. Triggers vary, hall reluctor, optical. All inductive car coils output Approx 50 millijoules or 90 millijoules. The Ford coil of the P-mag, use off the shelf automotive coils LIKE ALL EI's. May be you are confused the P-Mag mounts a dual coil pack on the unit it self, verses remotely with wires. Th Ford pack is not small or weak. All auto induction coils have same ball park output, provided enough voltage and dwell. There are aftermarket racing FORD coils, by Accel and Mallory that fit on the P-Mag. I would not bother. The demand on the ignition in an aircraft is not extreme. The P-Mag spark is beaucoup hot, Muy Bueno. Say 60 millijoules vs 80 millijoules will not make much if any difference, but I have no idea what the output of any coil is of any EI, except claims, not data.

3) A magneto in an aircraft has a coil with no commonality or interchangeable with a car or any EI, including P-Mag. Factually the way a INDUCTION EI ignition works and magneto are very different. I invite you to study it. Magnetos are inductive and use a rotor and cap. The spinning magnet in the coil generates the field, which collapses. The P-Mag basically has an alternator that powers the EI circuit to saturate the coil unit, as if it was coming from ships power. The E-Mag was converted to P-Mag with the addition of the dynamo. The P-Mag has no distributor rotor or cap. The principle of collapsing magnetic field is used in both Magneto and P-Mag, SDS, Electroair, EFII, Lightspeed-I (not the -II). Fun fact, induction ignition was invented in 1908, developed by Charles Kettering. The old points burned out and needed gap and dwell adjustment. After the transistor they figured out an "electronic" way to trigger the field. Then distributor less EI came along. So basically your $5000 EI is rocking 115 year old Tech...

4) You say a P-Mag will be no better than a Magneto. You are categorically and objectively wrong. How do I know? First an aircraft plug is gapped at about 0.018 and that is about all it can do, may be 0.022 on a good day. The P-Mag can spark across 0.040 to 0.044 gap no problem. Also the P-Mag out for 16 years, over 10,000 hours flown, has empirically derived data, Users notice, easy starts, smoother running, better power, better economy over the Magneto. So what the heck are you talking about?

5) They all have high energy spark (higher than a magneto), use automotive plugs with larger gaps, advance timing at lower power based on MAP/RPM. All this is better efficiency; The PRO's going for Pmag's are easy installation, easy setup, and has self sustaining internal power, if you lose ships power. No other EI has this self power ability. That is nothing to sneeze at. No one has done it. Some EI's may have slightly higher spark energy and have more flexibility in timing map. Is that important. Not as much as ease of installation and being independent of ships power to keep engine going. I have mechanical fuel pump and and carburetor.

Yes, if you can find that lucky sweet spot where your particular engine is happiest with the canned curve the Pmag forces you to run, you will not see any improvement compared to any other “well maintained” ignition. Good luck being the rare configuration and use case where the Pmag curve is actually correct though. For most of the rest of us, we turn to the ignition that allows us to make those choices on the fly, set it, and then forget it. That’s the ignition side.

You don't need choices or "sweet spots" in an aircraft engine for normal operations flying at fixed power settings. That is the design philosophy of the P-Mag, install it and go fly. For people enamored with bells and whistles and wires going everywhere and needing redundant electrical systems to keep from saying ** #$%& ** when the electrical system fails, I salute you. All the ignitions are great. I mean it. No need to bash one or the other. As I said 3rd party EI Commander (or laptop with software) you can change P-MAG mapping. You can watch the timing advance and other metrics. Some P-Mag operators put a switch in cockpit to go from A to B curve in flight. There is no real need as we are either at base timing (take off power) or efficient WOT low power cruise at altitude (Max Advance) most of the time. Lyc 360 cruise is from 2100-2400 RPM and 17"-24", a narrow power band. Your "curve" worship or importance of "sweet spot" is overstated. The early EI's like Jeff Rose got 6% gain over magnetos. The ROSE ignition did not leave much on the table. New EI's may be better but we are talking 1% not quantum jump. There is only so much ignition can do.

I concede some EI's have fancy bells and whistles and you can play with timing mapping to your hearts content in the cockpit while you fly.... The fancy display will not change physics or how engine runs. What if you advance while at high power? Can you say blow a hole in your piston boys and girls? You will be in deep kimchee. In a car timing curves can make a big difference in acceleration and peak torque and HP. They also are water cooled with anti knock detonation detection to retard timing. In a plane we are limited and at steady power settings. "We" should be careful and conservative for safety IMHO.

I concede the P-MAG is a good all around proven EI, with simple installation and only one that is self powered. Repeat only one that is self powered. I concede that. However they do provide easy starting, smooth operation, improved fuel economy and power. P-Mag does not make claims to be the hottest best timing curve. It just works. The proof is in the eating of the pudding. It works well. All EI's work similarly and have similar utility, but only one is self powered, compact and not spread out all over the plane with wires.

To say P-Mag offers no increased performance or efficiency over a magneto or other EI's have superior (unproven) performance, is ludicrous. The biggest names, Van's Aircraft and engine builders Aero Sport Power, Barrett Precision Engines, Pen Yen all put P-Mags on their engines. Not because it is better performance (or worse) but because it is easy to install and set up. Plus a great reputation in customer service I can attest to. as well as overall reliability and excellent performance. I'll leave un proven claimed better timing curve efficiency to Brand X, Y or Z... They all have nice features. For me the P-Mag was a perfect fit.

 

[M McGraw]

….
I concede the P-MAG is a good all around proven EI, with simple installation and only one that is self powered. Repeat only one that is self powered. ….

I too believe the P-mag is a proven EI and I have always been impressed by the level of support Brad provides. He runs a very good company. I’m not convinced the P-mag is the only self powered system available unless the definition of self powered is a rotating mass that can generate power above a minimum RPM.

If there were a product with a battery (removable) that is automatically charged by the aircraft electrical system and automatically switches to that same battery in the event of aircraft electrical failure, would that qualify as self powered? Once you run out of fuel does the rotating mass still help? Or is a battery sized to last beyond fuel starvation sufficient?

Both systems would require conditional maintenance. Lets say we examine the rotating mass on a 100 hour interval or we replace the battery on a user defined schedule.

 

[DanH]

I concede the P-MAG is a good all around proven EI, with simple installation and only one that is self powered. Repeat only one that is self powered.

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.

 

[andoman]

If there were a product with a battery (removable) that is automatically charged by the aircraft electrical system and automatically switches to that same battery in the event of aircraft electrical failure, would battery sized to last beyond fuel starvation sufficient?

SDS CPI2 with backup battery installed meets this definition of auto charging and switching. Won’t outlast fuel supply though. IIRC the battery is good for about 45 mins. In the event of an alternator failure that 45 mins begins after the ship’s battery is exhausted. might outlast the fuel in that case.
My -4 has a Pmag and a Slick. At Slick overhaul time it will get a second Pmag.
My Rocket has a CPI 2 and a Slick. At Slick overhaul it will get an upgrade to the dual CPI2.
If I were starting from scratch with either I would go dual CPI2.

 

[Walt]

The slightly added installation complexity of the SDS ignition is more than offset by the lifetime of maintenance free flying you will enjoy AFTER that first installation. The Pmag is “easier” to install initially, but you will remove, inspect, reinstall and time your Pmags every year you own them. SDS is install and forget.

No such thing as “maintenance free flying”, a lifetimes worth, thats a fantasy.

 

[Toobuilder]

Who is "we KNOW…

Please work on your reading comprehension and get back to me. You are arguing phantom points. I’m not even going to attempt to correct your misrepresentation of my post.

 

[Toobuilder]

No such thing as “maintenance free flying”, a lifetimes worth, thats a fantasy.

lets not be pedantic, OK? The SDS system has no moving parts and requires no removal or tuning once installed. Just like a new car, it requires “no maintenance” to keep performing. Sure, the components should get a once over every time the cowl is off (just like EVERY other component under the hood), but you can expect the coil to keep firing, the hall sensor to keep doing its thing, the plug wires to keep funneling electricity, and the brain box to keep thinking perfectly - without you having to lift a finger. I know it’s a hard concept to get your head around, but cars go 100k+ miles without so much as a change of plugs these days, and that benefit is now available to us- If you just accept it.

Compared to the Pmag - SDS is “maintenance free”

 

[Toobuilder]

Won’t outlast fuel supply though.

How long does the CPI-2 last? I have flight tested the original CPI at 1.69 amps at 2700 RPM for a 6 banger. Does not take much of a battery to outlast an RV fuel supply at that small draw. Curious to know the facts on this one.

 

[gmcjetpilot]

Please work on your reading comprehension and get back to me. You are arguing phantom points. I’m not even going to attempt to correct your misrepresentation of my post.

That signals you lost the debate. Answer the question please.

Who is WE? Clearly I (and many others) respectfully disagree with you and your "we" group. Let's not be biased, but let us use math, physics, science and facts. May be it is your opinion? You state P-Mag has no advantage over a Magneto axiomatically. Did I misread that? To make is simple, you are wrong and you concede my point based on your non-response response.

As far as who has the best EI or "hottest spark" (yet to be defined but let's go with joule of energy) who cares. There is little to no data on performance differences. It is all opinions until there is rigorous side by side testing. We can go on empirical data. We can go on history. I have no dog in the fight. Use magnetos (not a bad choice for most) or whatever EI you like.

It comes down to tangible things like: Price, customer support, longevity of company (will they be around in 10 yrs), ease of installation. My OPINION is the performance difference for a typical stock Lyc RV driver and the top 6 EI's on the market are going to be close. BTW "we" are spoiled with so many great choices.

If you want that last tiny bit, sure get what you think is the best, which is an EI totally infinitely customizable timing mapping and cockpit display showing all parameters. My position for most that is wasted and a P-Mag's "curves" and adjustable base line timing is all you need. I estimate about 4-6% improvement in cruise fuel Econ, smoother, easier starting over a Magneto. If going for best power a few MPH gain. Again magnetos are no slouch; however magneto fixed timing and quantifiably less (but adequate) spark energy from EI's makes them less efficient.

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. I never said having an electrically dependent ignition is bad, but it is something that must be addressed seriously. 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, however I would trust his CPi-2 product any day. Bottom line let's recognize that P-Mag makes a good and unique well supported product in the choices we have. Not for everyone. Fine. But don't spread fake news it does not perform well. That is categorically false.

ALL EI's are a step up in economy, ease of starting over Magnetos. Are EI's worth it? Well no if you don't fly much or at high altitude (+8000 ft) long distance. Not sure what you expect? These are just ignitions with technology that has been around 40 yrs or more. The fundamentals of the ignition are over 100 yrs old. You can not change the fundamentals of how the engine works either.

The other part of the equation is fuel delivery (Carb, Mechanical FI, EFI). Exhaust choice? Tuned 4 into 1 is an advantage. More over is how you fly, Airmanship, picking the right power, leaning, flying the best altitude. You can have best EI, Fuel delivery, exhaust and fly sloppy and not be efficient. If you are just hopping around local, doing aerobatics, flying formation fuel savings is not paramount, your Mags are fine. BTW Autopilot and GPS is probably the biggest gain in XC flying efficiency, more than EI.

This is why I can't care too much about EI wars. it is like freedom of speech, we don't have to agree. However in my opinion I think you made a fallacious statement as consensus. I disagree with your characterizing the P-Mag has sub par performance. Fine if you think there are EI's that perform better. How superior are we talking 1%? Bold claims need data.

You don't seem to have data, which is fine. Data is hard to come by. Please read first than answer. What observable, recorded data do you have. I am going on 30 yrs of following the topic, personal experience, *Cafe' Foundation test of Mags vs EI*, reading VAF forums , sale information, talking to EI manufactures by phone or at airshows, Car guy/hot rodding w/ aftermarket EI s, and other pilots and their experience. I understand people have strong opinions. Great but don't bash an EI with false information. There are legit criticism of P-Mag like you need cooling air, but like electrically dependent EI it can be mitigated. No one has seriously complained that the P-Mag performance is sub par.

* Recommend reading the Mags vs EI Cafe' test along with their exhaust testing, 4 into 1, cross-over, Y exhaust and separate pipes testing.

https://www.electroair.net/pdfs/ignition_dynamicsl.pdf

https://www.electroair.net/pdfs/ignition_dynamicsll.pdf

How Magnetos Work (very good)

Simple Magneto explanation - please understand both Mag and EI use Kettering Inductive principle, it's accomplished very differently. One mechanical one electronic.

 

[Toobuilder]

You state P-Mag has no advantage over a Magneto axiomatically. Did I misread that?

Yes. 100%. In fact, if you would slow your roll just a touch you would realize that I agree with the majority of your posts in this thread (except for your direct responses to me).

I have many years and hours flying Pmags. I have many years and hours flying SDS. In contrast to the plethora of anecdotal option on this forum, I have performed disciplined flight test, collected data and published results on this very forum. As a result of mine and the few others who actually do flight test and publish results, “We” are those that take the time to read the reports. If you do not include yourself in that group, it is not for the lack of effort on my part to share knowledge.

 

[andoman]

I hope Ross will chime in here. I just looked through the CPI2 install manual and I couldn’t find the 45 min reference anywhere.
I just looked back at the OP’s question and it looks like it’s between Pmags and SDS’s full Monty EFI/EI. Not really an apples to apples comparison to Pmags.
Ref CPI2, here’s the power consumption chart from the manual:

 

[DanH]

Again magnetos are no slouch; however magneto fixed timing and quantifiably less (but adequate) spark energy from EI's makes them less efficient.

McQueen, better read that one again. I suspect it's not what you wanted to say. However, it does seem to be correct for p-mags, which are relatively low energy by design. Don't take my word for it. From their website:

High Energy Spark – When is enough… enough?

Ignition shoppers are sometimes encouraged (by our competitors) to compare the spark energy output of different electronic systems. The implication and challenge being, the greater the energy – the better the ignition. E-MAG has a distinctly different perspective that runs counter to some, if not most, in the industry. To explain, we’ll start with our own design objectives: Spark energy should be increased ONLY to the extent necessary to achieve the intended result – AND NO MORE.

This approach stems from a simple truth. The benefits of high energy spark are non-linear. Meaning, after an initial boost there is little or no benefit derived from more (and more) energy. There is, however, an increased burden in the form of additional heat, stress, wear, and weight associated with the creation and constraint of excess spark energy. These can be managed, but if the additional energy doesn’t produce a benefit – why do it in the first place?

It's fair to assume they elected to run with low current draw to reduce internal heating of the generating system. Good design is the art of compromise; I happen to agree with their view. Lighting an NA Lycoming isn't difficult.

Our friend Robert Paisley did a nice job with a data based argument ( https://www.flyefii.com/products/efii-systems/ignition-comparison/ ) showing his system generates more spark energy than competitors. Again, I think the need for high energy (watts x time) is a corner case best implemented as very long duration to light very lean mixtures...but I don't want to fly that slow, so I don't care. I'd rather have low system power draw, same as p-mag, but for battery duration rather than for reduced generating load.

Even Ross at SDS had an off field landing in his Subaru powered RV6 due to ignition.

Due to a battery main disconnect. He learned.

You don't seem to have data, which is fine.

Actually Mike posted quite a lot of data, but it's been a while. Might want to re-read Nigel Speedy's work too. And then consider blanket pronouncements in light of the very different timing requirements for parallel valve and angle valve engines. An owner running p-mags on a 390 without clocking and a jumper really, really needs guidance.

*Cafe' Foundation test of Mags vs EI*...

...was largely a comparison of fixed timing with variable timing. Again, let's not conflate the method of spark generation with when it is delivered.