SDS Ignition

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kr2pilot

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I want to convert my Revmaster 2100D with a Bendix 3000 mag to an SDS ignition. Looking for ideas on what you have done in your engine. I would also consider other recommendations. Lost my faith in the Bendix mag...
 

103

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I want to convert my Revmaster 2100D with a Bendix 3000 mag to an SDS ignition. Looking for ideas on what you have done in your engine. I would also consider other recommendations. Lost my faith in the Bendix mag...
The SDS would be high on my list if replacing the Mag you need a system level view without a self powered mag understand the time you can fly on battery alone should your dynamo fail. I am considering full SDS EFI/Ignition but defering until I complete my flight training since everything is running well today.
 

osprey220

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Hi kr2pilot,

Sorry for the delayed reply - I dont check this forum regularly.

If your ignition is working well, resist that urge to jigger it up with bright shinny improvements. Fly!

That said, the SDS system has a very good reputation in the homebuilding community even though it was developed around "failed" auto conversions (subaru and mazda). With SDS and almost any EI you'll see improved performance (smoother idle, stronger starts, and increased efficiency). But these come at some cost (cost :) , and increased chance of catastrophic failure). The clunky old Bendix is heavy and requires ongoing preventive maintenance, but it tends to fails slowly. With SDS, once your electrical power goes, off goes the engine. I've lost electrical power a few times in my 3700 hours and I am very happy the engine kept running.

Sounds like I'm down on EI - but thats far from the truth. I put a Pmag on my Osprey that I am very happy with, and I am putting an EI on my son's KR. (Thought I think I am going to use a MSD Midget Ignition that I picked up cheap from a friend.)

If you are the new owner of a KR2 and are looking for things to improve, would suggest a few other items I would go after first. #1) On all other VW conversions I would first make sure your engine does not have the oil flow restrictor to the pulley (prop) bearing. You can tell this by ensuring it has the screw out plug rather than the original press in plug - but I think the Revmasters all did this. #2) pay extra care to ensuring your baffling is air tight and that you have the inter-cylinder baffles. #3) dynamically balance the running engine/prop/spinner assembly. #4) instrument the engine - 4 chts, 4 egts, air/fuel gauge. Consider building a simple light weight cowl flap assembly (maybe oxymoron?) to improve cooling while climb, yet reduce drag during cruise.

Have fun and safe flying!
Cheers!
Owen
 

rv6ejguy

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That said, the SDS system has a very good reputation in the homebuilding community even though it was developed around "failed" auto conversions (subaru and mazda). With SDS and almost any EI you'll see improved performance (smoother idle, stronger starts, and increased efficiency). But these come at some cost (cost :) , and increased chance of catastrophic failure).
Owen
You sound like quite the authority on SDS. We've been producing EFI/ EI systems for 27 years and produced over 10,000 of them, nearly 2500 for aviation. They have accumulated over 20 million hours collectively and about 800,000 flight hours to date. They were not developed around "failed" auto conversions. They were developed originally for the automotive market, then moving to aviation to become the most popular user programmable systems in the world for Experimental aircraft. The CPI-2 was specifically designed for legacy aviation engines like Continental and Lycoming.

The CPI, which we generally sell to the VW crowd, has had zero failures reported and lately the VW market is the largest consumer of the CPI (I'm filling 4 orders for VW systems this week). Most folks buying want their mags gone. They don't want the weight or maintenance of a mag, especially one with a single drive. The CPI has no moving parts outside of the flying magnets on the crank. There are no maintenance intervals specified outside of plug and plug wire inspections annually. You may opt for single or dual controllers and crank sensors for redundancy. Current draw in cruise is less than 2 amps per unit so your starting battery will run these for several hours if the generator crumbles. Add a small backup battery if you wish even more redundancy.

I'm still flying my Subaru after 18 years so I don't think that would be considered a failure. We've supplied around 500 systems for Subaru powered aircraft (many gyros) over the last 24 years. We don't supply for Wankel engines generally- only one I can recall way back. Our main market is Lycoming powered aircraft where we've supplied over 1700 controllers to date. I am not sure where your comment about "increased chance of catastrophic failure" comes from. Any insight on that?
 

103

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The CPI, which we generally sell to the VW crowd, has had zero failures reported and lately the VW market is the largest consumer of the CPI (I'm filling 4 orders for VW systems this week). Most folks buying want their mags gone. They don't want the weight or maintenance of a mag, especially one with a single drive. The CPI has no moving parts outside of the flying magnets on the crank. There are no maintenance intervals specified outside of plug and plug wire inspections annually. You may opt for single or dual controllers and crank sensors for redundancy. Current draw in cruise is less than 2 amps per unit so your starting battery will run these for several hours if the generator crumbles. Add a small backup battery if you wish even more redundancy.
Ross can you break down the merits of CPI vs CPI-2 for us VW fliers? Thanks for considering us!

Matt
 
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rv6ejguy

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The CPI-2 is more expensive and bulky than the CPI- two things that don't fit into the VW world generally speaking. The main extra features of the CPI-2 over the CPI are a remote programmer/ gauge head for the panel to take up less panel space than the integrated controller/ programmer of the CPI and auto battery switch over which the CPI doesn't have. The CPI-2 uses a much larger, separate controller which can be challenging to fit in many small VW powered aircraft.

The CPI can be blind mounted if you don't have the panel space. Feature wise, as far as ignition control goes, they have similar capabilities, both allowing user programmable timing with both RPM and MAP. LOP advance is available on both, though usually not used on VWs.
 
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kr2pilot

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RV6ejguy could you please PM me and give me the specifics of what I will need to convert my Revmaster? I am sold on the idea that I want to convert.
Best regards

Luis
 

103

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The CPI-2 is more expensive and bulky than the CPI- two things that don't fit into the VW world generally speaking. The main extra features of the CPI-2 over the CPI are a remote programmer/ gauge head for the panel to take up less panel space than the integrated controller/ programmer of the CPI and auto battery switch over which the CPI doesn't have. The CPI-2 uses a much larger, separate controller which can be challenging to fit in many small VW powered aircraft.

The CPI can be blind mounted if you don't have the panel space. Feature wise, as far as ignition control goes, they have similar capabilities, both allowing user programmable timing with both RPM and MAP.
Thanks perfect layout. between the two options the CP is more optimal for us VW aviators but not inferior. Proper dynamo and back up battery scaled to the mission makes this a logical choice to replace the MAG as primary.
 

Vigilant1

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Thanks perfect layout. between the two options the CP is more optimal for us VW aviators but not inferior. Proper dynamo and back up battery scaled to the mission makes this a logical choice to replace the MAG as primary.
The SDS CPI does look like an attractive ignition option for the VW. And, just to mention it, once a person is headed down that road, going whole hog and investing in the fuel injection to go along with the electronic ignition starts to look good. By my estimate it's about an extra $1k (above the CPI cost) to go with the SDS EM-5D and the other needed stuff (injectors, injector bosses, fuel pump, etc). Whether that's a good value would depend on how cost-sensitive a builder is and some other factors. A lot of VWs have fairly unbalanced induction systems, the ability to individually trim the mixture to each cylinder can be pretty useful, it seems to me.
Peter van Schalkwyk's SDS installation on his VW powered Sonex is very good looking and is giving him very good performance.

Another nice aspect of the venerable Type 1 VW in airplanes: It's got a lot of flexibility. It can be built as a reliable, low-cost, no-frills engine (magneto or magnetron, no electrical system, hand propped, etc). Or we can sprinkle a bit more $$ and technology on it to produce a refined and efficient powerplant with most of the modern bells and whistles.
 
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lelievre12

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I am not sure where your comment about "increased chance of catastrophic failure" comes from. Any insight on that?
Electronic ignition relies on a battery supply, wiring harnesses, remote sensors/pickups etc. All of which introduce new failure modes not found in a magneto. Loss of ignition may not be a catastrophic failure but it sure gets your attention. On my engine I replaced one mag with an electronic alternative and within 10 hours of flight managed to experience an in-flight failure (due to pilot forgetting to turn on ALT). Luckily the 'old' mag filled the gap however in my case the electronics increased the chance of failure as I expect it will for all pilots.

On the flip side, mags are cranky, hard to keep in time and suspect to arcing at altitude. On my TSIO engine an overly advanced out of time mag will lead to catastrophic detonation and so if electronic timing is more accurate over time, this to me seems to be an advantage. Electronic timing stays where you set it, mags do not.

To get the best of both worlds, it seems prudent to keep one of both on your engine, or at least fail safe the electronics if this can be done.
 

Toobuilder

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I sure find it funny that people are so quick to expound on how electric motors are the "future" of GA, despite significant technical hurdles of sustained, high power delivery. But when it comes to the infinitely simpler, and technically feasible task of providing just a trickle of energy to an electronic ignition, the fear ratchets up a hundred times.

Make up your mind people.

I have measured the single SDS CPI system on a 6 banger Lycoming at a real time draw of 1.69 amps at 2700 RPM. This level of energy can be maintained on a total loss battery for many, many hours. The battery you are using on your cordless drill would START a VW and run the ignition for far longer than you would be willing to sit in it at one time.
 

BJC

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Electronic ignition relies on a battery supply, wiring harnesses, remote sensors/pickups etc. All of which introduce new failure modes not found in a magneto.
My PMag needs minimal external power below 1,000 RPM. Above that, it internally generates its own power. It mounts just like a magneto. No separate crank position sensor required. Plus, it is really simple to time.


BJC
 

lelievre12

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My PMag needs minimal external power below 1,000 RPM. Above that, it internally generates its own power. It mounts just like a magneto. No separate crank position sensor required. Plus, it is really simple to time.


BJC
Sounds perfect. All the benefits with none of the drawbacks. I think when I installed Surefly, it was the only one with a STC for my P210N. Hopefully that will change as time moves on. I noticed dramatic improvements in smoothness and LOP ability up high when I went electronic. However Surefly needs volts all the time from the aircraft and is not internally powered.
 
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dwalker

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Mags fail far more often than an EI. Now, while I am NOT talking about a "EIS" that mounts in place of the distributor/magneto and may be of lower than acceptable quality, a proper crank triggered EIS like the SDS and similar using proper harnesses are quite reliable. The fact is mags fail so often that airplane engines have two of them! And that should be the first reason to ditch the things.

Lets examine what does fail in an EIS along the lines of the SDS. The computer has no moving or wearable parts, and if properly potted, shielded, etc. there is literally nothing to fail internally. The crank pickup it appears SDS is using is a "flying magnet" arrangement, using a Hall effect sensor. Again, no moving parts. Nothing to wear. Nothing to fail. They are sealed and do not care about being wet, cold, or pretty much anything else.

The coils can fail for sure, but failure modes on most modern coils are not violent or total, you just get a random misfire, but the engine does not stop running. Same for the plug wires and sparking plugs.


Now lets talk maintenance-
Mags- check often, rebuild as needed- I think like 500 hours?, special plug wires, special plugs, and of course, expensive.
EIS- set it and forget it. Check your plugs when you change the oil, as you should. Replace as needed.

As to electrical failure- surely could happen. Cables come loose, batteries go bad, pilots forget to turn on the alternator, things happen. However a simple dedicated battery backup is all it takes to ensure operation.

Long ago, I did not trust most EIS/EMS solutions. I worked with Electromotive, Haltec, and a bunch of others and they all had issues, usually software. These things would randomly brick, there were many instances of corrupted cal files, etc. and I just did not trust them for much of anything That said however the Electromotive EIS based largely on GM components actually worked pretty well, and used a VR (mag) trigger which was more than accurate enough.
Nowadays EFI has gotten ridiculously reliable. I did a lot of beta work for AEM and some others, and have at this point used most motorsports ECUs you will find in the wild, including some that are no longer with us.

As to the SDS I am not particularly familiar with it myself, I do not know and have never met or talked to Ross or anyone at his company.
I had a single customer years ago with one on a Mazda Protege turbo that I tuned on the dyno, but I hoestly do not remember much than that but it worked well enough. Pretty much everything I see SDS doing as far as thier systems and methodology is sound. If I were not already a disciple of AEM and invested in using their display and peripherals I would strongly consider using SDS on my Corvair flight engine.
 

drwet

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When we built out Murphy Rebel in the early '90's we used a Lycoming O-320H2AD for power. It has that stupid 'two mags on one drive' system which wouldn't fit between our engine and firewall. Our solution was to install a single mag and an Electroaire electronic ignition system. The system has worked well for 25 years and about 1000 hours with only one minor failure (which was picked up on runup). The company has since been sold and the purchaser has had the system STC'd for a number of engines with the result that the cost of the system has increased substantially. If I were shopping for a system today I would certainly be looking at the SDS system as an affordable alternative. I have heard some good things about it. As for the potential for failure, that's why we have two ignition systems. Ours is wired with an emergency power source which is simply a direct power feed from the battery which is switched on in the even that the main electrical system has to be shut down. It strikes me as a little absurd that we are flying with ignition systems that are at best 1940's technology. The electronic ignition system gives us more power and better fuel economy. Plus the fact that I can run NGK plugs at about $3 a pop. I don't even bother cleaning them.
 

TFF

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Most mags are abused. 500 hours is if you wear them out in 4-5 years. Some point they are too old because the plastic inside gets brittle. That is what 500 hour inspection is checking/ replacing the plastic stuff and a set of points. But don’t think it’s good because it’s got 300 hours on it if it’s 30 years old. If you have flown around with the CHT at redline, you are cooking the mags too extra crunchy too.

Hopefully the OPs Bendix 3000 is unmodified. It’s worth a chunk as a core even. The biggest issue with the duel mag is if it’s got an impulse on it. Impulse 3000s are great for starting but it can hit the gears so hard, they strip earlier than normal. A lot more inertia in the two mags for one shaft. I have seen them strip in a couple of hundred hours. I have lived with shower of sparks ones for at least as a mechanic for at least 15,000 aircraft hours with only one real failure and a couple that just did not work 100%. Probably a bad block, at that point, I sent them to the O/H. Not my favorite, but I had to make them work. In certified aircraft. It would be nice if there was a certified electronic replacement as an option.
 

rv6ejguy

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The CPI is dirt simple. Not many wires, easy to understand. Here is a VW installation on a friends Q2.

A bit of fab work to build the crank sensor mount and coil mount. Flying magnets are embedded in the tips of the prop bolts. One coil can mount in the old mag hole.

quick8.jpg

pauld3.jpg

In an RV panel, though most blind mount the controller or install on a hinged fold down panel as below.

karsten1.jpg
 
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