# SDS Ignition

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#### kr2pilot

##### Member
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

##### Well-Known Member
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

##### Member
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

#### dwalker

##### Well-Known Member
HBA Supporter
A fellow from the Dragonfly group just put the SDS on his Limbach VW that he flies almost daily and loves it.

#### rv6ejguy

##### Well-Known Member
HBA Supporter
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

##### Well-Known Member
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

##### Well-Known Member
HBA Supporter
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

##### Member
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

##### Well-Known Member
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

##### Well-Known Member
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.

#### TFF

##### Well-Known Member
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

##### Well-Known Member
HBA Supporter
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.

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