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I purchased this Sonex that the previous owner had just installed an SDS EFI system on. He only flew it a few hours before selling it. It's a good upgrade in terms of performance. My engine at "static" is pulling almost 100 RPM more than "book".

My issue is the electric only fuel pumps. The system requires two, but runs on one. (back-up) This system continuously draws about 9 amps of power. 4.5-5 for the pump and another 4 amps for the EFI system. This along with the normal electrical load of radio, transponder and other puts such a load on the 20 amp alternator that it barely keeps up, let alone recharge the battery. It would take about 1.5 to 2 hours at cruise power just to replenish what gets sucked out during start up taxi and runup.

I am seeking input on either a lower draw electric pump that will put out 40 psi (better yet mechanical drive pump) or a bigger alternator. Has anyone tried adapting a motorcycle stator/rotor system to one of these AeroVee engines? Those will put put 50 amps!

Appreciate any feedback.

This recent topic might be of interest
viewtopic.php?f=7&t=5937&hilit=alternator

Two things can help you 1. moding the aircraft to have an alternator like the linked post I originally made that post and am planning to go that route with a 50 Amp Alternator. otherwise the biggest savings would be going with lower power coils but honestly the alternator mod is probably the best option and it would be easier in your case since you will not need to use the stock ignition at all since you are running the SDS EFI system assuming you also have the ignition system they offer.

Without knowing the details I can make a couple of suggestions for direction. Easiest is install a PWM motor controller on the primary pump. Note that this pump should also have an oil pressure cutoff switch so it will stop pumping in the event of a crash. Or a g switch, but I believe those are more expensive. https://www.pegasusautoracing.com/produ ... p?RecID=87

With the pwm you can dial back the output of the pump motor to provide the pressure and flow you need with minimum current. Do not try to control a motor with a resistance controller.

For more power, does your motor have provision fir a belt driven alternator? This is the way to get the most power including at idle. Second choice would be a three phase permanent magnet generator, basically the big version of what you have. I think this is what you are referring to. You will also need the correct rectifier/voltage regulator.

Best of luck, keep us informed. Gordon

Thanks for the feedback everyone. I'm looking into Gordon's suggestion of the pump motor controller, but I think I may pursue the bigger permanent magnet generator adapted from a motorcycle use. I really don't want to add the weight of a 40-50 amp alternator because I am already pushing the forward CG limit as is.

Keep us updated on how that goes if its a good fit and doesnt have temp problems it gives us glass guys another power option.

Keep us updated on how that goes if its a good fit and doesnt have temp problems it gives us glass guys another power option.

Just wanted to post an update on this issue. I am still in search of a flywheel alternator option that will fit into the AeroVee aft case. This is not proving to be easy because Sonex used what is basically a lawnmower engine alternator that is quite small. The motorcycle flywheel alternator systems that are 3 phase can easily put out 50 amps, even 25 amps at idle. But, the stator/rotor are much larger in diameter and won't fit in the aft case without some serious modification to the aluminum mounting plate. I really wish Sonex offered something bigger, but multiple emails and contact with them pretty much tell me we're on our own with this issue.

Meanwhile, I am very much enjoying flying this great little airplane. I just don't wander far from home yet due to this charging problem. The 20 amp system barely keeps up at cruise and is loosing the battle at anything below 2400 RPM. Makes for an immediate emergency landing if/when this alternator gives out due to my electric only fuel pump.

Blue skies all!

It would be interesting if one of the Aerovee/Aerovee Turbo guys could get their hands on a prop hub and develop a new version that has an integrated pulley to drive an external alternator on the "front". Not sure if that would put too much force on the end of the engine that is driving the prop but it certainly could be an option. There are some talented people in our community that are great with solid works so maybe there will be a design sometime in the future. The lack of electrical output from the Aerovee is one of the reasons that drove me to the 65 amp alternator on the Aeromomentum. Either way I will follow this thread as I know this will definitely help other builders.

I came up with a working fix for the inadequate 20 Amp AeroVee alternator. Here is what I did.

I purchased an Ultima 32 Amp Heavy Duty charging system. (used on late 90's to early 2000's Harley Sportster). This included a new regulator. It is quite a bit bigger so required some Yankee engineering. Guess that's why we fly "experimental" aircraft!

I purchase a 1.5" thick spacer to get the rotor to run outside of the accessory case. This spacer had a flange on one side that I had the center of the rotor machined out to fit over. This helped to keep everything concentric. (VERY important) I then drilled the holes through the rotor and spacer to match the ones in the original rotor so it would all attach to the crankshaft as did the original. This was the most difficult part of the operation. Keeping everything concentric is critical so there are no bad vibrations. Attach the rotor to the flywheel first using high grade machine screws.
Then attach the original E-mag trigger plate and shaft to/through the rotor with longer (again) high grade structural screws that go all the way into the flywheel.
I fabricated an outer and inner ring to attach the new stator and E-mag plate to the accessory case. I had to make 1.7" spacers to attach to this outer ring to get it to clear the larger new rotor.


I lined everything up and drilled/tapped holes into the accessory case to secure the stator/E-mag assembly to the case. Again, assuring concentricity is critical. Make sure everything rotates without any contact issues.

Another note: I had to rotate the starter 180 degrees so the drive unit would clear the larger rotor.

I now have 13.0 volts at idle and 14.2 volts at any RPM above 1500. I'm happy! My plane is happy!

PLEASE READ THIS! You can do what I did, but I would highly recommend that you pull your engine, remove the accessory plate (X-plate) and mill that out to fit the larger rotor inside the case as with the original. Doing this on the aircraft was far more work and very difficult to keep everything concentric and lined up. My thought was to do this for now and then mill the plate out the next time I have the engine off and make it more professional at that point. Take my advice and do it right from the beginning. This took me weeks when I could have done it in days had I just pulled the engine.