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SDS Usage / Setup Report

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Marc Zeitlin

Exalted Grand Poobah
Dec 11, 2015
Tehachapi, CA
I've had some requests for an engine/SDS system report, as well as tuning information, so here you go. This is long and broken up into a few parts. It was originally posted to a couple of canard mailing lists, but I figured it might be useful here as well.

Introduction - Overview:

When I had my engine rebuilt in January - April, 2023, I had an SDS dual ECU EI/EFI system installed. This is the system shown here:

as produced by @rv6ejguy. I have the previous EM-5 system, not the latest EM-6 system - I NEVER use the first version of anything anymore (it took a while, but I eventually learned my lesson with Emagair products). Maybe I'll upgrade after a few hundred EM-6's have been out for a few years.

As of this writing, I have approximately 110 hours on the engine and SDS system since the first flight with it in early May, 2023. There were some minor issues during the installation - the fuel injector housing fuel fittings were weeping a bit - either not enough or the wrong sealant was applied to the NPT threads, but that was easily remedied and reported to both SDS and Aerosport Power (who built the engine in 1998, and rebuilt it this time into an O-375-A1A [a designation that doesn't exist for Lycoming, but is the closest we could come up with from a parts procurement standpoint]) for future build quality control checks.

Currently, the only squawks are that the MP and O2 sensor outputs are pretty jumpy, but that doesn't seem to affect the engine performance at all - it runs like a top and very smoothly - I actually haven't even felt the need to dynamically balance the engine/prop combination since the install - it's way smoother than the original engine was (although it's still a Lycoming, so "smoother" is definitely relative). I believe that (after tuning/optimization) I'm also getting better economy - burning maybe ~0.2 - 0.3 gph less than I used to at the same power setting/RPM (say, 8.2 - 8.3 gph vs. 8.5 gph).

I've spent a lot of time tuning the system, mostly with the advice of @Toobuilder (Michael Robinson), who flies a Harmon Rocket out of Ancient Valley airport in Mojave, CA (not on the sectionals). He provided a basic roadmap for tuning (with all due respect to the SDS folks, who are wonderful and helpful and produce a terrific product, the SDS documentation is substantially less than optimal with respect to tuning guidance). Now, Mike has a C/S prop on his O-540 Rocket, while I have a fixed pitch prop on my COZY, so there are some additional considerations I have that he didn't.

There are about a zillion (well, that's a slight exaggeration - actually, there are 102 ignition related, 166 fuel related, and 37 miscellaneous, for a total of 305) parameters that you have full control over in the SDS ECU, so you have the ability to totally prevent your engine from running at all if you don't know what you're doing. So you want to change things slowly and incrementally, if at all. SDS supplies default settings and "maps" for both fuel and ignition (based on what engine you have) that will allow the engine to start and run in a reasonable fashion, but will not provide optimal performance, nor will it allow engine damage. Many folks never tune the maps - their fuel economy and/or power output will be marginally sub-optimal.

SDS also provides a "Lean of Peak" button that has the ability (if set up) to set a fixed timing advance and fuel map offset. SDS also has the ability to change the fuel level for each cylinder independently, so you can ensure that all four/six cylinders peak at exactly the same time. I have not found the need to use this cylinder specific tuning capability (yet), but some folks do need/use it.

To Be Continued in Part 2: