Vern,
I intend to do a weight comparison at the aircraft level after my installation and expect a net reduction, but as I’m doing some significant remodeling it will be very hard to do an apples to apples.
That said, I’ve documented the
rebuild process here, and I might be able to shed some helpful insight below.
Without weighing each related component, I’d say there is a weight advantage to the SDS fuel pump configuration, a significant weight advantage to the SDS throttle body vs. servo or carb, and a significant advantage to the SDS coil/hall sensor compared to the magnetos. On the other hand, the weight edge goes to the legacy parts when comparing the injector bodies and lines.
Then there is the ECU to deal with. It’s not required in either fuel or ignition system for legacy, so it’s really just added weight in a comparison scenario. Of course there is the extra fuel lines for the return system too. If I had to guess, after handling all these parts, I’d have to say the installed system is pretty close to a wash, with maybe a slight edge to the SDS (if comparing a Bendix style FI)
Of course, the backup power scheme is a huge variable – ranging from no requirement (for a Reno race only aircraft), to an elaborate IFR, ocean crossing scheme. I’m adding a second battery to my airplane and I still think I’m going to come out lighter than it was (again, due to a bunch of other work).