I did some poking around to see what I could find about about a possible firmware upgrade. Based on the always 100% reliable information found on the internet, it appears there is some possibility that there might be a change. But I'm pretty confident it means pulling the unit and sending back to the factory. I'm guessing they use something like an EPROM for the firmware rather than non-volatile memory. Some miscellaneous interesting unverified comments I ran across, plus my impression:
- The Lycoming-branded units might have different advance maps for different engine families. This does make sense to me. Has anyone looked into Lycoming units? The giveaway would likely be different part numbers for different engine groups.
- Currently there is a built-in 100 ms delay in the SIM unit becoming functional. I can see that it is necessary to take a bit to boot up the unit as it needs to react to the current environment (like which direction the unit is rotating). Apparently SF is looking to get approval for a 1 ms delay. A 100 ms delay in an inflight reboot situation at 2400 RPM means 4 revolutions (2 combustion cycles per cylinder) running on the non-SIM during this reboot.
- One statement said that when switch between mags - such as in runup when you're on the right mag and need to switch to left just to get back to both - the transition between the 2 momentarily un-grounds both before grounding the right mag. In control-system parlance, it's break-before-make operation. I have to say it doesn't feel like that to me during runup. The delay in SIM activation could be the culprit, though it seems like more than 100 ms and I feel like the speed with which the key is turned influences that delay when neither ignition unit is firing, with more-rapid movement shortening that delay. But my subjective impression could easily be wrong, especially since there isn't that hiccup switching in the other direction.
- One Mooney owner has a lengthy review currently posted on the Aircraft Spruce page for the SIM4N unit. He had a similar weak-spring situation in his installation that I initially had, though his was even worse.
2002 DA40: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5