The Viking HF-110 is a geared engine. The PSRU has a ratio of 2.33:1. On the one hand, the traditional thing to do is show engine RPM on your RPM indicator, which of course is what the Dynon does by default. The down side to this is that the RPMs displayed are meaningless to pilots raised on traditional aircraft engines without having to do some mental math. And sitting in the cockpit isn’t the best place for mental math. For example, quick, what’s 1400 RPM? Is that high or low? That’s pretty close to idle on a Viking, but something like 50% power on an O-200. If you go into the configuration menu on your Dynon, you can scale the RPM reading (SETUP > EMS SETUP > ENGINE INFORMATION > PUL/REV (PIN C37 P32/34)). If you set the value to 2.33, the Dynon will then display prop RPM instead of engine RPM. It just makes your plane a little more friendly to a wider range of pilots, as the RPM now shows values they’re used to. I tried it this morning, and it works great.