Absolutely. I am about to start a software NMEA2K project to convert tacho input to fuel flow rate output, via a suitable conversion graph; not unlike the custom gauge approach. This can be displayed on Garmin kit.
For diesel engines that have flow and return diesel to the injector rod and back to the tank, this is a simple solution with no added hardware.
Adding that to the EMU-1 for the second tach input as mentioned would be superb!
I have been monitoring the data in practise and tacho gives a pretty accurate answer – infinitely better than dodgy analogue fuel gauges!
