I have been reading a lot of the older threads when I find time.
With some oild/fuel additives and other upgrades, engine smoothness is mentioned. This remains largely anecdotal so it is not really quantifiable.
Our smartphones now have fairly capable sensors (accelerometer, microphone). And apps do exist that can utilize and process this data. Are we using any of them?
Such as this one:
https://blog.faberacoustical.com/wpb...scope-for-ios/
Thai is a paid app i think but there are free ones around aswell. These could be very usefull in quantifying vibrations and smoothness.
Cutting edge technology is using this kind of info to predict machine failiures.