for a good example - current emission number is a mix of several toxic gases (correct me if im wrong)
would be cool to see a drop down menu of some sort to see all the gases right beside it, so we could compare to real life engines
i have no idea how to translate smoothness to something other then it is now
loudness could be done in 2 ways - right at the engine, the air intake itself and of course exhaust loudness
hope you got the idea