Bro, ECON feature i changes gear response, which is reduced. so to get more acceleration you need to floor it a little harder to make the car down shift gears. I am not sure if it alters gear ratios or not.
also, this reduces other things that affect fuel avg, such as AC, electronics etc... so it optimizes the overall electrical system. I have tested this on Motorway and it makes alot of difference. even in city...helps if you are a rash driver....
my rule is that for city drive i go without ECON on, because i want quick response all the time. for motorway i use ECON.
hope this helps