I've heard somewhere that the ECU on my 1.8 Focus is self learning, its adapts to your driving style or something?

How does this work exactly and what effects does it have on performance?

Please enlighten me!

 

As with all modern ECU's, they do indeed have a learning capacity.
All the ecu contain a base map for ignition and fuelling, the learning bit to which people refer, is merely a programme built in to the ecu to fine tune the running parametres of the car, it does NOT adapt to driving style at all, but to the engine and it's needs, the trouble is it can also adapt to certain faults and mask them, making them harder to find.
The learnt setting will be stored as trim values + or - in a seperate chip which are then added or subtracted from main map memory, which is burnt in on the "CHIP", that som many refer to, so is permanent, in the sense that it cannot be altered by disconnection of the power source, but can of course be adjusted with software.
These trim values can be deleted, normally with taking out a fuse marked "KAM" or Keep Alive Memory.
tabetha

 

The ECU has an adaptive strategy which is designed to compensate for mechanical variance and wear and tear. Basically the ECU will adjust a setting and use feedback from the sensors to see if it has made things better or worse. If it has made things better it will store the setting and use it from now on and so on.

This is just fine tuning, it is not the same as a remap and it Is not clever enough to adapt to a different engine etc. Every now and again it does not hurt to wipe the KAM as it could be hiding faults etc.