What does ecu flashes/re-flashes do exactly ........"electronically/mechanically"

 

overwrites the stock ignition mapping (typically fires earlier--dependent upon fuel -- octane, etc), can remove speed limiter, increase rev limit/fuel cutoff, remove boost taper (as best as possible). All or some of these thing as well as others possibly? But these are the most popular for the Evo. Search on WORKS, Dynoflash, Buscher flash, you'll see LOTs of discussion on this..

 

OH. and to further clarify, perhaps the whole point of your question.. all this information is stored on an EPROM (Erasable, Programmable Read-Only Memory?? -- something to that effect)/EEPROM/EAPROM/FLASH memory chip . In any case, it's an embedded chip that can be reprogrammed. Nothing happens mechanically, everything is changed programmatically. The EPROM is located on a circuit board that's part of your ECU. Some of these are on a socket that you can pull out (usually by bending pins unless you have a PROM puller handy) and sometimes they're part of the board. These days you send the entire ECU to the vendor and they send it back. Easier to hook it up and reprogram than pulling PROMs.