RomRaider

my friend's car is a forester xt (2.0turbo <--ej205 ) sweped an 257 , but still using the 205's ecu . is it able to flash the rom and replace some maps for his new engine ( form a sti ecu) ?

if this will work , which maps will i need to replace?

thanks

I think you'll want to list the complete mod list of the car...see the Analyze my Log" Minimum Posting Requirements at the top of the page...as it has everything stated in it that you'll want to mention in your posts.

i think you misunderstand me, i 'm thinking to tune with the 205 ecu or the sti ecu.

if my idea doesn;t work ,then i;ll have to spent alot more money to buy a sti's ecu.

details on the swap would be helpful but yes you can tune a WRX ecu to run an STi motor...
i'm assuming that you are using the STi longblock with the WRX intake manifold/throttle body/engine wiring harness? did you get the necessary cam position sensor bracket from either cosworth or gruppe-s? if not you'll need that but everything else adapts right over.
then you just get to tuning...

he swaped the complete engine. using sti intake manifold, the throttle body changed to dbc. able to start the cat with the 205's ecu , but not running smooth <--- so i didn;t do any logging from this car. i'm afraid that WOT will blow up the engine.

i was thinking if flashing a few maps will work? fuel and timming

where do you live? what year is the original car and what year is the new engine?
is the original car drive by wire or cable throttle? and is the new engine drive by wire or cable throttle? did all of his wiring plug right in on the swap?
did he keep the original dash and chassis wiring in his car, and just swap the engine and engine harness? did he have to merge harnesses or did it just plug in?
in the US thats not possible because of wiring differences and going from a cable driven throttle to a drive by wire setup, so i'm not sure what you're dealing with here...

the most basic thing initially though is that you probably went from 440cc injectors to 550cc injectors and the ecu doesnt know that. however i did a similar swap a week ago and the car idled pretty solidly on the stock wrx ecu, and was alright at very light throttle (but of course started breaking up with any throttle pressure)

I'm running an EJ257 with a EJ205 ECU. It works.

Things to keep in mind:
EJ257 is DBW. I hope you changed it out to the WRX parts since the EJ205 ECU can not control throttle.
EJ257 does not have a cam sensor on the front pulley. The EJ205 ECU needs that to get engine position. Wont run right without it.
EJ257 has AVCS. EJ205 does not. the 205 ECU can not control AVCS. But the AVCS defaults into zero advance mode without a signal so its not a big deal.
EJ257 front oxy sensor is different than EJ205. You'll need to put the 2.0L one in there.

Besides that everything else plugs in, bolts up, and works right.