l have a subie without turbo (rs 2.5) which I am thinking of upgrading to sti engine. Now l would like to know whether anyone has ever done that? consider my car use a different ecuis that means l need to buy a new ecu for turbo engine? should l get oringinal or after market brands? where can l find these people that can do the tuning. Thx guys

It would be easier and maybe cheaper just to buy a STi. Dont forget everything that you need to upgrade if you go from 160hp to 300hp. You will need a new transmission, transfer case, axles, and driveshafts. You should also get bgger brakes. All of these parts with labor will get you a STi.

Also, the stock Impreza is a SOHC engine and the Sti is is a DOHC. That means that along with everything listed above by [Tim H], you would also need to replace the valvatrain. l agree with the person before me, you're much better off to just buy an Sti.

If u have a 2.5rs pre-2002, get an ej20(wrx) engine. The power to wieght ratio would be great. Plus, since the motor is already turbo'd, it is not hard to unlock noticable power gains for low money. You can find wrx motors for relatively cheap, & they r pretty easy to find, along with ecu is which usually run a few hundred bucks. In addition to the motor u can get a custom tune & full exhaust piping & be above sti power levels. You should go to nasioc.com & post ur questions & look for tuners in ur area if u r serious.

Those cars r pretty much the same as far as mountings & bolt patterns & such. Many people swap engines & transmissions regularly even before the ST l trim was available in the U.S. The best information about tuning would be on Australian websites. Google & u will find tons of information, everything is in english & the Aussies love subaru is & love to help out.

l would just build the RS block & buy the ST l upgrade parts (many boosted RS is on the street). As far as ecu is go, l would go full standalone with all the goodies. But be warned, the scooby doo is r an advanced tuner is car & the best pick for heavy duty off road racing.

check out http://nasoic.com quite a few transplants there. Personally you'd be better off just buying a used STi, but if u got an itch, the transformation is possible. Also, as was previously noted, I'd stick with upgrading to a wrx motor, or a JDM 2.0l STi unless u want to change ur ENTIRE driveline. The USDM 6 speed throws a monkey wrench in the works because it has a different length, & a different output ratio(and there is no way ur RS tranny would survive an STi motor). For an EJ25 transplant u will need motor, tranny, ECU, main shaft, rear diff, front & rear half shafts, rear hubs, rear brakes, just WAY too much hassle. An EJ207 transplant would be a nice one, & it is not too hard to get 300whp out of 2.0l(PE1820 will do nicely).

l looked at the same thing with a WRX wagon, l was at 330whp on pump gas & wanted more. l was planning on going to an EJ25, a non DCCD 6 speed, & a few other goodies, then realized all of the other hassle involved & decided to sell my wagon & pick up an STi. l am SOooo glad l did. After a GT35R & a few other minor goodies she lays 438hp to the ground on a mustang dyno(which is about 550 at the crank), has great brakes, great suspension, & is one SEXY beast. With wingless trunk, RS hood, & black APS FMIC noone ever guesses they r about to have their ass handed to them by a cute little 4 door. You should be able to pick up an 04 STi in good shape for right around $20K

Good luck either way.