I have read throught the entire post from Pi7467mp, ( STI block SOHC heads completed ). It is quite a beautiful thing, whitch I am about to undertake as well.........I was hopeing to find from all the hits there some info on the limits of the stock ECU on the 2.5 RS when gone turbo with a RRFPR. I know that a stand alone will be a much better choice but $ as always is an issue. So if anyone can give some info on its limits in the sence of how much boost it can deal with till it freeks out. That question is intailing stock heads but an upgraded fuel system ( larger injectors-pump-ect.) As well as the heads themself. I'd like to start at 15psi if that is possible for the heads and ECU

any and all info is a big help here
thanks a lot

 

Cobb sells some rebuild 2.5 motors with upgraded but non-forged internals and they say that 400-450hp is the limit. I think that puts you around 18 PSI with a 2.5 block. You will need a bigger fuel pump and injectors if you want a decent-sized turbo, but from what I understand, fuel rails are not necessary until you start topping 450HP.

 

Perhaps I will refrase my question......

After a STI short block has been swaped for a 2.5 rs short block with its original SOHC,but an upgraided fule system with ( RRFPR-larger injectors-fule pump-ect...) How much boost can the 2.5rs ECU deal with under its Factory programing.

If there is no, or very limited info on what I am asking, due to the new ness of the STI block and the llimited number of swaps of this nature, that is fine. Please forgive my ignorance, but any and all info is just another tool in my box of "pree-swap preperation"

 

ah. RS ecu doesn't normally manage boost at all so it won't have any programing to deal with boost whatsoever. I also believe that ANY change in injectors requires ECU re-tuning. The ecu sees fuel delivery in terms of injector duty cycles, so a higher volume injector would deliver too much fuel at the duty cycle it the ecu would use given the volume of air the sensors tell it is there. You'd be running perpetually rich, and probably have lots of drivability issues. I think you'd be better off with an STi ecu..but you'd still need custom tuning. Any time you swap blocks like that and start mixing and matching parts you pretty much commit yourself to custom tuning to get it working right.

i think the larger injectors are going to be a bigger problem than the boost.

any way you slice it, a motor upgrade is not a cheap project...that's why more people don't do them.

 

Ah ya!...... that was the stuff I had hoped for.....but not the news I wanted to hear

 

The problem with running stock RS ecu for management is that timing is too advanced. you can do a lot of things to deal with fueling, like SAFCs, but pulling timing requires different piggy backs or a standalone. At a minimum, I would run Link on an RS-T, but preferably either a WRX ecu conversion with a reflash, or full standalone like a Tec3 or Hydra or Haltech.