In an unusual move, Subaru are proposing an update of the ECU ROM update for the MY08 STi. Subaru Australia generally don’t make changes to the ECU ROM, indeed the only other times this has been done recently for turbo-charged Subaru’s was for the Liberty B4s back in 2002 and the MY00 (Version 6) STis in 2000.
The ECU update makes changes to the mid range fueling (mildly richer) as the comes on the boost, and some minor changes around redline to reduce throttle opening before the car hits the rev limiter (effectively softening the impact of the rev limiter when hit).
Also, the changes make fuel cut (which occurs when either preset boost levels have been exceeded or RPM limiter has been hit) effectively last longer by halting fuel delivery (and therefore engine operation) until boost drops to a lower level (MAP levels shown in absolute levels, not more commonly quoted gauge pressure). In simple terms, previously as long as manifold pressure was below 24 Psi when fuel cut had been triggered, engine operation would resume within a few hundred milliseconds, now manifold pressure must be below 10 Psi. This is to prevent the driver banging the car off the rev limiter repeatedly, with the longer pause in engine resumption ensuring the engine is at much lower torque levels when operation resumes.
These changes are designed to rectify some issues that have been mainly experienced by some MY08 STis that are seeing track time.
