Prodrive (WRC team and builders for Subaru) have done preliminary work on the STI ECU for better power and a wider power band without sacrificing throttle response or reliability. The kit consists of a Prodrive rear muffler section and center pipe and a revised ECU program. This kit is $999 and is available now in limited release to Southern California owners.

Torque is higher, as seen in the accompanying charts, but more importantly the power band is wider. In this case the wider power band gains have done as much to improve acceleration as the actual peak power increase. When you print out and compare the before and after charts, note the huge increase in midrange torque achieved. It makes the car accelerate effortlessly in any gear at any engine speed above 3000 rpm. With a peak 407 Nm torque at 3500 the engine has a minimum of 380Nm from 3200rpm to 5200rpm. The stock figure is 320nm for the same range with a peak 368 Nm. Put in the most simple terms possible, this is a huge "C-YA" difference.

The STI engine is rated 300hp/300ft lbs torque.  In development testing Simon discovered some interesting facts about the STI engine tuning. First, on 91 octane fuel the engine does not quite make the 300/300 numbers corrected at the crank. This is not surprising. If we had used 93 octane the engine would have made its target horsepower number. Far more interesting was the random and almost 10% variation in the power figures between individual runs. This variation was despite a full 80mph fan on a full SAE/DIN calibrated dyno.

The first implication is that it would be very hard to make "A"-"B" power comparisons of physical component changes such as intakes, up pipes or down pipes. It is difficult to imagine looking for a 5-10% "improvement" when changing parts if the stock engine has 10% changes in power between runs without any modifications. That the following anaylisis by Simon Lines of Prodrive shows is two fold. 1) It is meaningless to search for power claims on the STI engine unless the ECU is tuned during testing as well, and 2) Tuning the ECU alone makes far more difference than just changing parts.