Project STi Gets EcuTeK'd

Excperts from Modified Magazine, by Peter Tarach

With over a year of design and testing, EcuTek has probed the US-Spec Subaru STi’s ECU extracting all the necessary data to be able to write/alter/control virtually any of the functions found n the very complex ECU. Most important and of most interest to us, is it can now access the fuel, ignition and timing maps to tweak the factory settings into more aggressive settings resulting in more ponies under the hood. For those that don’t know, a reflash isn’t an ECU you bolt on or anything physical for that matter. It is software that is flashed into the ECU via a laptop that is connected to the car’s OBD-II port and replaces the factory ECU settings. Also, the EcuTeK software can’t be accessed by any Joe Shmoe either. A trained and certified EcuTeK dealer is the only person that can alter the parameters.

Ben Dagenais arrived -- EcuTeK’s head trainer for North America -- and our STi was loaded on to the rollers. Tuning was about to commence. To get an accurate air/fuel ratio reading, Ben quickly hooked up the Innovate wideband O2 sensor into the exhaust then proceeded to plug his laptop into STi’s OBD-II port. With some quick keyboard strokes and a turn of the key in the ignition, the stock STi fuel, ignition and timing maps were downloaded and available for viewing. Ben looked at several of the maps and noted that the stock map is very rich. The car is running at about 9.5 to 1 AFR (Air/Fuel Ration) on the top end. Before we went ahead with tuning the car, a base line pull was needed to show before and after results. After making almost ten pulls on the rollers, we decided that the median run would be used as our baseline. The results 231whp and 278 lb-ft of torque!

The actual tuning began now that we had a base number to work with. The first task was to remove some fuel. About 25 percent of the fuel was taken out throughout the lower RPM range to 5,500rpm. For the top end (5500rpm +) we wanted to keep things more conservative and safe so only 20 percent of the fuel was removed. With a better-looking AFR now in place, our search to unlock more trapped hp was on.

The simplest form of adding horsepower in a turbocharged car is upping the boost. Knowing that the injectors were already close to their operating limit and that the turbo couldn’t feed much more air into the motor (without grenading or causing an extremely heated charged) we were very limited as to how much more boost we could add. With Ben’s tuning expertise he knew we could set the boost to 20psi in the lower part of the powerband and taper it off to 14psi as the engine hit redline without any ill effects. On the timing side of things we were able to add a few degrees here and there in the powerband to squeeze out the last remaining untapped ponies.

With the new EcuTeK tune in place the STi spun the rollers to the tune of 270whp and 321 lb-ft of torque. Giddy up! That’s a gain of nearly 40whp and just a tad off 40 lb-ft of torque. Of course many more urns were made to verify that this one pull wasn’t a fluke and they all came within 5whp each time. Armed with more power and a lot of anticipation we hit the streets. Seat of the pants reaction says, “Wow!” “What a difference!” The first and second gears used to be power gears but now with all that torque in place the five, six gears pull just as strong if not stronger. Luckily, we had the Rotora big brakes to quickly slow us down from the insane speeds we reached during the testing.

Words cannot describe the overall improvement; it’s a whole new car. We are confident the car will take well to a bigger turbo and supporting mods, which is already in motion.

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