Modifying Subaru's 03 WRX STI Version 8

Becoming NZ's ECUTEK dealer in 2004 was a great leap forward in the tuning scene for the team at Torque Performance. When it comes to factory Engine Control Units (ECU) it's a big advantage in being able to edit and adjust all the factory data without going to an aftermarket ECU or an interceptor style computer.

In 2004 we were approached by the owner of a near new 2003 JDM WRX STi Version 8 who wanted more than “just the basics” done to his car.

The standard Version 8 STi puts out around 175 - 185kw at the wheels (aw). The budget was established, and the aim was to get the best “bang for buck”, without sacrificing any drive-ability, reliability or modifying the engine internals. We aimed to achieve around 230kw aw on a conservative tune.

From previous research and development we knew that the twin scroll turbo on this model, with some basic modifications maxed out at around 210kw aw. The same could be said about the standard fuel injectors, fuel pump and air intake.

Finding a replacement twin scroll turbo within our budget proved to be a challenge, so we opted for a single scroll ball bearing unit instead, along with a set of stainless steel headers. The exhaust was soon taken care of with a full 3inch system right from the turbo back and the standard air box was replaced with a revised intake sucking cold air from the inner guard. The factory plastic inlet pipe under the manifold was removed to make way for a moulded silicon item instead. We settled on a large top mount intercooler in place of the factory STi unit - the Version 8 STi bonnet scoop is well up to the job. A front mount intercooler was considered but due to the added “lag” time to fill the long pipework we decided against this.

Next on the list was the fuel pump and injectors. The pump was replaced with an in-tank higher flowing unit.

As on all earlier WRX's, replacing the injectors only, without re-plumbing the fuel rails, can lead to engine damage. Replacement billet rails were obtained and plumbed in parallel using a dual regulator system. The standard 500cc injectors were replaced with 650cc items.

With all the dirty work done, it was time to put our recipe to the test. A lengthy dyno session followed and changes were made to fuel, ignition, cam timing, boost control, knock control, backup maps, limits and more. Launch control was also setup through the factory ECU!

We chose to keep the boost within the factory limits for longevity. At around 18psi the turbo is still well within its efficiency range and more boost is available should it be required at a later stage.

The end result was even better than expected. Peak power at the wheels was up nearly 60kw and large torque gains were obvious right from 3000rpm. The engine pulled strongly all the way to the factory rev limit of 8000rpm. An easy 244.5kw aw was recorded with a conservative tune and the boost peaking only 0.5psi higher than factory, Needless to say the owner was very happy with the result.

Project WRX Sti Gets more grunt - Part 2

Nearly 12 Months on and the car hasn't missed a beat. Its time to see if we can extract any more power and torque from this already rapid Version 8.

Latest additions include boost level switching (through the standard ECU), a custom fabricated oil catch can and a WRX Spec C 12 litre water sprayer reservoir in the boot.

A few more hours on the Torque Performance dyno were clocked up and the results were well worth waiting for. A healthy 260kw aw was recorded with a substantial increase in torque.

On the road the car feels like its had an even bigger wake up call. It pulls strongly from under 3500rpm and doesn't let up until the engine touches the limiter at around 8000rpm.

Stay Tuned for more developments in this space...

When 260kw doesn't enough - Part 3

Lucky for some..
the novelty wears off fast.

With this package well proven on and off the track for many months with no issues, it was time to take the ultimate step.

Why stop now? Or I think it went like this "Can I have 300kw at the wheels for raceday...?"

We won't bore you with the finer details.

Take one EJ25 semi closed deck new Subaru engine block.
Fill it up with forged bits, head studs, steel head gaskets and original cylinder heads.

Refit to vehicle.
Add larger Garrett turbo, custom intake manifold, front mounted intercooler, monster injectors and oversize MAF sensor.

Using ECUTEK the standard ECU is futher retuned to suit the new engine (using BP98 fuel) during an extensive dyno session on our state of the art DynoTorqure chassis dyno, netting some very impressive figures.

The latest development from ECUTEK allows us to run full dual maps in the ECU i.e.: x2 ECU's in one, which includes different boost tables for each gear and launch control. We programmed a map for the track and a map for road use - switchable on the fly. Not intending to push boost levels beyond known reliable limits, 336kw at the wheels for street use and 304kw aw for the track was achieved.

With dual maps, boost-per-gear, presise cam control, Subaru's patented advanced ignition learning, safety backup maps and factory diagnostics, the ECUTEK modified standard ECU out performs leading aftermarket ECU's.

On the road the car is absolutely rapid! With no noted turbo lag, the engine pulls hard right from the word go all the way to the rev limiter.

This is now one of the quickest Subarus we have tested.

One year on, numerous track days and the engine is still going strong.

This is one tough sleeper. Watch out!

If you would like to discuss modifications for your car, don't hesitate to contact Torque Performance