Speedy Subaru

Update by Tom Suddard to the Subaru Impreza WRX project car
Dec 18, 2012

An all-wheel-drive dyno is the best place to tune a WRX.
The top bolts were easy to access.
The bottom bolts weren’t so easy.
We modified our factory heat shield to fit the new TurboXS downpipe.
The exhaust was hitting in one spot, so the Mach V techs marked where it would need to be cut and rewelded.
Once the modification was finished, it was barely noticeable.
The AccessPORT looks like a cell phone but does so much more.
The Kartboy short-shifter installed quickly and easily in place of this stock one.

Put simply, our WRX is much, much faster than before.

With our suspension sorted out, it was finally time to add power to our 2002 Subaru Impreza WRX. We needed an all-wheel-drive dyno in order to properly tune our car, but unfortunately our local dyno shop doesn’t have one.

Luckily, Mach V Motorsports not only has an all-wheel-drive dyno, but they have an expert Subaru tuner, too. They were more than happy to help us with our WRX.

First, we needed to address our car’s weak points, namely a restrictive exhaust system with too many catalytic converters (they are known to break apart, ruining the turbocharger in the process). Both AJW Performance and Mach V Motorsports had warned us about the factory uppipe’s catalytic converter, so removing it was a top priority.

We replaced the car’s factory exhaust system (except for the factory exhaust manifolds) with pieces from TurboXS. While we were upgrading, we also installed a TurboXS air intake. The TurboXS parts fit well overall, though we did have to modify the exhaust slightly. It wasn’t a big deal for a professional shop, which is why we did the upgrades at Mach V. They had the issue corrected in 15 minutes flat. The shop also put a 2.2 kΩ resistor in the plug for the EGT sensor that’s no longer used with the new uppipe. This prevents the computer from throwing any trouble codes due to the missing sensor.

To complement our physical modifications, we also needed to upgrade one intangible part of our car—the ECU’s tune. To do this, we sourced an AccessPORT from Cobb Tuning. This simple digital tuner has become the industry standard for turbocharged cars and combines a reasonable price with an intuitive interface. The AccessPORT can also function as a code reader, show live data from your car’s OBDII port, measure zero-to-60 times and much more.

The AccessPORT comes with different tunes based on a general idea of what cars with different levels of modification need. These tunes work well enough, but to get the full benefit of our upgrades, we had Mach V tune our car on their dyno. They offer a tuning discount for AccessPORT owners, which gave us even more of a reason to buy Cobb’s tuner.

Once our car was tuned, there was only one thing left to do—fix the shifter. The previous owner had installed a short-shifter, but it was terrible, so we replaced it with a Kartboy short-shifter. Not only does the car now shift smoother, but the shifts are even shorter.

The modifications certainly worked, and we’ll publish the full details and dyno charts in an upcoming issue of Grassroots Motorsports. Put simply, our WRX is much, much faster than before. If you’re not a subscriber, it’s time to become one!

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