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Old 01-20-2009, 01:48 PM   #1
GRD Tuning
Former Vendor
Member#: 141400
Join Date: Feb 2007
Chapter/Region: MWSOC
Location: Villa Park, IL
Drag STi, 996 911TT
built TT, Built s15+more

Default GRD Performance 08 Sti Shop Car Build

After having put a little over 2200 miles on our shop 2008 Subaru STi we felt it was time to load our vehicle on our 4wd Dynapack Dyno to take some base line pulls. This enabled us to have a reference point of where we started with stock wheel HP figures over any future performance modifications. Subaru rates the crank HP at 305 and torque at 290 lb-ft, and our shop/test car managed to pull a best of 234 WHP and 280 lb-ft. This is about 5-7 WHP less than our previous 2005 STi which was rated 5 HP less from the factory than our current car! Below are the results of the 2 best baseline pulls that our car could manage.

After taking care of our baseline pulls we decided to install a Cobb Accessport. We married it with their Stage one 93 octane calibration. The OTS map provided with the Accessport made 278WHP at 5250 rpms and 317 lb-ft at 3700 rpms. Results are shown below along with our stock baseline as a reference.

With some minor tweaking using Cobb’s Protuner software we were able to make some slight gains, and deliver an extra 10-15 lb-ft torque throughout the rev band peaking at 291 WHP.

While increasing HP and Torque over stock and Cobbs OTS Stage 1 map we were also able to increase our MPG by 5-10 percent. This was helpful on our wallets during the time when gas was over $4.30/gallon for 93 octane fuel.

For our next modification we fitted an Invidia downpipe, an HKS catback exhaust and an AEM Cold air intake system.
We did some baseline pulls with Cobbs Stage 2 OTS map and yielded 305 WHP and 352 LB/FT. After our custom tune we were able to extract 8 WHP and 5 LB/FT of torque.

On pump gas our 08 STi managed to make an additional 77 WHP and 67 lb/ft of torque over stock, with some bolt-ons and custom tuning. So far it has adapted very well to the additions we have made and served as a fun daily driver. Drivability remains great and is much smoother throughout the rev band and throttle position. Throttle response has also been finely tweaked to give better drivability.

Our next stage was to fit a larger turbo but one that would not negatively affect any daily drivability, and our answer was the APS SS45. A very cost affective turbo for those looking for more HP without giving up any throttle response or low end torque.

Throughout the testing and dyno tuning on our stage 2 setup we found that the stock injectors would not support a large turbo application so we proceeded to install 850cc injectors with the SS45. The stock fuel pump was adequate for this setup but we will upgrade it in the near future. We felt the stock topmount intercooler was also sufficient for this setup. However, after numerous hours of street and dyno tuning we concluded that we need a more free flowing exhaust to maximize the potential of the SS45. Back pressure for the HKS exhaust measured at an astounding 4.5psi at 20psi of manifold pressure. We believe this to be comparable to the stock exhaust and should have some data shortly. Those looking for a stealth system which makes 350whp with 93 octane with better street/autocross drivability than stock should look no further.

Keep a lookout for our updated thread as we will eventually move to larger turbo and built motor setup.
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