2006 Subaru Impreza WRX - Power Pages

DC Sports Downpipe

Pros
The DC Sports downpipe is designed using 100 percent 304 stainless steel (including the flanges) and deletes the catalytic converter to eliminate restriction, delivering maximum performance gains for your turbocharged vehicle. We liked the fact that the turbo exhaust flange is CNC-machined to ensure a leak free setup.

Cons
Because the DC Sports downpipe is a cat-delete unit, it's labeled for off-road use only. Disclaimer aside, the Subaru nuts and bolts holding the factory downpipe in place are notorious for cross-threading when being removed. Offer ample time for your engine to cool down before attempting to install the new downpipe, while checking the integrity of your downpipe gasket for any cracks or rips.

Dyno 4

Parts
Downpipe, gasket, mounting hardware

Tools
10-, 12-, 14- and 17mm sockets, 10-, 12-, 14-, 17- and 22mm open ends, ratchet, extension, screwdriver and WD-40.

Install Time
50 minutes

Notes
To show the potential of the non-catted downpipe, we installed the unit without tuning the Accessport and noticed from 2,000 to 5,700 rpm a gain of 17 hp and 15 lb-ft of torque over our previous run. At 3,400 rpm, the EJ25 netted 7 hp and 17 lb-ft of torque in the mid-range.

Cobb Tuning Accessport (Stage 2 Tuning)

Pros
The Accessport allows you to upload pre-programmed maps to the Engine Control Unit (ECU) via the diagnosis port found on OBD II-equipped vehicles. This simple-to-use, hand-held device doesn't require a computer, wire cutting/splicing, or tools of any kind to install the software. Within minutes, one of the pre-installed performance maps or a custom map can be easily uploaded into the vehicle's ECU to alter and optimize air/fuel ratio, ignition timing and boost. Added features when using the Accessport include the ability to monitor fuel economy, troubleshoot ECU codes, estimate 0-60 and quarter-mile times, and even monitor real-time data as you drive around town.

Cons
While the Cobb Accessport is marketed as a simple plug-and-play device, we highly recommend employing a qualified tuner to tune it specifically for your vehicle/mods/fuel/climate, etc. Trust us on this one.

Parts
Accessport unit, user guide, USB cable, OBD II connector, software CD

Tools
None

Installation Time
80 minutes

Dyno 5

Notes
Our final testing phase commenced with HB Speed's Jon Drenas tweaking the fuel/ignition maps and AVCS timing, while raising the boost to 16.89 psi. Using the Accessport, the WRX managed to gain an additional peak 18 hp and 36 lb-ft of torque. Upon analyzing the dyno charts, the WRX had gained an impressive 46 hp and 73 lb-ft of torque at 3,300 rpm. Midrange power gains continued at 3,500 rpm as the tuned 2.5-liter engine developed 34 hp and 52 lb-ft of torque.

Conclusion
Three bolt-on products, along with an Accessport, helped improve power output by 44 hp and 70 lb-ft of torque over our baseline numbers, and the Subaru is now delivering an impressive 273 hp and 317 lb-ft of torque. With proper tuning and careful monitoring of the engine's air/fuel ratio, we turned up the boost to 16 psi and were rewarded with an increase of 46 hp and 73 lb-ft of torque at 3,400 rpm over our previous dyno. With additional upgrades planned in the near future, including an equal-length header and front-mount intercooler, we expect this Subaru to make over 400 lb-ft of torque without breaking a sweat.