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WRX Turbo-Back Shootout - 2003 Subaru Impreza WRX

Round Two

Robert Choo
May 1, 2003
0305_turp_03_z+2003_subaru_impreza_wrx_exhausts+exhausts Photo 1/5   |   WRX Turbo-Back Shootout - 2003 Subaru Impreza WRX

The last time I checked, there are roughly 290 million people living in the United States. And of the 290 million inhabitants, roughly 2.5 million tie the knot every year. However, of the 2.5 million people who get married, roughly one-third end up in divorce court.

You might be wondering what in the world the United States census has to do with a WRX turbo-back shootout. Call me crazy, but have you checked how many turbo-back systems are available today for the WRX? Using any internet search engine you can probably find about a dozen systems available on the market. And, just like finding your ideal mate, how would you know if the turbo-back system you are purchasing is "the one" for you?

Turp_0305_02_z+2003_subaru_impreza_wrx_exhausts+dyno Photo 2/5   |   WRX Turbo-Back Shootout - 2003 Subaru Impreza WRX

Leave it to Turbo to help you find true love! We were able to gather seven different turbo-back systems for this shootout. Yes, we did install every single one and, of course, we tested them all on the dyno on the same day. Kids, don't try this at home.

As with any shootout, we wanted to ensure the playing field was level. First, we found a bone-stock 2003 WRX with 5,000 miles on the odometer. Second, we installed a Turbo XS UTEC programmable fuel computer to ensure the boost pressure is kept constant and ignition timing does not change from exhaust system to exhaust system. Any qualified engineer can tell you that with today's on-board diagnostic systems, any tweaking of the engine can alter fuel and ignition tuning drastically. With the Turbo XS UTEC, we were able to set the boost pressure at a constant and set a standard ignition map for every system we tested. This way it'll be up to the exhaust system to determine if power is increased and not the ECU, which would correct and alter ignition maps for the power increase. (We'll be featuring the Turbo XS UTEC in a future issue of Turbo.) All testing was performed at XS Engineering on the company's DTS four-wheel dyno.

MSRP Tip Peak Peak Max HP TQ Piping Dia. System Downpipe Downpipe
dia. (mm) HP TQ* Boost Gain Gain* dia. (mm) Construction Dia. (mm) Construction
Stock $1,227.00 dual 72 178.9 699.4 15.1 -- -- 52 Mild-steel -- Mild-steel
HKS $865.00 120 191.5 767.7 16.28 53.3 227.1 75 Aluminized mild-steel 75mm Aluminized mild-steel
AVO $1,495.00 70 193.4 746.5 16.25 41.8 177.8 75 Polished stainless-steel 75mm Polished stainless-steel
Zero Sports World Leaguer $1,698.00 {{{100}}} 192.9 776.1 16.3 53.9 230.6 75 Polished stainless-steel 100mm collector to 75mm Polished stainless-steel
Invidia $1,198.00 100 198.6 763.7 16.74 60 263.8 75 Polished stainless-steel 100mm collector to 75mm Polished stainless-steel
Kakimoto "R $1,358.00 120 {{{200}}}.9 {{{740}}}.6 16.7 63.8 289 75 Polished stainless-steel 75mm Polished stainless-steel
Kakimoto {{{GT}}} 1.0z $1,938.00 {{{90}}} 203.8 774.5 16.54 65 285.7 75 Titanium 75mm Polished stainless-steel
Turbo XS $1,126.00 120 196.9 781.6 16.98 56 239.2 75 Stainless-steel w/polished canisister 100mm to 75mm Stainless-steel

AVERAGES (excl. stock) $1377.00 102.86 196.86 764.39 16.54 56.26 244.74 75.00 -- -- --
*Peak torque was measured at the rollers not the wheels as is usually the case.

By Robert Choo
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