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Old 11-12-2011, 02:04 PM   #1
Full-Race Geoff
Scooby Specialist
Member#: 133386
Join Date: Nov 2006
Chapter/Region: Tri-State
Location: AZ/NJ
13 F150

Default 2007 STi: Twinscroll BorgWarner S300SX FMW vs Twinscroll Garrett GT4088R

years ago, when Full-Race had just begun to use the BW Airwerks turbos, we had a lot of people ask for a back-to-back comparison of the S300SX 8375 (60mm inducer) against the twinscroll 35R (60mm inducer). We did this test on a 2.0L evo click link for old test


update for 2011 - nasioc member "philthy" (a longtime customer/friend of Full-Race and all-around hardcore car nut) runs Full-Race twinscroll turbokits on his fully built 2.5L 2007 STi AND his fully built 2.2L evo8 for over 3 years now. Hill McCarty @ Agile Auto has built and tuned the STi over the years and both cars have been thoroughly flogged at high boost with Garrett GT4088R's in all types of street driving and racing conditions so he knows the turbo's behavior inside and out. He has always wanted even faster spool on his STi - but didnt want to lose power. After learning about the new airwerks S300SX FMW a direct plug-and-play for his twinscroll kit, i guaranteed him it would do what he was looing for so he wanted to try it out. "FMW" technology (aka forged billet aluminum compressor wheel) combined with their tried and true airwerks turbine wheels and housings makes for a massive performance potential despite an incredibly value-minded pricetag

one very special feature of this turbo is the ability to order it with (2) different turbine blade shapes, cupped tip OR flat tip to suit the engine and application at hand:

the exact day this turbo became available, Philthy drove his Subaru w/ 4088R twinscroll setup down to Agile Auto in MD for the turbo swap and retune. This turbo is also unique due to the 2.5" compressor outlet, making it an even easier plug-and-play compared to the older gen s300sx. Hill @ Agile auto tuned & dynoed the 40R, swapped the turbos and then tuned & dynoed the BW S300SX FMW.

Final Dynoplot comparison of Philthy's 07 Subaru STi w/ Full-Race twinscroll turbokit: BW S300SX FMW .91 a/r flat tip (Solid Lines) VS. Garrett GT4088R .95 a/r (dotted lines):

video of final dyno pull on pump gas + meth spray:

comments: we believe the flat tip and .91 a/r is the optimal combination from the airwerks S300 lineup for the STi engine. It is a great match for this engine's unique VE and airflow requirements. For an engine with higher VE such as s2000 or 13B rotary then the cupped tip would be worth consideration obviously - it completely destroyed the garrett from idle to rev limit.

Phil says this turbo made him LOVE his subaru again. The turbo can make 6-7psi at 1/4 throttle before 3000rpm at part throttle cruising. He says the sounds this turbo makes are unlike anything he's ever had before, and it transitions into boost effortlessly. I will ask him to post up with some long term comments after driving more

The exact specification of the build:


Borg Warner S300SX FMW Flat tip .91 a/r
Full-Race T4 Twinscroll Turbokit
Full-Race Twinscroll Up-Pipe w/ 2x Tial 38mm MVS WG
Full-Race 3" Downpipe
Cobb 3” Turboback Exhaust
HKS Twin Power DLI II
Built Motor by Agile Auto
K1 Billet Crank & K1 Connecting Rods
Cosworth Pistons
Headgames Motorworks Ported/Polished Heads
Ferrea Valvetrain
GSC S2 Cams
ARP Studs
Agile Auto Intercooler piping
Cosworth Intake Manifold
Koyo Radiator
Killer B Oil Pick up
Beatrush Aluminum Cooling Panel
Beatrush Pulley Cover
Crawford Air Oil Separator
Cusco WRX STI Radiator Cap 1.3 Bar
Samco Radiator Coolant Hose Kit
Samco Ancillary Hose Kit
Tial BOV
AEM V2 Standalone ECU
Cusco Engine Mount
Injector Dynamic 1000cc Injectors
Walbro Fuel Pump Kit 255Lph (in-tank)
External Bosch 044
External Fuel Surge Tank
APS DR525 Subaru Front Mount Intercooler
NGK One Step Colder Spark Plugs
Aquamist Meth Injection Kit
Spec C 12L Intercooler Tank Used for Water/Meth Injection

Carbonetics Carbon Triple Plate Clutch
Stainless Steel Braided Clutch Line
Motul Gear 300V 75W-90 100% Synthetic
Cobb Double Adjustable Billet Short Shifter
Cobb Six Speed Shifter Bushings
Cusco Transmission Mount

Enkei NT03+M (17x9.5 Front & Rear)
NT05 (255/40/17 Front & Rear)
Rays Engineering Lug Nuts

Stainless Steel Brake Lines
DBA Slotted Rotors
Hawk HPS Pads
Motul RB600 Brake Fluid

Innovate XD-16 Wideband Air/Fuel Ratio Gauge
AEM Serial Gauges
Aquamist Flow Meter

RobiSpec.com Full Race Preparation
KW Clubsport Coilovers
Whiteline 26mm Adjustable Front Sway Bar
Whiteline 27mm Adjustable Rear Sway Bar
Whiteline Rear Toe Lock Kit
Whiteline Front & Rear Endlinks
Whiteline Race Anti-Lift Kit
Whiteline Steering Rack Bushings
Whiteline Lateral Links
Cobb Tuning Billet Adjustable Rear Sway Bar Mounts
Cusco Rear Strut Tower Bar
Cusco Rear Camber Plates
DMS Front Camber Plates
M-1 Tubular Race Under Body Brace

Last edited by Full-Race Geoff; 11-12-2011 at 03:22 PM.
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