RallySportDirect 2011 STi, Tomei M7960, 91 Octane

Event: Dyno Tune/ Product Testing
Location: ZipTie Dynoworks, Salt Lake City Utah.
Ambient Temp: 80-85F
Ambient Pressure 12.7psi/ 86kPA
Elevation: 4600ft
Weather: sunny

Car: 2011 STi
Tuner: Christian of Cobb Tuning
Dyno Info: Mustang
Transmission: 6spd,
Gear: 4th
Peak HP at RPM: 313WHP @ 5600RPM. Corrected
Peak Torque at RPM: 329WTQ @ 4600RPM Corrected
Baseline hp/tq for a stock on same dyno: Stg2 2011 STi 262HP and 286TQ.
Target Boost: 19 PSI tapering to 16-17PSI at redline
Target AFR:
Fuel: 91octane with 10% ethanol

Engine/Power Modifications:

Cobb Tuning AccessPort
Cobb Tuning Down Pipe
Cobb Tuning Heat Shield
Invidia Q300 Ti Tip Catback
Samco Radiator Hose Kit
Koyo Aluminum Racing Radiator
Omni Power 4 Bar MAP Sensor
DeatschWerks Fuel Injectors Top Feed 1300cc
DeatschWerks 300lph Fuel Pump
Process West Top Mount Intercooler
Tomei Fuel Pressure Regulator Type-S
Tomei Fuel Pressure Gauge
Tomei M7960 Turbo
Tomei Expreme Unequal Length Exhaust Manifold
GrimmSpeed Air Oil Separator
GrimmSpeed Manual Boost Controller
GrimmSpeed Electronic Boost Controller
GrimmSpeed External Waste Gate Bracket
AMR Performance Cast Turbo Inlet
GTSpec 44mm V-Band 3-Bolt External Wastegate Uppipe
TurboSmart Duel Port Blow Off Valve
Turbosmart Hyper-Gate45 Wastegate
Prova Radiator Cap


MODE RACING Double Adjustable Short Shifter
Kartboy Shifter Bushings (Front/Rear)
PST Carbon Fiber Driveshaft

Conclusion from our Test:
Ill start with saying that this is a very fun setup. The spool up is good, and on the road hits 19 PSI by about 4100RPM, and 25 PSI by about 4500RPM (whoops ). And given that this is a TMIC setup with EWG, Phenolic TGV’s from Cosworth (think of it as a massive phenolic spacer), this is a very responsive setup once the turbo is in boost.
The turbo is the mid-size turbo from Tomeis new ARMS series of turbocharges. And from the test results is behaved somewhere in between a 18G and a 20G.
Using a hybrid boost control system we are able to quickly reach our peak boost level and be able to have great response thanks to GrimmSpeed’s manual and electronic boost controllers
The fuel is feed with DeatschWerks 300lph fuel pump and 1300cc top Feed fuel injectors, coming to the end of a the line with a Tomei Type-S Fuel Pressure regulator. We built the setup to run almost all the fuel we would ever need for the stock motors power and to change up to E85 when need to.

We are running this setup to see how this turbo reacts with a Us EJ257B motor along with high altitude, and get the results for the manufacture and for the Subaru community.
The numbers are a little lower then we initially expected but contribute this to a couple things. The altitude has allot to do with this, reason being is that the turbo is better suited for lower altitude. We where able to get the turbo to hit as high as 25PSI, however it would start tapering to about 16-17PSi by redline. The peak boost was to high for our fuel (if you can even call it that), and the tapering to the 17psi is not much boost. However considering that our atmospheric pressure is about 2 pounds down on sea level, this would mean that this turbo should be able to hold closer to 18-19psi at seal level. Then add some 93 octane, a few degrees of timing and you got a solid 350WHP setup.
We had a plan to run the turbo on E85 and see what type of power we could make. But spinning the turbo out of efficiency range would have yielded little gains so we opted to keep it in efficiency.
The thing we like allot about this setup is how simple it is, with no major custom parts. The Cosworth TGV’s along with the Process West Intercooler produce a intake manifold that after 4 back to back WOT runs was only a few degrees above ambient. The Tomei manifold once warmed up (it is heat wrapped) provided great exhaust flow and quick spool up. We also chose to run a EWG setup to allow for fitment (at this time the ARMS series is not compatible with the GR/GV chassis do to wastege to intercooler clearence), quicker spoolup, and more solid boost control. We opted to go with the Turbosmart hypergate 45mm Wastegate and on the compressor side went with a Turbosmart Duel Port Blow-off valve for consistent boost response.

This is a great turbo for someone looking to make 310-350WHP range, great for auto-X, canyon carving, stock motor applications, and quick on off throttle response. This is not a powerhouse turbo, but we though that the findings we got where great and are planning on using this turbo for the next couple more months to get some more data and from there test some other different turbo’s.


Huge thanks to the following manufacturers:

Cobb Tuning





For more information on the build please click here





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