TR GTX2971 Ball-Bearing Twin Scroll Turbo Kit Stock Replacement for Subaru 02-07 WRX & 04-18 STI
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TR-TS1100
TR GTX2971 Ball-Bearing Twin Scroll Turbo Kit Stock Replacement for Subaru 02-07 WRX & 04-18 STI
Now available for the brand new GTX2971 Twin Scroll Turbo, the TR Equal Length Exhaust Manifold with Up-Pipe and TR Twin Scroll High Flow Catless Downpipe! The perfect combination for a complete twin scroll turbocharged setup for your WRX or STi. Rated up to ~430whp, the twin scroll technology ensures spool speed that is night and day in comparison to single scroll turbos. Thought your turbo spooled fast before? Think again.
This twin scroll edition features a ball-bearing cartridge, billet compressor wheel , and 10cm2 housing. Thanks to the billet compressor wheel the overall weight of the wheel is lighter than competing turbochargers and allows for maximum airflow throughout the unit with the help of point milling on each blade. A unique wheel and blade design, featuring a 20% larger wheel with 17% longer blades than the factory turbocharger. In addition, the GTX2971 features a port and polished exhaust housing to minimize exhaust flow turbulence. All hardware is included with purchase.
Catered to the die-hard Subaru fans! The twin scroll turbo is an efficient way to replace or upgrade your current twin scroll set up on your Subaru. With the rarity of twin-scroll turbo applications, we have created yet another direct bolt-on system, this time for the 2002-2007 WRX and 2004-2018 STi. The GTX2971 is already an efficient turbo but now paired with a complete twin-scroll system, spool time is dramatically decreased!
The Twin Scroll High Flow Catless Downpipe features larger diameter piping with ported flanges for a quicker and faster exhaust air flow compared to the standard OEM downpipe. Each downpipe is constructed of SUS304 grade stainless steel that gives it shine and durability that will last for years to come. Installation is a snap! The downpipe will fit like your OEM downpipe and comes with all the necessary hardware and gaskets.
The Twin Scroll Equal Length Headers feature a lost wax finish with 3-1 connectors and a smooth inner surface for the best air flow. A stable & effective connection s made by the slip joint bracket and air leakage is avoided by the 3 bolt flange design up-pipe.
All in all the entire system will bolt together without any issues and make way for quick installation, having all components sit in their stock locations in the engine bay.
TR has partnered with Motul USA to offer a free 2L can of 300V 5W30 or 5W40 with any purchase of TR turbos! Choose your oil of choice in the options and we will include it in your order!
Do you need more Motul 300v? Add some more HERE!
Turbo Specifications:
|
Bearing Type: |
Ball-Bearing |
|
Flange Type: |
Standard Subaru 5-Bolts |
| Billet Compressor Wheel: | In: 54 mm |
| Ex: 72 mm | |
|
Turbine Wheel: |
In: 60 mm |
| Ex: 57 mm | |
|
Turbine Housing: |
10cm2 |
|
Actuator: |
1.1 bar / 16 psi |
|
Horsepower: |
500 HP |
Downpipe Specifications:
| Material | Stainless Steel SUS304 |
| Pipe Thickness | 0.25 Inch / 6.3mm |
| Flange Thickness | 0.5 Inch / 12.5mm |
Applications:
2002 - 2007 Subaru WRX
2004 - 2018 Subaru STi
Turbocharger (TR-TS1047)
Gaskets
Upgraded Billet Actuator
Oil Drain Pipe
Water Pipe
Twin scroll Downpipe (TR-ES1005)
Down pipe to Exhaust Gasket x1
Down pipe to Exhaust Nuts & Bolts x2
Exhaust Manifold (TR-ES1002)
Up Pipe (TR-ES1002)
50' x 2" Exhaust Wrap
Wastegate actuator spring choice: 1.1 bar vs 1.3 bar (what customers need to know)
What the spring actually controls (and why it matters)
On a pneumatic internal wastegate, the actuator spring sets your gate pressure (often called base boost): the boost level where the wastegate starts to open because boost pressure overcomes spring force. Haltech describes it simply: changing spring pressure changes the default boost pressure, and when boost exceeds spring pressure the valve opens and begins regulating boost.
Choose 1.1 bar (16.1 psi) / Red if:
You want a lower boost map (street/traction/valet) around the mid-teens. Remember: you can’t go under the spring.
Your normal target boost is roughly 18–22 psi and you want good controller authority and flexibility.
You’re building a setup where drivability and multiple boost modes matter (daily + weekend map).
Choose 1.3 bar (19.1 psi) / Silver if:
You will not run low boost—your “low boost” is still ~19 psi or higher. (If you need 15–17 psi sometimes, don’t pick this.)
Your normal target boost is roughly 22–28 psi and you want:
less “work” from the boost control system to hit target, and
typically better resistance to the wastegate being pushed open early (especially in higher load / backpressure situations).
There are two different “maximum boost” questions people ask:
1) Maximum boost your boost control can hold consistently
Using the GFB rule-of-thumb (target boost ≤ ~2× gate pressure) :
With a 1.1 bar / 16.1 psi spring, the “control stability ceiling” is roughly ~32 psi (2 × 16.1).
With a 1.3 bar / 19.1 psi spring, the “control stability ceiling” is roughly ~38 psi (2 × 19.1).
Reality check: that does not mean “safe to run 32–38 psi.” It means beyond ~2× gate pressure, boost control tends to get inconsistent because the actuator isn’t receiving enough meaningful reference signal for correction. GFB explains that once you go beyond double, boost control becomes less stable and more affected by variables like RPM/load/backpressure.
2) Maximum boost your turbo/engine can safely run
That’s not spring-limited. It’s limited by:
turbo efficiency and speed/heat,
fuel quality and knock margin,
intake temps/intercooling,
exhaust backpressure,
engine/clutch/trans limits,
tuner strategy.
FAQ:
Can I run less boost than the spring rating?
No. Spring pressure is the lowest boost level you can reach.
Does a stiffer spring automatically mean higher peak boost?
Not automatically. It mainly raises minimum boost and changes how the wastegate behaves. Boost above spring comes from the control strategy.
Why do people say “don’t exceed 2× the spring”?
Because boost control gets less stable as target boost gets too far above gate pressure; beyond ~double you tend to lose correction authority.
What spring gives the best spool and boost stability?
A spring that puts gate pressure about 10–20% under your target boost is a strong general guideline for best performance.
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