Introducing the twin scroll GTX2971 for Subaru 02-07 WRX and 04-18 STi! Just like the GTX2971R,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.

 

This is the ultimate replacement for Twinscroll VF36 VF37 and VF38 

 

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! 

 

NOTE: This turbocharger requires the usage of twin scroll headers and downpipe.

Bearing Type:	Ball-Bearing
Flange Type:	Standard Subaru 5-Bolts
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:	550 HP

 

Feature	TR-TS1047 Twin Scroll GTX2971	TR-TS1027 Tomioka Racing TD06-20G Billet
Compatibility	2002-2007 WRX, 2004-2018 STi	2002-2007 WRX, 2004-2020 STI
Bearing Type	Ball-Bearing	Journal
Compressor Wheel Material	Billet	Billet
Compressor Wheel Size (mm)	In: 54, Ex: 72	In: 52, Ex: 68
Turbine Wheel Size (mm)	In: 60, Ex: 57	In: 61, Ex: 54
Turbine Housing Size	10cm2	8cm2
Weight of Compressor Wheel	Lighter than competing turbos	10% improvement over standard wheel
Wheel and Blade Design	20% larger wheel, 17% longer blades	Not specified
Exhaust Housing	Port and polished to minimize turbulence	Not specified
Maximum Horsepower Support	550 HP	530 HP
Spool Characteristics	Twin-scroll design for optimal spooling	Fast spool, ideal for maintaining high HP
Installation	Requires twin-scroll headers and downpipe	100% bolt-on

 

Applications:
2002 - 2007 Subaru WRX
2004 - 2018 Subaru STi

Kit Contents:
Turbocharger
Gaskets
Hardware Kit
Actuator
Oil Pipe
Water Pipe
Motul 300V 2L

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.