Tomioka Racing TD06-20G Billet Wheel Twin Scroll Turbo – 2002-2007 Subaru WRX / 2004-2021 STI

Tomioka Racing TD06-20G Billet Twin Scroll Turbocharger — 2002-2007 Subaru WRX / 2004-2021 STI

The Tomioka Racing TD06-20G Billet Wheel Twin Scroll for the 2002-2007 Subaru WRX and 2004-2021 STI combines twin scroll spool speed with billet compressor efficiency. The billet material improves airflow by at least 10% over the standard cast wheel. At 530 HP it is the highest-output journal bearing bolt-on turbo in the TR GD lineup. 100% bolt-on.

DETAILS

• Platform: 2002-2007 Subaru WRX EJ20/EJ255 and 2004-2021 STI EJ207/EJ257
• Billet compressor wheel — at least 10% airflow improvement over standard cast wheel
• Twin scroll turbine housing — improved spool vs single-scroll at same size
• Journal bearing construction
• Compressor: 52 mm inlet / 68 mm exducer (billet)
• Turbine: 61 mm inlet / 54 mm exducer
• Turbine housing: 8 cm²
• Actuator: 1.1 bar / 16 psi
• Max. power: 530 HP
• 100% bolt-on
• Complete kit included

Turbocharger Specifications

Bearing Type	Journal bearing (billet compressor)
Flange Type	Standard Subaru 5-bolt
Compressor Inlet	52 mm
Compressor Exducer	68 mm
Turbine Inlet	61 mm
Turbine Exducer	54 mm
Turbine Housing	8 cm²
Actuator / Gate Pressure	1.1 bar / 16 psi
Max. Power	530 HP

Turbocharger Design and Specifications

Billet compressor wheels are machined from a solid forged aluminum billet rather than cast. Cast wheels have the grain structure of the pouring and solidification process — adequate but limiting stress tolerance and blade geometry precision. Billet wheels machined from forged billet have a more consistent and favorable grain structure throughout. Tomioka Racing uses point-milling on their billet compressor wheel blades, a machining process that allows the cutting tool to reach precise geometry between blade profiles, creating surface finish and blade profile accuracy that casting cannot achieve. The improved surface quality and geometry directly contribute to compressor efficiency and durability. A twin scroll turbocharger divides the exhaust pulse inputs from the engine into two separate scroll passages within the turbine housing. On a four-cylinder engine, the exhaust pulses from cylinders 1 and 4 enter one scroll while pulses from cylinders 2 and 3 enter the other. By keeping these paired cylinder pulses separated, each pulse arrives at the turbine wheel with higher energy and less interference from adjacent cylinder exhaust events. The result is improved exhaust scavenging efficiency, more consistent turbine wheel loading, and faster spool speed compared to an equivalent single-scroll design at the same turbocharger size.

Installation, Kit Contents, and Wastegate Spring Guide

Each Tomioka Racing turbocharger kit includes all hardware needed for the installation: the turbocharger unit, wastegate actuator, oil feed and return pipes, water cooling connections, all gaskets, and the hardware kit. All current production TR turbos include a billet wastegate actuator. Professional installation is recommended for turbocharger swaps — the oil feed and return line routing, water cooling connections, and boost line setup all require attention to detail for correct long-term function. For DCBB turbos, a Turbosmart TS-0811-0012 OPR V2 Turbo Oil Pressure Regulator is recommended to ensure correct oil pressure at the bearing unless otherwise noted.

Wastegate Spring Selection: 1.1 bar vs 1.3 bar

The actuator spring sets the gate pressure — the minimum boost the turbocharger will produce. You cannot run boost lower than the spring rating regardless of ECU or boost controller settings.

Choose 1.1 bar (16 psi) if your boost targets include values below approximately 22 psi, or if you run multiple boost maps including a low-boost street mode. The 1.1 bar spring provides good boost controller authority across a wide operating range.

Choose 1.3 bar (19 psi) if your minimum target boost is 19 psi or higher and your normal target is in the 22-28 psi range. The 1.3 bar spring provides better control stability at higher boost targets and better resistance to premature wastegate opening under high exhaust backpressure conditions.

As a general guideline, peak target boost should not exceed approximately 2x the gate pressure for stable boost control authority from the solenoid.

What’s in the Box

• Turbocharger
• Billet wastegate actuator
• Oil feed pipe
• Water pipe
• Gaskets
• Hardware kit

Why Choose Tomioka Racing (TR)

Tomioka Racing has been building direct-fit turbocharger upgrades for Subaru performance vehicles since the early 2000s. Every TR turbocharger is engineered around the factory connection points — oil feed, water cooling, mounting flange, and charge pipe inlet all match OEM positions — so installation is genuine bolt-on without custom fabrication. TR covers the full span of EJ-series and FA-series Subaru platforms, from the GC8 through the current VB WRX, and their turbochargers are proven in both street and motorsport use including rally racing. Each kit ships complete with turbocharger, actuator, oil pipe, water pipe, gaskets, and hardware — everything needed for the swap in one box. RallySport Direct stocks the full TR turbocharger catalog because their engineering quality and fitment accuracy are what our customers expect.

The RallySport Take

The TR Billet TD06-20G Twin Scroll for the GD WRX and STI is the top journal bearing bolt-on option for these platforms — billet wheel efficiency combined with twin scroll spool speed at 530 HP. The definitive turbo for GD builds targeting maximum bolt-on power at the standard flange and location.

Fitment

Year	Make	Model	Notes
2002-2007	Subaru	WRX	EJ20/EJ255 MT
2004-2021	Subaru	WRX STI	EJ207/EJ257 MT