GrimmSpeed Equal Length Header | 2022-2025 Subaru WRX

Unlock more from the FA24 turbo system with the GrimmSpeed Equal Length Header for the 2022-2025 Subaru WRX. Engineered specifically around the factory twin-scroll turbocharger, this header improves exhaust flow while maintaining the equal runner lengths that are critical to proper twin-scroll operation.

GrimmSpeed didn't simply replace the factory manifold with larger tubing. The entire header was engineered around runner length, bend angle, collector geometry, flange sealing, ground clearance, and long-term durability. The result is a true equal-length FA24 header designed to improve flow without sacrificing the factory skid plate or requiring an ECU tune just to install it.

Why Equal Length Matters on the FA24 WRX

The FA24 WRX uses a twin-scroll turbocharger, which relies on properly timed exhaust pulses from opposing cylinders. Maintaining equal-length runners helps preserve that exhaust pulse separation and allows the twin-scroll system to operate as intended.

GrimmSpeed CNC bends and trims each runner to achieve less than 1% variance between the longest and shortest tubes. This provides a true equal-length design while keeping runner bends and transitions as consistent as possible.

Engineered for Better Exhaust Flow

At the center of the design is GrimmSpeed's low-restriction 304 stainless steel cast merge collector. Rather than joining multiple fabricated sections together, the cast collector creates smooth transitions between the runners and turbo inlet while allowing GrimmSpeed to precisely control runner spacing and merge angles.

The runners are constructed from 1.75-inch, 14-gauge stainless steel tubing and use single-piece bends wherever possible. Reducing unnecessary welds and internal steps helps create a smoother exhaust path while also eliminating potential failure points.

Heavy-Duty 304 Stainless Construction

The header uses 304 stainless steel throughout, including the runners, flanges, collector, and badge.

The cylinder head flanges are CNC cut and faced from 1/2-inch-thick 304 stainless steel. Their additional thickness helps maintain flange flatness and provides a strong sealing surface for the exhaust manifold gaskets.

The runners are welded to the flanges on both the inside and outside. GrimmSpeed then finishes the internal transition to create a rounded entry from the cylinder head into the runner for smoother airflow.

Features

• Designed for the 2022-2025 Subaru WRX FA24DIT
• True equal-length runner design
• Less than 1% runner-length variance
• Full 304 stainless steel construction
• 1.75-inch 14-gauge stainless steel runners
• CNC-bent and trimmed tubing
• Low-restriction cast stainless steel merge collector
• 1/2-inch CNC-cut and faced stainless steel flanges
• Runners welded inside and outside of the flanges
• Smooth internal transitions for reduced flow restriction
• No ECU tune or recalibration required for installation
• Maintains factory ground clearance
• Clears the factory skid plate without spacers
• Installation gaskets and hardware included

GrimmSpeed Dyno Testing

GrimmSpeed performed back-to-back Mustang dyno testing against the factory FA24 exhaust manifold using a 2022 WRX 6-speed. Testing included the factory calibration, a COBB Stage 1 OTS map, and a custom JRTuned calibration.

On the stock tune, GrimmSpeed reported average torque gains of more than 15 lb-ft across the powerband, with gains reaching approximately 35 lb-ft during spool below 3,000 RPM. They also reported an average increase of nearly 11 WHP, with some of the largest horsepower improvements occurring between approximately 4,000 and 5,500 RPM.

With a Stage 1 OTS calibration, the difference at peak power was smaller, but GrimmSpeed still recorded approximately 10-15 lb-ft of additional low-end torque leading up to peak torque.

During custom-tuned testing, the GrimmSpeed header continued to show an advantage during turbo spool, with approximately 5-10 lb-ft of additional torque before 3,500 RPM and roughly 1.6% higher peak torque compared with the factory manifold.

Dyno results are provided from GrimmSpeed's testing and are not guaranteed. Actual results will vary based on vehicle condition, modifications, fuel, calibration, transmission, elevation, temperature, and other factors.

No Tune Required

A major advantage of this header is that an ECU tune is not required simply to install it. GrimmSpeed designed the header as a direct mechanical upgrade for the factory FA24 turbo system.

A properly calibrated tune may still be used as part of a larger performance setup, but ECU recalibration is not required after installing the header itself.

Fitment

• 2022 Subaru WRX
• 2023 Subaru WRX
• 2024 Subaru WRX
• 2025 Subaru WRX
• All supported WRX trims

What's Included

• (1) GrimmSpeed Equal Length Header Assembly
• (1) FA24 turbo-to-manifold gasket
• (1) Pair of cylinder head-to-manifold gaskets
• (3) Stainless steel M10x1.25 turbo studs
• (9) M10x1.25 flanged nuts

Installation

GrimmSpeed estimates installation at approximately 2-4 hours depending on the condition of the factory hardware. Installation requires access from underneath the vehicle and removal of the factory underbody panels and exhaust manifold.

A torque wrench, E10 Torx socket, standard metric tools, and extensions are required. GrimmSpeed also recommends having penetrating oil and an M10x1.25 tap available when removing and replacing the factory turbo hardware.

Because this installation involves the exhaust manifold and turbocharger mounting hardware, professional installation is recommended if you are not comfortable performing this type of work.

Why Buy Your GrimmSpeed Header From JD Customs USA?

A performance header isn't just another part number. How it fits into the rest of your setup matters.

JD Customs USA specializes in parts for modified performance vehicles, and we focus on giving enthusiasts the fitment, technical information, and installation context they need before spending money on a major upgrade. We don't want you guessing about whether a part fits, whether a tune is required, or what actually makes one header different from another.

When you order your GrimmSpeed FA24 Equal Length Header from JD Customs USA, you're buying from a performance-focused shop that understands the VB WRX platform and how individual upgrades work together as part of a complete build. If you have questions about fitment, supporting modifications, installation, or how this header fits into your plans for the car, our team is here to help.

Product Details

• Manufacturer: GrimmSpeed
• Part Number: GRM113401
• Engine: FA24DIT
• Construction: 304 Stainless Steel
• Header Design: Equal Length
• Runner Size: 1.75-inch, 14-gauge