GrimmSpeed Equal Length Exhaust Header | 2015-2021 Subaru WRX/2014-2018 Forester

Improve exhaust flow and get more out of the FA20DIT twin-scroll turbo system with the GrimmSpeed Equal Length Header for the 2015-2021 Subaru WRX. Rather than simply replacing the factory manifold with larger tubing, GrimmSpeed redesigned the runner layout, collector geometry, flange construction, and turbo support to address restrictions found throughout the OEM exhaust manifold.

The result is a true equal-length header built to maintain consistent exhaust pulse timing, reduce unnecessary restrictions before the turbo, and provide the durability needed to support the factory or stock-location turbo system.

Best of all, this is a true bolt-on upgrade that does not require an ECU tune simply to install it.

Why Equal Length Matters on the FA20 WRX

The 2015-2021 WRX uses a twin-scroll turbocharger, which works best when exhaust pulses reach the turbine at consistent intervals. Runner length, bend angle, and collector design all play an important role in maintaining that pulse timing.

GrimmSpeed designed all four runners together with the merge collector to closely match both their overall length and bend angles. The finished runners have less than 1% variance between the longest and shortest tubes, with no more than a 5-degree difference between the most and least-bent runners.

This creates a genuinely equal-length, equal-bend design intended to deliver more consistent exhaust energy to the twin-scroll turbine.

Designed to Improve on the Factory Header

The factory FA20 exhaust manifold contains multiple areas where the tubing diameter narrows and exhaust flow becomes restricted. The OEM collectors also use shapes and merge angles that prioritize mass production rather than optimal exhaust flow.

GrimmSpeed addressed these areas with consistently sized runners, smoother transitions, and a higher-angle merge collector designed to direct exhaust flow into the turbine without opposing exhaust streams interfering with one another.

This is the kind of detail that separates a properly engineered header from one that simply looks better than stock.

True Equal-Length Runners

Each exhaust runner is CNC bent and trimmed from a single piece of tubing. This eliminates unnecessary welded sections that can create internal steps, interrupt exhaust flow, or introduce additional potential failure points.

• Less than 1% total runner-length variance
• Maximum 5-degree bend variance between runners
• Single-piece CNC-bent and trimmed runners
• 14-gauge stainless steel tubing
• No unnecessary runner welds or internal junctions

Cast Merge Collector

Instead of fabricating the collector from multiple welded sections, GrimmSpeed uses a single cast 304 stainless steel merge collector.

The cast design allows the runner spacing and merge angles to be tightly controlled while creating smooth internal transitions into the turbocharger. It also eliminates five additional welded junctions that would otherwise create potential flow interruptions and structural failure points.

The compact collector design also allows the header to fit between the oil pan and factory skid plate without sacrificing ground clearance.

Built for Strength and Long-Term Durability

The turbocharger and exhaust system place significant weight and stress on the FA20 exhaust manifold, so GrimmSpeed designed this header with durability in mind.

The cylinder-head flanges are CNC cut and faced from 1/2-inch-thick 304 stainless steel. The additional thickness helps resist distortion during welding and allows the finished flange surfaces to be machined flat for reliable gasket sealing.

The runners are also welded to the flanges from both the inside and outside. The internal weld area is finished with a rounded transition to provide a smoother path from the cylinder head into each runner.

Features

• Designed for the FA20DIT twin-scroll turbo system
• True equal-length header design
• Less than 1% runner-length variance
• Maximum 5-degree runner bend variance
• Full 304 stainless steel construction
• Single-piece CNC-bent and trimmed runners
• 14-gauge stainless steel tubing
• Low-restriction cast stainless steel merge collector
• 1/2-inch CNC-cut and faced cylinder-head flanges
• Runners welded inside and outside of the flanges
• Smooth internal exhaust transitions
• No ECU tune required for installation
• No loss of factory ground clearance
• Clears the factory skid plate without spacers
• J-pipe/turbo support bracket included
• Installation gaskets and hardware included
• Manufactured and welded in the USA

No Tune Required

GrimmSpeed designed this header to be safely installed without requiring an ECU recalibration. You can bolt the header onto a compatible vehicle without needing a tune solely because the header was installed.

A custom calibration may still be beneficial as part of a larger performance build, especially when combining the header with additional airflow, boost, fueling, or exhaust modifications, but a tune is not required for the header itself.

Turbo Support Matters

One detail that is easy to overlook on the FA20 platform is the amount of weight supported by the exhaust manifold. The turbocharger and J-pipe place considerable stress on the header, and eliminating the factory support can increase the load placed on the tubing and welds.

GrimmSpeed includes its adjustable J-pipe/turbo support bracket with the header so the turbo system remains properly supported after installation. This is an important durability feature that many aftermarket header setups overlook.

Fitment

• 2015-2021 Subaru WRX
• 2014-2018 Subaru Forester XT

50-State Legal

GrimmSpeed currently lists its 2015-2021 WRX Equal Length Header as approved for legal use in all 50 states, giving street-driven WRX owners an emissions-compliant option for upgrading the factory exhaust manifold.

What's Included

• (1) GrimmSpeed Equal Length Header
• J-pipe/turbo support bracket
• Required installation gaskets
• Required installation hardware

Why Buy Your GrimmSpeed Header From JD Customs USA?

A header is not a part we believe should be purchased based on a picture and a part number alone. Runner design, turbo compatibility, tuning requirements, supporting hardware, and how the header fits into the rest of the build all matter.

JD Customs USA specializes in performance parts for modified vehicles, and our goal is to give you the technical information you need to make the right decision before ordering. We take the time to understand what makes this GrimmSpeed header different from the factory manifold, what is included, how it interacts with the FA20 twin-scroll system, and what you should consider as the rest of your WRX build evolves.

When you purchase your GrimmSpeed Equal Length Header from JD Customs USA, you have a performance-focused shop behind the order. If you have questions about fitment, supporting modifications, installation, or how this header fits into your build, our team is here to help.

Product Details

• Manufacturer: GrimmSpeed
• Part Number: GRM113008
• Primary Application: 2015-2021 Subaru WRX
• Engine: FA20DIT
• Header Design: Equal Length
• Material: 304 Stainless Steel
• Tubing: 14 Gauge
• Flange Thickness: 1/2 Inch
• Manufacturing: Made and welded in the USA