GrimmSpeed Equal Length Exhaust Header | 2015-2021 Subaru WRX FA20DIT | GRM113008
GrimmSpeed Equal Length Exhaust Header – 2015–2021 Subaru WRX | FA20DIT | GRM113008
⚠️ CRITICAL FITMENT — This header fits the 2015–2021 Subaru WRX with the FA20DIT engine ONLY. It does NOT fit the Subaru WRX STI (EJ257 engine). The WRX and STI use completely different engines and headers are not interchangeable. Confirm your model is the WRX (not STI) before ordering.
⚠️ ECU TUNE STRONGLY RECOMMENDED — An equal length header significantly changes exhaust flow and scavenging characteristics. A professional ECU tune or reflash after installation is strongly recommended to maximise power gains and ensure proper fuelling. Running without a tune is possible but leaves power on the table and may cause minor running irregularities.
GrimmSpeed’s equal length exhaust header for the 2015–2021 Subaru WRX (VA chassis, FA20DIT). Replaces the factory unequal length exhaust manifold with an equal length design — improving turbo spool, exhaust scavenging, and peak power. Stainless steel construction, TIG-welded. 16 lbs.
Equal Length vs. Unequal Length — Why It Matters
The stock WRX exhaust manifold is unequal length — the four primary tubes that feed the turbocharger inlet are different lengths, a result of the horizontally-opposed (boxer) engine layout. Unequal length primaries create exhaust pulse timing differences at the turbo inlet, causing pulse interference that reduces scavenging efficiency and contributes to turbo lag. The unequal length design is also responsible for Subaru’s characteristic “burble” exhaust note — a byproduct of the pulse timing, not a designed feature.
An equal length header makes all four primary tubes the same length, ensuring exhaust pulses arrive at the turbo collector in a consistent, timed sequence. Benefits:
- Reduced Turbo Lag: Consistent pulse timing improves turbo spool efficiency — boost builds faster in the mid-RPM range
- Improved Exhaust Scavenging: Equal-length primaries allow exhaust pulses to assist in drawing spent gases from the cylinders — improving volumetric efficiency
- Increased Peak Power: Better flow and scavenging throughout the RPM range supports higher peak power output, particularly with supporting modifications (intake, tune, intercooler)
- Loss of Subaru “Burble”: The characteristic Subaru unequal-length exhaust note is a result of the stock manifold design. An equal length header will produce a smoother, more conventional turbocharged exhaust note. This is an expected and normal outcome, not a defect
GrimmSpeed Construction
- Stainless Steel: Primary tubes and collector fabricated from stainless steel for corrosion resistance and heat cycling durability
- TIG-Welded: All joints hand TIG-welded for clean, strong, leak-free construction
- O2 Sensor Bungs: Factory O2 sensor bung positions retained for compatibility with the factory ECU oxygen sensor inputs
Emissions Note
A performance exhaust header replacing the factory manifold may not be legal for road use in all jurisdictions. Check local emissions regulations before purchasing and installing this product.
Fitment
- 2015–2021 Subaru WRX — VA chassis — FA20DIT engine
- Does NOT fit WRX STI (EJ257)
- Does NOT fit 2022+ WRX (VB chassis)
WRX only — does not fit WRX STI or 2022+ WRX VB. ECU tune strongly recommended after installation. Check local emissions regulations before purchasing. Professional installation recommended — header installation requires working around the turbocharger and requires proper torque on all fasteners and gaskets. Inspect for exhaust leaks after installation and after first heat cycle. Allow the header to heat cycle before final torque inspection.
Specifications
- Brand: GrimmSpeed
- Part Number: GRM113008
- Type: Equal length exhaust header
- Material: Stainless steel
- Construction: TIG-welded
- O2 Sensors: Factory bung positions retained
- Weight: 16 lbs
- Application: 2015–2021 Subaru WRX VA — FA20DIT