Grimmspeed Unequal Header 2002-2014 WRX/2004-2021 STI

While other aftermarket unequal length headers use different runner lengths for each cylinder, our proprietary design utilizes an innovative setup where each bank of runners are equal length, but one set is 1.5 time the length of the other, providing the rumble sound that we all love while maintaining the performance of an equal length setup. Grimmspeed utilized a single piece, mandrel bent runners to minimize disturbances to the exhaust gas along with an extremely durable cast 304 stainless steel collector to achieve keep each back of runners truly equal length which would be difficult to accomplish with a 4-into-1 welded collector. The low angle merge this collector makes for faster spool and unbeatable off-boost throttle response. To match this flow, the collector features machined internal diameters to perfectly match the 1 ¾” primary runners and 2” secondary pipe, eliminating unwanted “steps” in the exhaust flow.

Grimmspeed’s Unequal Length Header features ½ inch flanges for both the heads as well as the up-pipe side. These combined with the 14 gauge runner pipes make for extreme durability and heat retention.

The GrimmSpeed Header out spooled the competition’s equal length header by 50rpm while making similar boost levels. Their header produces more torque than the equal length manifold right out of the gate, producing about 15ftlbs more throughout spool up. At peak, the GrimmSpeed Header was able to produce and extra 2 ft/lbs of torque and an additional 21 hp compared to the equal length setup.

QUICK SPECS:

• Innovative 1.5 to 1 Unequal Length Runners – Each bank of runners is equal length, allowing for equal length performance with an unequal length sound
• 4-into-1 Low-Angle Merge Cast Collector – Ensure minimal restriction and maximum performance
• Smooth, Restriction-Free Flow Throughout – Single piece mandrel bent tubing welded to a single piece merge collector removes unwanted “steps”
• Substantial Power/Torque Gains – +25hp and +25ft/lbs of torque over stock
• Quickest Spooling Aftermarket Header – Faster spool and more power compared to the competition
• No Tune Required – Safe to run, just bolt on
• Gaskets and Hardware Included – Everything you need to get installed and on the road
• Designed To Fit With Aftermarket Oil Pans – Fits with the STI oil pan or popular aftermarket options
• Full 304 Stainless Steel Construction – 1/2″ flanges and 14ga runners for extreme durability
• Manufactured and Welded In The USA – For consistency and top quality control

Fitment Notes:

• 2002-05 Subaru WRX & 04-08 Forester XT Requires STI Oil Cooler and STI Oil Pan
• 2006-07 WRX Requires STI Oil Cooler

The Grimmspeed Header and fits all 2002-2014 WRX and 2004-2021 STI.