GrimmSpeed Unequal Length EJ Series Exhaust Manifold 2008-2014 WRX / 2004-2021 STI
The OEM unequal EJ exhaust manifold really hasn’t changed much in the past 20+ years and it shows. The tight geometry and long cross-pipe between the two collectors are not optimized for flow or power, although it does give Subarus their signature sound. While the smaller diameter and volume may be good for low-end spool, the factory manifold gets choked out higher in the rev range. Simultaneously, it's known that swapping to a more-equal length header with larger diameter runners offers additional performance potential. Grimmspeed set out to create a header that would be the best of both worlds, offering great performance and the unmistakable rumble that Subarus are known for!
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. One set is 1.5 times the length of the other, providing the rumble sound that we all love, while maintaining the performance of an equal length setup. Grimmspeed utilized single piece, mandrel bent runners to minimize disturbances to the exhaust gas along with an extremely durable cast 304 stainless steel collector to keep each bank of runners truly equal length, something very difficult to accomplish with a 4-into-1 welded collector. The low angle merge of 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.
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 - Ensures 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 for installation to get 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 14 gauge runners for extreme durability
- Manufactured and Welded In The USA – For consistency and top quality control
FITMENT:
- 04-21 Subaru STI
- 08-14 Subaru WRX
- 09-13 Subaru Forester XT*
- 05-09 Subaru Legacy GT*
- 05-09 Subaru Outback XT*
- 02-05 Subaru WRX 5MT (Requires STI Oil Pan and Pickup)
- 06-07 Subaru WRX (Requires STI Oil Cooler)
- 04-08 Subaru Forester XT* (Requires STI Oil Pan, Pickup, and Oil Cooler)
- 04-06 Subaru Baja XT* (Requires STI Oil Pan, Pickup, and Oil Cooler)
*Unconfirmed, may require further modification