Grimmspeed Equal Length Exhaust Manifold 2015-2021 WRX

Over the years, GrimmSpeed has proven that our exhaust products are some of the highest-quality and best-performing in the industry because of the detail oriented approached that we put into their development. When it comes to improving on an OEM design, this attention to detail and overall exhaust knowledge allows us to identify aspects of the factory parts that can be greatly improved upon. One of the first things to note about the OE exhaust manifold are the several points where flow is decreased due to a neckdown in piping diameter. These disruptions in exhaust flow result in decreased turbine efficiency which ultimately limits boost and power production. Furthermore, the OE merge collectors are made specifically with ease of manufacturing in mind and the result is a compromise on performance. The collectors contain very odd shapes that are bad for smooth exhaust flow and have several diameter restrictions that make them one of the biggest weaknesses of the stock manifold. Finally, the angle of the exhaust flow merge is also not ideal, causing the exhaust pulses to “fight” each other, which can add to flow differences for the twin scroll turbine, sacrificing spool and performance.

After isolating the inadequacies of the OEM exhaust manifold, we were able to start identifying key areas of improvement: correctly sized and consistent exhaust runners that are more equal length, a consistent and non-bottlenecking merge collector inlet and outlet and a higher angle merge collector to direct flow into the turbine and prevent opposing flow disruptions. Beyond that, we decided on using thicker tubing and flanges for increased durability and longevity to more-effectively support the overhanging turbocharger. All four of our exhaust runners are designed in conjunction with the merge collector to equal out the lengths as well as the overall bend angles. This is especially important in the FA WRX twin scroll turbine configuration because it makes the strength of each pulse, or “push” on the turbine wheel, at equal timing and consistency.

QUICK NOTES:

• Full 304 Stainless Steel Construction – Flanges, tubing, collector and badge
• True Equal Length Runners – CNC bent and trimmed, less than 1% variance from the longest to the shortest
• Innovative Cast Merge Collector – Low restriction inlet and outlet, smooth flow and consistent performance
• Smooth, Restriction-Free Flow Throughout – Single piece mandrel bent tubing welded to a single piece merge collector removes unwanted “steps”
• Thick 1/2in CNC Cut Flanges and 14ga Tubing – Added durability and longevity
• No Tune Required – Safe to run, just bolt on
• No Ground Clearance Loss – Clears factory skid plate without using spacers
• J-Pipe/Turbo Bracket Included – Retain the support that other aftermarket header lose
• Gaskets and Hardware Included – Everything you need to get installed and on the road
• Manufactured and Welded In The USA – For consistency and top quality control

FITMENT:

• 2015-21 Subaru WRX

• 2014-18 Subaru Forester XT