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- Full 304 Stainless Steel Construction
- 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 headers lose
- Gaskets and Hardware Included – Everything you need to install and hit the road
- Manufactured and Welded In The USA – For consistency and top quality control
Grimmspeed Equal Length Header 15-21 WRX Overview
Grimmspeed Equal Length Header 15-21 WRX Dyno
The GrimmSpeed Equal Length Exhaust Header is designed to free up exhaust gas flow to improve the performance of the FA20 motor.
Its equal length structure ensures the efficiency of the exhaust gas flow, resulting in faster overall spooling of the turbocharger. Constructed from stainless steel and polished to a brilliant finish, this exhaust manifold will make a great addition to your power aggressive 2015-2021 Subaru WRX.
Improve your turbocharger response time while also increasing horsepower and torque, AND saving weight all at the same time with the all new GrimmSpeed Equal Length Exhaust Header! The equal-length layout will produce an aggressive, race-inspired exhaust tone throughout the entire RPM range, and makes for an excellent bolt-on modification. This header will work with the factory turbocharger or factory-like aftermarket turbochargers.
Spec Info From GrimmSpeed
Over the years, GrimmSpeed has proven that their exhaust products are some of the highest-quality and best-performing in the industry because of the detail-oriented approach 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 is 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 manufacture 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.
Grimmspeed Equal Length Header 15-21 WRX Install
Performance Gains You Need
All four of their 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.
Since the exhaust runners are CNC bent and trimmed as a single piece there are no additional welds to introduce points of failure or junctions that would interrupt flow, resulting an in impressive difference of less than 1% in total length. In addition, maximum variance is only 5 degrees from the most bent to the least bent runner, this mean we were able to produce what is a truly equal length, and equal bend manifold. The collector being cast, allows for the runner spacing and angles necessary to obtain the equal bends and lengths of all the tubes. This part is a major player in the GrimmSpeed manifold’s ability to fit between the stock skid plate and the oil pan while still providing the ideal performance from the rest of the design. The cast collector also allows for more smooth and consistent flow in the interior compared to a welded variant. This greatly simplifies the overall design, removing five more welded junctions, which could be a point for flow interruption or structural failure that we see with other headers.
The head flanges of their header are CNC-cut and faced from a 1/2in thick piece of 304 stainless steel. This design is much thicker than OEM to increase reliability and longevity, as well as to provide additional material to be removed after welding to ensure flatness from flange to flange. This additional measure allows for greater gasket sealing which results in increased performance. The final touch is that the exhaust runners are welded inside the flange as well as outside, this is an extra step in manufacturing, but it provides a rounded lip to improve flow from the flange through the runner.
All of these things come together to make The GrimmSpeed 15-21 WRX Header not only the prettiest on the market, but at the top when it comes to performance and durability.
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