GrimmSpeed Equal Length Exhaust Header Subaru WRX 2015+

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.

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 the structural failure that we see with other headers.

Features:

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 1/2 in 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:

Subaru WRX 2015-2021

Other Part Numbers:

GrimmSpeed #grm113008