2022+ WRX Header Upgrade - Is it Necessary?
There have long been debates on forums about turbo headers on Subarus. Equal vs Unequal Length, runner size, runner length, collector merge angles, materials, the list goes on and if you ask 5 people for recommendations, you will likely get 5 different answers. Our engineers here at GrimmSpeed have spent the better part of the last 10 years testing and optimizing header designs that are the PERFECT blend of innovation, performance, and aesthetics.
Our Unequal Length header for the Subaru EJ20/25 engines has been a crowd favorite since it was released a couple of years ago. That header represents a perfect example of innovating in a market that has been saturated with the dichotomy of perfectly equal length headers and wildly unequal length models for decades. We tested out the most popular examples of both and found a midground where you still get a breath-taking rumble at idle and cruising but performs more like an equal length when you are on the pipes and have the engine loaded up.
In contrast to the multitude of options available for the EJ model engines found in the STI and earlier WRX models, the Subaru FA series of engines have a completely different configuration for the turbocharger system, including a factory twin-scroll turbine housing, which is able to spool much more efficiently than the older “STI-Style” turbos. This twin scroll setup does limit options when it comes to headers though. From the factory, the 2015 and up WRXs (as well as the 2014-18 Forester XT and other newer models with the FA24DIT) come with an equal length header and swapping that out for an unequal length unit does bring back the classic Subaru rumble, but nets significant losses in turbo spool and overall engine performance.
In order to fully take advantage of the benefits of a twin scroll turbocharger, the runners must all be exactly the same length to balance out the exhaust pulses coming from the opposing heads. That knowledge was the basis for our design of the ALL NEW Grimmspeed Equal Length Header for the Subaru FA24.
The Proof is in the Pudding
As we do with all of our products, we needed to prove our theory. We sent a prototype of our new Equal Length Header for the Subaru FA24 over to our friends at Six Star Motorsports in Pittsburgh, Pennsylvania for them to do some back-to-back tests on their Mustang dyno comparing the GrimmSpeed Header to the factory unit from Subaru. They ran a few tests for us on their 6-speed manual 2022 WRX with the stock tune, the Cobb Stage 1 OTS tune, and a custom pro tune from JRTuned. They did 3 pulls with each configuration and the graphs below are the average of that data.
Disclaimer: The data shown below represents the figures that we were able to achieve during our time on the dyno. The power figures you see may not carry over perfectly to all vehicles depending on various factors ranging from elevation and temperature and also tuning limitations of the CVT vs the manual transmissions, but they are a good baseline to look at.
On the stock tune, we were astounded to see average torque gains over 15 foot pounds across the entire power band. The biggest difference on the low end with up to a 35 foot pound increase during spool-up before 3000 RPM, so you will definitely feel that jump in how the car pulls coming off of the line. On top of that, because horsepower is a function of torque and RPM, there was a substantial bump in power to the wheels as well. Across the board, we saw an average gain of nearly 11 WHP, with the largest gains coming in the sweet spot of the power-band between 4000 and 5500 RPM.
Loading up an OTS tune on your Accessport is just about the easiest way to add power and performance to your Subaru. With the tune loaded, there is definitely a narrower margin in the performance between the factory header and the GrimmSpeed Equal Length, but there is still a pretty big gain in low end torque with 10-15 ft/lb gains all the way up to peak power at 3400 RPM. One thing to note is that when it comes to peak power and torque figures, the factory header slightly edges out the GrimmSpeed Header, but this is likely down to limits that Cobb has added into the tune to keep the engine safe.
With the protune from JR, we once again could see that the performance was very close throughout the entire rev range, but the GrimmSpeed Header did retain the same advantage early on in the power band where there was a 5-10 ft/lb increase in torque while the turbo is spooling before 3500 RPM. On top of this, the GS Header also managed about 1.6% higher peak torque (6 ft/lbs) over the factory manifold.
Okay, Wrap It Up Already
So to answer the question at hand - is a header upgrade worth it on a 2022+ WRX? I would say absolutely YES! Especially if your WRX is completely stock and you do not wish to get a tune, there a big gains to be had over the factory header. If you are planning to tune your vehicle, either with an off-the-shelf map or a custom protune, the difference is a little more marginal, but if you are looking to squeeze maximum performance out of the factory turbocharger, upgrading is definitely worth it to help mitigate any restrictions.
