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GrimmSpeed StealthBox Intake - 2015-2017 Subaru WRX

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Have questions about fitment or applications? Contact Us

Product Description

It appears that you’re not the only one with excellent taste in premium automotive components! Unfortunately, BLACK 2015+ WRX INTAKES are temporarily out of stock. They should be available again soon. Please contact customer service via phone (612-379-0000) or email for details!

** INSTALLATION NOTE - Take care to install the air filter onto the intake tube properly. Push the filter onto the tube no more than 1" before tightening the clamp. This will ensure that the velocity stack within the filter is allowed to function properly! **


Inspiration for the StealthBox Intake came from internal discussions about what we wanted from an intake system for the 2015+ WRX. Of course performance is the highest priority, but at GrimmSpeed so much more than that goes into a product. We wanted an intake that purred quietly under normal driving circumstances, but would roar at wide open throttle. We wanted an intake that looked at home in the well-sported 2015+ WRX engine bay instead of a shoebox stuffed into the fender area. From here, the SteathBox was born. We took the concept one step further and referenced the F-117 Nighthawk as inspiration for the stealthy look of the GrimmSpeed heat shield. It should come as no surprise that the performance it packs is equally unique.

Quick Specs

  • +32wtq (14.3%) and +21whp (9.6%)
  • Designed in CAD - Perfect mating with the factory turbo and ram-air scoop
  • Low bend angle aluminum tube - Minimize restriction and maximize performance
  • Shielded MAF sensor placement - Protects MAF from heat, which increases accuracy of readings
  • Made in the USA - Manufactured right here in Minnesota


MAF diameter and placement, total bend angle, filter location, and heat shield design were the primary variables during the design phase. To ensure accurate readings, unaffected by the intense heat of the engine bay, MAF sensor placement absolutely must be within the heat shield. To minimize restriction, it was important to keep the total bend angle in the intake tube as low as possible, but still raise the filter location away from the ground to protect it from the elements. Lastly, testing showed the importance of utilizing the factory ram air scoop to feed the otherwise stagnant air in front of the fender.

Our engineers created a 3D model of the intake system and fender area in order to optimize each of these variables. The result is an intake with a total bend angle of 74 degrees, and a filter that is placed neatly within the fender, such that it offers protection from the elements without being unnecessarily exposed to the heat of the engine bay. Lastly, the shape of the heat shield follows that of the factory air scoop, feeds the filter with fresh air evenly and promotes swirl which prevents pockets of motionless air on the cold side of the shield.

We have made the decision not to sell the intake without the heat shield. It seems that others have done this to hit a lower price point at the cost of performance. We'd prefer that everybody using a GrimmSpeed StealthBox Intake have the best possible experience and the use of the heat shield is critical to the function of the intake system.

Materials and Fabrication

Each intake begins with a CNC bent and laser cut 6061 Aluminum tube. Contrary to popular belief, particularly from those producing composite intakes, we found that the increased thermal mass of using thicker aluminum tubing (1/8” wall thickness) kept the intake from being vulnerable to rapid temperature change. This is called the ‘thermal flywheel effect’ and will keep the rapidly fluctuating temperatures inside your engine bay from affecting intake temps as drastically.

Custom MAF flanges are machined from the same 6061 alloy and are placed on the straight nearest the filter, where we observed the most consistent cross-sectional flow. Mounting brackets are laser cut from 3/16” thick aluminum plate and CNC bent for perfect and repeatable fitment. Finally, heat shields are laser cut, CNC bent and hand assembled before going to powdercoating for a durable wrinkle black finish.


Dyno testing and long-term road testing are where all of this theory meets reality. Knowing that the same application of these design techniques resulted in intakes that performed extremely well on both the BRZ/FR-S and the 08-14 WRX/STI, we were confident in our chosen configuration. Dyno testing and tuning verified the intakes ability to make power and 6mos of road testing through winter/spring in Minnesota confirmed real-world performance.

We chose to use the exact same pull that tested the performance of our J-Pipe/Downpipe as the baseline for our 2015 WRX. This proves that our baseline is not somehow artificially low. We then installed the intake and had the car retuned using the same boost levels and air fuel ratios (AFRs). This is an extremely important part of evaluating an intake system. If the before and after results aren’t showing the same boost levels or AFRs, performance increases can be attributed to tuning rather than to the performance of the intake hardware itself. The chart below shows the before and after just described with both boost and AFR plotted along with whp and wtq. It should be noted that the stock baseline for this car was 174whp, so this particular dyno reads very low.

The GrimmSpeed intake produced an additional 32ftlb (14.3%) at 3000rpm and 21whp (9.6%) at 5500rpm, with healthy gains all the way across both curves. As mentioned before, the AFR and Boost curves are also included to demonstrate that the gains shown are from the intake alone, not the manipulation of other variables.

As with any intake for the 2015+ WRX, tuning is required after installation to maximize gains and safety.

GrimmSpeed Stealthbox Intake Kit Includes

  • 1x CNC bent intake tube w/ MAF flange
  • 1x GrimmSpeed high-flow air filter
  • 1x Aluminum heat shield
  • 1x 12" MAF harness extension
  • 1x Silicon hump coupler
  • 3x Stainless steel worm gear clamp
  • 3x Rubber gasket material cut-to-length
  • 2x MAF sensor machine screws


While only a very small portion of the intake is visible after installation (nearest the turbo), we still decided to offer a color choice for the intake tube. The heat shield will always be our stealthy black wrinkle, but the tube can be either a matching black, or a wrinkle red.


  • 2015-2017 Subaru WRX

** INSTALLATION NOTE - Take care to install the air filter onto the intake tube properly. Push the filter onto the tube no more than 1" before tightening the clamp. This will ensure that the velocity stack within the filter is allowed to function properly! **

Product Videos

GrimmSpeed StealthBox Intake Install - 2015+ Subaru WRX (06:03)
Important Note: When installing the air filter, push the filter onto the intake tube only as far as is shown - 1" from the end of the tube. Pushing it farther on will affect the function of the velocity stack that's built into the filter! Introducing a meticulously designed intake system featuring a low bend angle intake tube, stealthy heat shield, protected MAF sensor and a filter with an integrated velocity stack. The video will guide you through the very easy installation procedure. Please contact us directly with any questions or concerns at 612-379-0000 or sales@grimmspeed.com! For more information or to purchase, please visit www.grimmspeed.com
  • GrimmSpeed Ste...
    Important Note: When installing the air filter, push the filte...

Product Reviews

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Product Reviews

  1. Better than Cobb's!

    Posted by Joneil

    I had the Cobb Big SF intake for a while and it was very inferior to what GrimmSpeed has to offer. The GrimmSpeed air box is a much cleaner setup, hence the "stealthbox" moniker. No fitment issues whatsoever and seems to be louder than Cobb's. Yes you need to get a pro tune with this intake but it would be all worth it in the long run. Don't make the same mistake I did and settled for another brand. Just get this the first time around. Installation was very simple although I did it with ramps to access the bottom (it's much easier than doing it all from above. My car has all sort of GrimmSpeed goodies now: intake, j-pipe, pulley cover, charge pipe, top mount intercooler, and even their Delrin shift knob. Gotta love GrimmSpeed :D

  2. product that im super happy with

    Posted by Nicholas

    Well I ordered my grimmspeed intake for my 2016 wrx, and just like the video shows its a breeze to install and everything fits great no forcing anything and bending was easy. I do notice that while running an off the shelf tune the car was a little more on the laggy side off the line but after a tune it's great. Noise wise it's a little loud WOT but when you have a loud exhaust like we all do it's just another sound to annoy your passangers and make you smile. I would definitely recommend this product hands down. O and you will get the bov sound with this intake

  3. Grimmspeed Intake

    Posted by Ty. G

    I just installed this part on my car and it sounds amazing. Obviously there is going to be an increase in performance once tuned but you can definitely hear it sucking up that air! As for the installation, it is a piece of cake. The fitment is perfect and the fact that it utilizes the oem air duct is pretty cool! The seal that they use is kind of a pain around the turns but still is pretty easy to do. It also comes with a harness extension for the maf Sensor which is great and new bolts for the maf sensor as well which I really liked except that they are alan key bolts ;) No complaints here, I definitely recommend this. The sound is intoxicating.

  4. stage 1 install.

    Posted by justin

    installation was pretty easy in combination with the GS EBCS. Decided to get E-tuned with clark turner tunning using a Cobb AP before installation. Car drives much more smoother with the GS CAI installed and Clark E-tune. Cobb stage 1 stock(no CAI-EBCS) was also a huge improvement. intake gave me a nice loud BOV sound, car seems to have more torque when spooling and really pulls all the way through the entire RPM Range. Great intake.

  5. Excellent.

    Posted by Andrew B.

    Fit and finish on this intake are excellent as is performance. Installation was mostly a breeze. I had some issues with the rubber gasket things that bend around the intake box. Patience won out and everything worked great.

    My tuner really enjoyed working with the intake and seemed impressed with its function.