GrimmSpeed Cold Air Intake Subaru WRX STI (15-21) Black or Red StealthBox

Fitment Information

• Subaru WRX STI (2015, 2016, 2017, 2018, 2019, 2020, 2021)

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!

Specs & Features

• +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 the accuracy of readings
• Made in the USA - Manufactured right here in Minnesota
• Hybrid Cold Air/Short Ram Design - Combining the advantages and eliminating the negatives of both traditional intake designs
• Air straightener - Dimensionally mimics the factory configuration for accurate MAF sensor readings
• MAF sensor location - Inside heat shield, isolated from engine bay heat
• Custom reusable high flow air filter - Integrated velocity stack entrance smooths incoming air
• StealthBox Heat Shield - Sleek, unique design looks KILLER in your engine bay and keeps the heat of the engine bay from affecting performance
• 30min Installation - Extremely simple with our written and video guides

Includes everything

• 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

Product Description

Inspiration for the StealthBox Intake came from internal discussions about what we wanted from an intake system for the 2015+ WRX/STI. 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/STI 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.

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/STI. 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/STI, tuning is required after installation to maximize gains and safety.