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Part:   21-478WR

AEM 21-478WR Cold Air Intake

AEM Cold Air Intake System
Rating Star 1 Rating Star 2 Rating Star 3 Rating Star 4 Rating Star 5   4.9
  • Increased horsepower
  • Tuned and dyno-tested to improve acceleration and engine sound
  • Low restriction aluminum tubing
  • Easy to install using commonly available tools
  • Air filter lasts up to 100,000 miles before cleaning is required (depending on driving conditions)
  • Washable and reusable oil-free filter media
  • AEM Lifetime Limited Warranty

The AEM 21-478WR fits some Subaru Impreza WRX, Subaru Impreza WRX STi, Subaru WRX, and Subaru WRX STI models. See vehicle applications for details.
The AEM 21-478WR Performance Cold Air Intake System produces horsepower and torque gains by replacing your vehicle’s restrictive factory air filter and air intake housing. This air intake system was designed, tuned and dyno-tested to fit specific Subaru WRX, WRX STI, Impreza WRX and Impreza WRX STI models. Air enters the system through an oversized AEM Dryflow synthetic washable air filter for outstanding air flow, filtration and performance. The air filter is located in the original air box space and is protected by a heat shield which is designed to reduce intake air temperature and increase horsepower. The intake tubing is constructed from mandrel-bent aluminum featuring a durable textured red powder coated finish. This air intake system was developed to accommodate the engine’s factory emissions control devices including the mass air flow sensor. The cylinder shaped AEM Dryflow air filter is made from an oil-free, synthetic filter media that can be used for up to 100,000 miles before cleaning is needed (depending on driving conditions). The air intake system is easy to install with commonly available tools and it is backed by AEM's Lifetime Limited Warranty. Some AEM air intakes are not legal for sale or use in California and other states adopting California emission standards while others are 50 state legal. View the 21-478WR vehicle applications to determine the legal status for each vehicle.

[More Information on AEM Cold Air Intake Systems]
Specifications AEM 21-478WR Product Specifications
Estimated Horsepower Gain36 HP @ 5300 RPM
Replacement Filter21-2029DK
Air Filter ColorRed
Air Filter MaterialNon-woven Synthetic
Air Filter Outlet ShapeRound
Clamps Included3
Clamp MaterialSteel
Clamp StyleRegular
Couplers IncludedNone
Product StyleAEM Cold Air Intake System
Air Filter Height9.125 in (232 mm)
Intake Pipe Color / FinishWrinkle Red
Intake Pipe MaterialAluminum
CARB EO NumberD-670-21
Street Legal In All US StatesYes
TUV Approved (Europe)No
Weight7.4 lb (3.3 kg)
Air Filter Large End Diameter6 in (152 mm)
Product Box Height12.25 in (311 mm)
Product Box Length20.25 in (514 mm)
Product Box Width12.25 in (311 mm)
Mounting Hardware IncludedYes
WarrantyLimited Lifetime

Horsepower gains based on similar vehicle dynamometer test. Results will vary.
WARNING: Cancer and reproductive
Reviews Product Reviews

Matt B. from Maryland
December 19, 2018 - Part 21-478WR
This review is more so towards the excellent customer service at AEM. Last year I purchased this intake for my STi along with several other performance parts and was waiting about a week before my pro tune to install everything and use a base map to get me to the shop. Upon opening the package to install the intake I noticed that the bag with all of the installation attachments was missing. In a panic because it was on a Friday and I was leaving Monday morning to get tuned I called AEM. I wish I could remember the guys name I spoke with, but he went above and beyond. With very little questions asked he had an installation kit overnighted to me so that I complete the install with no cost to me. I have used aem products in the past on different vehicles, but after my one run in their customer support, I’m die hard fan of them and their products, in fact I have used a few other of their products on my build along the way and have plans on buying their gauges soon too. Best customer service I have ever received. Keep up the great work! Oh and the intake is excellent as well. So good, that my tuner recommended it, which is why I bought it Do not hesitate to buy anything from this company. You will not be disappointed.
Sebastian Cianciolo from Ellicott City, Maryland
December 10, 2017 - Part 21-478WR
Easy install. I updated the mapping using COBB input and felt performance gain... not sure how much, but smoother performance and easier and faster spool up. Good price and overal nice gain.
Anthony Ruffini from Moravia, New York
October 2, 2016 - Part 21-478WR
I am very satisfied with this system. There is a noticeable improvement in horsepower and throttle response on my 2009 Subaru WRX. I highly recommend this product.