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Part:   21-685C

AEM 21-685C Cold Air Intake

AEM Cold Air Intake System
Rating Star 1 Rating Star 2 Rating Star 3 Rating Star 4 Rating Star 5   4.0
 
  • Increased horsepower
  • Tuned and dyno-tested to improve acceleration and engine sound
  • Low restriction aluminum tubing
  • 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 21-685C fits some Honda Civic Si models. See vehicle applications for details.
The AEM 21-685C 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 Honda Civic SI and Acura ILX 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 relocated to the driver-side wheel well which is designed to reduce intake air temperature and increase horsepower. The intake tubing is constructed from mandrel-bent aluminum featuring a durable gunmetal gray powder coated finish. This air intake system was developed to accommodate the engine’s factory emissions control devices including the mass air flow sensor, a couple replacement silicone breather hoses as well as a replacement radiator hose. The tapered 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 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 21-685C vehicle applications to determine the legal status for each vehicle.

[More Information on AEM Cold Air Intake Systems]
Specifications AEM 21-685C Product Specifications
Estimated Horsepower Gain6.27 HP @ 5100 RPM
Air Filter ColorRed
Air Filter Height5.125 in (130 mm)
Air Filter Large End Diameter6 in (152 mm)
Air Filter MaterialNon-woven Synthetic
Air Filter Outlet ShapeRound
CARB EO NumberD-670-21
Clamp MaterialStainless Steel
Clamp StyleMini
Clamps Included11
Intake Pipe Color / FinishGunmetal Gray
Intake Pipe MaterialAluminum
Product Box Height12.25 in (311 mm)
Product Box Length20.25 in (514 mm)
Product Box Width12.25 in (311 mm)
Product StyleAEM Cold Air Intake System
Replacement Filter21-203DK
Street Legal In All US StatesYes
TUV Approved (Europe)No
Weight8.2 lb (3.7 kg)

Horsepower gains based on similar vehicle dynamometer test. Results will vary.
Reviews Product Reviews

Jaime Lopez from Los Angeles, California
May 4, 2015 - Part 21-685C
I have a 2009 Honda Civic Si. Installation was a bit complicated but it was done. Performance wise, the vehicle runs amazingly. Would do business again.