2015 and 2016 Subaru WRX STi 2.5L H4 Turbo with AEM Cold Air Intake Delivers Huge Power Increase

AEM CAI 21-735WR replaces the restrictive factory air filter box and places the AEM Dryflow Air Filter outside of the engine bay to help bring cool, dense, air into the engine
AEM CAI 21-735WR replaces the restrictive factory air filter box and places the AEM Dryflow Air Filter outside of the engine bay to help bring cool, dense, air into the engine

Subaru has given its flagship model, the WRX STi, a near complete redesign for the 2015 and 2016 model year. The 2015 and 2016 Subaru WRX STi, can’t be called all new because one thing hasn’t changed, namely the EJ257 intercooled and turbocharged 2.5L H4 boxer engine. Some critics are disappointed that the base model WRX would receive the cutting edge 2.0L FA20DIT engine, while the 2015 and 2016 WRX STi would carry over the same engine from the 2014 model year.

AEM cold air intake, number 21-735WR, for the 2015 and 2016 Subaru WRX STi with an EJ257 engine is powdercoated in a wrinkle-red finish to complement original equipment components
AEM cold air intake, number 21-735WR, for the 2015 and 2016 Subaru WRX STi with an EJ257 engine is powdercoated in a wrinkle-red finish to complement original equipment components

For those critics Masuo Takatsu, program manager for both the base WRX and upgraded WRX STi, had this to say “I felt the STI’s weaker area was the handling side. If we didn’t have the chassis, why add more power to overwhelm it? Also, this EJ engine has proved itself in competition. It’s an engine we confidently bring to the track. The new FA-series in the WRX has not been proven in motorsports. Plus, we knew the aftermarket could supply more power to those STi owners who demanded it.”

Advanced Engine Management (AEM) has done exactly what Masuo Takatsu predicted would be accomplished in the aftermarket with the AEM cold air intake system for the Subaru WRX STi. AEM has a solid reputation for making Subaru WRX intake systems as the AEM cold air intake for the previous generation Subaru WRX STi made impressive power gains. AEM intakes has once again stepped up to the plate with cold air intake (CAI), number 21-735WR, and produced an amazing estimated 32 horsepower maximum increase at the wheels of an otherwise stock 2015 and 2016 Subaru WRX STi. Dyno testing on the 21-735WR cold air intake was performed to back our substantial claims of increased horsepower. AEM dyno tests prove that CAI, number 21-735WR, produced an estimated maximum gain of 32 horsepower @ 5400 RPM and an estimated increased in torque of 31 ft-lbs @ 5400 RPM.

The 2015 and 2016 Subaru WRX STi, shown here in WR Blue Pearl paint, is powered by the EJ257 intercooled and turbocharged engine and equipped with an AEM performance cold air intake
The 2015 Subaru WRX STi, shown here in WR Blue Pearl paint, is powered by the EJ257 intercooled and turbocharged engine and equipped with an AEM performance cold air intake

The AEM cold air intake for the 2015, 2016, and 2017 Subaru WRX STi positions the AEM Dryflow Air Filter in a location near the front of the car to help pull fresh air from outside the engine compartment. Bringing in cooler outside air can result in more power. The AEM synthetic Dryflow air filter is designed for low restriction without compromising engine protection. The 21-735WR 2015, 2016, and 2017 Subaru WRX STi cold air intake Dryflow filter is washable and reusable. An AEM dry filter uses a synthetic filter media and does not require oil allowing for quick, easy cleaning. An application specific powdercoated aluminum heat shield is included in the AEM CAI for the 2015 and 2016 STi to help prevent engine heat from increasing the inlet air temperature. "Excellent air inlet temperature management ensures consistent and reliable power," says product engineer John Concialdi.

A mandrel bent aluminum air intake tube is utilized to direct cool intake air smoothly from the AEM Dryflow filter and into the turbocharger. This aluminum intake tube is protected by a wrinkle-red powdercoat finish to ensure the AEM cold air intake will look just as good as it performs. The wrinkle-red powercoat finish was chosen in order to match original equipment parts visible under the hood of 2015, 2016, and 2017 Subaru WRX STi models. The entire AEM cold air intake, as well as the AEM Dryflow air filter is backed by the AEM limited lifetime warranty.

The 21-735WR cold air intake system is a perfect upgrade for any 2015-2017 Subaru WRX STi enthusiast looking to add more power and better performance to their Mustang or Camaro beating import car. To find all AEM products for your vehicle, use the AEM Product Search link on AEMintakes.com. AEM products are available for purchase online, or to find an AEM dealer use the Where to Buy link on AEMintakes.com.


Estimated Horsepower Gain for AEM 2015 and 2016 Subaru WRX STi Air Intake System

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Dyno Chart - AEM cold air intake 21-735WR was shown to make an estimated 32 more horsepower at 5400 RPM<
Dyno Chart - AEM cold air intake 21-735WR was shown to make an estimated 32 more horsepower at 5400 RPM
  • Estimated Gain - 32 Horsepower @ 5400
  • Protects Your Engine
  • Reusable Dryflow Synthetic Air Filter
  • Excellent Air Filtration
  • Lifetime Limited Warranty