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K&N 57S-4000 Performance Air Intake System

57i Series Kits > Performance Air Intake System
Rating Star 1 Rating Star 2 Rating Star 3 Rating Star 4 Rating Star 5   4.9 out of 5 stars   15 Customer Reviews
  • Guaranteed to increase horsepower
  • Designed to improve torque and acceleration
  • Replaces entire factory air box and air filter system
  • Washable and reusable lifetime air filter
  • Easy to install, usually in 90 minutes or less
  • Lasts up to 100,000 miles before service is required (depending on driving conditions)
  • K&N Million Mile Limited Warranty
The K&N 57S-4000 Performance Air Intake System fits some Ford C-Max, Ford C-Max II, Ford Focus, Ford Focus II, Ford Focus III, Ford Focus RS, Ford Focus ST, Ford Focus XR5, Ford Grand C-Max, Ford Kuga, Ford Kuga II, Ford Tourneo Connect, Ford Transit Connect, Mazda 3, Mazda 5, Volvo C30, Volvo C70 II, Volvo S40 II, Volvo V40 Cross Country, Volvo V40 II, Volvo V50, and Volvo V70 III models. See vehicle applications link for details.
The K&N 57S-4000 Performance Airbox replaces the restrictive factory air filter and air box lid. K&N performance air boxes are designed to dramatically reduce air flow restriction as well as smooth and straighten air flow. This allows your engine to inhale a larger amount of air than the factory air filter assembly. More air means more usable power and acceleration throughout the engine’s RPM range. The 57S-4000 Performance Airbox comes with an oversized conical K&N high-flow air filter and an injection molded air box lid with the K&N logo embossed on top. The air filter can be used for up to 100,000 miles before servicing is needed depending on driving conditions. This performance air box is relatively easy to install into the air box base with commonly available tools. K&N builds these air box systems to last for the life of your vehicle and they are backed by K&N's Million Mile Limited Warranty. Some K&N 57S Series Performance Airboxes are compliant with the latest TUV emissions and sound regulations. Check the K&N catalog or website for vehicle applications and specific TUV status for each vehicle and air intake.

[More Information on K&N 57S Performance Airbox Systems]

Product Specifications

Air Filter ColorRed
Air Filter Height7.688 in (195 mm)
Air Filter MaterialCotton Gauze
Air Filter Outlet ShapeRound
California RestrictedNot legal for sale or use in California
Clamp MaterialStainless Steel
Clamp StyleRegular
Clamps IncludedNo Clamps Included
Product Box Height11.81 in (300 mm)
Product Box Length15.34 in (390 mm)
Product Box Width11.81 in (300 mm)
Product Style57i Series International Kits
Replacement FilterE-9289
Street Legal In All US States No
TUV Approved (Europe)See Application Link Above
TUV Certificate NumberTU-025979-C0-206
TypeGen I
Weight4.2 lb (1.9 kg)

K&N 57S-4000 Performance Air Intake System Product Reviews

Monday, April 17, 2017 - Part 57S-4000
Sounds great and gives your car the Extra HP.

Juan Aguilar
Tucson, Arizona
Monday, March 20, 2017 - Part 57S-4000
This is my second time ordering from K&N and the second time that the service has been fantastic. Ordered Sunday and arrived Tuesday. As for the part itself, it's clearly well made. Much better standard than the Ford original. I bought this for my Focus ST TDCi, which I have a bluefin on and this just completes the package. The turbo seems to spool quicker and is able to reach higher pressure (seen through OBD readout), plus there's a great induction sound that boarders on chavy but i like it and I blast Killswitch... I think this is a great mod if you're just starting on your ST voyage as I am... Now just to cut down the mileage so I can get an RS... Thanks K&N

Daniel Clark
Mansfield, United Kingdom
Friday, November 11, 2016 - Part 57S-4000
I am very pleased with the Air Filter kit, and it was very easy to fit as the instructions where very clear. I have not yet gotten around to measuring the improvement, but I will eventually.

Ian Crowe
Sunderland, United Kingdom
Tuesday, August 16, 2016 - Part 57S-4000
The best purchase I have ever made, car feels, sounds and drives better. Had so many compliments on the car. It feels like a new vehicle with just this new kit. Great purchase and would recommend to all. Easy to install. Looks great!

Casey Raw
Exeter, United Kingdom
Wednesday, August 10, 2016 - Part 57S-4000
1s class service. Easy to install and sounds great.

Lee Brown
Sunderland, United Kingdom
Monday, July 25, 2016 - Part 57S-4000
2013 Focus ST I had watched numerous videos of lots of different applications from basic filters to full CAIS, so I knew what I was getting.The filter itself is top notch and the box lid does make noticeable improvement over stock, although patience is required when fitting as it is quite rigid. With this kit, I found personally that throttle response is improved and the performance sound is great, you actually get to hear the recirc valve now. I can't say that there is any difference in outright performance as I can't notice but over long runs the engine temp is cooler and takes less time to cool. I would recommend this kit 100% to anyone thinking of replacing stock.

Falkirk, United Kingdom
Saturday, June 18, 2016 - Part 57S-4000
Excellent product. Made a difference straight away - great sound and performance. Working well in my C-MAX

Aberdeen, United Kingdom