The K&N E-0664 is a round, cylindrical replacement filter for the 4.0-liter twin-turbo V8 in the Audi RS6 and RS7. It has a large surface area and uses K&N's oiled-cotton gauze filter media. Wire mesh screens on each side of that gauze support both airflow and particle capture. The part is reusable and engineered to last for the entire lifespan of your vehicle. Compared with a disposable paper element, you avoid repeat purchases, and the manufacturer says the design is meant to improve airflow and capture contaminants. Owners on user forums are less certain about real gains. One reported no noticeable difference, perhaps a bit more air noise when you open it up, while another noted the throttle response being slightly sharper at lower revs. Expect a modest change, not a dyno-sheet jump.
Fitment is listed by the manufacturer as AUDI RS6/7 V8-4.0L F/I, 2013-2017, and the OEM cross-reference is Audi 4G0133843L. Because it is a drop-in element, it installs into the stock intake system rather than requiring a full intake kit. Search terms buyers often use include "K&N E-0664 RS6 RS7 drop-in air filter," "C7 RS6 4.0 TFSI reusable cotton gauze filter," and "RS7 4.0T washable intake filter." The manufacturer's general guidance for its intake systems says to follow the installation instructions and use the provided hardware, since failure to do so may damage the intake tube, throttle body and engine.
The manufacturer lists the E-0664 for the Audi RS6/RS7 V8-4.0L F/I for 2013 through 2017. Published model-year coverage varies, so confirm your vehicle's year and VIN with the manufacturer before ordering.
The manufacturer describes the filter as washable and reusable. Follow the manufacturer's cleaning and re-oiling instructions for the element, since the oil layer is what captures dirt.
The manufacturer states the filter is designed to provide an increase in horsepower but does not publish a figure for this vehicle. Owners on user forums report mixed results, with some noticing little change beyond extra intake sound.
Installation is a filter swap inside the factory intake, so a home mechanic with basic tools can handle it. The manufacturer's instruction sheets for other K&N intake systems start by turning off the ignition and disconnecting the negative battery cable, which erases pre-programmed electronic memories. Some radios may also require an anti-theft code to be entered after the battery is reconnected. Those same sheets involve removing the engine cover, loosening hose clamps at the airbox and throttle body, and reusing the factory hardware. Keep the factory intake components on hand, because the manufacturer recommends that customers do not discard factory air intake. After reassembly, check that all clamps are tight and that the intake connections are sealed before starting the engine.
