The K&N 57-0047 is a 57i-series induction kit for the 1.6L 16V MX-5, designed to replace the factory airbox and filter with a larger cotton-gauze element. The manufacturer designs each 57i kit around the specific vehicle, and the kits take different forms depending on the engine's characteristics and the space available under the hood. This kit uses a red, round-outlet filter that corresponds to K&N part RU-5131.
The main reason to choose this over stock is the reusable filter. Rather than replacing a disposable paper element, you wash and re-oil the cotton-gauze media, and the manufacturer lists a service life of up to 100,000 miles before service is required, depending on driving conditions. K&N also states the kit is designed to improve throttle response and engine sound. The manufacturer's horsepower claim is not backed by a published figure on its spec page, so if you need dyno-verified numbers for this MX-5 setup, request K&N's test data before buying.
Confirm fitment before ordering: the kit is sold under the MX-5 1.6L 16V designation, so check the manufacturer's application guide against your model year and VIN. Note that the kit is not legal for sale or use in California on pollution-controlled vehicles, and it is not legal for sale or use in California on any pollution controlled motor vehicle. Enthusiasts searching for MX-5 1.6L 16V cold air intake, K&N 57-0047 induction kit, or reusable cotton gauze air filter Miata setups will find this kit among the 57i options.
No. The manufacturer states the kit is not legal for sale or use in California on any pollution-controlled motor vehicle, and it is also not legal for highway use in states that have adopted California emission regulations.
The manufacturer says the washable, reusable filter lasts up to 100,000 miles before service is required, though the interval depends on driving conditions.
The manufacturer says the kit is guaranteed to increase horsepower, but a specific gain figure was not confirmed on its spec page, so none is listed here. Ask K&N for its dyno data before buying if you need a number.
