This video looks at the results of laboratory engine air filter test & a magazine test, carried out in Japan by Revspeed magazine.
The testing looked at filtration quality ie how much dirt the engine air filters let through, how well the filters flowed when new, and when exposed to dirt and how much power the filters made.
The first laboratory test looked at engine air filters which all fitted in the factory airbox. It included a range of stock replacement paper filters and two high performance cotton based panel filters.
The test by the Japanese magazine looked at performance cone filters from K&N, HKS, Sard and Apexi.