a1exander said:
I wonder why the manufacturers do not fit them as standard equipment.
NVH ratings (Noise, Vibration and Harshness) as well as reliability concerns.
First off, cone filters have a loud induction roar - heck, even drop-in panel performance filters will make the induction noise a bit louder - while it's not a concern on a supercar, it is on your average mid-range family sedan, where cars are evaluated and praised for being as quiet and inobtrusive as possible. The same principle applies when putting restrictor plates / smaller diameter "trumpets" onto airboxes, to keep the intake noise down, as well as why average cars don't come with freeflow exhaust systems from the factory. They know it strangles the power potential from the engine, but it's a sacrifice that needs to be made for the sake of NVH levels and emissions control.
As for reliability, if you miss a paper air filter service for whatever reason, the dirty filter will impede performance, but the thick paper substrate won't let through dirt. Compare this with an oiled cone / performance pad filter, where if you miss a cleaning interval, oil in the filter dries out & gets absorbed by the dust caught in the filter, and you risk particles pushing through - hence, aftermarket oiled cotton performance filters have regular cleaning cycles recommended on the box and cleaning kits - as little as 5000 km in very dusty conditions.