Originally posted by Phazer
Nice reply thanks. What about putting a cone filter in but building a cover around it, so it's more or less in it's own "airbox" instead of putting it down by your foglight. That means bigger air intake aswell as cold air, right? So it should be good for town and highway driving. Anyone using BMC or K&N cone filter's? I have read now on a couple of places that engines with them on don't last so long, cause more dirt goes through them, than your normal BMW paper filter.
Cone filter setup that Gizmo is using.
A properly designed heat shield would help to sheild the engine's hot air from being sucked into the motor. However, it still isn't as efficient as a real "CAI" which is placed behind the brake duct or foglight. This is the best most efficient option. However, each option has it's own pros and cons.
I'm using a K&N cone filter w/ my own custom heat shield. If you're worried about damaging your motor then just use the stock paper filters with the "fogged" airbox. K&N says that the dirt particles that the filter does not filter just burns up in the motor anyways.
I've used the K&N flat panel filter in the stock airbox as well as a K&N cone filter with heat sheild. On cooler days the cone filter definitely shows more significant gains. On warmer days, with the cone filter, the car would bog and feel like there's no torque. The whole purpose of using the cone filter is that your car should always be moving, and quite fast I might add. That's why cone filter setups are often referred to as "racing filters". When your racing on the track, the car is constantly in motion (hopefully), so there is a constant supply of air being fed into the engine bay. The airbox works better for city driving and traffic jamming conditions. The cone filter works better for higher speed highway driving, reguardless of whether or not you have a heat shield. You can't beat the factory airbox design even if you paid someone $300 to design one for you.
Gizmo has a proper heatshield setup. You want to leave room around the filter, so if you make a heat shield or air box, try not to make it too tight fit.