Quote:
Originally Posted by mc3456
Cosmetic.
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BMW OEM air ducts are "passive," meaning they require a vacuum to pull fresh air from the vents to the filters. If your OEM box is in tack, air scoops won't do much for your car as the vacuum is strong enough to feed the filters fresh air. If you decided to remove your OEM box then upgrade to BMS or other open air intakes, the "passive" air ducts won't feed the filters any fresh air (no vacuum). Adding the scoops with after market intakes like BMS will reduce the chance of heat soak and improve performance.
In order to convert the OEM air ducts from passive to active, air scoops are required (re-direct the incoming air by 90 degrees). See sample below.