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2X The Air Restriction: Airbox Has Two Air Filters?
Hi, I recently took a peek in the airbox of my 2006 525i to look at the disposable paper air filter resting on the bottom when I noticed what appears to be a 2nd air filter that is attached to the top of the airbox (under the lid of the airbox). It doesn't seem to be removable and even has "do not remove" stamped on it.
Does anyone know what this mysterious thing really is? Is this extra layer of air restriction really necessary? I would like to remove it to help improve air flow (and possibly HP/torque). Has anyone tried removing it in the past and noticed any improvement in engine performance? Thanks!
| | Reply » 2X The Air Restriction: Airbox Has Two Air Filters? |
It's a hydrocarbon trap. The trap adsorbs hydrocarbons that are emitted when the engine is stopped. Once the car is started and driven, the trap releases the hydrocarbons into the engine where they are burned.
http://www.engelhard.com/Lang1/xDocI...up1/SubSiteID0
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2X The Air Restriction: Airbox Has Two Air Filters?