Re: horn inside intake box... (archive)

: there is a small rectangular horn funneling air into the intake located inside the air cleaner on my 90 325is. is this necessary, and does it give better fuel economy, thermal transfer, or power? it must do something or they would not have put it in there...
: is it just to deaden noise? has anyone removed it and noticed any differences? how much do you think increased air velocity helps? perhaps only at higher rpms?
: thanks for any info.
: --brandon
: -85 535i
: -79 320i
: -90 325is

Buddy,

That horn is there for a reason. BMW rarely puts non-functional ancillary components for cosmetic appeal. Removing it will;

a) Allow heavier foreign paricles to enter the intake system *choke*

b) Cause excess unmetered air to create an intake leak, affecting overall performance & mileage

c) Render the Motronic ECS ineffective by running
the motor in "open-loop" mode, due to intake leak

d) Give your car a nasty, throaty sound that may
warrant being pulled-over. Not tomention failing smog and emissions tests

I'd suggest you leave it, and replace the OEM filter element with the K&N reuseable one. Performance improves by 1-2hp.

Or better yet - get the MSDS cold air system, that is volumetrically designed to operate with the OEM Motronic value mappings. End result; that
E30 M3-like throaty sound and 5-6hp.

Hope this helps...

Zach

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