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View Full Version : E34 95 540i Air box Mod


mikes95540i
11-20-2008, 10:31 AM
OK guys I have installed a K&N filter in my stock air box. While I had the box out cleaning it I noticed that BMW had put cone shaped piece in the air intake (lower box front). This piece reduced the air intake size by a good 1.5". I removed the cone so now the opening on the intake is the same size as the output and while it sounds really great I believe it has given me a decrease in gas mileage. My train of thought was "mo air - mo better".
Should I assume that the designer of the factory box knew what he was doing and just put the thing back in?

bimmer dot info
11-20-2008, 12:50 PM
They knew what they were doing. There is not much you can do to the factory air box to get it to allow more air in.

That said.. If you like the sound keep it the way it is. I think you will go back to getting your original mileage after you get bored with the new sound.

mikes95540i
11-21-2008, 07:26 AM
Thanks for your input. My question was a little facetious, their is no question they know what they are doing, far more than I ever will. I'm more interested in why it works better.
I am planning to install a chip and high performance ignition coils, after that I will try pulling the cone out again to see what happens.

Rodrick Msuya
11-26-2008, 05:26 AM
Why don***8217;t you take a pic of your new K&N filter showing all the mods that you have done on the air intake system. I would like to see this; maybe I will be motivated to do the same

mikenite!!!!
11-28-2008, 07:39 AM
i took the cone out on mine then took a dremel too the bottom part u and cut it in half flipped it upside down on the maf and created a DIY open air filter heres some pics http://http://iampix.bmezine.com/5/w/kieqoj/rgywjhci.jpg

http://iampix.bmezine.com/5/w/kieqoj/dncbfsdu.jpg

mikes95540i
11-29-2008, 02:57 PM
For some good information on the factory air-box I would suggest that you look at the DINAN website. They have several videos describing various performance upgrades they offer. One video talked about the science that went into BMW's air-box design, the long and short of it is that you should not mess with it.
I've used K&N filters in everything that I have owned for many years, (I'm 54). I have a lot of faith in them and will continue to use them, but I put the cone back in the air box yesterday after hearing what the people at DINAN had to say.
The car still pins me back in my seat, and makes my wife fuss so why mess with a good thing.