I took an hour today to mod my M44 OEM airbox. I wanted to set up for more potential airflow for my DASC install next month while retaining the BMW airbox. I looked at Shawn Fogg's threads on fogging the OEM airbox, but I wasn't so keen on pulling the additional air from below, but he listed an option to draw air from the grill. I saw a thread from Mad-Machine in 2009 and liked the setup in the M42 air draw location. This will also save me from setting up heat barriers for heated air as compared to a cone setup.
Here are the three pieces I used to make a snorkel per Mad-Machine's post: A 4" round to square adapter, a 4" connector and a 3" to 4" male adapter ring. I picked them all up at Lowes for less then $10. The 3" adapter ring is already installed in the airbox in this image.
Here's the stock intake port on the side and the new intake port in the front of the airbox. After taking out the internal framing/sound deadening in the airbox, I used a hole saw to cut a 3" hole, then opened it up a little with a rotary rasp on my cordless drill to allow the adapter to screw in-place.
Here's the airbox in place with the snorkel and connector in place. The snorkel fits inbetween the driver's side headlight and the radiator, Similar to the M42 setup. I took some plastic off the new snorkel to fit more snugly and straighter in place.
Here's the finished product in place.
The airbox installs and deinstalls as normal with just the addition of aligning the new snorkel. I left the original snorkel in-place, so I'm getting airflow from both inboard sides of the headlights. I do plan to swap out the K&N and go back to a paper filter.
Accelleration seems zippier over 3500 rpm. (Sean... See zippy reference...
). Not really any louder, I'll listen harder tomorrow.
I'll zip around a bit more tomorrow to see if I notice more of a difference.
Thanks to Shawn Fogg and Mad-Machine for their ideas and configuration.