I have a JDM S2k and there's that extra compartment in front of the filter, as well as a small hole at the top right (plan view) of the airbox that leads into a smaller compartment as well.

I've gutted the first wall...

In anycase, the stock airbox cover has a pipe that leads over the wall into the filter chamber. I figured the first chamber was for resonance to reduce noise?

 

somehow i can envision someone not all to bright filling up that box with you know,, that powder... and of course the surprize on his face after he starts the engine and later wonder's where'd it all gooooooooooooooooooooooooooo

 

i have an OZ spec s2000 and that chamber is pretty much a resonator. I just blocked mine off. Not much increase in sound after gutting the box as well as a k&N filter and metal intake pipe.

if you want sound id recommend an aftermarket intake.

 

Or taking your lid off.

Not really sure what the point of that first chamber actually is, as mentioned above part of the lid is a tube that connects the mouth of the intake to the chamber where the filter is, there-by bypassing that whole chamber. IIRC there is even a groove in the underside of the tube that rests over the wall, furthering the fact that it is sealed off from the actual intake.

 

It is the secret manual pocket...

Come on folks, its been discussed 1x10^6 times: http://people.seas.harvard.edu/~jones/csci..._helmholtz.html

 

That makes sense for the small chamber (what I usually refer to as the resonating chamber) but what about the the part of the intake that is seperated from the filter by the wall in the middle. This section won't work as a resonating chamber because it is actually not connected to the rest of the intake. There is a tuber attached to the lid of the intake box that connects the mouth of the intake, to the chamber that the filter is in. This tube is sealed by the wall dividing the two chambers. Seams more like a structural element then anything.

 

maybe so the heavier stuff like small rocks fall into that chamber instead of flowing with the elbow to the intake side???

 

Its just a low pressure trap for bugs, water, and small mammals. Cut most of it out, remove the plastic L tube section that is riveted on, and you'll get a throaty sound at WOT. Leave the cover on though.