Does anyone know the purpose of the semi-elaborate filter/screen in the 355 airboxes?? I assume the two small holes in the bottom of the air boxes are for water to drain out but what's with the filter material in the bottom? I'm kind of thinking it might be for noise reduction from sucking sounds as air is drawn in through those little holes. On the other hand the padding material could also trap water instead of allowing it to drain quickly. Having said that the boxes are made from aluminum so rust would not be an issue and the heat from the muffler would probably evaporate moisture fairly quickly. Interestingly, you can see two dark spots on the filter material where it covered those drain holes. There is actually a significant depression in both dark spots on the filter material (which you can't really see in the photo). In other words there is some serious suction there. I would have thought there would be plenty air from the air hoses feeding the air boxes. Maybe the fact that the air hoses are very long has something to do with it. Ideas/thoughts? Image Unavailable, Please Login Image Unavailable, Please Login
Check out my thread. My airboxes showed the same dark depressions on the filter material. Look like yours may also be showing signs of paint separation. Check your top covers on the inside for loose paint. don't want that getting sucked into the intakes! http://www.ferrarichat.com/forum/showthread.php?t=269692
I remember reading your thread when it was posted. Why do you write "Look like yours may also be showing signs of paint separation."? There is none on the inside, although I agree it's a good idea to check. The black stuff shown on the filter material is just dirt that has been sucked into the airbox. So.... I'm still at a loss what this whole filter business is for.
There must be some good reason...Ferrari wouldn't spend extra $$$ on the parts for no reason. Maybe acoustics?? In that case I'll take it out! Edit: what about insulation from the heat? that makes more sense, the bottom of the air boxes is right over the heat shield, they probably were trying to minimize heat pickup by the inlet air.
There is a closed evap system but some newer cars have emissions absorption pads in the induction. (these cars may predate that, I don't know)
I agree. They didn't just do it for the heck of it. If what some people say about the additional intake box is true (that it is to cancel noise/resonance) then I could see them taking this extra step for acoustics too. It just seems a bit odd that they go to this trouble on what is a relatively loud sports car to start with. I don't think customers would have a big issue with additional sound unless it's a really unpleasant/annoying frequency. It seems to me I read that the carb'd 308's had a bunch of this type of material in their large air box to reduce intake sound. Someone on this list removed it in theirs along with the metal screens holding it in place to help improve air flow, as I recall. I suppose additional heat insulation, as you mention, is another possibility.
I wasn't aware of that. That would seem kind of dangerous though if you're trying to store fuel/fuel vapor in a pad just above the very hot muffler. Also, how could it be absorbed and stay there? It's an open system with both air and heat available there to evaporate the fuel into the air (exactly what they try to avoid with closed fuel tank systems).
In your second picture, the lower half of the airbox, looks like wavey lines. That is what mine looked like at first. No break in the paint surface just a "delamination" However in your photo the lines could be waves in the airbox from the stamping process to make them and not the paint separating. I assumed the holes in the bottom of the airbox are to get rid of moisture buildup in the airbox.
I see now why it might look like that. You're right though.. it's waviness from the stamping/stretching process and the paint is adhering (not raised) to the metal at those weird looking areas. In any event, it might not be a bad idea for me to bead blast the paint off the inside of the top sections of the airbox to avoid future problems you allude to.
I know it would just be theorizing but... do you think it's "general" sound deadening or it's there for the drain holes and any noise they would create?
Drain holes are for water Filter-looking-like-thingie looks to be a noise absorber. Also note that with this sound absorber, the only parallel surfaces are the sides. A very long time ago I worked in a high-end stereo shot that had a room constructed with no parallel sides and a pitched roof. The sound in the room was so good, string quartetts would pay money to practice in it.
