Big Jimbo

I have been reading that many of you with stock air boxes remove the charcoal filter because it just adds to restriction, and after looking at mine was wondering why in the world MB spent the time and money to engineer and produce them. I understand the purpose of cabin and water charcoal filters to remove bad odors and tastes, but why in the world would you put them downstream from the engine intake filter? Those German engineers must have had some reason to spend the time and money as they always seem to save every possible penny! And if they do actually filter out something that would harm the engine, how often should they be replaced? Does anyone have an engineering explanation? Do any other models of MB cars use a charcoal filter?

hachiroku

charcoal filters capture particles smaller than a standard paper or cotton fiber filter.

roadkillrob

It is an emission item actually to help with fuel vapor removal

Mort

I believe this is correct, they collect fuel vapors after the engine is switched off. They are not a maintenance item and are not available separately from the air box covers.

Big Jimbo

That makes sense since I don't believe there is a separate charcoal canister like most other gasoline cars have. Seems like an odd way to take care of the vapor problem if it can potentially add restriction to the engine air intake but the engineers must have thought it was a good idea. Thanks for the information, mine are now going on my parts shelf!

Vladds

I don't think it's fuel vapors. If it were possible to collect them in the intake, the regular filters would collect them, with ROW boxes, or at least there would be some trace of them passing through, some condensation or smell.
Then the charcoal filters themselves would smell like gas and would be damp with it.
I think it's a sound damper.
Many cars have intake sound mufflers, snorkels and so on.
This has to be some kind of noise regulation that they had to meet, for US/Canada.
Because it's a sound damper, it can be designed not to ever need replacement and the intake design can be so that it doesn't loose any power.
The first thing that people notice with ROW boxes is louder intake. I can add that there is no change in gas mileage.

bhamg

IIRC the purpose is to trap gas vapors from what I read at model launch. If so you can thank the friendly ***** at California Air Resource Board.

roadkillrob

Ya it is a CARB mandated thing, traps vapors when you turn the car off so any unburnt fuel vapors can't leak out into the atmosphere.