I have been reading the discussion in this thread (http://e90post.com/forums/showthread...=carbon+filter) for a while. Since no one post DIY yet, I decided to do it myself.

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just did this mod BUT didnt do the charcoal filter delete. i left it in there. everything went smoothly otherwise. im wondering if i should do the delete? did you guys just cut it out; seems glued in. again car seemed much more responsive but that could also be just in my head. thanks for the excellent write up!

You cut it out with a sharp knife and then file ALL the glued bits off the intake box...so that no garbage goes into your engine!

true. i guess i should go back in there and do that. what exactly does the charcoal filter do?? just another filter in there? i am going to try this later when i install my strut bar...i see on the m5 forum that you can just pull that one out. can you do the same or is this one in there good? sorry for all the questions, just dont want to F it up...

Apparently it keeps certain pollutants from leaving the airbox once you stop the car.

Guys, dumb question. Is the the same air filter for the AC/cooling unit or there another filter for that system? In other words, all cars require air filter but is this the filter you guys talking about here or this is the filter for the recirc system? thanks.

OOHH YEAAAH! just did it took like ten minutes (what can i say i'm good with my hands)

I dont really notice that much of a difference-guess i'll have to got out and do some spirited driving

Do you need to take the airbox out, if all you want to do is change the stock filter to K&N ?

if all you're doing is changing the filter then no, you don't need to take out the airbox. Just have to remove the air box cover.

Are there any clips for that ? all i see is the 10 mm bolts and the torx screws.. doesnt make sense to me..

the 10mm bolts hold the air box in the car and the torx screws hold the two halves of the air box together... To make your life easier, you can pull the entire air box and then seperate it outside of the car and do what you need to do, reassemble and drop it back in the car.

Just be careful not to hack up the mass air flow sensor that resides behind the air box when you pull the air box and reinstall. Also, if you pull the air box, ensure a good seal between the air box and the tubes that connect to it.

thanks.. So in theory, i can just loosen the torx screws (they dont completely come out right ? ) slightly pull the 2 halves apart and replace the filter.. ?

Awesome write up.....I just did this mod tonight and the shifts do feel smoother, I HAD IT OUT BEFORE AND AFTER THE MOD. For those yet to do this,,be careful of the O2 sensor...it is a liitle bulb looking thing and very delicate. I used a dremmel to clean up the sides after cutting the carbon paper out and it worked perfect....just use a shop vac to suck all the debris out as this side of the filterbox will be unfiltered when you start the car. I also wiped down the edges of the K&N I put in to suck up any excess oil. So far so good.

sweet I always love these types of mods! I'll give it a shot!

If you go back some pages I warn about the O2 sensor. I took mine off the box, because I actually washed the whole thing with soap and water, since the charcoal dust made a mess.

Copy of post #21

After doing this DIY, I have added an observation. Once you cut the filter out there is a very rough syrface, and it's COVERED in black charcaol dust.

I removed the MAF sensor from the airbox.( Just two #20 torx screws) BE CAREFUL with this part, it's fragile!! Then I used a dremel to smooth all the rough edges. Sandpaper will work too, but a dremel is faster.

Whether using sandaper or dremel it will create a TON of dust. I then washed the entire airbox, and let it dry completely. (this is why I removed the MAF sensor)

It's an easy mod, and the combination of adding a K&N filter, plus this mod, added a very noticeable improvement in throttle response, trust me. As for HP, probably not much, but it's still worth doing since down the road having that stupid charcoal filter in there will definitely cause airflow restriction since it's not replaceable!! It's almost like having two air filters, a poor design IMO. But, I guess a few states (CA for example) were concerned with vapors escaping into their precious atmosphere when the vehicle is turned off!? We have greater air concerns, believe me! OK, off my soap-box.

Well thanks. Everyone else....what he said. Be careful with it.

Happy driving.

I just did this last night and it took me about an hour.
I notice a sharper trottle response definitely.

great diy :rocks:
thanks guys

ok I looked at my intake and being a 335 it looks completely different. Is there still a charcoal filter in there somewhere??

after about a month, ive noticed it being a bit faster but my mpg has gone down. dont know if its just me driving or what....anyone else?

edit: i took everything apart and noticed the filter housing was not seated properly against the front mount intake duct. i also cleaned it but did NOT use the k&n oil as i heard it damages MAF.

Well done! now I know how to drop in my ITG

Guys,

Looking at the pictures of the K/N and the stock air box, the filter
is not completely covering the air box. Any potential problems from
this?

Wig

just curious. just bought the filter from the K&N website. why is that "drop in filter" needs cutting and using a dremel for our cars? the website says just remove and replace without doing any cutting or modifying. removing the air box was easy but fitting it back in was a pita especially the piping by the air sensor.

Did this yesterday. Good mod, like others have said, noticeable at lower rpm.
I still have the stock filter.