CAUTION: Drop in Air Filter Install
 

Just a heads up for all of you who have installed drop in air filters, I was doing some head scratching trying to get the damn airbox to click back together and I couldn't quite get everything to line up. I searched in the owners manual and thought it was weird that there wasn't instructions for replacing the air filter. I assumed that if it wasn't in the manual then it was slightly more involved than a simple drop in replacement...

It turns out that if you aren't careful you could close the metal clips on top of the airbox yet not have a true seal. If you press on the top of the airbox you can look to the underside and see the two halves of the airbox separating.

There shouldn't be any bending or flexing of the sides of the airbox, everything should sit flat and flush. The plastic teeth on the sides of the airbox should not touch or be pressing against each other.

I had to take the whole airbox assembly off just to get the two halves to sit securely. This involves removing three bolts.

One bolt is on the front side of the actual airbox.
One bolt is on some plastic box thing that sticks out of the left side of the airbox.
One bolt is on a plastic arm on the rear bottom right of the airbox.

All three of these bolts are 10mm.

Once you remove the bolts you just slide the airbox assembly out of the snorkel. This gives you much more leverage to securely close the airbox and make sure there is no play in the fitment. Slide the airbox back around the foam on the snorkel and rebolt. (I'm not sure if that is the correct way to replace the snorkel, but it is on the dirty side of the air filter so at least your engine will be getting clean air regardless of the snorkel situation)

You will know that your airbox is sealed correctly because the two halves will not move or give any play. (the airbox itself will move, but the two halves will stay completely sealed)

This might be general knowledge but I was reading some people say that they just forced their aftermarket filter to fit. I want you to know that just because you forced the metal clips back onto the airbox doesn't really mean that the airbox is secure.

If there is enough interest, I can take some pictures of the process.

It could also depend on the filter that is used. When inspecting the stock filter, I had no problem getting the airbox back together. After installing the TRD filter (thicker flange), it was a pain in the ass to line up the two halves properly.

handy tip :) The Evo X airbox was very similar and had the same issue... used to cause all sorts of wonky maf readings from time to time as the filter and lid shifted around and allowed air to sneak around the filter.

I had problems putting the stock filter back too, thats when I knew 100% I was doing something wrong.

Good point OP, I had to take off the air box when installing the perrin drop-in, but wasted half an hour trying to get it to close properly prior to that.

Also keep in mind that the filter itself has to go in a specific way. There are two indentations on one side of the filter (and should be on most aftermarket filters) that are matched up to the air box itself. Even though it's a rectangle, if you get it upside down, it won't fit properly.

Yes, I recently installed my K&N drop in and while I clearly had it facing in the right direction (toward the front), I first installed it upside down and I don't think it was making a proper seal. I flipped it upside down and now it fits easily and flushly. I think there might be a larger corner that needs to go to the bottom/passenger-side for the filter to fit properly. Please correct me if I'm wrong!

Here is a pic of the filter:

http://i171.photobucket.com/albums/u...psa0ee40ba.jpg

You can see that that corner is different from the others. Again, I think this corner should go to the bottom/passenger-side. Maybe this is all super obvious, but I actually put mine in upside down at first and was able to close the air box clips. So just make sure you have it in right, because it seems to fit much better now!

I broke one of the clips trying to get the seal. I still don't think I got it. I may have to pull out the whole box out

You have to make sure the bottom pegs are lined up first before you try to close the top. It is a lot easier with the tube disconnected or airbox removed.

I wound up breaking the bottom bracket trying to get the thing closed. I was installing a Zeta dry stage 2 filter. I think I got it closed ok, though.

-Gary.

Is there a thin red line exposed all around the filter when closed? My trd drop in is facing the correct direction and the clips on top closed but i can see the outline of the red surrounding the box when closed......weird

I found this especially frustrating with the Apexi because of the plastic flanges on the edge. I finally got it back together at the same time the wife found this thread...our Evo and our current lancer were a pain too but this is way worse. I better get my advertised 5 hp lol!

Hmmmm.... Maybe I just got extremely lucky with my K&N drop-in last week, as I had no problems getting everything to fit back together in one shot.....

this is part of the reason why i decided to go w/ an intake. even if it IS slower. much easier to maintain.

I just did this today with a K&N, was fairly painless thanks to this DIY guide: http://www.ft86club.com/forums/showt...010#post881010

Pay special attention to step 4 and you'll be fine.

No, its a bad seal. You might see a bit of the red from the tab on the bottom of the filter but you most definitely should not see any filter stick out around the seal.

You really can't just wedge the two things back together and shove the clips back on. It's doable, but its not going to seal correctly on the bottom. They definitely could have made it easier but it's not too hard once you "get it". Just follow my DIY and you'll get it, the box wants to stay closed and the clips should just pop on without any forcing.

Thanks for the post, just realized I did it wrong... going back to fix it tonight.

Mine is doing the same thing. The rubber polyurethane border is exposed a little on 2 sides. Was this normal or did you figure out a way to have the filter totally enclosed without any part of it showing?

Good looking out. It's the little things people tend to overlook.

First time I tried to install my K&N filter I didn't take the whole airbox out, just the back half. I put it back together but really had to force it, so I ended up redoing it - this time taking out the front half as well. That time it went in much smoother so I think I got a better seal.

I'll probably put in an actual intake at some point down the road (more for the sound than the performance gain, TBH) but I'm happy enough for now. I notice more intake noise at WOT than I did with the stock filter.