Dealer scolded me for using a K&N filter.

full of shit.

My dealer will offer you K&N or stock and they recommend you for the K&N.

The oil can cause a dirty maf and can run lean, However if you have never wash and oil it, it should NOT be an issue. K&N knows this and drenching it in oil is wasteful. You just need a little enough for dirt to stick on and not too much where you can shake off the oil.

Aftermarket air filters do screw with the finicky 2008+ MAF sensors because it changes the flow through the intake tract thereby throwing off MAF calibration and the ECU leans out the A/F. You need to be tuned for these filters.

http://www.iwsti.com/forums/2719460-post7.html

user1029 said:

Aftermarket air filters do screw with the finicky 2008+ MAF sensors because it changes the flow through the intake tract thereby throwing off MAF calibration and the ECU leans out the A/F. You need to be tuned for these filters.

http://www.iwsti.com/forums/2719460-post7.html

Click to expand...

This.

I did have an over oiled panel filter screw up my MAF readings and cause a rough idle and CEL for a lean bank. The dealer wouldn't touch it and it took a independent shop an hour to figure it out.

The stock airbox is quite good, I wouldn't jack with it.

user1029 said:

Aftermarket air filters do screw with the finicky 2008+ MAF sensors because it changes the flow through the intake tract thereby throwing off MAF calibration and the ECU leans out the A/F. You need to be tuned for these filters.

http://www.iwsti.com/forums/2719460-post7.html

Click to expand...

Good info, Thanks!

Are there off-the-shelf maps available that are tuned for these filters?

If not, will it work on my friends NA Impreza?

Re: Re: Dealer scolded me for using a K&N filter.

EyeOutThere said:

Good info, Thanks!

Are there off-the-shelf maps available that are tuned for these filters?

If not, will it work on my friends NA Impreza?

Click to expand...

No. The OTS maps are calibrated for the stock filter or aftermarket aem or Cobb CAI.

Not sure about the N/A impreza box but I would be surprised if it worked.

Butt posted from my Galaxy Note II

The first thing I did to my new '11 was put a HKS Super Hybrid Filter in the box. Did not hurt a thing.

I just put one in my truck and it came with a card to put in the glovebox. The card basically states the K&N guarantee that you won't have any problems with the car or the dealer and if something arises, to call the provided number and K&N will handle everything.

Even on cobbs website it says don't use a high flow filter on the 08+. It's not like its really helping you anyway. The stock one is cheaper and works just fine.

The dealer is right. I have seen multiple people with WRX's running lean personally. All were running oiled panel filters. Cleaned the filty MAF and they began running properly immediately.

I use the Apexi paper panel filter.

Scargo said:

The first thing I did to my new '11 was put a HKS Super Hybrid Filter in the box. Did not hurt a thing.

Click to expand...

Did you datalog with a wideband O2 sensor?

user1029 said:

Did you datalog with a wideband O2 sensor?

Click to expand...

Nope. Next thing I did was to go with Cobb stuff (AP, downpipe, ...), and then shortly after, Cobb SF intake. I then did the SF Stage2 map upgrade to 93 octane. It's all here.

slightly off topic, but what is the best method to clean the maf on the gr?

Dealer is not exactly wrong on K&N messing up maf sensor.

I used a K&N filter on my old RX-8 from Racing Beat (a very very reliable mazda aftermarket company) so the filter itself is custom to Racing Beat spec. K&N themselves have released their own product line for the RX-8 and the result was abysmal, heatsoak, car wouldnt idle properly however the main reason is not directly caused by the filter itself.

MAF sensor requires laminar air flow to work properly therefore some sort of wire mesh a few inches before the sensor itself can cause intake air to flow smoothly across the maf sensor so idle will be stable.

As for filter gunking up sensor, it happens because owners re-oil the filter too thick after cleaning it. This can be solved by simply replacing the filter instead of cleaning and re-oiling or re-oiling properly.

mooshoo said:

slightly off topic, but what is the best method to clean the maf on the gr?

Click to expand...

Use electronic cleaner and spray it liberally when its out of the filter box, let dry and don't touch the wire element. When securing it back, make sure you don't pinch the o-ring that seals the system if one is present.

Lastly DO NOT let the o-ring get in contact with any cleaner of any sort. Some o-rings will expand when that happens and the maf sensor will not seal properly unless o-ring is replaced. Easy to replaced if you know the exact size but if you wanna get one from delaer, chances are you have to buy it together with the sensor itself. Don't ask me how i know

mooshoo said:

slightly off topic, but what is the best method to clean the maf on the gr?

Click to expand...

It is my personal opinion that, although they work in a similar manor to any other filter, wet filters create more problems than they solve. Throw the crap K&N away and get a dry cone filter to replace it. I am sure AEM has a similar shaped filter with the same flange size that will work just as efficient and keep everything dry and clean.
To clean the MAF, first remove it. Then get yourself a can of electric contact cleaner and spray the hell out of it till its clean and clear. Reinstall and make sure you get all the oil out of the hoses and AI box post filter. This should take care of it.
GL
Kravur

**edit** tastetickles already answered your question, my bad.

I stopped using K&N filters when my car and my dad's car had a fine silt layered on all of the inner walls of intake piping after the filter. I use AEM DryFlow on larger intakes and a stock paper filter on the stock box.

K&N (and any other oiled filter) are complete garbage. When (not if) you improperly oil it, you will cake your intake tubes, maf, and turbo in oil.

Man o man, such hyperbole. I am running a K&N cone filter on my race car and have never had an issue. I don't think I ever oiled the piss out of it though.
Don't care for the "take K&N (or others like it), out and lynch 'em" mentality.

I have seen multiple vehicles with MAF issues stemming from oiled filters. GM had problems with K&N filters back into the 90's. It is a real issue. Generally, if the filter is oiled correctly, you're ok. The trick is knowing how much oil to use, and there's no easy way to know for sure.