Onlu use paper filters.

Any change to the intake such as a short ram require the vehicle to be tuned

 

Just stick with the Subaru oem paper filter. Adding a K&N filter to your stock air box will do absolutely nothing.

 

I used a K&N oiled filter in my Buick and it gummed up the throttle body flapper valve.

 

Thanks for the replies. Paper filter it is! I'll replace it when I do my oil change. Thanks again

 

A long time ago there was someone that worked at K&N that was posting here as a member. They were very fond of the product and didn't seem willing to let the facts get in their way. I remember asking about increased Si levels detectable in engine oil samples, increased wear, any plans for making their intake legal with CARB, reproducibility of dynamometer data and so on. A fun discussion was about warranty issues when using an intake that is neither up to OEM standards nor legal. I wonder what happened to that guy.

 

A lot of people think that because your engine can pull more air it will pull more air. Your basic paper filters do have a little resistance, however it's worth it for the exact filtration issues you mentioned. I've heard positive things about the aem dryflow however the more flow you have the less filtration so I suspect that even with a non oiled filter it's not filtering as well

 

https://www.youtube.com/watch?v=GS69owXpGdY


Engineering Explained did a video on this with a Subaru as a test vehicle no less. There were definitive, measurable gains with the K&N compared to the stock air filter.

 

Run with it, it's your car. Just don't come complaining when you have endless issues because of fouled maf sensors and high levels of contamination in your oil.

 

To be fair EE compared gains & didn't test for filtration or extended use.

 

I have two Subies, both with a K&N oiled filter and short ram intake: a 2002 WRX (now with ~200,000 miles) and a 2017 STi (now with ~30,000 miles). I bought both cars new. Both filters/intakes were installed within the first 1,000 miles. I've had zero problems with either install.

On the STi, I put in the filter/intake together with Cobb catback and flashed a new Stage 1+ map. But back in 2002, I didn't even know about tuning or maps or any of that. (My son is now the primary driver of that car, and he put in a Cobb turboback and flashed a new Stage 2 map a couple of years ago.) Maybe it was running lean all that time, but I never noticed any stumble or lack of throttle response and I've never had a maintenance issue.

As for performance gains, K&N will give you graphs showing purportedly from dyno runs with your particular year/make/model showing the HP and torque gains on your particular car. Who knows how accurate that stuff is. I think I noticed a slight gain in torque and throttle response on the WRX (but that was a LONG time ago), but certainly no real performance improvement on the STi.

The real reasons to go with a K&N or similar oiled filter are (1) lower overall maintenance costs and (2) really sweet turbo whine.