Here's the deal.

I finished reading an independent test conducted over a two year period on equipment that could measure both the flow AND the filtration properties of many brands of air filters. Take 5 minutes and read link below ~

***** http://home.usadatanet.net/~jbplock/ISO5011/SPICER.htm *****

Guess what? The K&N absolutely sucked in both catagories ~ in fact, a cheap paper Fram filter posted WAY ahead of the K&N!

Which brings me to this. I now, or shortly will have, two oiled air filters (which can and DO foul the MAF sensor with oil residue ~ even from the factory BEFORE a 're-oil'). These would be the K&N and a Green (both cotton based and oil soaked).

Then I have an HKS (3 layer ~ closed cell foam technology) dry, with NO oil (therefore no chance to foul the MAF sensor).

Finally an STI OEM paper drop in (dry. no oil foul issues either) as well as the original OEM from my OBS.

I am using a 'snorkus' delete with fresh air coming from the inner fender (simple 3" straight pipe right out the back of the box into the inner fender)

Anyone? Thoughts... opinions... impressions from using one of these brands listed above?

 

I don't know, i went with a cold air, but everything i've read on the subject i've seen ALOT of people talking about using foam filters. 'specially on the wrx's which alot of people argue that CAI are not worth anything.

 

I've been using K&N for years myself. Maybe Subarus are just incredibly sensitive because I haven't had a single problem with MAF fouling, even on my modified GTI. It was in there for 4 years in a modified factory airbox. When I was delivering packages, I put 62k miles on the one in my van, again with no issues.

 

subaru and Drop-in filters doesnt seem to want to mix..

 

Huh?

There are a s***load of modified snorkel-less modified air boxes with drop ins.
I just have all these filter choices and felt I should try another after a very bad review on K&N ~ air flow and filtering was WAY on the bottom of others tested!

Will go search for this thread now ~ stay tuned! Here it is ~ added it to orginal post as well!

***** http://home.usadatanet.net/~jbplock/ISO5011/SPICER.htm *****

 

There must be hundreds of Imprezas out here running 'drop ins' VOTE!

bump

 

Foam degrades after a bit doesn't it? I wouldn't want any of that flyin into the turbo.....just wondering if that is something to worry about.

I would think that if you want to avoid any damage to anything i.e. MAF sensor or turbo then paper might be the best solution. Still a noob but thats my .02.

 

You have to replace foam (like paper)... but that's OK, the HKS is like $29, compared to $67 (my cost with employee discount) STI paper. But, I am leaning towards the STI version at this point... may just run 'em all and see if one feels better then the other, or even sounds better. The 'butt dyno' should feel NO difference!

 

I don't doubt the test results, but I'm a diehard K&N fan and here's why. A few years back I had a '78 FJ40 Toyota Land Cruiser that spent alot of time on trails. One spot we frequented had this fine silt that made it's way past the stock paper filter and collected on the throat of the carb. I told one of my friends about it and he recommended a K&N drop-in, so I tried it. After that no more silt. In fact I never found anything on the carb throat anymore. That made me a believer. I'm also not to concerned about the 3.13% difference in filtration between the AC and the K&N filters. Especially with my Suby which sees alot less dirt then the FJ40 did. I'm more concerned with flow.

It's unfortunate that the K&N's mess with MAP's in WRX's, but I've had a K&N drop-in on my CAI equipped '04 RS for over 35k miles with no problems.

 

im rockin the STi filter from now on...the oil was coatin my MAF, now im all G

 

I had some problems with the oil from my K&N messing with the sensor too. It eventually cleared out with some carb cleaner and a little time, but it was frustrating to loose power from an "upgrade". The Subie MAF's are probably not more "sensitive" to oil, they are just closer to the filter or they are right in the path of the mist of oil. I'm not sure.

I think it comes down to this: If you spend time dirt rallying or live on a dirt road, you should go with the K&N (or similar product) and go light on the oil. If you drive strickly street, you should use something cheap like a Fram, so it won't break the bank when you have to keep replacing it.

 

K/N air filters will flow the most CFM's.

 

I took one of my Subaru techs (I am a salesman at a Subie dealer) for a few runs at night a month or so ago. Here's what we did.

I had a new Green, K&N, STI (SPT high performance part) and HKS 3 layer foam filter. All 'drop ins', all new. We took a road loop with me driving 1st and then him. Stop and go and then a quick hard run on a twisty country road. With each change of filter, the ECM was reset and re-calibrated.

We felt no difference between the K&N, Green and STI. When we threw in the HKS he (the tech) felt the difference with the HKS from the pass seat! When he drove he confirmed as well as did I. Better throttle response and acceleration seemed to be had from the HKS.

The HKS was the butt dyno favorite ~ The STI offered the same performance as the K&N and Green, but because it was un-oiled has no chance of fouling the MAF sensor. The STI and HKS were both louder at full WOT then the Green or K&N.

The HKS is three layers of none oiled foam and therefore not going to foul the MAF sensor either.

So, I kept the HKS in and I am running it now with great results. Sold off the other three (STI/Green/K&N) at work.

Would be interesting to do the same with a dyno, but don't have the time or $$$. So, settled on our crude but conclusive test...

...for what it is worth.

 

Would you happen to have the part number for that hks. I have had hks in all my cars and I wanna keep it that way. I have an 06 2.5i, even though I don't think that should matter.

 

Would you happen to have the part number for that hks. I have had hks in all my cars and I wanna keep it that way. I have an 06 2.5i, even though I don't think that should matter.