K & N Air Filter

http://www.vfaq.net/mods/AirFilter.html

Shows the part and how to make it work. I have used the K&N air filter for about 50k in a 2001 Prius, and am satisfied that it is at least as good as the OEM paper. Saw no change in mpg or performance, but that was not my aim. I wanted to buy 14 less filters.

There are three "knocks" against these. One is that they may not prevent dirt ingestion into the engine as well as paper filters do. My engine oil analyses have not shown elevated sodium, so I feel safe about that.

Second is that these (oiled) filters could drip on the mass air flow (MAF) sensor. I have to be cautious about that in the classic, but the new model Prius has the air filter on the other side, not over the MAF.

Third, this link only recently came to my attention

http://www.labbb.org/BBBWeb/Forms/General/...News_ID=126&sm=

Read it and form your own opinion.

 

I know a number of guys that were using K&Ns in their Jeeps and removed them after finding dust in the air intake (post-filter). I don't know if K&N has changed their filters or not, but it seemed like the increased airflow came at the expense of filtering capability.

 

Despite all claims to the contrary, the K&N lets through a lot more particulate matter than a conventional filter.. There are sufficient open holes in the gauze that even if the thing were fairly dripping with oil (which would cause other problems), and the air flow as as turbulent as you could make it, a great deal of air would still make it through without any contact with the filter material.. The only way you can increase airflow without losing filtration efficiency is to increase the surface area of the filter, so that means making it as large as possible with as many pleats as possible... Unfortunately, in the cramped engine compartment of the Prius, there's really no way to do this, and in any case, increased airflow has virtually no benefits for the Prius- its rev-limited and low displacement Atkinson-cycle design means that it really doesn't have a very high air demand (the air demand is barely at 300 CFM at max RPM by my calculations) and the computer likes to adjust the throttle valve to limit the air flow if there's too much as evidenced by the hoops that had to be jumped through by Julian Edgar in Australia to turbocharge the vehicle..

That said, I do have a K&N filter for the Prius, but only use it in the winter season when the air particulate count is comparatively low and the moisture content of the air (which can clog up conventional filters but is well handled by the oiled K&N design) is higher. As soon as spring arrives, I swap out the K&N and put in a brand new genuine Toyota filter for the rest of the year..

 

Other than the "No oil required" comment everything negative said above is dead on. Since Walker1 will not take my word for it, as I know nothing, lets let the giant truck/SUV owners prove it! The chart and text below were started from a place called the Dieselpage that is dedicated to Duramax trucks also known as Chevys. The people on the forum bought and sent in their own air filters for testing. In the end they learned the factory filter not only worked the best but flowed more air than needed for their big motor application.

Simply put K&N's suck and anyone who says different needs to read this story before commenting. Toyota builds some of the nicest air filters out there. That is being said after 18 years in the automotive field from this Master Technician.

ISO Air Filter Test

 

Anyone tried AMSOIL air or oil filters?

 

Price for a factory Toyota air filter at my dealer: $8.

 

If that's still the case, I'd like to line up 8 more for the life of my car. The one I just installed was like $16 at my dealer.

Please provide the details...

 

Can someone who got a K & N for one of their vehicles lay out the cost difference.

What does it cost for the filter as compared to a paper one.

What does it cost for whatever solutions, oils and whatever it takes to 'clean' it... What is the cleaning process, how long does it take, does it generate some kind of acetone by-product that I have to dispose of 'properly'... etc.. What is this process?



I happen to really like the idea of a nice fresh filter in my vehicle about every 10,000 miles. All fresh, all new.. I'm not wondering if sand is getting past the K & N into my valves, etc.. When it's over, it goes in the garbage, in goes a new one.

I also was under the impression the k & n's are semi-expensive... so.. by the time I buy the filter, and all the junk to service it.. I'm about 5 or 6 paper filters into the non-serviceable plan.

 

Evan- I understand your argument, but in fact most filter media *does* consist of roughly square holes.. This comes about due to the construction method of laying down a mat of perpendicular fibres (generally resin coated celluose, ie paper) to create the filter media; there is some degree of randomness when you're dealing with microscopically fine fibres, but in general the opening do tend to be roughly square/rectangular..

In any case, if you think of holes per square inch of media, you'd only increase your hole count by a few percent by going circle to square.. On the other hand, if you a sheet of media that is 10x as long (take your pick, circular or square holes, the idea works all the same), and then pleat it so that it fits in the same space as the old flat sheet, then now, in that same area, you have 10x the holes.. Now there is a practical limit to how much you can pleat- there has to remain sufficient space in between the pleats for air to flow into/out of, but anywhere from 30-50 pleats is a reasonable number for typical small-to-mid-sized automotive panel filters.. It's a matter of surface area- yes you can increase the number of holes per unit area in the media, but you can only get so far, as I said, a few percent at best- to really increase the total number of holes, you must have more area and thats where the pleats come in- you're talking hundreds of percent increase vs just a few..

In terms of the K&N cost- I got my K&N on sale for $33 CDN; but the cost was not my main driving factor- I noticed moisture trails inside the air box in wet weather, and just a small amount moisture can clog up a paper filter faster than a shovelful of dirt. The K&N oiled media is virtually immune to moisture clogging, so I use the K&N in the winter when the air particulate count is lower (ie, less dust in the air, so I feel that I can live with the K&N's poorer filtering), but there is more moisture content.. As soon as things dry out in the spring, I put in a brand new Toyota filter.

The other costs involved are the cleaning kit, which cost about $18 CDN. It contains a pump bottle of detergent and a spray can of oil and will probably last you for years (assuming cleaning once or twice a year). The process is that you tap the filter against something gently and knock out as much of the loose dirt/etc as you can, then you spray with the detergent and rinse thoroughly with hot water from the back side of the filter. Then you have to allow the filter to dry *completely* (this is very important and may take a full day, so if you are planning on cleaning the filter, make sure you have a spare paper filter to put back into the car if you plan to drive, or do it on a day when you know you won't have to go out).. Once the filter is completely dry, you take the spray can of oil and apply the oil to the filter, waiting as directed in the instructions between applications to ensure that the oil gets absorbed, then fit the filter back in the car...

Basically, figure that if you do yearly filter replacements, it will take you roughly 5 years to break even with paper filters.. The impact of the reduced filtering capability of the K&N and more dirt getting through to the engine is thus far unproven- many cars have done hundreds of thousands of miles on K&N filters, seemingly without damage, but tests do show a significant amount of dust getting through.. That's why I only use it in the winter when the amount of airborne particulate is comparatively low.. You may also want to consider sticking to the manual's recommended oil change intervals vs. extended drain if you use the K&N air filter..

 

I purchased new - in Canada - a 1990 4Runner with V6. Living back in Utah, in 1994 I ordered a bunch of parts off Downey Toyota: front torsion bars, rear coils (The OEM were already sagging), rear limited slip, Downey headers and crossover/Y pipe, K&N intake filter, and Borla cat-back.

The suspension parts were barely 1.5 inch lift but dramatically improved the ride and handling of the 4Runner. The engine parts really helped the performance, especially driving to ski resorts at high elevation.

I will caution that I had problems with my mass air meter. The stock airbox was behind the driver headlight, with the mass air bolted to the airbox. A duct led into the throttle body/intake manifold.

The cone-shaped K&N filter replaced the air box assembly. I found that I had a lot of oil carryover into the mass air vane meter, sometimes causing problems in cooler weather. When I moved back to Canada, on very cold mornings the vane meter would seize up.

I finally ended up needing a new mass air meter. Although the performance gains for my 4Runner were substantial, I doubt the same gains will be had for the Prius. It's not worth gumming up the throttle vane either.

As Evan mentioned, there really isn't enough oil in the filter to be as effective as a stock OEM paper filter media. Industrial oil bath air cleaners are an entirely different matter. I have an oil bath pre-cleaner on my tractor at my hobby farm, and that thing works.

It's also a God Awful mess to clean too.