K & N Air Filters

I have seen a couple of posts where the mass air flow sensor became contaminated with the oil that is applied to the air filter. This can be a $400 repair at the dealer.

Some vehicles with platinum wire MAF sensors will heat the wire upon startup to burn off dust and other impurities. I understand that the Toyota engine control system does not have this feature.

My approach is to replace the engine air filter with the correct Toyota part at 15K mile intervals.

 

Hello, what you might remember about the Prius is that you control when the ICE runs. I drive 19 miles of dirt roads on a mail route most days. When an approaching car stirs up dust, I back off on the gas and shut down until the dust settles. I change filters more often than most but I don't suck in the dust like a normal vehicle. I used K&N on my Jeep but can't justify it on the Prius. Jerry

 

I used to have a 1990 Toyota 4Runner with the 3.0 V6, purchased new. In '94 I put on a bunch of Downey parts, including their K&N cone airfilter.

I had to replace the vane meter MAF in '97 due to the oil from the K&N clogging it up. I would have similar concerns about the wire MAF in the Prius

I think the K&N work fine with industrial motors, they are easy to clean. For the average car though, you won't see any performance improvment and could harm the MAF

 

I would never use a K&N or anything but a paper air filter. There is good reason car manufacturers use paper filters, they are the best. Heavy earth moving and mining machines also have paper filters, why?

As for dust in a paper element, just gently tap it out every few weeks in dusty conditions, can't do that with an oiled filter.

 

The Atkinson cycle, our Prius engine, keeps the intake valves open for about 1/3d of the compression stroke pushing part of the fuel air charge back into the manifold. Unlike a regular Otto cycle, the Prius is not 'starved' for fuel-air and the low pressure drop of the K&N filter is not really providing a benefit to an Atkinson cycle engine.

The second claim is that an oil soaked screen is a more effective dirt and pollen trap. I can thing of several approaches including electrostatic systems that would be much more effective. But you might do a test to find out.

Modify the air filter assembly to allow two stacks of K&N and paper filters to handle all air flow into an engine. In one stack, the K&N is first and the other has the paper filter first. After six months or a year, remove the filters and evaluate the relative amounts of trapped dust and dirt.

Bob Wilson

 

Have you considered the AMSOIL EA filters? They're similar to the K&N filter in that they can be cleaned and reused, but they don't use oil in the filter media.

Also, my recommendation is to STAY AWAY from the K&N filter. They're great in vehicles that don't have a MAF sensor directly under the filter, but in the case of the Prius, forget it. I gave up on it in my 2002 Prius because the MAF sensor has to be cleaned constantly while you're using the K&N. IMO, go for the AMSOIL filter, or use an OEM Toyota filter.

 

In 2003 and early Prius the MAFS is under the engine air filter. In more recent Prius, it is not.

I like jdchappie's comment about allowing the gasoline engine to shut off while driving through local dust clouds. Do the same thing myself.

 

I work in the automotive industry, in tool sales. I have relationships with many shop owners. Most have told me that K & N filters have caused drivability problems.
It has to do with air/fuel ratios and the ecm's ability to
cope with commands to the injectors. This in turn can
cause other parameters to be out of sync.
Best to stick with mfg's oem equipment.

 

When Caterpillar start using oiled filters on earth moving equipment instead of paper filters
I'll think about switching over to K&N but until that happens I'll stick with what is used to protect the engines in million dollar machines over the ricers choice any day.

 

The only reason I contemplated one is that paper filters are quite costly in the long run. I've used K&Ns on nearly all my cars/trucks since 1993 and never had any problems but I was aware of oil issues so I used it sparingly when I cleaned the filters and I regularly checked the MAF elements for oil residue.

Unless I find a place to purchase paper filters for check I may end up getting a K&N.

 

Buy 3 of these and you have 6 years worth of filters at 15,000 miles a year and a fresh element every 30,000 miles and free delivery!!
Auto Parts and Accessories Catalog -))

I remove my air filter each service and tap it on a clean bench to knock out the dust.

 

oops

 

I have been using K&N on my new Mazda CX-9 for 1000 miles now.
I can see and feel two advantages
- engine breathes more freely
- slight MPG increase (less than 1mpg but not scientific here)
The cost was $38. OE paper filter is $10. The former lasts for 50K miles.
The latter for 15k miles. Over oiling is the major cause of MAF failure. One guy suggested replacing it instead of cleaning & re-oiling it. That prevents mistakes on your part. With that you are not getting the cost benefit, but the engine power increase (albeit very few hps - due to less restrict air flow).

K&N filters have been proven to increase horse power on many modern vehicles thru dyno testing. It is not a hype. On Prius, I will not install K&N on it since I will never push it very hard.

 

Exactly! The Atkinson cycle is significantly different from a regular Otto engine. An Otto engine cycle is to some extent fuel-air starved for power. But the Atkinson cycle actually pushes part of the fuel-air mixture back into the manifold.

Bob Wilson

 

Good point. I think the Case tractor at my hobby farm has the best of both worlds: it has a large primary paper element filter, and it has an oil bath precleaner at the very top of the air inlet stack

The oil bath is gross to clean, but it does seem to do a good job of catching bugs and dirt. The paper element filter does appear to have a very slight oily residue on the exterior, no doubt oil carry from the precleaner.

That slight oil carry doesn not migrate past the primary filter. I last changed the primary filter 5 years ago, but since I don't use the tractor much it tends to stay clean

 

Most pre-cleaners I am familiar with have a dry dirt collection system and a lot of newer ones are self cleaning in that they have a dump port which allows dirt to fall out.

 

K&N air filters provide less of a flow restriction than paper air filters. Thus, they allow the engine to "breathe" easier. They also allow a lot more dirt into your engine. That is easily verified through higher than normal silicon content on engine oil analysis. I would never put one on my daily driver.

Like everything, it is a trade-off. Do you want more dirt in your engine or more air restriction. Just dont let the marketing hype lead you to believe that the K&N is filtering better than a stock paper filter, because it is not, nor does K&N make that claim.