K & N Air Filters

[Walker1]

HI, I was wondering if anyone is using a K & N air filter instead of the stock one. I have used K & N's on previous cars, but is this OK on a Prius? Thanks.

[Patrick Wong]

Originally Posted by Walker1

HI, I was wondering if anyone is using a K & N air filter instead of the stock one. I have used K & N's on previous cars, but is this OK on a Prius? Thanks.

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.

[jdchappie]

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

[jayman]

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

[patsparks]

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.

[bwilson4web]

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

[ozyran440]

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.

[tochatihu]

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.

[mdt]

Originally Posted by Walker1

HI, I was wondering if anyone is using a K & N air filter instead of the stock one. I have used K & N's on previous cars, but is this OK on a Prius? Thanks.

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.

[patsparks]

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.