K&N Air filter...

I know someone must have asked this question before but....when replacing the Air Filter to a K&N..has anyone or do you.. remove the top filter in the lid(I guess thats what it is)? Sure would flow better air but not quit sure what its for. ANYONE....?

that top piece is a carbon filter.
as a carbon filter, it's job is to trap any funes that might leak out of the engines intake. (sitting while off)

it's for pollution. removing it, altering, adding an air dam, etc. does nothing. the car monitors itself rather well. In order to take in more air, you would have to reprogram something.

there was 1 case of a company installing a turbo. that was blitz i believe. they said it was a complete pain and requires a lot of custom pieces to make it work.. not worth their time.

Not realy talking about more air..were talking about air flow. The better and ease of Air flow will make the engine more efficient. The Computer should compensate for any Air/Fuel raito difference's it detects.

The Atkinson cycle that the Prius engine uses actually kicks back some of the intake charge before closing the intake valve(s). So lowering the resistance to flow probably does not have as much positive effect as it would with a "normal" Otto cycle engine.

There was some lengthy discussion about this on PTS (Prius Technical Stuff - Yahoo group) and the consensus was that a K&N probably wouldn't help. Don't ask about it without reading the archived posts because there are several members who are vehemently opposed to their use.

Exactly! I tried some experiments with changing intake air and the car did not like it all. The K & N is a waste of money imho. You will see no change except in your wallet. A true K & N style intake would be cool as I have them on other cars but THIS car would not like it unless like V8 said you could chip it & change the air/fuel map. That map on this car is very strict indeed. Any intake change pre maf really seemed to effect the air/fuel map and the car ran like sh*t. Now a CAI and a muffler and a properly programmed chip would be cool but your mpg's would go out the window.....which kinda defeats the main cool thing about the car.

K&N filter makes a difference in my CX-9. I can definitely feel it. It revs more freely (less restricted air). If I drive more aggressively, my CX-9 shows you less hesitation (due to lack of air). If one drives slowly, someone claimed to see better MPG. I will report about MPG since this is my 1st tank with K&N on CX-9.

"waste of money"?
I am willing to try it (K&N) myself before I make any judgment. For $40, this is a good science experiment for me.
P.S. best price can be found on autoanything.com

This is true of most K&N free-flow filters, although there will be some performance benefit in some applications (like larger displacement V8 engines).

My biggest problem with K&N air filters is that the negligible benefit is not worth the hassle it is to keep them clean, oil, and reuse. It's a whole lot easier to simply replace the stock filter when it gets dirty with another of the same quality.

i have to agree with most folks here. i am a kn fan but not on the prius. it seems, in general, that staying bone stock seems to work the best with this vehicle. i do have a kn in my vrod harley and it makes a diffence there. but im keeping "mr red' stock except for dumping those silly plastic halos.

I have an kn filter in my 04 prius. I did not buy it for the extra hp gains website advertise for. I bought it because i travel about 5000 miles a month going from home to work, and mini vactions. I bought my 2004 prius used with 47,000 miles on it in 2006 from toyo dealer, today the mileage is at 153,437 So i do an oil change practically every month and everytime i check my old paper air filter, it is dirty like hell until i couldnt just take it out and tap it upside down on the floor to clean it before i stuck it back. Thats when i decided to get the kn filter because i can just wash it and re-oil it every other month and bam basically a new air filter instead of buying a replacement paper filter for about $15 twice or 3 times a year.

I just ordered a k&n for the same reason. If it does happen to hurt my MAF I'll clean it. It's not a big deal it's just a wire, it's rarely actually damaged just dirty. Have you had luck with it sofar? How about the car in general? I'm at 60k now.

I just installed a K&N performance air filter myself on my '06 Prius. I got it partly because I was sick of being unable to find air filters anywhere (where as this one is cleanable, so I don't have to play that insipid game anymore), and partly because my wife just got a cold air intake on her '05 Honda Civic SI and I was jealous. :lol:

Needless to say, I really wasn't expecting any actual better performance. I mean such an undertuned ICE as the Prius has, and not even using it all the time, how much of a difference could an air filter possibly make, right?

Boy was I wrong!

You really can feel the difference in performance, right off the bat. (Or at least I can, but then I like playing with tuned cars.) Unfortunately in a Prius with stock tires, this mostly just means more chirping. (I'll definately be fixing that before this winter. I've done enough winters on stock tires and praying for my life, thank you Toyota.)

Still, there was one other noticeable difference after installing the K&N air filter. It used to be that after a complete stop (stop signs, stop lights, etc.) if I absolutely floored my Prius, there'd be this pretty consistent hesitation in acceleration before it would finally decide to go vroom. Same if I absolutely floor it to pass someone on the highway in a hurry.

It was quite annoying.

But once you got used to the fact that the Prius didn't like being floored, and that hesitation was just always going to be there, you could at least plan for it by flooring it just before anyone in a normal car would do so, and with the timing difference it'd work out just fine.

I used to think the hesitation was the computer unable to decide whether to use the ICE or the electric or both, and to what degree.

After installing the K&N filter, that hesitation is completely gone. What I could easily provoke at the drop of a hat has now vanished. And good riddance I say!

So then it wasn't the computer unable to decide how to interpret you flooring the accelerator. It was an airflow problem making the ICE cough. Better air filter, no hesitation.

To me, that alone, made the K&N filter extremely worth the money.

But it'll also be very nice to no longer have to play hide and seek to find a darn air filter.

Good for you! Let us know if it affects FE at all.

Patrick

That's odd. Taking the filter completely out had no effect on my 1/4mile times vs paper filter in. How dirty was your paper filter when you made the swap?

K&N now extends it's guarantee to the MAF sensor. If there is a problem, have your dealer send the defective MAF sensor to K&N. If the filter caused the problem, K&N will reimburse you, if not they will provide proof to the dealer. I read on their site they have yet to find one that was fouled with their oil. K&N's, however, don't filter quite as well as a paper filter.

K&N Consumer Protection Pledge

The vast majority of MAF problems with K&N filters is simply because of too much oil being used. I have had the same oil spray can for five years and I have K&N filters ofn four different vehicles. The same can will probably last me a whole decade or longer. Just a very fine mist is all that is necessary.

I would expect the benefit of a K&N on a Prius to be minimal, unlike my 1998 Mercury Sable wagon which is consistently achieving a 2mpg increase with the K&N.

The oil never caused the breakage of a MAF that I know of. In GM cars and trucks, the problem was that the MAF would get coated in oil and cause a change in values recorded by the MAF and it would disrupt shifting patterns in the automatic transmission and supposedly cause transmission failures.

Ditto. That is identical to my information as well.

KN is the worst ( as tested on a very expensive testing machine) for filtering dirt. Its followed a close second by uni filters. Both tested so bad that you do not want to run them on your engine. They will damage your engine. The stock filter is not restricting air and you will not improve HP. All you will do is raise the dirt level in your oil.

Of course it is, we both drag race/raced GM vehicles with MAFs.