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Why use a K&N air filter?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Another, Jul 24, 2021.

  1. Another

    Another Senior Member

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    I’ve seen that a number of people here list it as a mod they’ve done. My question is why? Are disposable filters inferior or just more expensive or both?
     
  2. Mendel Leisk

    Mendel Leisk Senior Member

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    upload_2021-7-24_6-20-44.png

    More importantly, how was that Spanish flu, the one that arose in the aftermath of World War One? And the stock market crash in '29, and ensuing world-wide depression? I've got so many questions...
     
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  3. Pulse07

    Pulse07 Active Member

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    Not a fan of them for several reasons.
    1. Although it touts performance gains, in real word it is undetectable. Like putting premium in you car, The car just cant use that "extra air" to make power.
    2. Less Efficient. The holes are bigger in the filter to let more air in, but that just lets in more dirt. The K & N is less efficient in catching dirt.
    2a. I know some one here will say the filter is oiled and oil will catch more dirt... (have fun getting oil out of your MAF sensor) Which brings me to my next point.
    3. Maintenance. The K & N is washable, but you have to re-oil it.
     
  4. Mendel Leisk

    Mendel Leisk Senior Member

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    Too, the stock (disposable) filter can last a LONG time. I replaced ours around maybe 88k kms, and it was with reluctance: maybe our environment is cleaner than a lot, but that filter was still looking very clean, just a light sooty-looking patina apparent, and only if you looked on a shallow angle.
     
  5. sam spade 2

    sam spade 2 Senior Member

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    The K&N air filters were originally designed for RACING applications........where performance is more important than long engine life........and the engines were designed for the air flow that they provided.

    "Street" cars are NOT designed for that free intake flow and will NOT make more HP because of it.
    Also more fine dirt gets by and that is not good for an engine that you want to last a LONG time.

    Marketing hype is just a bunch of big LIES.

    OH......and technically it is ILLEGAL to modify either the intake or exhaust on a modern street vehicle because that is likely to make it's talipipe emissions worse.
     
  6. Isaac Zachary

    Isaac Zachary Senior Member

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    A lot of people believe that the lower the restriction you have in your intake the more efficient your engine is...

    However, the biggest restiction in your intake is the throttle valve. At any load, except full throttle, the total restriction is the same. In otherwords, to cruise at 60mph down the highway in one car with a clean, non-restrictive filter and one with an old clogged up filter the difference is the one with the clean non-restrictive will have the throttle valve slightly more closed causing the same total restriction.

    There are only three types of engines that benefit from less restrictive intakes, diesel engines that don't have a throttle, engines from people that drive with the throttle valve completely open most of the time and carbureted engines that start going rich if you have too much restriction.
     
  7. PriusCamper

    PriusCamper Senior Member

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    Main value of having a K&N air filter is that there's less waste... After almost a decade of using a K & N I did a tune up and didn't have time to clean the filter and had a spare paper filter I bought for someone else's Prius that I put in temporarily. The biggest difference noticed was engine intake noise was slightly more muffled.

    In terms of a performance boost, like most things in an engine, that's most noticeable at high RPM and Prius don't do that too often...
     
  8. mr_guy_mann

    mr_guy_mann Senior Member

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    'because buying speed parts is "cool". The stickers you get with it gotta be worth 5 hp- each.

    Posted via the PriusChat mobile app.
     
  9. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    If you put a K&N on a carbureted dirt bike, you'll improve the intake flow and develop a little more engine power. More dirt will go through, but that's cool because your sponsor promised you a new engine at the end of the race season.

    If you put a K&N on a fuel injected passenger car, the ECU will invisibly compensate for the flow characteristics of the new filter, at least until oil contamination from an enthusiastically over-oiled filter invariably finds its way to a sensor and starts sending bad data.

    It's not like they don't work, it's just that they are more trouble than they are worth unless you are using them on their original application: small carbureted racing engines in filthy environments.

    The fact that people are trying them on the family hatchback is a testament to the power of successful marketing.
     
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  10. sam spade 2

    sam spade 2 Senior Member

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    Well if you want to pursue that line of thought to it's logical end.......there is less waste if you stop using toilet paper too !!!
    :ROFLMAO:
     
  11. PriusCamper

    PriusCamper Senior Member

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    And in general most modification to boost engine power like porting the heads, using a larger throttle body, adding a turbo, high performance cams, etc all realize their most benefits at super high RPM.

    In contrast a high mpg car is designed for maximum efficiency so once you get past peak horsepower at 3500rpm the entire design premise of the engine is no longer valid so it being able to breathe better up above that RPM is not useful.

    On the other hand, I bought an old Honda GX 390 engine that was seized up for $100 and I'm gonna rebuild it for my woodchipper and in doing research for engine mods I discovered that go-cart racers tune these engines to run as high as 20,000 rpm. And clearly that's the opposite of relevant here, but a worthwhile perspective of the main value in getting an engine to breath more efficiently.
     
  12. PriusCamper

    PriusCamper Senior Member

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    I actually have a friend that stopped using toilet paper 30 years ago. She uses a washcloth instead... Also many countries in Asia and Europe very little toilet paper is sold because their toilets have lots of far more comfortable way to clean your butthole. It's only in stubborn closed minded countries that people still wipe their butt with an outdated deforesting method like toilet paper.
     
  13. fuzzy1

    fuzzy1 Senior Member

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    The BSFC charts for the Gen2 and Gen3 engines very clearly show that peak horsepower is also at maximum RPM, which I believe is 5000 RPM on the Gen2, 5200 RPM on Gen3. With increasing RPM, the Gen2 engine's torque never shrinks, while the Gen3 torque doesn't shrink fast enough to produce less total power.

    2010 Prius 2ZR-FXE engine efficiency map | PriusChat

    [​IMG]

    I don't have a Gen4 BSFC chart handy to comment on it.
     
    #13 fuzzy1, Jul 24, 2021
    Last edited: Jul 24, 2021
  14. ChapmanF

    ChapmanF Senior Member

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    Even so, among people who drive pointy fast things, a Prius maximum of 5000 or 5300 hardly counts as "super high RPM".
     
  15. Another

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    maybe you should try Wikipedia
    Otherwise not sure what your point is.
     
  16. Another

    Another Senior Member

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    too much information
     
  17. Another

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    Thanks for all of the substantive comments. Pretty much confirmed what I thought. The air filter is so easy to check and inexpensive to replace probably once a year with a genuine Toyota or a Fram, that I thought I was missing something on performance, but was not. In addition it’s a PITA to have to wash and oil the K&N it seems to me. Already doing my conservation part owning a Prius and other ways. Can only do so much.
     
  18. Mendel Leisk

    Mendel Leisk Senior Member

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    Well at your age, you must have seen a lot.
     
  19. ChapmanF

    ChapmanF Senior Member

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    Born right at the turn of the century, no less. Depending on the time zone.
     
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  20. mr_guy_mann

    mr_guy_mann Senior Member

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    I think that HE considers it (the use of K&N) to be another interesting but not really useful question.

    For most car owners, check the air filter once a year, replace as needed- for me that's every 2-3 years.

    Posted via the PriusChat mobile app.
     
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