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Performance air filters claim to increase horsepower and improve acceleration, but do they actually work? I took four air filters, included dirty & clean OE filters, a low cost aftermarket filter, and an expensive performance filter and put them to the test. To measure differences in horsepower and torque, each filter was put on a Mustang dynamometer, with multiple runs. A VBOX was used to measure real world acceleration differences.

The idea behind performance air filters is that a less restrictive air filter means the engine doesn’t have to work as hard to bring in air. That means it’s more efficient, and makes more power. It could also mean the engine pulls in more air, and with more air, the engine can inject more fuel to make more power.

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    • Klick E
      Klick E

      What filter do you use in your crosstrek

      about 5 hours ago
    • Will Roberts
      Will Roberts

      Haven't seen results. Just want to appreciate someone on YouTube setting up a relevant scientific test. Two controls, a theorectical test, a practical test. Thank you.

      about 10 hours ago
    • Alaxander GW
      Alaxander GW

      Wish you would of tested w/o any filter just for funs.

      about 13 hours ago
    • Chris D
      Chris D

      Need standard deviation for these numbers to mean anything. Interesting video nonetheless.

      about 13 hours ago
    • Mohammed Gangat
      Mohammed Gangat

      No air filter is the best!

      about 14 hours ago
    • Jason Sarrio
      Jason Sarrio

      I have the same car do you remove the charcoal filter in the air box ?

      about 15 hours ago
    • Farina Marcini
      Farina Marcini

      Air filter upgrade for me is more important for sound produced than a couple of extra horses.

      about 21 hour ago
    • Jack Chang
      Jack Chang

      Great video. I like the logic flow also.

      Food for thought:
      “Random testing” isn’t random. It’s why Design of Experiment taught in engineering curriculum. “Random sequence” is actually a carefully designed sequence in order to randomize the effect of any potential external factor. That, plus each condition is run multiple rep’s at different points in the overall sequence.

      Simply having “randomized” the run sequence, does not eliminate the effect of lesser fuel & lighter car at the later half of the test day.

      All that said, 0.2 seconds improvement on a base of 8 seconds is... negligible.

      about 1 day ago
    • merp ius
      merp ius

      Too bad there's no good way to check each filter's effect on engine life. This info is useful if you're racing or something and aren't very concerned about your engine lasting a long time, but in the real world we'd want sustainable gains that don't cost engine life. (Not that I'm saying these filters will reduce engine life... just that, without testing, who knows?)

      about 1 day ago
    • Franco M
      Franco M

      Yo.. I didn't expect a great video!! I only clicked here to say this: Since an engine is just an air pump, restricting flow will decrease top end performance. An air filter is similar to a throttle... Think about what a dirty filter is really doing. Restricting air. The computer controls fuel. A filter can only stop big chunks of dirt... It never can "improve your gas mileage"... Only detract performance.

      about 1 day ago
    • Val Gauvreau
      Val Gauvreau

      K and N filters also let fine dirt into your engine, causing premature engine wear. Buyer beware.

      about 1 day ago
    • Gianna Filicia
      Gianna Filicia In reply to Val Gauvreau


      about 1 day ago
    • Stanley Kania
      Stanley Kania

      Ford tech Said don't use nothing but paper filters..

      about 2 days ago
    • N Mello
      N Mello

      The K&N Filters definitely increase air flow. Is there any difference in filtration? Am I putting more particulates through my 2013 WRX is I switch to the K&N replacement and will that hurt the engine or turbo long term?

      about 2 days ago
    • My Thoughts on Faith
      My Thoughts on Faith

      I have heard that the K&N are less restriction because they dont filter as much, and larger particles can pass through, which lowers engine life.

      about 3 days ago
    • Milorad Menjic
      Milorad Menjic

      You should do one test without any filter just the empty box and not without the box.

      about 3 days ago
    • B T
      B T In reply to Milorad Menjic

      would be a little more power than with a good filter... with a HUGE risk of getting contaminants into your block

      I did it on an 02 grand cherokee "overland" just for kicks. Even took it through a mud pit. Before it went through the pit, there was already stuff on the inside of the air tube, probably stuff in the block as well. after the pit, I had to tear the block down and clean it because the top end was filled with dirt and mud.

      about 2 days ago
    • CitizenX

      what other cheap upgrades can you do to gain few % like that? (aside from the magic sticker boost once added ^^)

      about 3 days ago
    • John

      Awesome video. I've always known that K&Ns do work, which is why I have used them for 20 years on several vehicles.

      about 3 days ago
    • Max Brier
      Max Brier

      You should test a cold air intake for the car

      about 4 days ago
    • Markus Patients
      Markus Patients

      I wish someone would make a low cost language, so you wouldn't have to use as many words just to say;

      K&N filters are better, dirty or clean than are all the rest.

      about 4 days ago
    • J Law
      J Law

      yea the K&N gave my 2014 Mazda 3 GT 2.5 a noticable pick-up off the line. K&N to stay, I'd pay an extra 40$ for a 3-5HP gain any day. next will be the exhaust upgrade

      about 4 days ago
    • daryl townsend
      daryl townsend

      From my experience of putting a K&N Filter in my '98 Honda CBR600F bike (carb version) it was more responsive at the throttle.

      about 4 days ago
    • Nasrul Azran
      Nasrul Azran

      More air more FC

      about 5 days ago
    • Nadeem Warsi
      Nadeem Warsi

      Never seen such a cool explanation..simply defined..great video

      about 6 days ago
    • John
      John In reply to Nadeem Warsi

      Me too. I've been waiting for a video like this for ages being a long time K & N user.

      about 3 days ago
    • Vincent Spencer
      Vincent Spencer

      Great test. I would be curious how well the K&N filter actually worked as far as particules. Also what kind of real world MPG savings with each filter?....

      about 7 days ago
    • Reel Heel
      Reel Heel

      A 2% power increase isn't worth the 200% price increase over a regular parts store filter imo.

      about 7 days ago
    • valerio pilla
      valerio pilla

      I’m lost can, you repeat ?

      about 8 days ago
    • B L
      B L

      Do the same with after market induction kits

      about 8 days ago
    • Ben Corbett
      Ben Corbett

      I would be curious to see if forced induction had more dramatic results.

      about 9 days ago
    • Ralph Hleihel
      Ralph Hleihel

      Is your Subaru turbocharged?

      about 9 days ago
    • turbocharged9589

      If we're not looking at filtration efficiency, then test without having a filter at all. I'm more interested to see how many pollutants are entering the engine in exchange for a few more horsepower.

      about 9 days ago