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I’m not here to step on toes or crush anyone’s dreams about obtaining better MPG or more horsepower by using a K&N air filter. I am only presenting another side to the OEM vs. K&N air filter debate. If you have read my past articles on this board, you know I call it like I see it. I don’t hold back any punches.


The fact is that most street racers along with many commercial and industrial applications utilize some sort of oiled-media air filter. In working with industrial generators and military applications, many had some sort of oil bath air filter or pre-filter application. But is this what is needed on a street application? Does specifically a K&N air filter provide better filtration? Does a K&N air filter give you more MPG? Will a K&N Air filter give you more horsepower? Let’s discuss it.

It’s obvious that people will spend anywhere from $50 to $300 for a K&N air filter all the way up to their High Performance Air Intake Kits on the belief that it will increase MPG and horsepower. Keep in mind, that the auto manufacturers are aware of the K&N air filters and have a much much more extensive research laboratory than K&N, and not one auto manufacturer installs a K&N air filter in their vehicle. Not ONE! In this MPG and horsepower war from one vehicle to another, wouldn’t a manufacturer want to increase its MPG and horsepower by simply installing a K&N or some very similar style air filter? This had me puzzled and actually kept me awake at night. Yes, these are the things I think of in my sleep. This is troubling (yes troubling that I dream about air filters too). Not ONE manufacturer believes that a K&N air filter will increase MPG or Horsepower!!!

I’ve read probably thousands of threads of people who installed K&N air filters and some claim 10% better MPG and more power. Others claim identical MPG and the ‘SOUND’ of more horsepower, but no real HP benefit. Seems nobody can really state what is happening with the air filter. Are K&N owners having buyer remorse after spending $50 to $300 and just claiming they are getting better MPG and Horsepower to justify this expense?

Why isn’t there an absolute test, to test an air filters efficiency? Well, there is. It is called the ISO 5011 test. If you want to test your Purolator, Baldwin, AC, K&N, or AMSOIL air filters it will cost you about $1700 per filter, to send them in and have them tested. For that price you would have real data about your filter. These ISO 5011 machines cost upwards near $300,000.00.

The ISO 5011 standard (formerly SAE J726) defines a precise filter test using precision measurements under controlled conditions. Temperature & humidity of the test dust and air used in the test are strictly monitored and controlled. To obtain an accurate measure of filter efficiency, its very critical to know exactly the amount and size of test dust being fed into the filter during the test. By following the ISO 5011 standards, a filter tested in England can be directly compared to another filter tested in California. The ISO 5011 filter data for each filter is contained in two test reports. Capacity Efficiency and flow restriction.

Without boring you about how the test works, suffice to say they add a controlled amount of dirt to the filter while monitoring its flow capacity. They also monitor the amount of dirt passing through the filter. Various filters were tested being the: AC Delco, Purolator, Baldwin, K&N, and AMSOIL.

Comparing the AC Delco (rated the best from the test results) to the K&N: The AC Delco filter test ran for 60 minutes before reaching its max restriction while the K&N and AMSOIL filters each ran for about 24 minutes before reaching their max restriction. Another interesting bit of information is that the AC Delco accumulated 574 gms of dirt and passed only 0.4 gms. After only 24 minutes the K&N had accumulated 221 gms of dirt but passed 7.0 gms of dirt. Comparing the K&N to the AC Delco the K&N plugged up nearly 3 times faster, passed 18 times more dirt and captured 37% less dirt. The AC Delco filter which passed the smallest amount of dirt and had the highest dirt capacity and efficiency but also had the highest relative restriction to flow. Obviously the better filtering media is also the most restrictive.

Have you tried taking a K&N air filter right out of the box and compared it to an OEM air filter? Try holding them both up to the light? Which has larger holes that you can see light coming through? It will be the K&N. Get out your magnifying glass and examine both filters again? You can actually see the small holes and gaps in the K&N. Dirty air can get through these holes. Also, try typing into GOOGLE the words ‘K&N Scam’. You don’t get one or two sites, but you get the Corvette Forum, Audi Forum, Nissan Forum, Chevy Forum, Suzuki Forum, BMW Forum, Jeep Association, Ford Ranger Forum, Acura Forum, and on and on and on, well, I stopped after 50 pages of this. There were actually 1.66 million results.

Think logically for a moment. Your engine needs the correct amount of air and gas for combustion to happen. An air filter is not a turbo or super charger and cannot force more air into your engine. To be honest, when studying the K&N website and their research, the visions of the infomercials of the Tornado air intake that PROMISED more HP and more MPG popped up in my head. You can still purchase these Tornados on the Internet, but please don’t.

Your engine needs filtered air with as little restriction as possible. That’s a difficult balance to obtain as all air filters start to restrict air flow the more they accumulate dirt. I really have to believe that people on this forum most likely check their air filter a bit more often than other CT owners. Can this filtration be achieved with an OEM paper filter? Honda and ALL the other car manufacturers believe so. Do you think Honda wants their engines being damaged by a cheap air filter if they didn’t work?

I’m going to stick with the OEM or perhaps an AC Delco air filter. I cannot find any justification for spending $50 to $300 to upgrade to something that not only does not appear to benefit my stock engine, but there appears to be logical rationale not to use it. Honda believes so too. If I spent $300 on a K&N high performance air intake kit, and then spent hours more on the installation, I might become defensive by this article. I’m not looking for an air filter thread battle, but just presenting another view. It’s likely that people with K&N air filters wash them frequently which would minimize the amount of passing dirt. Likewise, the K&N high performance air intake kits do give a stock engine a much more aggressive look when you pop the hood to show off your engine.

Logically, how can adding a K&N air filter ADD more HP? Or give you better MPG when comparing a new K&N to a new OEM air filter? They both pass the same amount of air to make up the 14.7-1 air fuel ratio your vehicle needs. It makes no sense and therefore falls into the same category as the Tornado above.
 

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Air Filters

Thanks for the very informative post. I for one agree 100% as a few years back I took the K&N route and with in the year I had it in the trash bin, just my O 2 on the topic.
 

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Agreed. Doesn't anyone think that if simply changing a filter would yield any mpg or hp benefit, automakers would have done it in the design? I love talking with automotive engineers who laugh at all the aftermarket crap people put on their cars that actually make it perform worse! Ultra high performance applications notwithstanding (ie shorter engine life)
 

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K&N Filter

Crashmaster - You have taken the wind out of my sails Bud. I really like the noise the filter produces but, I do think I have gained mileage - but a very small amount - actually negligible. As for HP increases - it seems there is more oomph, but only at high revs. Your explaination makes complete sense. And I think I have to agree. I plan to run it for awhile longer then go back to my OEM. The growl you get though is very cool, I must admit. With the OEM, you get nothing, which can be good too as the growl is loud enough to penetrate the cabin. Thanks for the detailed explaination.

BTW - have you felt the slight side to side vibration at around 20 - 25MPh? A number of us have it - I think ithas somethiong to do with the way the engine is mounted but would like to know your thoughts. It doesn't happen at higher speeds.

I have the 2010 Pearl White EX-L 4WD.
 

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Discussion Starter #5 (Edited)
I’ve looked at K&N air filters, cow magnets, Slick 50, Tornado Air Intake swirlers, water injection, electric superchargers, numerous fuel and oil additives, eBay chips and modules, moth balls, and much more. Don’t get any of them!

I was involved in a case once where a fellow with an older Dodge Ram Truck was on his 4th fuel pump. It was going out about every 6,000 miles and he was getting ready to sue the dealership. The dealership hired me to find out what was happening. After the 4th fuel pump I spoke to the owner and we decided to go have lunch together. On the way to lunch, he stopped at the gas station and filled up his gas tank. He then grabbed a bottle of fuel additive from his glove box and put it in the tank. I asked him why he added the fuel additive? He said that his buddy swore by this additive to get him better fuel economy. I asked him for the container which he gave me. It turns out that this additive was causing the seals on the fuel pump to go out. He obviously did not sue the dealership. Just another case of someone believing the wild claims of advertisers for better MPG.

Now, instead of saying what doesn’t work, lets discuss what does work to give you better performance and better MPG.

1) Lighten your vehicle. Remove the golf clubs, books, and anything else in your car that you don’t need. A lighter car requires less fuel to move it.

2) Drive your vehicle like there is an egg on your gas and brake pedal, or in other words, gentle on the gas and gentle on the brake. Your personal driving habits can make a big difference in MPG. Remember, every time you press on the brake, you are basically converting gasoline into heat.

3) Tire pressures. A drop of 15 PSI in just one tire can rob you of 2 - 4 MPG and even worse if all four tires are under inflated. Upping your tire pressure to the maximum pressure as stated on your tire sidewall will give you a rougher ride and shake your teeth, but your rolling resistance will be reduced resulting in better MPG. Find a comfortable middle ground.

4) Use your Cruise Control. It is not possible for you to keep your foot as steady as the cruise control. Try using your cruise control and it will help you save a few MPG.

5) Keep your air filter clean. Most cars have a larger than needed air filter. Check it every oil change and replace with an AC Delco air filter when needed.

6) Follow your owner’s manual for maintenance.

7) Pay attention to the signal lights. Most are computerize and memorizing them to know when they turn green or red can help you anticipate whether to speed up or slow down a bit.

8) The controversy of A/C on or windows down is very close with the use of modern efficient A/C systems. I would use the A/C or windows however you like and not ‘sweat it’.

9) Avoid rush hour - Try and leave earlier or later to avoid the morning or coming home rush. Sitting in traffic for 30 minutes averages in zero MPG; not good.

10) Stay away from all the MPG gimmicks. The manufacturer also wants you to get the most performance and best possible MPG. If you start altering the engineering of the vehicle it can cause a chain reaction and cause much more problems in the long run.

If you have any other tips, post them.
 

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I've enjoyed working on cars for many years (definitely used a lot of AC/Delco filters on my Corvairs- they were always the best...period) however I cannot fathom installing anything other than OEM parts in any vehicle I drive brand new off the lot these days. The manufacturers have put a lot of engineering time in on the designs and I'm good with what they recommend as opposed to spending even more money for questionable 3rd party "improvements".
 

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This is how I have to argue with people that believe puting Mobil 1, Royal Purple, Redline, Amsoil, etc, etc, etc is better than just puting in what the manufacturer recommends. I have a Mustang, that is very heavily modified, with stock internals. I've added pretty much everything available, including some stuff I had made as one-off items to boost power. I still run Motorcraft 5w-20 at $2 a quart with a $5 Motorcraft filter. I've run the other $5-15 a quart brands with $25+ filters in race engines and they've all died an untimely death whilst being pushed beyond their limits. They lasted just as long, if not longer on the factory recommended stuff. When I was literally going through 4-8 engines a year in my "race" cars, I saved several hundred dollars by not buying oil that was not only not recommended but also overpriced and offered no real improvement and if anything only detrement.

I have a stockish filter on my mustang with a blower, because the aftermarket intake setup was dropping my power tremendously due to excessive heat soak and sucking in hot engine air. High Intake Air Temps (IAT's) on a forced induction car is murder on an engine. I slapped the stock system back on it and the power returned.

Engine designers/manufacturers spend a LOT of time and money figuring out what works best, a lot more than any aftermarket company can afford to spend on developing a single product or even a complete line of products. It's because of that, I just take their word for it when it comes to making the engine last, and produce the power it was designed to make.
 

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TB/Gunk

Crashmaster the crap that gets through the K&N supports my prior experence.
Not to mention the OIL from the filter gunks up the throttle body's, Not Cool.. OEM is hard to beat. Thanks for the info..

Pete
 

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Crash, I liked your reminder about the effects the driver has on MPG. It reminds me of something I read in a computer mag some years ago: the best way to speed up your computer is to type faster.
 

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If anyone wants to do something that will really increase fuel mileage, then look at some of the sites for the "hyper-milers." Not all the techniques are practical, but utilizing some of them as often as possible will net gains, and cost absolutely NOTHING! Hell, just coasting to an intersection will help your brakes and tires last longer, I get baffled at all the people I see accelerating to a red light to mash on the brakes over and over and over. Braking BEFORE the turn, and accelerating out will help as well. It's a very basic tachnique for anyone that's ever driven on a race course.
 

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I think it depends on the auto manufacturers air filter design and cubic inches of filter media, Honda being an Engine company would certainly have the best air filtration and flow per application. However some automotive manufactures seem to have given the engine air filter a last thought. Some in there design really never get that dirty nor do they suck that much air , with long twisting plastic duct work to a massive cavern with a drum style pleated filter ect.... . I think the flat panel pleated media style is the most efficient and apparently so does Honda.
 

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I have it on all my vehicles including motorcycles. Guess what, I don't notice any differences.
The only reason I changed it is simply bcuz it's time to change out the OEM one, and I figured the cost is not much difference and I don't have to buy another filter again.
I do believe it makes a difference on the bigger motors like 4.0 + tho.
 

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I've seen them tested on a flow bench and when compared to OEM filter media a brand new K&N will flow 2-3% more air, mostly because it has larger "pores." That's when comparing identical sizes that would both be in the stock air box (for simplicity sake in this comparison. . .won't even talk about "cold intake" kits, that is topic deserving of its own debate).

First thing I'd say is with MAF sensors and very high tech computer controlled fuel injection and throttle bodies - does 2-3% more air available to the engine matter? Pure speculation - I don't think that the weakest link on a modern engine is constriction of air intake. Especially because a "used" air filter that needs changing will flow 50-75% less air on a flow bench, but a car will still run with it just fine.

That aside, say it actually does make a difference in delivering an extra 2-3% more useful air to the engine. . .Then it comes down to filter maintenance. For every 10 people I know that have a K&N, I want to say 1 of them has the K&N filter cleaning & recharge kit, but in all honesty, I'm the only one I know that has it. . .ha (and I don't have a K&N, I have it to oil other filters I own). So ya that 2-3%+ measurement drops precipitously over time, and obviously gets restrictive as it gets dirty, just like paper media. How many K&N owners clean their filters and re-oil them on a regular schedule? Not a heck of a lot I bet.

Between my two vehicles (2001 BMW 325ci & 2011 CT EX-L) high quality OEM air filters are between 4-8 times cheaper vs. drop in K&Ns. So for the cost of one K&N drop in, I'd rather use OEM air filters personally, I could even afford to double the rate that I change them (thus the engine is getting more CFM of air a higher percentage of the time). So for me, in my daily drivers, I go with the OEM paper filters. . .however if I had a car I vintage raced or when I get my special ops tactical assault boat, ya those will have K&Ns. :)



-ace
 

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Discussion Starter #16 (Edited)
For argument sake, and I do have an OEM system, but what about K & N website which shows their intake system delivering 10.23hp over OEM unit.

http://www.knfilters.com/dynocharts/69-1210_dyno.pdf

Any thought on this.

If I owned the K&N company, I would certainly prefer to test my own air filters (as opposed to any independent 3rd party). Just this fact alone makes their readings bias.

Explain to me how two different brand air filters that both have more than sufficient capacity to flow all the air that an engine needs (especially at 5217 RPM) will chart different horsepower readings?
 

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(QUOTE): I dont know how thats why I'm asking. I not for or against imtakes im just truley asking for knowledge sake. I know magazines like import tuner or other honda magazine do independent dyno tests that show HP gains with items like intake headers and exhaust.

Again like I said im asking for knowledge sake

accordy2g,

I like people who ask questions. ALWAYS ASK! I just hope that between myself and others here on the forum we can answer.

Let me ask this: If changing to a K&N air filter will give you 10 more horsepower, how much more horsepower would you get if you dyno’d without any air filter? Wouldn’t you think that it should gain you a bit more HP as no air filter is less restrictive than a K&N?

The whole thing makes no sense unless you are comparing a new K&N to a very very very very very dirty OEM air filter. Then I can easily imagine a 10 HP difference.

What is K&N claiming the reason for the HP increases? About the only thing it could be is due to lack of restriction. If that is the reason, then it must mean that the OEM filter they are comparing it to is very very restrictive.

Looking at the K&N website www.knfilters/hp_gains.htm , they admit that there are several factors that can affect the SAE corrected horsepower values as measured by K&N or at any other dyno facility. Some of these factors are.
1) Consistency of test parameters
2) Tire Pressure
3) Fuel octane rating
4) Vehicle Condition
5) Atmospheric Condition

K&N also goes on to state that SAE corrected horsepower values will vary from day-day, while testing the same vehicle, due to the manner in which the vehicle’s on-board computer adjusts for varying climate conditions.

I went ahead and emailed the technical support people at K&N with this issue. If I get back a response, I’ll be happy to share it with the forum.

Keep asking!
 

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Ok - good convo. . .a little confusing in the last post as to who is doing the talking (accord, did you somehow switch fonts to CM's font in the middle of that post?) but anyway.

First off the 10hp/10lb-ft dyno charts that accordy mentioned are first & foremost not for a K&N drop-in air filter, they are for an intake system that eliminates the stock air box and replaces it with a cone filter. Here is a picture of it.



So ya, no drop-in could ever give 10hp & 10lb-ft, that's impossible.

I'm going to give my thoughts on the pros & cons of cone intakes and also what kind of data is most needed to actually judge their efficacy in an unbiased way.

The pros of a K&N cone intake system:
- that air filter will sound manlier (it eliminates that whole resonator beneath your battery whose purpose is to quiet down your intake. . .it's a family car! :) )
- theoretically it's less "restrictive" than the factory airbox, if one could argue that the factory airbox was not delivering enough air to the engine
- Dyno testing shows a peak HP & torque increase of 10hp & 10lb-ft each, which sounds great

The cons of a K&N cone intake filter system:
- heat soak. . .look at your engine, see where the exhaust manifold comes off the front of the engine? how many inches is that from your airbox? not very many. . .and you want to put a metal pipe there? And you're going to replace computer designed pretty sophisticated OEM ducting that uses less obvious things like negative underhood air pressure to suck in air like a vacuum with something that visually looks like it is going to catch a lot more air. . .

But nobody tested that intake in a wind tunnel on our cars, nobody hooked up a codescanner to the OBD2 port to poll your live IAT (intake air temperature) and compare it to the ambient air temperature on that intake, have they? Cause that's important. . .you want to retard your performance? Go feed your car hotter air. . .(and yes, I actually have hooked up a codescanner to my OBD2 port right when I got the car because I wanted to see how hot that exhaust manifold was making things and I was shocked at how cool the IAT stayed)

Like I said in my earlier post, if I had a vintage racecar or some such application, I probably would have a K&N cone under the hood. . .but there would also be a lot less stuff in the air path; my exhaust manifold would be ceramic coated and my intake tubing would be either shielded or coated to keep it cool.

- Drivability. . .this is the biggest gripe I have with aftermarket parts that use real dyno data to convince semi-naive consumers of the efficacy of their parts.
1. A dyno test occurs under basically one identical condition (stock vs. modified), I drive in a seemingly limitless blend of conditions (humidity; air temp; vehicle weight/load; altitude, etc.) that end up being of a lot more importance to me than one moment in time. I'm not going to drive my car on a dyno only. . .ha.
2. A dyno test of that intake could be massively different if they tested it: after 45/90/120 days of usage; if the vehicle has been on for 5 seconds before the dyno test or 15 minutes
3. There is no "SAE chassis dynamometer testing procedure" - the amount of air and its temperature that are blown onto the vehicle during the test are up to the operator's discretion. . .some people, like when you're doing a balls to the wall pull to see how much your motor can lay down, will dyno with the hood up, while other dyno with the hood down - imagine the difference this could make to the results when the OEM intake relies more on a static air pressure drop and the K&N relies more on air being blown over it with positive force.
4. The coup de grace. . .look at this dyno chart carefully:



I'll admit this comparison isn't the best example of my point, but look at a bunch of these and you'll see some where the difference is big. You want to look at the overall behavior of the plot, the peak is sort of irrelevant. Sorry I accidentally cropped out the scale on the Y axis but you can still tell visually, for example in these plots - why does the stock intake perform a lot better until around 3000rpm? You will never see one dyno plot totally better or totally worse than another (if its the same engine and you're testing an intake/exhaust mod), you'll see tradeoffs. Now you have to think, in your daily driving - where does your tach spend the most time? Mine spends most of its time under 3k. . .so you better get used to that "wooshing" noise of the K&N because you're going to be needing to hold down the throttle longer (and use more gas too) to bang the first 3k out of every gear. Under light throttle our tranny shifts around 3k, so those high end benefits will never be felt! Oh and also, Honda already has a pretty ingenious system that modifies how much air your engine sucks in at higher RPM, it's called VTEC. As I further look at the graph, it's barely statistically significant, but look at the HP comparison, right around 6k rpm, the gap lessens there and then widens again. . .so what's my HP gain at 6k? 5hp?

Ok so I'm not crowning any winners here, I'm just trying to bring to light that there is a lot of other stuff going on with intakes and a lot of ways that test data needs to be gathered and also examined.

Also the term "cold air intake" has always made me laugh because they are trying to sell it on the point that their aftermarket intake is sucking in more cold air, but more often than not I'd be willing to bet that their IAT is higher than stock.

And another good way to test mods is to take your car to a drag strip. It's about 1/4th the cost of a dyno, and a lot more fun. It doesn't "exactly" replicate the driving you'll do in the real world unless you drive at WOT 100% of the time, but it does bring thing like heat soak, performance at speed, etc., into measurable stats that dyno testing can't quite replicate.

-ace
 

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Aceman:

Dont know how my last posts has the other font It looks like someone wrote that for me. ButI only wrote the first part.

And secondly thanks so much that was very informative!!!!
 

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Aceman:

Dont know how my last posts has the other font It looks like someone wrote that for me. ButI only wrote the first part.

And secondly thanks so much that was very informative!!!!
Sorry about the prior post, as a moderator I have too many buttons in front of me and obviously pressed a wrong one. As the youth now say: My bad. :eek:
 
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