K&N Air Filters

S

SeCX-9

Member
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2016 Mazda CX-9 Signature
Hi,

Anyone here install a K&N Airfilter on your CX-9?

I have a 2008 Mazda CX-9 AWD GT with 3.7L Engine. K&N Filter 33-2395 per their recommendation.

I have been using a ScanGauge II for the last 4 months and during my 25 minute commute have registered about 22.7 to 23.1 MPG using factory paper filter. All highway.

Installed the K&N filter 3 days ago and now getting 20.5 to 21.0 MPG doing the same commute under pretty much the same conditions.

Decrease. NOT what I expected at all.

So I email their support team.
I asked about a break-in period and they said none is required.
They indicate (via email from Paul at K&N) that their is no guarantee with MPG improvement since their are so many variables. He only claims improvement in Horsepower in his first email (and 100% satisfaction gurantee or money back)

Then I asked, how can I show the improvement in HP using my ScanGuage][ and he replies "A replacement air filter typically gains between 1-4 whp, but there is no guarantee for a horsepower increase with a replacement air filter."

So in reality, there is no guarantee of any improvement other than not having to throw away my airfilter which I paid $50 + $10 for the cleaning kit and $9 shipping. That's about 4.5 air filters at $15 a pop.

Has anyone tried the K&N filter and noticed any MPG or performance improvement? If you did, please tell me how.

Thanks
 
I have one and didn't notice a change in MPG at all.
In fact, I've had K&N filters in 4 of my last cars and never noticed a
change in MPG. Performance a little bit, but not MPG.
 
I've had K&N filters on a number of vehicles, including our CX9, and have never noticed an improvement in MPG or horsepower. While I admit that I didn't put it on a dyno to see if it gained 1-4HP, a 1HP difference on a 250HP vehicle is a 0.4% increase - about as insignificant as you can get!

I purchase them because they never have to be replaced and more than pay for themselves as we tend to keep our vehicles for a long time (>200K miles).
 
The only thing you might notice is a slightly higher silicon content if you do an oil analysis. Many people have experienced a decreased amount of filtration versus a stock paper filter.
 
I have K&N on for about 7000 miles now.
What you get is "response" of engine thru better breathing.
MPG? Not noticeable. K&N does not claim that on their website either.
 
I cannot imagine why you would expect to get any increase in gas mileage from a filter swap. Back in the days of carburetors, sure - because the filter would change the pressure drop at the inlet to the carburetor and therefore change the fuel / air ratio. That doesn't happen on a fuel injected engine. The mass air flow meter does not care if the filter is restricting air flow or if the throttle valve is restricting air flow, the fuel /air ratio doesn't change so the MPG doesn't change either. If your K&N filter has too much oil on it, it is possible some oil got sucked into the mass air flow meter and has messed up its calibration therefore resulting in worse mileage.

As far as a HP increase, even that is unlikely since the paper element is designed with a huge amount of surface area to make sure it does not restrict flow even when it is partially clogged with dirt.

K&N established their empire back when it was possible for a filter to make a difference, now they are just relying on people remembering those days and hoping that new customers won't look too hard at their claims or try to hold them to their advertisements. They know that most people will believe they are getting a benefit since they paid for a supposedly superior product - and if customers believe they will get a benefit, nine times out of ten they will convince themselves that they can "feel the engine response is better" or they can "feel the extra horsepower in the seat of their pants". Placebo effects only - you won't measure any increase on a dyno and you won't get any better gas mileage. All you will do is spend money on a product that is nasty to clean and oil and has been proven to increase wear and tear on your engine due to less effective filtering.
 
Rix6,
Believe in whatever you like.
I have swapped my filters (stock and K&N several times) just for experiements and funs.
I can tell the difference definitely. If you can't, you should not buy it.

As I said,
No MPG increase (new vs new).
No HP/Torque increase (no dyno data, either way) that I can feel
Definitely better engine response when pushed
(response = engine revs more responsively)
 
Rix6,

Placebo Effect or not, if you dont believe in it don't buy it. Just to clarify something on your tech review. The airflow meter always sits behind or after the air cleaner housing where the filter resides, and being part of an electrical sensor connected to the ECM which controls engine parameters including fuel/air ratio for optimum engine performance and operation. More airflow (K&N filter) will be measured by the airflow meter communicating to the ECM that more fuel is needed to optimize the air/fuel ratio which in turns equals out to better performace even if its minimal...better MPG...probably not since the ECM is requesting a bit more fuel so the ratio is within programmed parameters.

So believe what you will, as for me a drop-in K&N filter is in place and I will not go back to cheap obstructive paper filters.
 
Davicho said:
Rix6,

Placebo Effect or not, if you dont believe in it don't buy it. Just to clarify something on your tech review. The airflow meter always sits behind or after the air cleaner housing where the filter resides, and being part of an electrical sensor connected to the ECM which controls engine parameters including fuel/air ratio for optimum engine performance and operation. More airflow (K&N filter) will be measured by the airflow meter communicating to the ECM that more fuel is needed to optimize the air/fuel ratio which in turns equals out to better performace even if its minimal...better MPG...probably not since the ECM is requesting a bit more fuel so the ratio is within programmed parameters.
Click to expand...

Don't worry, I won't be wasting my money on one!

I am just trying to make some sense out of your explanation there.... sorry, you are not making any sense. The air filter does not determine air flow - that is the job of the throttle body. The mass air flow sensor is used the by engine ECU to determine how much fuel to inject to keep the air / fuel mixture within the parameters of the tuning map. This is further trimmed by the O2 sensors during closed loop operation. Whether the air flow is restricted by the air filter or not, the ECU will maintain the correct air / fuel ratio. As long as the air / fuel ratio remains correct, MPG will not change.
 
Higher flow filter = more air, at WOT only. The throttle plate controls the air intake, not the filter....until WOT. Before WOT, the ECU won't have to do anything differently.

And you certainly won't be getting better fuel mileage by letting more air in. That's just common sense.
 
Theoretically, a different type of filter can mess things up. For example the pleats and material likely result in different flow patterns at medium and high flow. This can affect sensors down the line.

My advice is unless there is proof that the stock filter is restrictive at your most frequent driving conditions, you are likely wasting your money.

A rule of thumb that I hold to be true in aftermarket performance add-ons is that for adding on to a stock motor, an advertised HP gain of 0-9 HP = 0 HP and an advertised gain of 10-25 HP = 5-7 HP.

Just my experience.
 
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Personally, I have used K&N filters in many different types of performance cars, some with substantial engine modification, among other upgrades. On all of them I noticed either no difference or a slight improvement. Further, BlackCherry06 is right, the filter's effect, if any, will only be felt at WOT.
 
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Same here...have K&N air filters in both the CX-9 and V8 4Runner, and noticed no diff with MPG, but there is a diff in power, especially in the V8 4Runner.
 
I don't own a CX-9 yet, but would stay away from K&N. Don't get me wrong, they are well made and a great concept, but they do allow more dirt to enter the intake system.

Over time this will affect reliability. They are great for racing as long term reliability isn't an issue, but daily use...I wold avoid. Just an opinion.
 
zoommx5 said:
I don't own a CX-9 yet, but would stay away from K&N. Don't get me wrong, they are well made and a great concept, but they do allow more dirt to enter the intake system.
Click to expand...

I am curious to know where you get this information from. The K&N is oiled which traps any "dirt" and if so much dirt was entering the intake manifold that it affected "reliability" then I would think the maf sensor would throw a code before that happened.

I know there are a lot of rumors and myths out there, but I would be interested in concrete testing to show that K&N filters allow an "unacceptable" amount of dirt into the engine. Are there any?

There are some people who try and say that rather than dirt, "oil" gets into the engine, however
it does seem like some people over-oil their filters and then blame the company.

http://www.knfilters.com/filter_facts.htm
http://www.youtube.com/watch?feature=player_embedded&v=UjwBiPm2W5Q
http://www.youtube.com/watch?feature=player_embedded&v=_SPd10AswCo
"what condition does it take to move oil off of our filter to potentially contaminate a mass air flow sensor?"
"we intentionally over oiled a filter....... found there was no weight change to the filter after testing...."

They even dipped a maf sensor in oil, and after a few cycles, the maf returned to normal operating, all the oil dissapated.

http://www.youtube.com/watch?feature=player_embedded&v=HrU-sXkN4UY
http://www.youtube.com/watch?feature=player_embedded&v=Ml8OIrMBfKU

Regarding dirt....

"Our filters are tested by an outside,independent laboratory. They have been proven to stop at least 99% of particles on a SAE dust test. This
test uses particles as low as the 0 - 5 micron range and goes up to 20 microns. For comparison, a paper filter also stops 99% on the same test and
the OEM minimum standard is 96%. Foam is generally the worst media with a typical efficiency rating of 75 - 85%. To get higher ratings, the foam must be more dense and therefore way more restrictive. The "tack" characteristic of a K&N allows for increase filtration without loss of flow as well.
The testing procedure used is SAE J-726 using ISO Test Dust. This test is the standard of the air filter industry. The test procedure consists of
flowing air through the filter at a constant rate (airflow rate is determined by the application) while feeding test dust into the air stream
at a rate of 1 gram per cubic meter of air.
As the filter loads with dust the pressure drop across the filter is increased to maintain the prescribed airflow rate. The test is continued
until the pressure drop increases 10" H2O above the initial restriction of the clean element (in this case .78" to 10.78" H2O). At this point the test is terminated. The dirty filter element is then weighed. This weight is
compared to the clean element weight to determine the total Dust Capacity.
The amount of dust retained by the filter is divided by the total amount of dust fed during the test to determine the Cumulative Efficiency.
The K&N filter achieved the following results:
Dust Capacity: 305 grams
K&N Cumulative Efficiency: 99.05 %
OEM Paper Efficiency: 99.29 %
Holding the filter to the light is useless, pin holes are normal. That is what makes a K&N filter. There are actually hundreds of microscopic
fibers that cross these holes and when treated with oil, capture and hold the very fine particles. On the same hand, they allow the filter to flow more air than paper or foam. The filter is 4 ply cotton gauze unlike some competitors synthetic material filters. The synthetics do not have the very small fibers that natural cotton does. Also, the oil can be pulled off of a foam filter contaminating electronic sensors. It will absorb into cotton and stay in the media. In fact, Honda and Toyota only recommend K&N filters when using aftermarket high flow filters as K&N is the only brand of filter
the oil does NOT come off of. They will not cover a failed sensor if foam filters were used.
We got started over 30 years ago making filters for motorcycles and off road racers. The filters did so well that these guys wanted them for their
cars and trucks. We started making filters for these applications and here we are today. If they did not work, we would not still be here and growing every year.
We now make filters for Chrysler/Mopar, Ford Motorsports, Edelbrock, Rotax Engines, and Harley Davidson. We come as original equipment on the
2000 Ford Mustang Cobra-R. We even made filters for the Apache helicopters used in Desert Storm because of maintenance problems with the original paper design. If they work in these conditions they will work for you.
Our filters have a 10 year / million mile warranty. The dealership may not void the warranty per Federal laws. The Moss-Magnuson Warranty Act of the Fair Trade Commission states that if a part is not covered under warranty, the consumer may use any brand they choose to. Air filters are not covered under the warranty so you are free to use any brand you choose.
We make the filters for Mopar Performance and Ford Motorsports. I find it highly unlikely they would endorse a product that causes problems with their
vehicles. "
 
My experience with them on a 1300cc high performance motorcycle showed a light dust coating on the "clean" side of the air box after about 15K of riding (various conditions-some rain, some dusty roads, mostly backroads and some with coal dust). OEM paper filter=zero dust. Swapped to a UNI oiled foam filter and zero dust. I even applied high-temp grease to the outer edge for better sealing. I also used one a dual sport motorcycle and it worked better, but water goes right through them. At least with oiled foam it would slow down water intrusion. Not a big deal but forging rivers and such it could be the difference between making it home and vapor lock.

I agree if oil is present on the "clean side" of the air box, MAF sensor or throttle body, it's been over oiled. Probably WAY over oiled.

I bet a few google searches would turn up similar reports.

Scientific..far from it, and no way I can back up my comments with measurable figures. With that said, the figures you've listed show a .24% decrease in cleaning efficiency. That does not sound like much, but as I said over time it makes a difference.
 
I have used K&N filters on different vehicles. On my motorhome (Chevy 454) it gave me more climbing power on hills. Don't think there was a major increase in gas mileage. On my F150 it gave me the same improvement when towing. I finally got one for the Cx-9. Not sure about mileage increase or towing power increase, but I will update this coming summer. I have noticed quicker response. Time will tell.
 
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