K&N Filters - Read and Decide

[oldndumb]

Here is one of the more empirical air filter tests that I have read in the last five years. There are also many other independent evaluations available on the net, but it is hard to get past all of the commercial links, especially since Amsoil has joined the market.

If you don't mind reading technical data, and your eyes don't glaze over, it is a good source of comparable information that you may/may not use to make your own decision.

I would add that a professional performance engine builder's air filter preference is valid for that engine's operational environment and purpose only, and that it has minimal correlation to ordinary consumer everyday driving.

If a K&N is your choice, that is fine since it is your bike/car/truck/etc. Please save your flames and respond with data if you are inclined, not emotion.

http://home.stny.rr.com/jbplock/ISO5011/SPICER.htm

[Calliway]

Very good article. Its odd that AC Delco wins in every dept. I have been a Wix guy for a long time and new that they were in the upper quality portion.

What I also find interesting is that Wix and Purolator make filters for many other labels including AC Delco. I also really like Mann filters but since they are European it is really hard to find any data on them.


Very good post OnD. I hope people can get through it.

[DaveM]

Originally Posted by Calliway

Very good article. Its odd that AC Delco wins in every dept. I have been a Wix guy for a long time and new that they were in the upper quality portion.

What I also find interesting is that Wix and Purolator make filters for many other labels including AC Delco. I also really like Mann filters but since they are European it is really hard to find any data on them.


Very good post OnD. I hope people can get through it.

OND you should know I DIDN"T READ IT!

When I used to smoke I never bothered with filters I just used straight Camel shorties, filters are for girls! (sorry female members)

My best buddy just gave me an oil article out of a Rapid magazine and I forced myself to read that, I think I learnt something but I am not really sure

Calliway, I like a Manly filter too.

DaveM

[Chillerguy]

I've got a K & N in my bike. I'll admit that, but the reason I did it was more to do with being able to reuse it as opposed to buying a $35 dollar filter from the dealership. $15 more to buy one I can re-use? Hell ya. But I never kidded myself in to thinking that it would make my bike faster, as if it needs it to be. I do wish I had seen this before I bought it though, might have made me think twice. Thanks OnD!

[3banger]

I find the the dust loading curve and resistance to flow the most interesting. This confirms what I have always believed about K&N's; they are the least restrictive because they do the poorest job filtering the air. If you take a brand new pre-oiled K&N out of the box and hold it up to the light you will see pin holes of unblocked light. This is not the case with a good paper element.

The dust loading curve also shows the K&N with the lowest initial pressure drop but then rapidly exceeding the rest as it is loaded with dirt. It seems to start loosing at about 150 gms, but what does this represent in terms of real world miles driven?

I have a calculator at work that can tell me the HP lost by a few inH2O pressure drop at the intake. On Monday I work out HP advantage of K&N vs stock paper filter. Looking at the data I'll have to do some clever normalizing to make this apply to the ST.

Does any body know if 350cfm is typical full throttle air flow on a GM Duramax?

[Calliway]

350cfm on a Duramax? Lets do the math. I have no idea what redline is on a duramax

if the displacement is 6.6L and you are spinning at 5000rpm you are displacing 6.6L 1250 times in a minute. 6.6L equals .23cf.

.23cf x 1250=287.5 cfm at 5000rpm.


Why 1250? Its a 4 stroke engine and only sucks in air and fuel 1 out of every 4 strokes. The more RPM you spin the more cfms of air you will use.

They used to rate carbs in cfms, the Holley Dominator 1100cfm etc. That is the maximum amount of air a carb can take at wide open throttle.

This is just a logic equation and there might be an actual equation to tell you exactly what the cfms are I just dont know it. I am sure someone can add to this.

[KitNYC]

I didn't read the article, but I bet it said K&Ns flow the most air & catch the least junk. Am I right?

Filters, from least restrictive to most:

Steel
Cotton/gauze (like K&N)
Foam
Paper

Filters, from least effective to most:

Steel
Cotton/gauze (like K&N)
Foam
Paper

It ain't exactly rocket science, though it is nice to see the issue addressed in a scientific fashion.

Cheers,
-Kit

[dolson]

Thanks again OnD,

When I bought my bike I asked Rod my dealer about putting a K&N on my new bike.
He reached up to the shelves and pulled a new stock Triumph and a new K&N out of their boxes, took a pair of shears and cut them apart, laid them open on the counter and told me to take a look and decide for myself and he would put whatever I wanted on my bike.

Looking at the number of pleats, surface area and eyeballing micron size I said no question I'd keep the stocker and he said, "good choice."

Prior to that I had put them on my car and truck. After that I took a look and found dirt downstream from the filter knowing that I had cleaned the tract out. Out they came and in the trash they went. They had about 5k on them.

I like my engines too much and learned.

Don

[Pickle Jim]

Excellent article. But! I suspect the K & N filter spec for a truck may be slightly different to the MC filters.
At one point it stated that the K & N had a linear loading curve whilst the washable and reuseable filters displayed an exponential curve as dirt built up. This leads me to believe that the K & N tested was not reuseable.
Also any data for reuseable filters only holds true in the as new state, once reoiled they are subject to variations in cleaning and oil loading which can alter the characteristics by a wide amount.

[lemansnz]

Well I could not understand why so many engine builders would recommend a bad filter.
After all it's what they do.

So I did some searching to find the answer.
It seems that there is different needs in filtration between a petrol and a diesel engine.
http://www.knfilters.com/efficiency_testing.htm

It seem that the filters have been made to the required needs of a petrol motor and can only guess that the smaller particles can pass though the motor with minimal damage to the motor.

This maybe not ideal but that could be the cost for the extra power.
After all it is still better than the dark old days when we use to ride and race with out any filter's at all and just a screen to keep out the stones.