K&N KN-171B/C Specifications
#1
12-09-2009, 06:07 PM
K&N KN-171B/C Specifications
In reply to my inquiry about the technical specifications of the K&N KN-171B/C oil filter (the ones that fit our bikes), K&N provided this information. My take on it is that a one-number quotation for a conventional filter is meaningless since efficiency and particle size are both variables for the filter media (for a paper or woven filter media - a stainless media as in some oil filters is another matter since they are evaluated differently). Read this information from K&N to suit your purposes:
Hello,
When referring to particle sizes in regards to oil filters, it is important to realize exactly how small the particles being discussed really are. Then, we can discuss the filtration effects of the filters in question in regards to engine life. There is a misconception when it comes to oil filters, that the smaller the micron rating the better the filter. Some companies rate their filter as a “5 micron” filter, which means the filter will catch particles microns in size with at least 50% efficiency. Let’s put a 5 micron particle in perspective. 1 micron is .001mm (or .00003937 inch), so 5 micron is .005mm (.00019685 inch). The tolerances in your engine will be no smaller than 2.5 thousandths of an inch (.0025”). So, 2.5 thousands of an inch which is equal to a 63.5 micron particle. A 5 micron particle is smaller than a human red blood cell, and too small to see with the naked eye. So how can a particle that size cause damage to your engine?
Next, let’s consider the purpose of an oil filter bypass valve. A bypass valve opens when the inlet side of the filter gets too restrictive. This can happen when the engine is cold and the viscosity of the oil is high (due to the weight of the oil), but this primarily happens when the filter media gets too restrictive or clogged. This is done to keep catastrophic engine failure from occurring. The lower the pressure relief rating, the sooner the valve allows oil to bypass the filter. The last factor that contributes to the bypass opening is the amount (surface area) of the filter media used in the filter. A filter that has a high surface area is going to hold more contaminant and promote good oil flow for a longer period of time, so the bypass will take longer to open.
If the filter you use is 95% efficient at 5 microns it is going to remove more contaminant than a filter that is 3% efficient at 5 microns. The question is, how long will it take for those filters to load up with contaminant and enter bypass? The answer is simple, the more efficient filter will load up sooner, but at what expense? Oil flow is necessary to lubricate rotating parts and prevent engine failure, and dirty oil flow is better than starving the engine of oil completely (the theory behind the filter bypass). Clean oil is best for long engine life, and a filter that can promote clean oil flow consistently for a long period of time is a key component of any healthy engine.
When you are talking about filtration, whether it be oil or air, there is a balancing act that has to be performed to ensure your engine gets the protection it needs while giving your engine the most flow possible. Unfortunately, when the focus is an oil filter that is catching extremely small particles at a high percentage, the tradeoff is flow rate. This put the consumer in a “Catch-22” situation. Do you use a filter with the most efficient media at the smallest particle rating, and have the bypass open letting unfiltered oil through the system? Or do you have a filter that does not filter as small a particle size, but filters more of the oil for a longer period of time? K&N filters are designed to give you the balance of oil flow and filtration. Of course, we would like to say we have the most efficient filter at the smallest micron range, but the fact is we are not going to sacrifice oil flow or the quality of filtration by having a high efficiency filter that operates in bypass mode for 80% percent of its life. I know for me personally it’s a simple decision, the small particle filtration does not mean anything to me since we are talking about particles I can’t see, especially if there is a remote possibility of unfiltered oil touching my bearing surfaces causing premature wear and eventual engine failure.
When you are comparing filters, to make the most informed decision possible, look at the following things (with the least amount of emphasis on micron rating): Filtration efficiency, Filter surface area, bypass setting, micron rating.
The KN-171 filter has a nominal micron rating of 25, meaning it will capture 25 micron particles with at least 50% efficiency. The filtration efficiency of the KN-171 at 5 microns is 3%. The KN-171 also has 165 sq.in. of filter area, partially the reason it flows 25% better than the OE, paired with a bypass that opens at 14psi. The equivalent Harley Davidson filter is 95.8% efficient at 5 microns and 98.6% at 25 microns. It also has 63 sq.in. of media and a bypass that opens at 10psi. This means the Harley filter will run in bypass mode for a significant portion of its installed life, whereas the K&N will allow oil to flow through the filter for a longer period of time.
If you have any questions, please contact our Technical Support department.
Thanks for writing,
Thomas Walden
Technical Support & Sports Marketing
800-858-3333
ThomasW@KNFilters.com
Hello,
When referring to particle sizes in regards to oil filters, it is important to realize exactly how small the particles being discussed really are. Then, we can discuss the filtration effects of the filters in question in regards to engine life. There is a misconception when it comes to oil filters, that the smaller the micron rating the better the filter. Some companies rate their filter as a “5 micron” filter, which means the filter will catch particles microns in size with at least 50% efficiency. Let’s put a 5 micron particle in perspective. 1 micron is .001mm (or .00003937 inch), so 5 micron is .005mm (.00019685 inch). The tolerances in your engine will be no smaller than 2.5 thousandths of an inch (.0025”). So, 2.5 thousands of an inch which is equal to a 63.5 micron particle. A 5 micron particle is smaller than a human red blood cell, and too small to see with the naked eye. So how can a particle that size cause damage to your engine?
Next, let’s consider the purpose of an oil filter bypass valve. A bypass valve opens when the inlet side of the filter gets too restrictive. This can happen when the engine is cold and the viscosity of the oil is high (due to the weight of the oil), but this primarily happens when the filter media gets too restrictive or clogged. This is done to keep catastrophic engine failure from occurring. The lower the pressure relief rating, the sooner the valve allows oil to bypass the filter. The last factor that contributes to the bypass opening is the amount (surface area) of the filter media used in the filter. A filter that has a high surface area is going to hold more contaminant and promote good oil flow for a longer period of time, so the bypass will take longer to open.
If the filter you use is 95% efficient at 5 microns it is going to remove more contaminant than a filter that is 3% efficient at 5 microns. The question is, how long will it take for those filters to load up with contaminant and enter bypass? The answer is simple, the more efficient filter will load up sooner, but at what expense? Oil flow is necessary to lubricate rotating parts and prevent engine failure, and dirty oil flow is better than starving the engine of oil completely (the theory behind the filter bypass). Clean oil is best for long engine life, and a filter that can promote clean oil flow consistently for a long period of time is a key component of any healthy engine.
When you are talking about filtration, whether it be oil or air, there is a balancing act that has to be performed to ensure your engine gets the protection it needs while giving your engine the most flow possible. Unfortunately, when the focus is an oil filter that is catching extremely small particles at a high percentage, the tradeoff is flow rate. This put the consumer in a “Catch-22” situation. Do you use a filter with the most efficient media at the smallest particle rating, and have the bypass open letting unfiltered oil through the system? Or do you have a filter that does not filter as small a particle size, but filters more of the oil for a longer period of time? K&N filters are designed to give you the balance of oil flow and filtration. Of course, we would like to say we have the most efficient filter at the smallest micron range, but the fact is we are not going to sacrifice oil flow or the quality of filtration by having a high efficiency filter that operates in bypass mode for 80% percent of its life. I know for me personally it’s a simple decision, the small particle filtration does not mean anything to me since we are talking about particles I can’t see, especially if there is a remote possibility of unfiltered oil touching my bearing surfaces causing premature wear and eventual engine failure.
When you are comparing filters, to make the most informed decision possible, look at the following things (with the least amount of emphasis on micron rating): Filtration efficiency, Filter surface area, bypass setting, micron rating.
The KN-171 filter has a nominal micron rating of 25, meaning it will capture 25 micron particles with at least 50% efficiency. The filtration efficiency of the KN-171 at 5 microns is 3%. The KN-171 also has 165 sq.in. of filter area, partially the reason it flows 25% better than the OE, paired with a bypass that opens at 14psi. The equivalent Harley Davidson filter is 95.8% efficient at 5 microns and 98.6% at 25 microns. It also has 63 sq.in. of media and a bypass that opens at 10psi. This means the Harley filter will run in bypass mode for a significant portion of its installed life, whereas the K&N will allow oil to flow through the filter for a longer period of time.
If you have any questions, please contact our Technical Support department.
Thanks for writing,
Thomas Walden
Technical Support & Sports Marketing
800-858-3333
ThomasW@KNFilters.com
#2
12-10-2009, 07:55 AM
Grand HDF Member
From reading this it sound like the K@n filter is more restrictive then a Harley filter, so why would you want that and possibly starve the motor of oil waiting for the bypass to open?
#4
06-07-2022, 02:55 AM
But I could be mis-understanding.
#5
06-07-2022, 11:56 AM
Tourer
Wow....the K&N oil filter is just like their air filters. Crap!...in terms of actual filtration!
"The KN-171 filter has a nominal micron rating of 25, meaning it will capture 25 micron particles with at least 50% efficiency." This means 50% of the time, the filter may no even catch a particle of 25 microns. Or in other-words it'll flow through! The rep goes on to say and justify the crappy filtration simply because he can't "see" a particle size...?
"the small particle filtration does not mean anything to me since we are talking about particles I can’t see," This is just ****-poor logic. The RnD at HD aren't going to base their design criteria based upon something superficial and speculative of being able to "see" abrasives.
I guess with K&N's ideology of filtration, this is why so many silicates (aka "sand-like" debris) get entrapped in oil. Hold up to the light your K&N air filter, and you'll "see" tiny pin-holes of light. I guess this is the metric of K&N's opinion of what necessitates "adequate" filtration. Let's just put this in perspective:
What is the typical size of a piece of sand? 0.02mm (depending on what sources you look at)
What is 25 micron to mm? 0.025mm
This would mean "sand-like" particles would pass right through the oil filter by that K&N rep's own admission!
Anyway, thank you for sharing, OP!
"The KN-171 filter has a nominal micron rating of 25, meaning it will capture 25 micron particles with at least 50% efficiency." This means 50% of the time, the filter may no even catch a particle of 25 microns. Or in other-words it'll flow through! The rep goes on to say and justify the crappy filtration simply because he can't "see" a particle size...?
"the small particle filtration does not mean anything to me since we are talking about particles I can’t see," This is just ****-poor logic. The RnD at HD aren't going to base their design criteria based upon something superficial and speculative of being able to "see" abrasives.
I guess with K&N's ideology of filtration, this is why so many silicates (aka "sand-like" debris) get entrapped in oil. Hold up to the light your K&N air filter, and you'll "see" tiny pin-holes of light. I guess this is the metric of K&N's opinion of what necessitates "adequate" filtration. Let's just put this in perspective:
What is the typical size of a piece of sand? 0.02mm (depending on what sources you look at)
What is 25 micron to mm? 0.025mm
This would mean "sand-like" particles would pass right through the oil filter by that K&N rep's own admission!
Anyway, thank you for sharing, OP!
The following users liked this post:
Glennstur (06-07-2022)
#7
06-16-2022, 05:21 PM
Just how many of you has had an engine failure from oil related/filtering from either HD or K&N. Filters ? Or worn out engine for that matter ?. Here is an interesting read. 540 Rat technical.
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