The general opinion around here is that K&N filters are not good for cars since they allow more dirt into the engine. This results in higher Si numbers. However, do we really know if these higher numbers are bad? Since we are dealing in ppm, would the increase be actually detrimental to an engine?
Are 'bad' filters really bad?
- Thread starter Scott P
- Start date
- Status
Patman
Staff member
Yes, any increase in silicon from dirt is bad.
You can often see on analysis when high silicon is dirt, and not other forms of silicon (gasket material, antifoaming agents, etc), because then the wear metals across the board are higher.
Not all cases with K&N air filters show very high silicon, but generally speaking they are not as efficient at trapping dirt as paper filters are.
Even if you only see a 2 or 3ppm increase in dirt over a 5k interval, it will definitely reduce your engine's life. By how much, it's hard to pinpoint exactly though.
You can often see on analysis when high silicon is dirt, and not other forms of silicon (gasket material, antifoaming agents, etc), because then the wear metals across the board are higher.
Not all cases with K&N air filters show very high silicon, but generally speaking they are not as efficient at trapping dirt as paper filters are.
Even if you only see a 2 or 3ppm increase in dirt over a 5k interval, it will definitely reduce your engine's life. By how much, it's hard to pinpoint exactly though.
I also know that many K&N owners over-clean their filters. Of the few others around me who have one, most of them clean it more frequently than they would replace a paper filter. This is in conflict with how K&N recommends using the filter, & (I suspect) leads to larger & more numerous fabric pores.
I think that the theory that people overclean K&N's is almost certainly correct. And then I imagine they damage the filter media, overoil it, and probably keep it too clean so it never reaches it's final efficiency when dirty. Most people do not understand that a dirty filter filters better.
I spoke with K&N today and they insisted their filters filter considerably better than OEM paper filters. They did not say they filter as good, or almost as good, but considerably better.
I am happy, because I ordered a filterwrap for my K&N today. This wrap is designed to keep water out and also for dusty, off road applications.
I do not drive in dusty applications, but felt extra protection could not hurt! Also, I think the waterproofing idea is great. I live in Florida where there are heavy rains and flash flooding, and I know one of the worst things for and engine is water getting in. So with the filter wrap, I have to think I am getting pretty good protection. Also, I will not clean my K&N before 30,000, and probably closer to 50,000 miles, so I should get the final efficiency numbers.
Finally, I think that K&N should more heavily market their filter wrap. Maybe it would ease peoples concerns. K&N did not make a filter wrap for my model filter, but they work with a company that will custom make them, the total cost was only $20.
I spoke with K&N today and they insisted their filters filter considerably better than OEM paper filters. They did not say they filter as good, or almost as good, but considerably better.
I am happy, because I ordered a filterwrap for my K&N today. This wrap is designed to keep water out and also for dusty, off road applications.
I do not drive in dusty applications, but felt extra protection could not hurt! Also, I think the waterproofing idea is great. I live in Florida where there are heavy rains and flash flooding, and I know one of the worst things for and engine is water getting in. So with the filter wrap, I have to think I am getting pretty good protection. Also, I will not clean my K&N before 30,000, and probably closer to 50,000 miles, so I should get the final efficiency numbers.
Finally, I think that K&N should more heavily market their filter wrap. Maybe it would ease peoples concerns. K&N did not make a filter wrap for my model filter, but they work with a company that will custom make them, the total cost was only $20.
Flag, honestly, what do you expect their phone reps to tell you?
BTW, the K&N topic comes up quite often. Enough that you won't find many people contributing who've "been there". Check the archives for some of the older discussions. Several have more depth than anything I've seen recently.
David
BTW, the K&N topic comes up quite often. Enough that you won't find many people contributing who've "been there". Check the archives for some of the older discussions. Several have more depth than anything I've seen recently.
David
hey cool...where did u get that? id like to see that type of discription on a normal air filter. hehe for a sercond i thought that was an oil filter but then i go it cant be. i wonder how many micron is a conventional filter
Is that picture of the one of the openings in the K&N? But doesn't the oil provide the additional layer of impediment?
That is an interesting picture. I have been able to document >200 micron pores in my K&Ns as well. It make you wonder how they work at all. There is clearly some design principle beyond simple particle size inclusion at work here. My guess is that the pleated design works sort of like a HEPA filter: negative pressure vortexes are formed on the clean side of the filter that deflect particles back to the oiled surface where they are trapped. If this is the case, larger or denser particles would be more likely to pass through this type of filter than smaller less dense particles. Maybe the system works because the particles that make it though can be efficiently removed by the full flow oil filter.
It's my understanding that the oiled cotton fibers have an electrostatic charge which attracts the dust particles. The dust is then trapped in the oil film.
If this is true, then the size of the filter pores isn't that relevant.
Does anyone remember the old "oil bath" air filters? They contained oil in the bottom of the filter pan, and the dust was captured there. The airflow was directed to the bottom of the pan, and then back upward to the carb. They worked because the air could change directions, but the inertia of the solid particles would carry them straight down, where they were captured by the oil.
If this is true, then the size of the filter pores isn't that relevant.
Does anyone remember the old "oil bath" air filters? They contained oil in the bottom of the filter pan, and the dust was captured there. The airflow was directed to the bottom of the pan, and then back upward to the carb. They worked because the air could change directions, but the inertia of the solid particles would carry them straight down, where they were captured by the oil.
If there's enough oil on the media to cross this size of pore then under power that oil will be pulled into the intake. Not good.
Ranger, go out and put your hand over the intake while you rev the engine. Think about an electrostatic charge catching and holding particles as they move in that airflow.
Not all of their filters have these holes. I've seen some that were very uniform, and others that had several areas like this, new out of the box. It appears to be a quality control issue with their media. This is likely another reason (beyond intake leaks) some people have analysis results that are just fine with K&N filters, and others show obvious problems.
If buying, not a bad idea to open and inspect before leaving the store.
Ranger, go out and put your hand over the intake while you rev the engine. Think about an electrostatic charge catching and holding particles as they move in that airflow.
Not all of their filters have these holes. I've seen some that were very uniform, and others that had several areas like this, new out of the box. It appears to be a quality control issue with their media. This is likely another reason (beyond intake leaks) some people have analysis results that are just fine with K&N filters, and others show obvious problems.
If buying, not a bad idea to open and inspect before leaving the store.
I don't think an electrostatic charge is involved. That's how a dry HEPA filter works. They are not effective at anywhere near the flow rates required for an engine air filter.
I agree with 1QL. They seem to have a quality control problem that could be inherent in the design/manufacturing process. There is some type of resin coating the cotton gauze that has holes in it of varying sizes. I have a K&N in my Honda that works very well. But when I put one in my 4-runner, I went from
Along with the difficulty of sealing many K&N models in the airbox, sample variation in the filtration media could explain why some units work well and others do not.
I still would like to understand their principle of operation. They sure do pass a lot of air without much restriction.
I agree with 1QL. They seem to have a quality control problem that could be inherent in the design/manufacturing process. There is some type of resin coating the cotton gauze that has holes in it of varying sizes. I have a K&N in my Honda that works very well. But when I put one in my 4-runner, I went from
Along with the difficulty of sealing many K&N models in the airbox, sample variation in the filtration media could explain why some units work well and others do not.
I still would like to understand their principle of operation. They sure do pass a lot of air without much restriction.
My opinion: K&N is good for short term benefits, but for those who keep their cars long-term it's
[ March 16, 2003, 09:17 AM: Message edited by: S2000driver ]
[ March 16, 2003, 09:17 AM: Message edited by: S2000driver ]
yeah same here...hahaha we should start making filters ourselves and experiment on filtration ability. now that would be some work
Wow, that was a lot of information. In regards to that picture, keep in mind that the hole is just one pore. I'm sure that the particle fitting through that hole would've gotten trapped in the material behind it.
I guess I'll wait until I get my oil analysis done to see what the numbers look like. I have an SLP airbox on my Grand Prix, so I don't have a lot of other options at this point.
I guess I'll wait until I get my oil analysis done to see what the numbers look like. I have an SLP airbox on my Grand Prix, so I don't have a lot of other options at this point.
True, but also keep in mind they ony use 3-ply of this material.
if some of you guys would ever bother to read up on things instead of speculating, you would understand why a k&n works so good inspite of its large openings.
http://www.knfilter.com/facts.htm
http://www.knfilter.com/facts.htm
Hey cryptokid, are you on the Kia forum?
Anyways, I do think that K&N filters at times do indeed let in more dirt. They are not speculating, it often shows up in oil samples as a high silica number. It may indeed be because people clean them too often, damage them ect., I can understand that it would be better to have soom dirt on the filter to aid in trapping more dirt.
Here another little tid bit- K&N filters don't always help performance. If you replace a restrictive airbox with a 6 inch K&N filter-yea, you most likely will see a improvement. If you just put in a K&N "drop in", then maybe not.
I've had two bad experiences with K&N filters, both were with "drop in" K&Ns. The first time was back when I was road racing motorcycles. I was running in a production class that allowed minimal performace mods. One of the mods allowed was to replace the factory filter with a drop in style. I rejetted the bike and put the filter in at the same time. I jetted the bike according to the directions and it was way rich. I figured I had installed the wrong jets by mistake so I pulled the carbs and checked-nope. So I put the stock jets back in-still rich. Figured I may have over-oiled the filter and washed it and re-oiled it. Still rich so I washed the filter and put no oil on it. Still rich!!
I called the manufacturer of the jet kit and asked them about my situation. He told me to put everything back the way it was before and try it out he also reminded me to check everything I had messed with to make sure I was not missing something. No dice. Took the filter out-bingo!!Better. Put the stock filter back in-bout the same as no filter.
Called the guy back and told him and he asked the part number and told me to call him back in a week or so and he would get one to test on his flow bench. He tested it and found that it did not flow as well. It was not much, I can not rember the exact amounts as it was something like 15 years ago but it did flow less air-not much but enough to have to jet down a number or two. Remeber, this was a production class and 2 or 3 horsepower was the difference between passing and getting passed.
I called K&N to try to return the filter and get my money back and was told that they did not say it would make more power-only last a million miles! I was seriously perturbed!
My second bad K&N was with my 2000 Firebird. Drop in K&N did not help a bit. I can swap them at the track and I don't see a bit of difference in mph-not a bit. On the other hand, I can take out the filter and I consistantly see around a 1/2 mph or so everytime. Also the filter that my car uses is also used on some other car, either that or they have had some engineer make a heck of a mistake. The filter comes with a jippy little gasket that you have to put on the airbox so it will seal because the K&N has a gasket that is too thin. I bought a Holley filter and it has more surface area, does it result in more power? Most likely not, but I could now throw away the jippy extra gasket.
Anyways, I do think that K&N filters at times do indeed let in more dirt. They are not speculating, it often shows up in oil samples as a high silica number. It may indeed be because people clean them too often, damage them ect., I can understand that it would be better to have soom dirt on the filter to aid in trapping more dirt.
Here another little tid bit- K&N filters don't always help performance. If you replace a restrictive airbox with a 6 inch K&N filter-yea, you most likely will see a improvement. If you just put in a K&N "drop in", then maybe not.
I've had two bad experiences with K&N filters, both were with "drop in" K&Ns. The first time was back when I was road racing motorcycles. I was running in a production class that allowed minimal performace mods. One of the mods allowed was to replace the factory filter with a drop in style. I rejetted the bike and put the filter in at the same time. I jetted the bike according to the directions and it was way rich. I figured I had installed the wrong jets by mistake so I pulled the carbs and checked-nope. So I put the stock jets back in-still rich. Figured I may have over-oiled the filter and washed it and re-oiled it. Still rich so I washed the filter and put no oil on it. Still rich!!
I called the manufacturer of the jet kit and asked them about my situation. He told me to put everything back the way it was before and try it out he also reminded me to check everything I had messed with to make sure I was not missing something. No dice. Took the filter out-bingo!!Better. Put the stock filter back in-bout the same as no filter.
Called the guy back and told him and he asked the part number and told me to call him back in a week or so and he would get one to test on his flow bench. He tested it and found that it did not flow as well. It was not much, I can not rember the exact amounts as it was something like 15 years ago but it did flow less air-not much but enough to have to jet down a number or two. Remeber, this was a production class and 2 or 3 horsepower was the difference between passing and getting passed.
I called K&N to try to return the filter and get my money back and was told that they did not say it would make more power-only last a million miles! I was seriously perturbed!
My second bad K&N was with my 2000 Firebird. Drop in K&N did not help a bit. I can swap them at the track and I don't see a bit of difference in mph-not a bit. On the other hand, I can take out the filter and I consistantly see around a 1/2 mph or so everytime. Also the filter that my car uses is also used on some other car, either that or they have had some engineer make a heck of a mistake. The filter comes with a jippy little gasket that you have to put on the airbox so it will seal because the K&N has a gasket that is too thin. I bought a Holley filter and it has more surface area, does it result in more power? Most likely not, but I could now throw away the jippy extra gasket.
yup, i dont recognise you though.
i have more miles than i care to say on a k&n, and my compression is still within 98% of factory spec. what have you to say about that?
- Status
Similar threads
