K&N vs Uni Filter

[Burdy]

looking at buying one of the above filters but cant decide which one i have heard different opinions about both so any info or your opinion is greatly appreciated
cheers Ian

[v840]

http://carl.outerlimits4x4.com/ftopic74 ... ht=filters

[coxy321]

^^^ What he said!! ^^^

[hudson44]

I use a finer filter and have to clean and oil it after every trip where dust is involved as it is very dirty. Means its doing a great job and not letting crap into my engine. K & N might make you go a fraction faster but they let a lot in.

[chicken]

they both suck ,

stick with paper

[GUte]

they both suck ,

stick with paper

Wrong.

What the foam filter does over the K&N is filter.
What the paper filter has over the foam filter is longevity.
I carry extra sleeves.
The foam filters are a two stage and the inner is always dust free.
I have never seen any dust past these filters.
They are very cost effective but a bit more labour intensive.

[ISUZUROVER]

I have never seen any dust past these filters.
They are very cost effective but a bit more labour intensive.

Unless you do oil analysis there is no way to know if your filter is working. Particles which are passing an inefficient filter are too small to be collected in ducting.

I have not tested a finer filter, but other foam filters I have tested have performed VERY poorly.

[PJ.zook]

Dont know about foam filters, but dont use K&N in dusty situations. They flow well, but sacrifice very fine particulate filtering.

Paper is great as it is reasonably cheap, and filters well.

[chimpboy]

Paper filters are the way to go.

[GUte]

I have never seen any dust past these filters.
They are very cost effective but a bit more labour intensive.

Unless you do oil analysis there is no way to know if your filter is working. Particles which are passing an inefficient filter are too small to be collected in ducting.

I have not tested a finer filter, but other foam filters I have tested have performed VERY poorly.

The second stage of the finer filter is always clean.
You would get evidence of dust particles here if the first stage was not working.
The forestry machinery we run use a two stage paper filter as the dust can get past the first.

[mkpatrol]

I have never seen any dust past these filters.
They are very cost effective but a bit more labour intensive.

Unless you do oil analysis there is no way to know if your filter is working. Particles which are passing an inefficient filter are too small to be collected in ducting.

I have not tested a finer filter, but other foam filters I have tested have performed VERY poorly.

Totally agree, use foamies in my old Poo, waste of money.

The foamie one my chook chaser used to always let dirt in during the summer when it was at its driest.

Nothing is perfect but paper is best. Any filter is only as good as the seal it sits in as well. Make sure the seal is good to the filter housing.

[GutSquisher Media]

http://www.bobistheoilguy.com/airfilter/airtest1.htm

Have a read of this may help.

[GUte]

I have never seen any dust past these filters.
They are very cost effective but a bit more labour intensive.

Unless you do oil analysis there is no way to know if your filter is working. Particles which are passing an inefficient filter are too small to be collected in ducting.

I have not tested a finer filter, but other foam filters I have tested have performed VERY poorly.

Totally agree, use foamies in my old Poo, waste of money.

The foamie one my chook chaser used to always let dirt in during the summer when it was at its driest.

Nothing is perfect but paper is best. Any filter is only as good as the seal it sits in as well. Make sure the seal is good to the filter housing.

You are not supposed to let them get dry.
They all need maintenance.

[ADAM 26]

i raced motocross for years, we always use foam filters. the best i found were twin air, as they are dual stage and they pull apart to clean both layers separatly.

every ride they were dirty and had to be cleaned. this enviroment could be compaired to that of being in convoy with a few trucks on a dirt road.

[chimpboy]

http://www.bobistheoilguy.com/airfilter/airtest1.htm

Have a read of this may help.

You are wasting your time. Test after test shows clearly that conventional paper filters are by far the best choice, but there is always a big contingent that will argue for the weaker options until long after you've given up trying to convince them.

It's like the run-your-engine-without-a-thermostat crowd.

[v840]

The foamie one my chook chaser used to always let dirt in during the summer when it was at its driest.

You are not supposed to let them get dry.

I think he's saying the environment he was riding in was dry, hence more dust. Not that the filter was dry.

[bazzle]

I have never seen any dust past these filters.
They are very cost effective but a bit more labour intensive.

Unless you do oil analysis there is no way to know if your filter is working. Particles which are passing an inefficient filter are too small to be collected in ducting.

I have not tested a finer filter, but other foam filters I have tested have performed VERY poorly.

The second stage of the finer filter is always clean.
You would get evidence of dust particles here if the first stage was not working.
The forestry machinery we run use a two stage paper filter as the dust can get past the first.

The 1st paper filter is just that a pre sizing filter, that is why there is a 2nd filter. :(

Paper FTW

Bazzle

[mkpatrol]

The foamie one my chook chaser used to always let dirt in during the summer when it was at its driest.

You are not supposed to let them get dry.

I think he's saying the environment he was riding in was dry, hence more dust. Not that the filter was dry.

Yep, exactly what I mean.

[ISUZUROVER]

i raced motocross for years, we always use foam filters. the best i found were twin air, as they are dual stage and they pull apart to clean both layers separatly.

every ride they were dirty and had to be cleaned. this enviroment could be compaired to that of being in convoy with a few trucks on a dirt road.

People always bring this up....

How long is an MX bike engine expected to last between rebuilds???
How long is a truck engine or mine vehicle engine expected to last between rebuilds?

ALL heavy duty, expensive (truck) engines run fibrous filters with pre-cleaners. None run foam or cotton gauze filters.

Have a read here:
http://www.aulro.com/afvb/technical-cha ... post681491

Foam filters weren't included in the test, but as I said, compared to past experiments I have done with them, they are usually relatively poor in both flow properties and filtration properties.

I have never seen any dust past these filters.
They are very cost effective but a bit more labour intensive.

Unless you do oil analysis there is no way to know if your filter is working. Particles which are passing an inefficient filter are too small to be collected in ducting.

I have not tested a finer filter, but other foam filters I have tested have performed VERY poorly.

The second stage of the finer filter is always clean.
You would get evidence of dust particles here if the first stage was not working.
The forestry machinery we run use a two stage paper filter as the dust can get past the first.

The 1st paper filter is just that a pre sizing filter, that is why there is a 2nd filter. :(

Paper FTW

Bazzle

Not at all. In off-highway engines running a dual element filter, the first filter is the main filter. The 2nd filter is a "safety" filter which is only there in case something goes wrong with the primary filter. It is usually lower efficiency (not as good at collecting particles) than the primary filter.

If FF/unifilter elements are designed that way, then you wouldn't see any dust on the inner foam part under normal conditions - but this does not mean the primary element is working well.

[ISUZUROVER]

For those two lazy to click the above link. A comparison between a Genuine (cellulose fibre = "paper") filter and a K&N filter for a 300Tdi defender.

[TheOtherLeft]

For those two lazy to click the above link. A comparison between a Genuine (cellulose fibre = "paper") filter and a K&N filter for a 300Tdi defender.

Interesting. How is a 20K km old filter more efficient then a new filter?

[ISUZUROVER]

Interesting. How is a 20K km old filter more efficient then a new filter?

Filters are not sieves. The pore sizes in a filter are much larger than the size of particles they are collecting. As particles collect they form a dust "cake" with a pore size that is smaller than the pore size of the filter, and improve filtration efficiency.

A new filter is least efficient. Efficiency increases as the filter loads with dust - so it is actually bad to change your air filter too often.

EDIT:
This image shows 3 very fine filter fibres crisscrossing each other, covered in collected particles (most of them were actually clusters/agglomerates of fine particles). Notice that the gaps between the fibres are huge.


Filter efficiency in fibrous filters is inversely proportional to fibre diameter.

[dumbdunce]

[dumbdunce]

For those two lazy to click the above link. A comparison between a Genuine (cellulose fibre = "paper") filter and a K&N filter for a 300Tdi defender.

without questioning the validity of your results for a moment, your efficiency curves for the K&N filters seem fairly forgiving compared to the actual data plotted. eg the little triangles at 8 um particle size lie at about 95 and 98% efficiency, but the curves sit at 100%? I would have thought that 2 to 5% of 8 micron particles getting into your engine is significant, especially in dusty/offroad situations?

on a related note, what does the efficiency curve and particle size look like for the "average" engine oil filter? ie does an oil filter effectively trap sub 10 micron particles? or once these sub 10 (20?) micron particles are in your oil, are they effectively turning your oil into lapping paste?

[KiwiBacon]

The 1st paper filter is just that a pre sizing filter, that is why there is a 2nd filter. :(

Paper FTW

Bazzle

Sure about that?
AFAIK the second filter is there incase the first filter comes apart or leaks. Essentially a safety device.

[ISUZUROVER]

For those two lazy to click the above link. A comparison between a Genuine (cellulose fibre = "paper") filter and a K&N filter for a 300Tdi defender.

without questioning the validity of your results for a moment, your efficiency curves for the K&N filters seem fairly forgiving compared to the actual data plotted. eg the little triangles at 8 um particle size lie at about 95 and 98% efficiency, but the curves sit at 100%? I would have thought that 2 to 5% of 8 micron particles getting into your engine is significant, especially in dusty/offroad situations?

on a related note, what does the efficiency curve and particle size look like for the "average" engine oil filter? ie does an oil filter effectively trap sub 10 micron particles? or once these sub 10 (20?) micron particles are in your oil, are they effectively turning your oil into lapping paste?

You have a good eye!

The data indeed does not go to 100%. The curves are calculated based on fibrous filter theory, so are not fits to the data. This is indeed a significant point. For some reason the filters in question (cotton gauze) seem to deviate from filter theory and do not go to 100% (I have seen similar results in tests done by others in the filter industry for the same type of filter).

You are right that that is significant.

As for oil filters, it is harder to remove particles in oil since it is more viscous than air. Full flow filters show a similar curve to the theory above, however the 50% efficiency point on the curve will vary between 30-50 microns. Bypass filters and bypass centrifuges can remove much smaller particles though - dependant on the device. Bypass centrifuges can generally remove smaller particles than bypass filters.

[brad-chevlux]

Nothing is perfect but paper is best. Any filter is only as good as the seal it sits in as well. Make sure the seal is good to the filter housing.

So true, the air box that comes with the AIT turbo kit on my GQ has a piss poor seal. it uses an 6CYL EB Falcon filter but doesn't seal well. I have resorted to using grease to seal the filter in.

Not happy with it either way though, the filter is very small.

[ajsr]

For those two lazy to click the above link. A comparison between a Genuine (cellulose fibre = "paper") filter and a K&N filter for a 300Tdi defender.

without questioning the validity of your results for a moment, your efficiency curves for the K&N filters seem fairly forgiving compared to the actual data plotted. eg the little triangles at 8 um particle size lie at about 95 and 98% efficiency, but the curves sit at 100%? I would have thought that 2 to 5% of 8 micron particles getting into your engine is significant, especially in dusty/offroad situations?

on a related note, what does the efficiency curve and particle size look like for the "average" engine oil filter? ie does an oil filter effectively trap sub 10 micron particles? or once these sub 10 (20?) micron particles are in your oil, are they effectively turning your oil into lapping paste?

You have a good eye!

The data indeed does not go to 100%. The curves are calculated based on fibrous filter theory, so are not fits to the data. This is indeed a significant point. For some reason the filters in question (cotton gauze) seem to deviate from filter theory and do not go to 100% (I have seen similar results in tests done by others in the filter industry for the same type of filter).

You are right that that is significant.

As for oil filters, it is harder to remove particles in oil since it is more viscous than air. Full flow filters show a similar curve to the theory above, however the 50% efficiency point on the curve will vary between 30-50 microns. Bypass filters and bypass centrifuges can remove much smaller particles though - dependant on the device. Bypass centrifuges can generally remove smaller particles than bypass filters.

so ben a little of topic here
do you recommend any easily available air filters ie burson/repco sold
ryco cooper wesfil etc or should I source genuine filters??
what about these brands in oil filters?
cheers andrew

[chimpboy]

So true, the air box that comes with the AIT turbo kit on my GQ has a piss poor seal. it uses an 6CYL EB Falcon filter but doesn't seal well. I have resorted to using grease to seal the filter in.

Not happy with it either way though, the filter is very small.

AFAIK the thing to watch, size-wise, is not the apparent size of the filter but the size it would be if you took the paper and spread it out flat. So a thick filter that looks kind of small can actually be quite "large" compared to one that looks bigger but has less paper.

The more paper there is the less restrictive the filter is as long as the folds aren't touching each other.

I could be wrong though, no doubt someone will tell me if I am

BTW I am not saying this applies to your Falcon filter, I have no idea what those look like. I just thought it was worth mentioning.

[ISUZUROVER]

For those two lazy to click the above link. A comparison between a Genuine (cellulose fibre = "paper") filter and a K&N filter for a 300Tdi defender.

without questioning the validity of your results for a moment, your efficiency curves for the K&N filters seem fairly forgiving compared to the actual data plotted. eg the little triangles at 8 um particle size lie at about 95 and 98% efficiency, but the curves sit at 100%? I would have thought that 2 to 5% of 8 micron particles getting into your engine is significant, especially in dusty/offroad situations?

on a related note, what does the efficiency curve and particle size look like for the "average" engine oil filter? ie does an oil filter effectively trap sub 10 micron particles? or once these sub 10 (20?) micron particles are in your oil, are they effectively turning your oil into lapping paste?

You have a good eye!

The data indeed does not go to 100%. The curves are calculated based on fibrous filter theory, so are not fits to the data. This is indeed a significant point. For some reason the filters in question (cotton gauze) seem to deviate from filter theory and do not go to 100% (I have seen similar results in tests done by others in the filter industry for the same type of filter).

You are right that that is significant.

As for oil filters, it is harder to remove particles in oil since it is more viscous than air. Full flow filters show a similar curve to the theory above, however the 50% efficiency point on the curve will vary between 30-50 microns. Bypass filters and bypass centrifuges can remove much smaller particles though - dependant on the device. Bypass centrifuges can generally remove smaller particles than bypass filters.

so ben a little of topic here
do you recommend any easily available air filters ie burson/repco sold
ryco cooper wesfil etc or should I source genuine filters??
what about these brands in oil filters?
cheers andrew

Donaldson, MANN+HUMMEL and Fleetguard/Cummins are the 3 largest automotive filter manufacturers worldwide. Chances are that one of these 3 make the (OEM) filter in your car. All 3 have a policy that the filters they sell are OEM quality or better.