K&N vs Uni Filter

[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.

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.

a bike motor will last a while, depends on how its riden. reving a 250 four stroke to 13000 rpm while racing will mean the 4 times a year ill pull the head off and re-valve it and put new springs in. iv never had a problem with dust in the motor, i replaced rings and pistons because i was chasing the fine edge of performance, we were running race fuel, bigger cams, more comp, and raised the rev limiter, all this put lost of additional streess on the engine.

then there is the buch basher 250, it will get reved to no way near limiter, which is set much lower anyway, mostly stock internals, it will last at least a few years without touching it.

a truck motor the has a red line of 3500-4500 @stock spec will have a much longer life expectancy. but you dont have to service them as offten as a bike.

in reguards to a foam filter they have to be oiled correctly, it not as easy as just slapin any old oil on there and away ya go.

if your chasing the fine edge for performance, the first thing to go is the old paper filter!

[dumbdunce]

if your chasing the fine edge for performance, the first thing to go is the old paper filter!

only if you want that performance at the expense of engine life. the price of good filtration (and therefore engine longevity) is a performance penalty. there's no such thing as a free lunch.

in a high rpm race engine, inertial effects will do the damage (flogged ring grooves, hammered valve faces/seats, flogged bigends) long before airborne particulates have time to cause significant abrasive damage. for most 4WD owners, protecting their "investment' (I use the term loosely - any vehicle, financially speaking, is a liability) is of higher importance than eking out a few measly kW at the top end of the range. there are so many better and less destructive ways to increase power and/or reduce fuel consumption - exhaust, computer remapping, forced induction, cam timing and duration, intake runner length, porting, there are dozens of ways to improve engine pwformace - the thing about changing a filter is its easy and cheap, and it will probably change the engine note and make you think you've got a seat of the pants improvement in power which on a dyno will be insignificant or invisible.

[KiwiBacon]

if your chasing the fine edge for performance, the first thing to go is the old paper filter!

How do you figure that?

Have you measured the pressure drop across a stock paper filter and found it was too high?
Or are you going by marketing claims that "tests prove we get 1kw more"?

[dumbdunce]

if your chasing the fine edge for performance, the first thing to go is the old paper filter!

How do you figure that?

Have you measured the pressure drop across a stock paper filter and found it was too high?
Or are you going by marketing claims that "tests prove we get 1kw more"?

Ben's data show that the K&N filters have a lower pressure drop than fibre element filters, however that does not necessarily translate to a significant measurable difference at the road wheels.

it would be good to see some pressure difference data for foam filters as opposed to the oiled cotton type - I'm pretty sure they would flow less air than a paper element, they just don't have the available surface area, and the oiling means they load up way too quickly - with a paper filter, most of the heavy bits end up in the bottom of the filter drum, with a sticky oiled filter, it all sticks.

[KiwiBacon]

if your chasing the fine edge for performance, the first thing to go is the old paper filter!

How do you figure that?

Have you measured the pressure drop across a stock paper filter and found it was too high?
Or are you going by marketing claims that "tests prove we get 1kw more"?

Ben's data show that the K&N filters have a lower pressure drop than fibre element filters, however that does not necessarily translate to a significant measurable difference at the road wheels.

it would be good to see some pressure difference data for foam filters as opposed to the oiled cotton type - I'm pretty sure they would flow less air than a paper element, they just don't have the available surface area, and the oiling means they load up way too quickly - with a paper filter, most of the heavy bits end up in the bottom of the filter drum, with a sticky oiled filter, it all sticks.

Of course there'll be a bigger pressure drop across the real filter, but even twice as much means little if it's 1kpa vs 2kpa.
I run a restriction guage on my 4wd (donaldson informer) and it shows I've got a good sealed system that doesn't currently need cleaning.

[dumbdunce]

if your chasing the fine edge for performance, the first thing to go is the old paper filter!

How do you figure that?

Have you measured the pressure drop across a stock paper filter and found it was too high?
Or are you going by marketing claims that "tests prove we get 1kw more"?

Ben's data show that the K&N filters have a lower pressure drop than fibre element filters, however that does not necessarily translate to a significant measurable difference at the road wheels.

it would be good to see some pressure difference data for foam filters as opposed to the oiled cotton type - I'm pretty sure they would flow less air than a paper element, they just don't have the available surface area, and the oiling means they load up way too quickly - with a paper filter, most of the heavy bits end up in the bottom of the filter drum, with a sticky oiled filter, it all sticks.

Of course there'll be a bigger pressure drop across the real filter, but even twice as much means little if it's 1kpa vs 2kpa.
I run a restriction guage on my 4wd (donaldson informer) and it shows I've got a good sealed system that doesn't currently need cleaning.

yes I just looked at the numbers, if a paper element drops 0.2kPa at 50l/min it could conceivably be around the 1kPa mark in 4000rpm territory; so even halving that (assuming all the extra available air contributes 100%) means a less than 0.5% power gain at the top end.

my 80 has the factory restriction switch but I've never seen the light come on, even with a grotty filter and running 17psi boost all the way to redline. wonder if it works

[ISUZUROVER]

yes I just looked at the numbers, if a paper element drops 0.2kPa at 50l/min it could conceivably be around the 1kPa mark in 4000rpm territory; so even halving that (assuming all the extra available air contributes 100%) means a less than 0.5% power gain at the top end.

my 80 has the factory restriction switch but I've never seen the light come on, even with a grotty filter and running 17psi boosy all the way to redline. wonder if it works

The pressure drop across the filter is usually insignificant compared to the losses in ducting and elbows. Corrugated pipe is especially bad.

[TheOtherLeft]

yes I just looked at the numbers, if a paper element drops 0.2kPa at 50l/min it could conceivably be around the 1kPa mark in 4000rpm territory; so even halving that (assuming all the extra available air contributes 100%) means a less than 0.5% power gain at the top end.

my 80 has the factory restriction switch but I've never seen the light come on, even with a grotty filter and running 17psi boosy all the way to redline. wonder if it works

The pressure drop across the filter is usually insignificant compared to the losses in ducting and elbows. Corrugated pipe is especially bad.

I agree, why snorkel manufacturers use corrugated pipe is beyond me. Cheaper then using elbows I suppose.

[brad-chevlux]

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.

i totally agree with you there.
the unfortunate thing for me is the falcon filters are not very 'deep'.
I'm not overly worried about the flow, i've seen the same filter 'make' 140RWK in an auto falcon.
It's more about filter life vs cost of filter. at this rate i'll be replacing it every 5000km, (my GQ spends 95% of its time on dirt)

I'm looking at modifying an EL falcon air box. cheap to buy and the filters cost the same as what i pay now, but they are twice the size

[ISUZUROVER]

i totally agree with you there.
the unfortunate thing for me is the falcon filters are not very 'deep'.
I'm not overly worried about the flow, i've seen the same filter 'make' 140RWK in an auto falcon.
It's more about filter life vs cost of filter. at this rate i'll be replacing it every 5000km, (my GQ spends 95% of its time on dirt)

I'm looking at modifying an EL falcon air box. cheap to buy and the filters cost the same as what i pay now, but they are twice the size

Car (on-road) air filters are usually specced to a lower efficiency than 4x4/off-road filters.

Added to that, a cyclonic pre-cleaner (either on a snorkel head of incorporated into the filter housing) will remove 50-80% of the mass of dust before it gets to your filter.

If I was spending 95% of my time offroad I would not be running a car filter. If space was a problem I would run something like a donaldson "powercore" or MANN+HUMMEL "compact plus" filter and housing.

[brad-chevlux]

i totally agree with you there.
the unfortunate thing for me is the falcon filters are not very 'deep'.
I'm not overly worried about the flow, i've seen the same filter 'make' 140RWK in an auto falcon.
It's more about filter life vs cost of filter. at this rate i'll be replacing it every 5000km, (my GQ spends 95% of its time on dirt)

I'm looking at modifying an EL falcon air box. cheap to buy and the filters cost the same as what i pay now, but they are twice the size

Car (on-road) air filters are usually specced to a lower efficiency than 4x4/off-road filters.

Added to that, a cyclonic pre-cleaner (either on a snorkel head of incorporated into the filter housing) will remove 50-80% of the mass of dust before it gets to your filter.

If I was spending 95% of my time offroad I would not be running a car filter. If space was a problem I would run something like a donaldson "powercore" or MANN+HUMMEL "compact plus" filter and housing.

I gather filter for light trucks 5T plus would have filters speced well enough?

[ISUZUROVER]

I gather filter for light trucks 5T plus would have filters speced well enough?

A truck filter should be a better spec. As long as it is appropriately sized.

[brad-chevlux]

I gather filter for light trucks 5T plus would have filters speced well enough?

A truck filter should be a better spec. As long as it is appropriately sized.

i should at least be able to get a good Donaldson filter the fit the housing too.

truck filter housings are cheap here

[GUte]

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.

Your such a chump Chimp! Thermostats?

The tests don't include the foam.
I'm going by personnel experiences.
Am I not entitled to that?
I've seen dust past a paper.
I haven't seen dust past my foam in extreme dust in a convoy.
If it is proven that the foam are no good I will happily except that and admit it.
It's in my best interests.
Can the foam/finer be tested Ben?
Filtering to me is more inportant than flow.

[Guy]

The tests don't include the foam.
I'm going by personnel experiences.
Am I not entitled to that?
I've seen dust past a paper.
I haven't seen dust past my foam in extreme dust in a convoy.
If it is proven that the foam are no good I will happily except that and admit it.
It's in my best interests.
Can the foam/finer be tested Ben?
Filtering to me is more inportant than flow.

I would have thought that was quite clear .. the paper\factory style has won against just about everything.
If you want less pressure drop, install a bigger (more surface area) paper\fiberous filter.

[ISUZUROVER]

Can the foam/finer be tested Ben?
Filtering to me is more inportant than flow.

If I ever get some time I will test a finer filter as I have one here. However this test done in the US included a whole range of filters available for a duramax diesel, including a (foam) unifilter. It was about on par with a K&N.
http://duramax-diesel.com/spicer/index.htm

One of the complaints about some (aftermarket) filters is that they don't seal properly in the housing. No filter will work if it isn't sealed.

[brad-chevlux]

The tests don't include the foam.
I'm going by personnel experiences.
Am I not entitled to that?
I've seen dust past a paper.
I haven't seen dust past my foam in extreme dust in a convoy.
If it is proven that the foam are no good I will happily except that and admit it.
It's in my best interests.
Can the foam/finer be tested Ben?
Filtering to me is more inportant than flow.

I used to have a CRF450. With titanium intake valves. Every CRF owner knows how much damage even the smallest amount of dust will do to the intake valves on these bikes.
the ONLY option was for foam filters. I couldn't buy anything els. As a result over 12 months it went through three sets of new intake valves, yet the S/S ehxaust valve never even needed a regrind.

It was solely due to dust that i had problems with valves.

I sold the bike as at $500 a go for head rebuilds it wasn't worth it.

[GUte]

The tests don't include the foam.
I'm going by personnel experiences.
Am I not entitled to that?
I've seen dust past a paper.
I haven't seen dust past my foam in extreme dust in a convoy.
If it is proven that the foam are no good I will happily except that and admit it.
It's in my best interests.
Can the foam/finer be tested Ben?
Filtering to me is more inportant than flow.

I used to have a CRF450. With titanium intake valves. Every CRF owner knows how much damage even the smallest amount of dust will do to the intake valves on these bikes.
the ONLY option was for foam filters. I couldn't buy anything els. As a result over 12 months it went through three sets of new intake valves, yet the S/S ehxaust valve never even needed a regrind.

It was solely due to dust that i had problems with valves.

I sold the bike as at $500 a go for head rebuilds it wasn't worth it.

Alot of bikes only run a single stage.
I have never had an issue with my KTM525.
The Honda's have had issues with valves and oil consumption and Yamaha's have had issues with valves.

[GUte]

I would have thought that was quite clear .. the paper\factory style has won against just about everything.


Like you say, just about everthing.

[GUte]

The tests don't include the foam.
I'm going by personnel experiences.
Am I not entitled to that?
I've seen dust past a paper.
I haven't seen dust past my foam in extreme dust in a convoy.
If it is proven that the foam are no good I will happily except that and admit it.
It's in my best interests.
Can the foam/finer be tested Ben?
Filtering to me is more inportant than flow.

If you want less pressure drop, install a bigger (more surface area) paper\fiberous filter.

As I stated, filtering to me is more important than flow.

[brad-chevlux]

The tests don't include the foam.
I'm going by personnel experiences.
Am I not entitled to that?
I've seen dust past a paper.
I haven't seen dust past my foam in extreme dust in a convoy.
If it is proven that the foam are no good I will happily except that and admit it.
It's in my best interests.
Can the foam/finer be tested Ben?
Filtering to me is more inportant than flow.

I used to have a CRF450. With titanium intake valves. Every CRF owner knows how much damage even the smallest amount of dust will do to the intake valves on these bikes.
the ONLY option was for foam filters. I couldn't buy anything els. As a result over 12 months it went through three sets of new intake valves, yet the S/S ehxaust valve never even needed a regrind.

It was solely due to dust that i had problems with valves.

I sold the bike as at $500 a go for head rebuilds it wasn't worth it.

Alot of bikes only run a single stage.
I have never had an issue with my KTM525.
The Honda's have had issues with valves and oil consumption and Yamaha's have had issues with valves.

The valve issues are because of the titanium valve and dust.
With no dust there is no problem. the only issue is you can't get a good enough filter that fits.
You'll find the KTMs have different valve material.

[ajsr]

The tests don't include the foam.
I'm going by personnel experiences.
Am I not entitled to that?
I've seen dust past a paper.
I haven't seen dust past my foam in extreme dust in a convoy.
If it is proven that the foam are no good I will happily except that and admit it.
It's in my best interests.
Can the foam/finer be tested Ben?
Filtering to me is more inportant than flow.

I used to have a CRF450. With titanium intake valves. Every CRF owner knows how much damage even the smallest amount of dust will do to the intake valves on these bikes.
the ONLY option was for foam filters. I couldn't buy anything els. As a result over 12 months it went through three sets of new intake valves, yet the S/S ehxaust valve never even needed a regrind.

It was solely due to dust that i had problems with valves.

I sold the bike as at $500 a go for head rebuilds it wasn't worth it.

Alot of bikes only run a single stage.
I have never had an issue with my KTM525.
The Honda's have had issues with valves and oil consumption and Yamaha's have had issues with valves.

GUTE I can assure you that even the twin air factory twin stage foam filters in ktm will still leak dust into your engine.
I raced ktm's for 10 years and in the warrigul 4day a few years back every team had dust problems (every one) ,not every brand of bike stopped but they are not all built the same ( ie Titanium vales). The bike I was riding ( 450 exc) was running a brand new factory pre oiled and sealed filter every change with the rim greased and when we started used oil after the event we pulled it down as well as the other two bikes also run and found all motors had been dusted. Just because you can't see it doesn't mean it isn't happening.
by the way the ktm rfs motors are notoiusly bulletproof compared to a crf engine so not really a fair comparison.
Anyway I spoke to a good mate who also rode the event who is a pro Yamaha sponsered rider who I might add runs finer filters and all their bikes had suffered from dust ingress as well and every bike from that team in that event was rebuilt.

ps you will find most bikes that run single stage foam filters are motorcrossers and with then its all about perfomance on usually moist tracks and if you look at their manuals they all have 15 - 25 engine hour rebuild scheduals, so a bit of dust ingress is not an issue. Ive never seen a modern enduro bike with a single stage filter and Ive owned or ridden most of them.

[coxy321]

A bit off topic, but i don't know of a single CRF that hasn't had vavle issues - it seems to be more of an issue in the 250's (probably moreso because they get revved harder than the 450's).

I don't know how dust can affect the intake valves - the issue they have is the valves stretch or the seating surface pulls into the seat, up to the point where shims can no longer make up the required tolerance. Generally we don't have too many issues after replacing the valves with good quality titanium units. We actually had a 2008 CRF250 come back in last weekend after 12 hours (race bike) and the valve clearances were spot on.

Better springs also help here too (to stop the valves hammering on the seat).

[brad-chevlux]

A bit off topic, but i don't know of a single CRF that hasn't had vavle issues - it seems to be more of an issue in the 250's (probably moreso because they get revved harder than the 450's).

I don't know how dust can affect the intake valves - the issue they have is the valves stretch or the seating surface pulls into the seat, up to the point where shims can no longer make up the required tolerance. Generally we don't have too many issues after replacing the valves with good quality titanium units. We actually had a 2008 CRF250 come back in last weekend after 12 hours (race bike) and the valve clearances were spot on.

Better springs also help here too (to stop the valves hammering on the seat).

the titanium valves have a coating on them to stop them wearing. once the coating is worn away its down hill real fast. the dust wears the coating very fast. from the research i did when my problems started, the intake valves in engines run in wet low/no dust areas last alot longer then engines run i dusty areas.

[dumbdunce]

my 80 has the factory restriction switch but I've never seen the light come on, even with a grotty filter and running 17psi boost all the way to redline. wonder if it works

ok I have seen it come on now, on the freeway on a cool evening at, well, say around about back to the future speed, and lo and behold the filter was pretty grotty.

if I remember next change I'll sample the oil and have it analysed.

[Toli]

I gather filter for light trucks 5T plus would have filters speced well enough?

A truck filter should be a better spec. As long as it is appropriately sized.

i should at least be able to get a good Donaldson filter the fit the housing too.

truck filter housings are cheap here

Have a look to see if a forklift housing might be able to fit.

Just a suggestion.

[Wilba]

On the subject of aftermarket filters. I have seen a k & n shrink under heat(thats what we are blaming) it was sold by with a performance upgrade turbo kit by a well known company.Dust got around the top seal of filter and dusted it bad.I love hp but will never compromise any of my motors with such filters.The company compensated and dosen`t recomend that type of filter any more.gu td42 Billy.

[Struth]

So what was the question again,

Should I use K&N or Uni Filters?

or

Which is best K&N or Uni fliters?

[coxy321]

I don't use any filter - it has the best airflow, and you can really hear the turbo whistle!! Its fully sick uleh - all the racers are doing it.

[mike_nofx]

So..... BEST option might be OEM paper filter, with a well sealed snorkle, fitted with an oiled foam pre-filter on the snorkle head?

Thats what i run on my cruiser in dusty situations.

Mike