Air Filters reviewed

[whiteknight]

Found this to be interesting. Why are K&N's rated so low :(

http://home.usadatanet.net/~jbplock/ISO5011/SPICER.htm

[dumbdunce]

this is a r3p0st of a r3p0st

http://www.outerlimits4x4.com/PHP_Modul ... spicer+htm

[mkpatrol]

Interesting, I have always used paper filters as they are superior. I dont have a high performance engine so I dont need the extra airflow for power I want the extra protection for longevity.

Every dirt motorcycle I have ever owned with a foam filter has passed dirt down the inlet manifold no matter what i did, they were not so bad when they were new but when they had been in the bike for a while they were not as effective.

If anyone wants a K&N filter for a CBR1000f you can have mine as I will be flicking it in favour of a paper unit when I have finished the top end rebuild , mucho dirto in the carbies with this one fitted.

[bazzle]

4 Ricers........

Bazzle

[ISUZUROVER]

Found this to be interesting. Why are K&N's rated so low :(

Because (IMO) K&N's are a a waste of money. They have a small surface area compared to a paper (cellulose fibre) filter, and a higher void space. So they may have a lower pressure drop (flow more air) but they sacrifice filtration efficiency to do it.

IMO if you fit a K&N to a 4x4 you are sacrificing engine life for slighly increased performance.

[dumbdunce]

Found this to be interesting. Why are K&N's rated so low :(

Because (IMO) K&N's are a a waste of money. They have a small surface area compared to a paper (cellulose fibre) filter, and a higher void space. So they may have a lower pressure drop (flow more air) but they sacrifice filtration efficiency to do it.

IMO if you fit a K&N to a 4x4 you are sacrificing engine life for slighly increased performance.

and even that increased performance is arguable - when the filter is freshly cleaned it does flow more air, but by the time it has accumulated 200g of dirt http://home.usadatanet.net/~jbplock/ISO ... age012.jpg it is more restricted than almost any other filter. This is with a 'control' dirt particle size and the cloggage may well be faster in real life under certain conditions.

[Rb25sil80]

I must say I am very dissapointed to read this after fitting a K&N filter. I would have thought who over wrote the Feroza power up guide would have taken this information into account. Or at least given some reference to the findings in his article.

Don't get me wrong, I drew quite alot from the article and it was very well written. I must say I am very surprised that K&N rated so poorly.

Can one just assume that if the filter is cleaned and oiled regularly that it will still perform to a reasonable standard as far as filtering dirt goes?

Im shocked folks are using these in their 4x4's if they clog up 3 times faster pass 18 times more dirt and campture 37% less dirt then other filters. Any theorys on the test results?

Cheers
Brad

[-Nemesis-]

I think it comes down to common sense really. K&N's are great, in road cars. But when you have an offroad vehicle, in offroad conditions, it needs to be protected. Just like we armour the exterior of our rigs, we should armour the internals. Which means the air filters most efficient at catching dust, not letting air through.....

You don't need that extra 5 kw's (etc) on the rough stuff. So if your that pedantic, maybe run a K&N daily whilst having a paper element ready to throw in as soon as you hit the dirt (hmmm i might have to follow my own advice here, thats a good one....)

[Patroler]

Most fourbys probably aren't going to gain stuff all from a free flowing filter on its own anyway, unless the engine has a few major mods to increase airflow (exhaust, cams, head work, boost, rev limit increased etc)
So I'd say that there'd be other factors limiting airflow than just filters alone - dependent on vehicle of course...

fwiw on my dirt bike i run foam filters (twin air) and have 4 of them, a new one (cleaned and oiled) goes on every time i ride it and when i ride sand i run a filter skin, which is like a stocking that you stretch over the outside of the filter, its designed to keep fine dust/sand out.
The fact that these are made by the same company is probably and admission that the standard foam job may not quite be upto sand and fine dust on its own?? But at least they acknowledge it..

[ISUZUROVER]

Can one just assume that if the filter is cleaned and oiled regularly that it will still perform to a reasonable standard as far as filtering dirt goes?

No, the exact opposite - filter dust collection efficiency increases as the filter loads up with dust.

Read this if you don't believe me...

http://www.outerlimits4x4.com/PHP_Modul ... ght=filter


If you want your intake air as clean as possible, the best 2 available filter media are:
Donaldson filters with "UltraWeb" and Mann Filter "Micrograde N" filters. Probably not available as retrofit systems for most vehicles though, unless you change your airbox.

If you fit the largest (highest surface area) fibrous (paper) filter you can fit into the engine gay, you will probably get more of a performance increase than you would with a K&N anyway.

[murcod]

You don't need that extra 5 kw's (etc) on the rough stuff. So if your that pedantic, maybe run a K&N daily whilst having a paper element ready to throw in as soon as you hit the dirt (hmmm i might have to follow my own advice here, thats a good one....)

That's what I do on my Feroza- K&N on road and fit the standard canister with the paper element off road. Only takes about five minutes to swap once you've done it a few times.

[bru21]

I used to make my own air filters out of petrol resistant foam. it costs about 1/3 of an aftermarket filter and you can choose different pore sizes. glue them with contact adhesive (don't rinse in petrol). at one stage i used a layer of each density.

i am going to run squares of oiled high density foam before the paper filter to catch the bulk dust which then can be removed quickly and exchanged when needed. running both is more restirictive short term but better long term or on average especially for things like the obc.

[murcod]

Be careful of too much restriction on turbo charged vehicles. The thrust bearing on the turbo can be prone to premature failure if there is too much restriction!

[ISUZUROVER]

I used to make my own air filters out of petrol resistant foam. it costs about 1/3 of an aftermarket filter and you can choose different pore sizes. glue them with contact adhesive (don't rinse in petrol). at one stage i used a layer of each density.

i am going to run squares of oiled high density foam before the paper filter to catch the bulk dust which then can be removed quickly and exchanged when needed. running both is more restirictive short term but better long term or on average especially for things like the obc.

It is really not necessary to do this when you have a decent filter. The best thing you can do is use a filter chamber with a cyclonic pre-cleaner - they remove 50-85% (depending on revs and design/efficiency) of the dust before it gets to the filter.

[dumbdunce]

Be careful of too much restriction on turbo charged vehicles. The thrust bearing on the turbo can be prone to premature failure if there is too much restriction!

and be very careful of using any kind of foam filter on a turbo engine - when they load up they can collapse, sending chunks of dirty foam through the compressor wheel. which sends chunks of dirty foam and chunks of broken compressor wheel foam through the inlet valves, to ge crunched between piston and head, before being crunched through the exhaust valves, where all those lovely, gritty, munched up chunks make a final appearance, clawing at the leading edges of the turbine wheel blades.

paper element filters win every time.

[beachbuggy]

I always thought foam was better in race engines where it can be replaced and serviced regularly. The manufacturers dont use foam ...but they charge so much for their paper ones its a rip off.

[-Nemesis-]

From a manufacturers point of view, they are never going to include a rechargeable foam element on a vehicle. The reason being that it doesn't need replacing, and they can't charge you for the replacements at every service.

[ISUZUROVER]

I always thought foam was better in race engines where it can be replaced and serviced regularly. The manufacturers dont use foam ...but they charge so much for their paper ones its a rip off.

We did some testing here for a Formula 1 filter manufacturer. Originally they supplied foam filters. When they saw the test results they switched to paper (cellulose fibre) elements.

And bear in mind that people who are selecting filters for race engines only want the engine to last one race and get maximum power. Those are completely different constraints to an engine you want to last many years.

There is an engineer on one of the UK LR forums who used to work for the Ford Focus WRC team - he said that one time he had both their drivers screaming at him because the engines in both cars had failed, because the air filters weren't up to the job.

[LuxyBoy]

ISUZUROVER wrote:
"The best thing you can do is use a filter chamber with a cyclonic pre-cleaner"

Has anyont seen one of these inline? I want one but the only ones i can find are like the Donaldson, that goes on top of your snorkel and they look crap.

[ISUZUROVER]

ISUZUROVER wrote:
"The best thing you can do is use a filter chamber with a cyclonic pre-cleaner"

Has anyont seen one of these inline? I want one but the only ones i can find are like the Donaldson, that goes on top of your snorkel and they look crap.

If you have a standard hilux(donaldson) air box you should already have one inside???

But what is more important - looking crap but having a good engine or looking good with a buggered engine.

[coxy321]

Just my 2c. I use K&N on road cars, which dont come into much contact with dirt/gravel/dust. I find that they work, provided they are serviced properly.

As far as "re-usable" filters (K&N) on 4x4's goes, they're basically piontless. I know for a fact that one trip down my parents 500M gravel driveway basically shags a new K&N filter full of red dust. I have spoken to the local diesel and truck service shops in town, and as far as they're concerned - you can't beat fresh paper elements. They're fairly cheap, can be "banged out" to remove excess crud, and again, they're cheap.

Have a pre-cleaner, and just stick with what the manufacturers put in it to start with. You cant loose.

Coxy