Don't replace your air filter!!!

[ISUZUROVER]

Too frequently anyway...


From Caterpillar

Filter manufacturers often say "dirty" filters are more efficient than new ones because dust cake buildup on the surface actually increases filtration.

http://www.cat.com/cda/layout?m=37499&x=7

Filter media becomes more efficient as it collects dust, so it is actually better to change your filter less frequently (why most truck filters have a pressure-drop guage so you can only change the filter when necessary).

The attached graph is for 2 filters from a major filter manufacturer, and shows the efficiency increase with dust load, and also the corresponding pressure drop increase across the filter (triangles). Both filters have integral cyclonic pre-cleaners that remove 95% of the dust by mass before it gets to the filter. Notice that it takes 3-4kg!!! of dust before the filter media reaches maximum efficiency - small changes in filter efficiency mean big changes in the number of particles reaching the engine.

More filter info in this thread...

http://www.outerlimits4x4.com/PHP_Modul ... hp?t=45580

[CRUSHU]

the only problem would be that as the filter gets more efficient at catching dust, it flows less air.

[ISUZUROVER]

the only problem would be that as the filter gets more efficient at catching dust, it flows less air.

Airflow is directly proportional to pressure drop across the filter, shown by the diamonds and the almost straight lines. You can see that the pressure drop increases relatively slowly while the filtration efficiency (initally) increases very rapidly.

For the 2 filters above - you would want to replace the filters at 2-3kg of dust load point, to get an optimum balance between efficiency and pressure drop (airflow).

[CRUSHU]

For the 2 filters above - you would want to replace the filters at 2-3kg of dust load point, to get an optimum balance between efficiency and pressure drop (airflow).

does that mean that a filter would weight 2 - 3 kg more than a new one??

[adam.s]

It's still going to filter the majority of shit out of the air.

I'd prefer a fresh filter to get optimum flow, specially since I run a petrol engine --> diesel's can sark my bawls

[ISUZUROVER]

For the 2 filters above - you would want to replace the filters at 2-3kg of dust load point, to get an optimum balance between efficiency and pressure drop (airflow).

does that mean that a filter would weight 2 - 3 kg more than a new one??

No - 95% of the dust in these filters is being removed by the integral cyclonic pre-cleaners - so the filter would only weigh 100-150g more than a new one. The 2 filters in question are filters for largeish trucks/earthmovers (6L diesels and even larger).

[ISUZUROVER]

It's still going to filter the majority of shit out of the air.

I'd prefer a fresh filter to get optimum flow, specially since I run a petrol engine --> diesel's can sark my bawls

These filters are very high efficiency with cyclonic pre-cleaners. A petrol engine with a paper element filter and no pre-cleaner could change from as much as 95% initially to 99.9% throughout its life (especially for the small pod-type filters). That is a huge number of particles getting to your engine - but it's your engine and you can do what you like.

[adam.s]

It's still going to filter the majority of shit out of the air.

I'd prefer a fresh filter to get optimum flow, specially since I run a petrol engine --> diesel's can sark my bawls

These filters are very high efficiency with cyclonic pre-cleaners. A petrol engine with a paper element filter and no pre-cleaner could change from as much as 95% initially to 99.9% throughout its life (especially for the small pod-type filters). That is a huge number of particles getting to your engine - but it's your engine and you can do what you like.

And it will still last forever if not thrashed and serviced regularly.

Air filter's arn't the main reason why some people's engines lack longetivity.

[fisho64]

That graph is a bit vague, how are they quantifying efficiency, there could be any number of ways? Volume of particles removed from air? If so it is "filtering efficiency" or "performance efficiency"? Any reduction in airflow (pressure drop) will reduce the efficiency of you engine.
What doesnt add up is the fact that somewhere along that efficiency line it should begin to decrease as it clogs up. Is this graph from an advert for a particular filter brand?

[ISUZUROVER]

That graph is a bit vague, how are they quantifying efficiency, there could be any number of ways? Volume of particles removed from air? If so it is "filtering efficiency" or "performance efficiency"? Any reduction in airflow (pressure drop) will reduce the efficiency of you engine.
What doesnt add up is the fact that somewhere along that efficiency line it should begin to decrease as it clogs up. Is this graph from an advert for a particular filter brand?

Filtration efficiency (standard industry term - also can be called "dust removal efficiency" - nothing to do with engine efficiency) is calculated as:

(1-MAF/MBF)x100

Where

MAF = mass loading of particles after the filter per volume of air (i.e. g/m3) and
MBF = mass loading of particles before the filter per volume of air (i.e. g/m3)

Unlike your statement, almost all dust filters become more efficient as they collect particles (clog), not less efficient. I can show you plenty of independant university research and theory which proves this.

The results obtained from standard experiments (according to relevant ISO/SAE standards) using arizona test dust (standard dust for these tests) and isokinetic sampling. The graphs are not from any company advertising.

[fisho64]

definition of "clog" from macquarie dictionarie
"to hinder or obstruct"
You obviously know what you are talking about, and would then realise that it doesnt matter if it filters 99.9% off the dust out if it only lets (say) 80% of the air volume thru

[Shorty40]

I have just thrown my "Hiclone" in the bin and have replaced it with 1/2 kilo of dirt in my air filter

I picked up 30hp and my fuel economy has improved out of sight

[ISUZUROVER]

definition of "clog" from macquarie dictionarie
"to hinder or obstruct"
You obviously know what you are talking about, and would then realise that it doesnt matter if it filters 99.9% off the dust out if it only lets (say) 80% of the air volume thru

OK - I was trying not to get into the really technical stuff, but what happens is this...

The first thing to think about is that air filters DO NOT work like sieves, if they did they would let just about all the particles through, because the average pore size of the filter is much larger than the size of the dust they collect. They work mainly by the combined mechanisms of: diffusion, inertial impaction and interception

Initially, a clean air filter, will operate as what is called a "depth" filter, where the particles will be collected throughout the entire thickness of the filter media. Because paper element fibrous filters are very thin, this part doesn't last too long.

As the filter collects more dust, and begins to build up a reasonable amount of dust on the front face of the filter, the filtration switches from "depth filtration" to what is called "cake filtration", where the particles are now collected by the porous "cake" or dust mass on the OUTSIDE of the filter. At this point all the filter material is doing is acting as a support structure for the dust, which is actually doing all the filtration. For most filters and most dusts, "clogging" will never occur, the pressure drop will continue linearly, until such a time when it becomes too high (i.e. engine performance starts to suffer noticeably). The filter will only "clog" if something called cake compression occurs. However the word "clogging" is often used for when the pressure drop becomes unacceptably high, the filter will never actually be clogged.

It is for this reason that trucks and earthmoving equipment have pressure sensors connected to the filter chambers, which activate when the pressure drop across the filter becomes too high. Then the filter needs to be changed but not before.

[ISUZUROVER]

I have just thrown my "Hiclone" in the bin and have replaced it with 1/2 kilo of dirt in my air filter

I picked up 30hp and my fuel economy has improved out of sight

I never once mentioned fuel economy or hp. Of course these are detrimentally affected by the dust load in the filter, however this only increases at a slow linear rate.

If you bought a hiclone, can I interest you in an electric turbocharger as well?

[fisho64]

bag it up, colour it a fluoro colour, call it something like "mega-turbo speed additive" and sell it on the internet
but put a note in with it saying "make sure filter is installed before adding product to airintake" or youll be up sh.t creek!!

[fisho64]

examining the graph will also tell you that at 4kg of dust the pressure diff is double from new, this will show that, all other factors being static, airflow will be 50% compared to the new filter. This should be sufficient (depending on the vehicle) to cause a "noticable reduction in performance/engine efficiency"

[adam.s]

I have just thrown my "Hiclone" in the bin and have replaced it with 1/2 kilo of dirt in my air filter

I picked up 30hp and my fuel economy has improved out of sight

Why stop there ?

I ditched my hyclone and air filter and replaced them both with a vacuum cleaner that drags along the ground. Sucks up all the dirt it can and pumps it directly into the engine.

She is running SWEET !

[CRUSHU]

definition of "clog" from macquarie dictionarie
"to hinder or obstruct"
You obviously know what you are talking about, and would then realise that it doesnt matter if it filters 99.9% off the dust out if it only lets (say) 80% of the air volume thru

most filters are bigger than required, so should be able to cope. maybe if it is a real hi-po engine, a bigger filter may be required to overcome it.

[Rainbow Warrior]

I have just thrown my "Hiclone" in the bin and have replaced it with 1/2 kilo of dirt in my air filter

I picked up 30hp and my fuel economy has improved out of sight

I never once mentioned fuel economy or hp. Of course these are detrimentally affected by the dust load in the filter, however this only increases at a slow linear rate.

If you bought a hiclone, can I interest you in an electric turbocharger as well?

I heard you can get elect supercharger for a Toyota Prius

Where can I buy this dust additive?

[fisho64]

just send a western union money transfer to Mr Singh for $5000, he'll give you a rebate of $4995 by return tranfer and the product will be dispatched to you immediately!
look forward to hearing from ya!!!

[Rainbow Warrior]

just send a western union money transfer to Mr Singh for $5000, he'll give you a rebate of $4995 by return tranfer and the product will be dispatched to you immediately!
look forward to hearing from ya!!!

Does this dust work with IFS?

[bogged]

wont someone please think of the children...

[-Richo-]

well shit aye, when a filter clogs up more it filters more, never knew that...

[Shorty40]

I have just thrown my "Hiclone" in the bin and have replaced it with 1/2 kilo of dirt in my air filter

I picked up 30hp and my fuel economy has improved out of sight

I never once mentioned fuel economy or hp. Of course these are detrimentally affected by the dust load in the filter, however this only increases at a slow linear rate.

If you bought a hiclone, can I interest you in an electric turbocharger as well?

It was a joke

But seriously, I replaced my air filter in my GQ today (EFI 4.2 on straight LPG) and I didn't lose anywhere near as much power as I had anticipated after reading this thread

But to be safe, I will fill it with dirt first thing tomorrow

[CRUSHU]

I understand your joke, but you don't seem to get the point.

When a filter is new it flows the most air (good for performance) but lets some dust thru. When it is partially clogged, it flows slightly less (not so good for performance, if the filter size is marginal for the engines breathing requirements) but cleaner air (better for the engine)

These are the basics as I understand it.

[matsmad]

I have just thrown my "Hiclone" in the bin and have replaced it with 1/2 kilo of dirt in my air filter

I picked up 30hp and my fuel economy has improved out of sight

Why stop there ?

I ditched my hyclone and air filter and replaced them both with a vacuum cleaner that drags along the ground. Sucks up all the dirt it can and pumps it directly into the engine.

She is running SWEET !

You guys crack me up!

[bogged]

But to be safe, I will fill it with dirt first thing tomorrow

Try Silastic.. its betterer.

[Josh n Kat]

so does the same apply with diesel fuel filters? no offence to the diesel boys but it is a rather "dirty" fuel, maybe u should start pouring dirt in your tanks?

[Shorty40]

I understand your joke, but you don't seem to get the point.

Umm. . . yes I do - I just dont care, hence the joke

[fisho64]

best just change your air and fuel filters at around the recommended intervals I think is the best conclusion-no joke!!!
Oh and oil as well !!!