Air filter cleaning

[AussieAub]

G'day all,
Was just wondering what preferred methods you guys use for cleaning of the original equipment air filters between servicing (ie, the standard paper panel filters, as opposed to the likes of the K&N style oiled filters), specifically on a V8 D2?

And preferably that can be done at home, as opposed to having any "proper garage" equipment to hand.....

Cheers,

..:: KIEREN ::..
2000 Disco II Auto V8
Object Of Mass Consumption
AussieAubs Disco Page (http://aussieaub.blogspot.com)

[isuzurover]

Automotive air filters are not really cleanable. It is easy to fracture the cellulose media and/or create pinholes.

Your filter works better with more dust on it.

Industrial "surface" filters are cleaned by a reverse pulse of compressed air. However the media is specially designed (and tested) to endure the forces induced by the cleaning process.



EDIT: You can give it a tap to dislodge loose dust, but that is all I would do. Do not blow compressed air from the outside (in the flow direction, as you will likely clog the filter further or move the dust further in where it can be more easily reentrained).

There are companies who clean auto air filters (using dry cleaning-like fluid I believe), but I wouldn't do iit.

[Sprint]

K&N's i wash, paper ones get cleaned out every bin day

[LOVEMYRANGIE]

As Ben said, washing paper filters is a no no. The fibres are technically bonded and any water will cause them to swell and separate.
You can lightly back blow them with low pressure air but be careful. Use something to diffuse the air jet and always blow it at a good angle.
Never blow it from the dirty side. This will force it in further blocking the element.

With all the different manufacturers now, replacement is the best option.

Cheers

Andrew

[AussieAub]

replacement is the best option

I was quoted $85 from one local place.....(hence my OP)! :o:o
Does that sound right? Coz it sure doesn't to me!! :(

Cheers,

..:: KIEREN ::..
2000 Disco II Auto V8
Object Of Mass Consumption
AussieAubs Disco Page (http://aussieaub.blogspot.com/)

[Crackerjack]

You should always replace a stock airfilter, they are designed to be disposable, $85 sounds off the scale, They are about $10 here in the UK you could always mail order one or better still buy a K&N or some sort of washable foam filter.

[JDNSW]

You should always replace a stock airfilter, they are designed to be disposable, $85 sounds off the scale, They are about $10 here in the UK you could always mail order one or better still buy a K&N or some sort of washable foam filter.

See the discussion on K&E filters elsewhere in this forum.

I was interested reading recently some background to the first Landrovers, there was discussion on the role of aircleaners. It was pointed out that in the UK, with a generally damp and largely dust free atmosphere and with almost all roads sealed, the main function of an aircleaner in the 1940s was as an intake silencer. In contrast, for export, particularly to places like Australia with (then as now) many unsealed roads, and a largely dry climate, and with not infrequent dust storms even in the major cities (e.g. Brisbane yesterday), the major use of aircleaners became one of supplying clean air. For this reason, the first Landrovers were fitted with an aircleaner which was specified by its UK manufacturer for use only in tractors. Clean air has remained a priority in Australia, where in the UK it is not a problem - It can be argued that as Landrovers have become less export oriented and more home market oriented, the suitability of the aircleaners has decreased. Compare for example the aircleaner on the Australian designed Isuzu installation with that on the latest Defender. The available surface area is much smaller, and no guard element.

John

[spudboy]

I was quoted $85 from one local place.....(hence my OP)! :o:o
Does that sound right? Coz it sure doesn't to me!! :(



Try a quick search on eBay. You can get filter kits for your particular vehicle with proper quality components (like Coopers filters). Stay away from the no-name really cheap offers.

This one for a TD5 is going for around $85 for air/fuel/oil filters including the copper sump plug washer!

Land Rover Discovery Series 2 TD5 Full Filter Kit - eBay Engine Parts, Engines, Components, Car Parts, Accessories, Cars, Bikes, Boats. (end time 11-Nov-09 22:37:34 AEDST) (http://cgi.ebay.com.au/Land-Rover-Discovery-Series-2-TD5-Full-Filter-Kit_W0QQitemZ220493960625QQcmdZViewItemQQptZAU_Car _Parts_Accessories?hash=item335676d5b1&_trksid=p3286.c0.m14)

You'll just have to search for the appropriate one for your model.

HTH
David

[spudboy]

.... or better still buy a K&N or some sort of washable foam filter.

There will be lots of people who disagree with that out here. Maybe OK for the UK where the dust level is negligible....

[isuzurover]

I was quoted $85 from one local place.....(hence my OP)!

Make sure you aren't replacing it too frequently. Fit a restriction (pressure drop) valve, and only change the filter when that says to.

Fitting a cyclonic pre cleaner (you will usually need to fit a snorkel to do this) should extend your filter change intervals by about 4x.


See the discussion on K&E filters elsewhere in this forum.

I was interested reading recently some background to the first Landrovers, there was discussion on the role of aircleaners. It was pointed out that in the UK, with a generally damp and largely dust free atmosphere and with almost all roads sealed, the main function of an aircleaner in the 1940s was as an intake silencer. In contrast, for export, particularly to places like Australia with (then as now) many unsealed roads, and a largely dry climate, and with not infrequent dust storms even in the major cities (e.g. Brisbane yesterday), the major use of aircleaners became one of supplying clean air. For this reason, the first Landrovers were fitted with an aircleaner which was specified by its UK manufacturer for use only in tractors. Clean air has remained a priority in Australia, where in the UK it is not a problem - It can be argued that as Landrovers have become less export oriented and more home market oriented, the suitability of the aircleaners has decreased. Compare for example the aircleaner on the Australian designed Isuzu installation with that on the latest Defender. The available surface area is much smaller, and no guard element.

John

As JD says, have a read about the K&N and then tell us if you still want to keep it...

Dust loads on auto air filters and the size distribution of said dust varies widely between countries and usage types.

Australia generally has very high dust loads, however nowhere near as high as the middle east. Vehicles which spend most of their time on highways and in cities mainly have a problem with soot particles. As soot particles are small and "sticky", they clog a filter much more rapidly (on a mass basis) than "outback dust". Filter manufacturers advise car manufacturers on appropriate filter efficiency for intended use, but the vehicle manufacturer chooses the spec in the end.

The Australian 110 countys have an "off highway" spec intake filter system. This is the time of filter you would generally find on earthmoving equipment, mine vehicles, tractors, etc...

The Tdi 110s have a similar or slightly downgraded spec - they still have a cyclonic precleaner, but no safety element. The discos on the other hand (at least from the flat filter models-on) have what is basically a car-spec element/filter setup.

This seems to generally be the case - discos and rrcs have a car-spec element as they are expected to spend most of their life on the highway. The 90/110 gets a better spec as it is expected to spend most of its like in a dusty environment.

However - wrt to the start of your post - in the 1940s, they really had very little idea about dust, and what it did to an engine. The first serious works on aerosol particle mechanics did not appear until the mid 1960s.

[midal]

Bummer:(......I have a D2 Td5 and thought I was being smart by ditching the paper filter and fitting a Uni filter just two weeks ago. After now seeing all the info and graphs etc it looks like a radical re-think is in order due to living in a dusty area (Pilbara).

Not now so cheery:confused:
Mick

[Tank]

If you hold a K&N filter up to the light/sun and you can see clearly the thousands of holes, why would anyone think that it could filter particulate matter out of the incoming airstream, you won't find holes in an OEM paper filter, unless it's stuffed, Regards Frank.

[JDNSW]

.........
However - wrt to the start of your post - in the 1940s, they really had very little idea about dust, and what it did to an engine. The first serious works on aerosol particle mechanics did not appear until the mid 1960s.

Despite this, largely on an empirical basis, air cleaners were extending the life of tractor engines right from the beginning of the century, and by the 1930s had become common in cars and trucks, although as I commented earlier, mostly for noise reduction, at least in the UK.

And despite the lack of empirical research, Rover clearly knew what they were doing when they fitted a large, effective aircleaner with a cyclonic precleaner in 1947, right from the start.

John

[JDNSW]

There are two ways of looking at how efficient an aircleaner is

1. How much does it restrict airflow

2. How much dust does it let through.

If you are after peak performance, 1 might be of interest, although the actual power loss of typical aircleaners is pretty small - most of the improvement from the oiled cloth type ones is the psychological effect of the added engine intake noise.

If you want your engine to last, 2 is the factor you will be interested in, and there is no doubt that modern paper element filters (with, as suggested, a cyclonic precleaner, and preferably a guard element) are far more effective and have added greatly to engine life of vehicles.

John

[AussieAub]

Try a quick search on eBay. You can get filter kits for your particular vehicle with proper quality components (like Coopers filters). Stay away from the no-name really cheap offers.

This one for a TD5 is going for around $85 for air/fuel/oil filters including the copper sump plug washer!

Discovery-S2-TD5-Filter-Set (http://cgi.ebay.com.au/Land-Rover-Discovery-Series-2-TD5-Full-Filter-Kit_W0QQitemZ220493960625QQcmdZViewItemQQptZAU_Car _Parts_Accessories?hash=item335676d5b1&_trksid=p3286.c0.m14)

You'll just have to search for the appropriate one for your model.

HTH
David

Thanks David,
Now THIS is more like it!! Discovery-S2-V8-Filter-Set (http://cgi.ebay.com.au/Land-Rover-Discovery-S2-V8-Filter-Set_W0QQitemZ220462258170QQcmdZViewItemQQptZAU_Car _Parts_Accessories?hash=item33549317fa).
Oil and air filters for a mere $60 inc postage.

Cheers for the initial link, bud! :D

..:: KIEREN ::..
2000 Disco II Auto V8
Object Of Mass Consumption
AussieAubs Disco Page (http://aussieaub.blogspot.com)

[nice1guv]

I was quoted $85 from one local place.....(hence my OP)! :o:o
Does that sound right? Coz it sure doesn't to me!! :(


Way too expensive!! :o

D2 V8 Coopers filter is $15 from British Parts! :D

[isuzurover]

There are two ways of looking at how efficient an aircleaner is

1. How much does it restrict airflow

2. How much dust does it let through.

If you are after peak performance, 1 might be of interest, although the actual power loss of typical aircleaners is pretty small - most of the improvement from the oiled cloth type ones is the psychological effect of the added engine intake noise.

If you want your engine to last, 2 is the factor you will be interested in, and there is no doubt that modern paper element filters (with, as suggested, a cyclonic precleaner, and preferably a guard element) are far more effective and have added greatly to engine life of vehicles.

John

In the filter world, FILTER EFFICIENCY purely means the proportion of particles which will be collected by a filter (either on a mass basis or a number basis). Penetration is also used which is 1-efficiency.

Pressure drop / Restriction (i.e. how easily air flows through the filter) is accounted for by using a metric called filter "Quality factor" - the ratio between pressure drop and efficiency.

In reality thouugh, for modern filters, the vehicle manufacturer specifies the efficiency, and the the "package" size (space available), and the filter manufacturer designs something which will fit with the lowest pressure drop possible for the given efficiency.

[discoveryseries1]

just picked up a k and n airfilter form auto barn and worked out a 16% power increse from my old filter (ryco) i used the dynolicus off my ipod. it seems to be repeatibul they were good quality and have a 1 milion mile warenty, 130 for the filter, comes pre oiled and the recharge oil kit is 27 bucks, . good value i reccon.

[isuzurover]

just picked up a k and n airfilter form auto barn and worked out a 16% power increse from my old filter (ryco) i used the dynolicus off my ipod. it seems to be repeatibul they were good quality and have a 1 milion mile warenty, 130 for the filter, comes pre oiled and the recharge oil kit is 27 bucks, . good value i reccon.

They have a 1 million mile warranty on the filter. All that says is that the filter will last 1 million miles when cleaned in the proper way at the specified interval.

If you look up their warranty conditions, you will note:

Therir warranty is for vehicles...
when used primarily on paved roads

WHAT IS NOT COVERED BY OUR WARRANTY
Any K&N product used for ... 2: any off-road use...

I won't bother to comment on the accuracy of a $13 dyno and a sample size of 1 with no test conditions listed.

As the end of the day, it is your engine and your money... But the cost of an engine rebuild will buy a lot of beer and hookers.

[spudboy]

just picked up a k and n airfilter form auto barn and worked out a 16% power increse from my old filter (ryco) i used the dynolicus off my ipod. it seems to be repeatibul they were good quality and have a 1 milion mile warenty, 130 for the filter, comes pre oiled and the recharge oil kit is 27 bucks, . good value i reccon.

Can't see how you can improve performance by 16% by just changing your air filter, unless the old one was unbelievably shagged.

You might have got 15% improvement just by putting on a new Ryco.....

[Crackerjack]

Can't see how you can improve performance by 16% by just changing your air filter, unless the old one was unbelievably shagged.

You might have got 15% improvement just by putting on a new Ryco.....

You won't get much improvement on any less restrictive element unless you have the vehicle retuned to make the most of the extra air capacity.

[Crackerjack]

See the discussion on K&E filters elsewhere in this forum.

I was interested reading recently some background to the first Landrovers, there was discussion on the role of aircleaners. It was pointed out that in the UK, with a generally damp and largely dust free atmosphere and with almost all roads sealed, the main function of an aircleaner in the 1940s was as an intake silencer. In contrast, for export, particularly to places like Australia with (then as now) many unsealed roads, and a largely dry climate, and with not infrequent dust storms even in the major cities (e.g. Brisbane yesterday), the major use of aircleaners became one of supplying clean air. For this reason, the first Landrovers were fitted with an aircleaner which was specified by its UK manufacturer for use only in tractors. Clean air has remained a priority in Australia, where in the UK it is not a problem - It can be argued that as Landrovers have become less export oriented and more home market oriented, the suitability of the aircleaners has decreased. Compare for example the aircleaner on the Australian designed Isuzu installation with that on the latest Defender. The available surface area is much smaller, and no guard element.

John

Lots of good points here, there is little dust here in the UK, I have K&N's in my V8 Discovery and BMW735, both been in a couple of years and not cleaned yet, the intake after the air cleaner on both vehicles is spotless so they are doing a good job.
In Australia I used to have a Finer Filter (oiled foam) on my RRC and it was fine, I generally did not go to dusty areas on my trips but did go to the NT and back and other long trips.
If I did live in a dusty area I would seriously consider some sort of precleaner such as a Donaldson type, engines are expensive, so they are cheap insurance, and I have always preferred reusable filters.
I would agree with Land Rovers being less export orientated (in this particular area) but also defend Land Rover for going down that route, as usual its all about cost, why fit an extravagant air cleaner system to a car that is only going to the shops etc, You could argue that all Land Rovers going to Australia should have Bullbars fitted, but that would be ridiculous, the people that want or need them fit them, if you need air filteration for very dusty areas it would need to be an aftermarket thing imo.

[JDNSW]

......
I would agree with Land Rovers being less export orientated (in this particular area) but also defend Land Rover for going down that route, as usual its all about cost, why fit an extravagant air cleaner system to a car that is only going to the shops etc, You could argue that all Land Rovers going to Australia should have Bullbars fitted, but that would be ridiculous, the people that want or need them fit them, if you need air filteration for very dusty areas it would need to be an aftermarket thing imo.

Fitting good filtration to all vehicles sold in Australia would seem to be good insurance against warranty claims. As far as your comment goes on bullbars, from my observations I would suggest that at least 90% of Defenders in Australia have them - suggesting that their being standard equipment would be a reasonable move. Nowhere near as high a proportion for other Landrover models though, probably reflecting their largely urban use.

John

[RoverP6B]

I have been using K & N air filters on my 4.6 litre engine that now powers my Rover P6B for the past two years. In that time the car has covered just under 31,000km.

The engine runs with twin SU carburettors, large diameter P6B aluminium alloy elbows and an air box with large 3" inlet to ensure adequate air delivery. Inside are two very large K & N cone shaped air filters.

Naturally I have been feeling rather concerned having read the posts within this thread and having viewed the post on the air filter test comparison.

So I removed the elbows and looked into the air box, seeing the engine side of the air filters, checked within the elbows and the throats of each carburettor. To say that I was relieved was an understatement.:D

I could see no evidence of dust at any point. Wiping with a clean white cloth on the engine side of the filters and in the carburettor throats resulted in no discolouration of the cloth. The inlet to the box and the surface of the filters displayed a layer of dust, but the inside surface of the filters appeared to be completely dust free.

The distance covered is a mixture of both urban and rural, with very little on unsealed roads.

From what I have been reading, I had contemplated having to replace them, but after a thorough inspection it would appear that they are doing their job quite well indeed, so they shall remain.

Ron.

[johnclv]

I was interested reading recently some background to the first Landrovers, there was discussion on the role of aircleaners. It was pointed out that in the UK, with a generally damp and largely dust free atmosphere and with almost all roads sealed, the main function of an aircleaner in the 1940s was as an intake silencer. In contrast, for export, particularly to places like Australia with (then as now) many unsealed roads, and a largely dry climate, and with not infrequent dust storms...



Thats right - if you are really concerned about dust etc you need to make your car Aussie proof especialy if it comes from somewhere like Europe.

Get a snorkle - it the only way for dust and water. Once I fitted a snorkle I had alot less crap in my airfilter

[PhilipA]

i tried a new to me approach when I went on my 3 month Kimberley trip. I have a RRC 3.9 with cylinder filter and a snorkle. I went to see the Unifilter man at West Gosford and inquired about the filter socks he sells for Toyotas etc. I had to modify the top of the LRA snorkle by gluing 2 thickness of beer can inside, so the rim of the socks didn't fall in. I used them while on dirt roads as they cause a pressure drop and are not recommended for fast bitumin work. The amount of dust they caught was amaazing with NO evidence of dust on the engine side, and a clean main filter after 20KK of travel. BTW he told me that the Unifilter oil did not cause similar problems with MAFs as the K&Ns' as his oil is very sticky whereas the K&N oil is thin and can migrate much more easily. I still will not run a unifilter as the last filter before the MAF but this application seems terrific. Regards Philip A

[Avrio]

pod filter works well for me ...a clean every 3 months and its fine. Also sounds awesome . I saw something on a cop show recently that leads me to believe pod filters are illegal. Can anyone confirm ??

[Sprint]

depends on how the pod is fitted......

[scott oz]

[QUOTE=isuzurover;1094001]

....The Australian 110 countys have an "off highway" spec intake filter system. This is the time of filter you would generally find on earthmoving equipment, mine vehicles, tractors, etc...

The Tdi 110s have a similar or slightly downgraded spec - they still have a cyclonic precleaner, but no safety element. The discos on the other hand (at least from the flat filter models-on) have what is basically a car-spec element/filter setup.

This seems to generally be the case - discos and rrcs have a car-spec element as they are expected to spend most of their life on the highway. The 90/110 gets a better spec as it is expected to spend most of its like in a dusty environment......
QUOTE]

So from what I read for a (110 TD5) the ideal filtering is a paper filter and a snorkel with a precleaner.

[isuzurover]

So from what I read for a (110 TD5) the ideal filtering is a paper filter and a snorkel with a precleaner.

"Ideal" is a bit difficult to quantify, because there is always something better if you have the money.

A cyclonic pre-cleaner (either integrated into the filter housing or as a snorkel head) will remove ~70-90% of the MASS of dust before it gets to your engine. These will likely be more efficient than any of the "sock" or stocking type things which have become popular, with the added benefit that they don't clog up and increase pressure drop over time. If you don't want to clean them you can use a Donaldson top-spin type which shoots the dust back out as it is collected.

That will improve the life of your filter element by almost the %age mentioned above. It will mean that your filter now only has to deal with the smaller particles.

In terms of the "ideal" filter, cellulose (paper) fibre filters have in general been proven to be significantly more efficient than foam or oiled cotton type filters. However for some applications, there are more efficient options again using synthetic media (polymer fibres) or nanofibre impregnated media. Both of these options are more efficient again - but more expensive.

Hope that helps???

[DiscoKym]

Bummer:(......I have a D2 Td5 and thought I was being smart by ditching the paper filter and fitting a Uni filter just two weeks ago. After now seeing all the info and graphs etc it looks like a radical re-think is in order due to living in a dusty area (Pilbara).

Not now so cheery:confused:
Mick

Don't worry too much Mick. Dirt bikes have used oiled foam filters for years as in the dirt oiled foam are the best.

I have been swapping to Unifilters for years in cars and bikes. Usually you can see a lot less dust after the filter with a unifilter.

I carry a spare scrubber (outer filter) cleaned and oiled for a quick change in the bush. :)

[isuzurover]

Don't worry too much Mick. Dirt bikes have used oiled foam filters for years as in the dirt oiled foam are the best.

I have been swapping to Unifilters for years in cars and bikes. Usually you can see a lot less dust after the filter with a unifilter.

I carry a spare scrubber (outer filter) cleaned and oiled for a quick change in the bush. :)

:angel: not this again...

Unifilters are commonly fitted to dirt bikes... The engines are not expected to last long. 100 hrs on one set of rings is good going for a 2st MX bike...

None of the multimillion dollar mine/earthmoving vehicles in the world come fitted with foam/cotton filters, and their engine warranty would be void if such filters were fitted. Their engines last millions of km or many tens of thousands of hours...

[DiscoKym]

:angel: not this again...

Unifilters are commonly fitted to dirt bikes... The engines are not expected to last long. 100 hrs on one set of rings is good going for a 2st MX bike...

None of the multimillion dollar mine/earthmoving vehicles in the world come fitted with foam/cotton filters, and their engine warranty would be void if such filters were fitted. Their engines last millions of km or many tens of thousands of hours...

I'm not saying they are the be all end all of filters. Just saying I have found them better than the paper filters that I have replaced them with. I have driven through central Australia and Victorian High Country with an oiled foam air filter and checked each time how much dust got through. Each time I was very happy to find none. I have found a fine layer of very fine dust that you can write in when using paper filters and that was after a road trip.

I would say it's not the air filter that wears out a 2 stroke. There are lots of reasons they wear quickly like extreme high power output per cc, no one warms them up, ports account for most of the cylinder wall, they rev like mad and they are made to last a race meeting before rebuilds. So that doesn't prove a thing. Modern 4 stroke bikes have foam filters too. The race ones the same as 2 strokes, high output per cc. The adventure bikes designed to travel around the world also use foam.

You are correct that heavy and earthmoving equipment do not use oiled foam filters. However from what I have read it is due to the lack of maintenance they receive in the quest for profits. Paper filters prove physically stronger and able to take more abuse before collapsing from being clogged.

Have a read of one I found years ago.. Internet BMW Riders - Air Filter FAQ/Info (http://www.ibmwr.org/otech/airfilter.html)

In the end I was just trying to help Mick de stress about his choice of air filter. However according to isuzurover your engine will die a quick death. In the end do your own test and use what YOU are happy with Mick. :D

[Jode]

G'day all,
Was just wondering what preferred methods you guys use for cleaning of the original equipment air filters between servicing (ie, the standard paper panel filters, as opposed to the likes of the K&N style oiled filters), specifically on a V8 D2?

And preferably that can be done at home, as opposed to having any "proper garage" equipment to hand.....

Cheers,

..:: KIEREN ::..
2000 Disco II Auto V8
Object Of Mass Consumption
AussieAubs Disco Page (http://aussieaub.blogspot.com)
In reply to your original query, you could hoover the outside of the filter to remove more of the dust than a good shake will do. I use paper filters (not too expensive here) and follow the standard LR maintenance schedules, despite the fact that Botswana's bush is similarly dusty as your outback.

But watch the vehicle's performance: on what was one of our first bush trips, driving a 109 with a very well-worn in-line Rover R6 petrol engine, the engine had lost all of its (very limited) guts; removing and dusting off the air cleaner as best we could in the bush (didn't have a spare - you live and learn) noticably improved engine performance.

[Davo]

:angel: not this again...

Unifilters are commonly fitted to dirt bikes... The engines are not expected to last long. 100 hrs on one set of rings is good going for a 2st MX bike...

None of the multimillion dollar mine/earthmoving vehicles in the world come fitted with foam/cotton filters, and their engine warranty would be void if such filters were fitted. Their engines last millions of km or many tens of thousands of hours...

Is your forehead hurting from that brick wall yet, Ben? :D

[donh54]

.......

You are correct that heavy and earthmoving equipment do not use oiled foam filters. However from what I have read it is due to the lack of maintenance they receive in the quest for profits. ....... :D

My son in law is a diesel fitter in the Hunter Valley, and I have spent a lot of my life working with machinery and trucks. Not even the most myopic accountant could justify destroying hundreds of thousands of dollars worth of gear to save a few dollars on filters. Maintenance in these industries is a huge cost, but the cost of breakdown and subsequent loss of production is far, far greater. The Cat C15 in the truck I currently drive has done over 1,500,000 klms. A couple of turbos, a water pump the other week, two, or maybe three sets of injectors since it rolled out in November 2007. Regular maintenance and daily checks mean it is still earning the boss money, not costing it.
Oh, and to get back on topic, it has 2 x Donaldsons with turbo tops, blown out every couple of months (using a proper air diffuser put up the guts) and replaced as per manufacturers recommendations.
Interesting discussion, folks ;)