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Justwatching
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PostSubject: Recycling air filters   Sun Aug 03, 2014 5:47 pm

Decided to clean rather than replace my Rover's air filter. They're not that expensive, but there's literally millions of these things going into landfill every year. Seems wasteful.

Started by removing large pieces of debris (dead bugs and leafs) then shock it vigariously over the the bin. Surprising how much stuff came out. With all the loose debris removed, I soaked it in a warm chemical soup of stain remover and washing detergent. Several hours in that, then rinsed and soaked in clean water for another few hours.

It didn't look 'as-new', but it was definitely cleaner. Smelt nice, too.  Thumb 

I think a method involving more active agitation might produce better result than passive soaking. Any thoughts?

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PostSubject: Re: Recycling air filters   Mon Aug 04, 2014 10:35 am

Second question - what's the best way to dispose of them once they're spent?
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edlithgow
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PostSubject: Re: Recycling air filters   Thu Aug 07, 2014 1:14 pm

That a standard paper filter? Interesting if so, cos I'd have guessed they'd fall apart if washed. All I've ever done is hoover them, sucking on the outside. Doesn't work very well.

What I havn't tried, it just occurs to me, is to hoover them in the filter housing, with the air intake taped to the hoover, sort of pneumatic back-flushing, though it'd be good if the reverse flow air was fairly clean

If they don't fall apart, I suppose you could try gentle back-flushing with water. If it was an old-stylee round filter, like on my car, if you put it in a shallow dish and ran tap water into the middle, some water would presumably flow through the filter.

If you've got, say, a vertical axis spin dryer, you might be able to centrifuge water (and muck?) off the surface.

If you make yourself a manometer you could do a before and after pressure drop comparison, though if it flows better after it could just mean you've damaged it, rather than un-clogged it.

Lampshades?
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edlithgow
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PostSubject: Re: Recycling air filters   Fri Aug 08, 2014 8:09 am

You could test for damage by doing a pressure-drop measurement on a new air filter before and after washing.

If it goes down you've increased its porosity (bad). If it goes up you've matted the fibres (also bad). I suppose you'd hope for no change.

A dirty filter isn't necessarily going to behave the same, though. Many, many years ago I bought an early model of a wet and dry ("Aquavac"?) vacuum cleaner, which had a big, car/truck-type pleated air filter in it, which was supposed be washable.

Nice idea, lousy implementation. The filter dropped off if the machine was bumped. The pleats clogged with dust, which set like concrete when I tried to wash it off (though I can't now remember what my washing method was. I think just under the tap). I ended up using hoover bags or cloth, secured with string, which worked a bit, but the thing was still pretty useless. Hopefully they've improved.

You can get foam filters which are supposed to be re-usable. I think they're mostly supposed to be oiled after cleaning, and are sold as "performance" filters, but tests I've read find them to do little for performance, and filter poorly.

As a prefilter, though, they should extend the life of the paper filter, assuming the total pressure drop is still acceptable, or you could improvise a cloth, foam, cyclonic (a la Dyson) etc, prefilter.

IIRC the guideline for max acceptable pressure drop is new filter drop + 10 inches of water.
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Justwatching
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PostSubject: Re: Recycling air filters   Sat Aug 09, 2014 12:29 pm

Pressure-drop testing the filter wouldn't give any meaningful insight to condition, so wasn't planning to do it.

The filters didn't fall apart at all. I'd still be reluctant to apply more water pressure for fear of damaging it though. Different chemical cleaning, something stronger?

Hadn't considered a pre-filter. Kinda drawn to trying cloth out. Something thin and breathable that wouldn't choke the engine too much. It'd be cheap and reusable, too. However, pressure drop would still be a concern. It would have a really small surface area (compared to a paper filter element), so might clog really easily. I'm not sure how much would be acceptable. I'm guessing not much. Lowering engine performance and economy would obviously defeat the purpose of the exercise.

Maybe just cleaning would sufficient. I was only thinking of extending service life from 1 year to two years, not keeping the same filter indefinitely.

Having similar thoughts about spark plugs. I've changed many plugs that were completely fine just because a book told me to. I don't see why cleaning and re-gapping couldn't extend service life.
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edlithgow
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PostSubject: Re: Recycling air filters   Sun Aug 10, 2014 8:50 am

Justwatching wrote:
Pressure-drop testing the filter wouldn't give any meaningful insight to condition, so wasn't planning to do it.

Why not? Pressure drop is one objective criterion for filter replacement. (I suppose the other criterion might be visible discoloration/dirt on the inside, though that'd be difficult to actually measure. There are gadgets available (as OEM and probably aftermarket add-ons) that measure the pressure drop, but it'd be easy to make your own.

That's to measure clogging, but it could also be used to detect any mechanical effect of washing, IF you used a new filter, so that cleaning wasn't a factor.

Justwatching wrote:

The filters didn't fall apart at all. I'd still be reluctant to apply more water pressure for fear of damaging it though. Different chemical cleaning, something stronger?

Needn't be high pressure, just sustained. If you do it with a dirty filter, there's little to lose anyway.

Chemical cleaning is unlikely to be a factor here, unless its oily, in which case you might try solvents, petrol being the obvious, cheapest but potentially dangerous candidate.

Particulate contaminants are likely to be silicates, soot, and spores such as pollen. Solvents that'd dissolve these (eg Flouric or chromic acid) are pretty close to that stuff in Alien, so not good for you, your filter or engine, and not readily available either.

What's needed is mechanical cleaning aided by dispersants, and because some of the contaminants will have infiltrated the medium, back-flushing to hopefully get them out again. Maybe vibration, ultrasonics, air bubbling or even boiling (though that might be too destructive) would help.

Justwatching wrote:


Hadn't considered a pre-filter. Kinda drawn to trying cloth out. Something thin and breathable that wouldn't choke the engine too much. It'd be cheap and reusable, too. However, pressure drop would still be a concern. It would have a really small surface area (compared to a paper filter element), so might clog really easily.  
I'm not sure how much would be acceptable. I'm guessing not much.

The surface area would depend on the design. The "traditional" pair of tights probably just keeps leaves and rocks out of your filter pleats, but there's no inherent reason a cloth filter couldn't be given a huge surface area/depth.

It'd then be bulky, and (especially on a modern car) might take up too much room in the engine compartment.

It might be possible to arrange a remote filter, say on the roof or in the cabin, snorkel stylee, which'd suit an off-roader for looks and because they might encounter more dust than your average car.

Justwatching wrote:

I'm not sure how much would be acceptable. I'm guessing not much.

Like I said, +10 inches of water is, IIRC, the guideline I've seen. I'll try and find a source for that later.

Justwatching wrote:

Lowering engine performance and economy would obviously defeat the purpose of the exercise.

Depends on the car. In general they seem to be surprisingly insensitive to this, especially modern fuel-injected cars where the engine management stuff compensates automatically.

Carburettors are more sensitive but even they need to be pretty clogged before they show much effect.

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Justwatching
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PostSubject: Re: Recycling air filters   Sun Aug 10, 2014 1:45 pm

"Why not? Pressure drop is one objective criterion for filter replacement."

Yeah, but it doesn't tell you what the change means. See your OWN previous posts explaining the ambiguity.

"Chemical cleaning is unlikely to be a factor here, unless its oily"

It was. Not all of it, but there were some greasy black areas which proved stubborn. From the PCV I suspect.

"The surface area would depend on the design"

Naturally, but I'm drawn to simple, accessible solutions. If it requires the fabrication of a new air box, it's taking the matter too far.

"especially modern fuel-injected cars"

None-point here.

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edlithgow
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PostSubject: Re: Recycling air filters   Mon Aug 11, 2014 7:32 am

Justwatching wrote:
"Why not? Pressure drop is one objective criterion for filter replacement."

Yeah, but it doesn't tell you what the change means. See your OWN previous posts explaining the ambiguity.

Which also suggest how to resolve the ambiguity. Does require risking a new filter, but if its that big a risk, there is also a risk of compromising the filtration on a recycled filter.

Of course, with a disposable banger, maybe that doesn't matter.

Justwatching wrote:


"The surface area would depend on the design"

Naturally, but I'm drawn to simple, accessible solutions. If it requires the fabrication of a new air box, it's taking the matter too far.

Fair enough, though, if there's space, I don't think it need be that big a deal

Justwatching wrote:


"especially modern fuel-injected cars"

None-point here.


Sorry. I don't understand this.
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edlithgow
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PostSubject: Re: Recycling air filters   Sat Mar 21, 2015 1:39 am

Some bad oil analysis results, claimed to be due to air filter cleaning (I assume with compressed air)

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This is an interpretation of the results and, while it seems reasonable, doesn't seem to have been definitively proved.

It also seems to assume that filter-cleaning is inherently wrong. In other words, it makes no distinction between cleaning them "well" and cleaning them "badly".

These may be cases where dirt has been blown into the engine or the filter has been damaged. The consequences of this are likely to be worse in South America (or here in Southern Taiwan) than in the UK.
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PostSubject: Re: Recycling air filters   Sat Mar 21, 2015 6:06 pm

I'm reluctant to accept these findings for a coupe of reasons.

Firstly, there's no delineation of cleaning method (as you've already mentioned) or number times the filter was cleaned, and the differential effects they have on filtration ability.

Secondly, there's no actual control condition. That is, the same vehicle is never tested using a new filter and then compared to using a recycled filter. If I'm understanding the article correctly, they're basing their analysis on some kind of 'average'. It's not detailed what assumptions go into forming this 'average', or how well the vehicle in question conforms to said assumptions. I'm speculating a little here, but someone that recycles air filters may be more likely to engage in other behaviours that have confounding effects on engine wear (may cheap-out on serving in other areas as well, may use their vehicle with less car, etc.).
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PostSubject: Re: Recycling air filters   Mon May 04, 2015 12:42 pm

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Pneumatic back-flushing gadget, (As I suggested above. Like most of my nominally clever/fairly obvious ideas, it's already being done.)

This is aimed at construction/farming/mining plant which of course will clog filters a lot quicker/more expensively than most private cars.

The testing they detail isn't very scientific, pretty close to anecdotal evidence in fact, though that doesn't mean its wrong.

In particular, "damage" is operationally defined as "light doesn't shine through it". That'd be a good way of spotting actual holes, but I might want tighter criteria before I  risked my shiny new bulldozer on it.
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PostSubject: Re: Recycling air filters   Mon May 04, 2015 6:05 pm

Good grief, that's expensive Shock

I agree completely regarding the 'research' they've done. Also, I don't trust the source - they're motivated to reach the conclusions they did. After all, they're not going to say "we tested it and it's crap".
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PostSubject: Re: Recycling air filters   Tue May 05, 2015 9:32 am

Justwatching wrote:
Also, I don't trust the source - they're motivated to reach the conclusions they did. After all, they're not going to say "we tested it and it's crap".

Sure, but that's endemic in the auto arena.

For example, I've never seen any actual data supporting operational superiority of synthetic oil, which I'd think would be an easy enough test for an oil company to set up. They could just sponsor and monitor the DHL delivery fleet, say, but if they have, AFAIK they are keeping quiet about it.
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PostSubject: Re: Recycling air filters   Tue May 05, 2015 12:29 pm

edlithgow wrote:

Sure, but that's endemic in the auto arena.

For example, I've never seen any actual data supporting operational superiority of synthetic oil, which I'd think would be an easy enough test for an oil company to set up. They could just sponsor and monitor the DHL delivery fleet, say, but if they have, AFAIK they are keeping quiet about it.

Surely there are research bodies independent of manufacturers that can test for differences between things like synthetic vs. mineral, effects of recycling air filtration equipment, etc. Lots of universities runs automotive engineering courses - don't they conduct research?
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PostSubject: Re: Recycling air filters   Wed May 06, 2015 9:27 am

Dunno. Synthetic v. conventional was just an example.

I havn't looked VERY hard, and maybe I havn't looked in the right places, but I sometimes look in on the BITOG oil-obsessives site, where such things (synthetic v. conventional, thin v. thick, does oil have a shelf life?, what's a rational oil change interval for a low-miles car, etc, etc) are argued about, rather repetitively, and without much evidence either way. If it was readily available I'd expect someone would score points with it.

Current example: Someone asked what (presumably "on average") was the source of most engine wear : wear metal in oil, combustion by-products in oil, or dirt injested with the air. Lots of opinion expressed, no evidence IIRC.

Here are some abstracts. Think access to the actual reports will cost money.

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PostSubject: Re: Recycling air filters   Wed May 13, 2015 12:29 am

I always blow out my air filter when im doing an oil change. I normally do oil changes every 6000 miles and only change the filters when they go black. Or during a major service. Tho iv only had paper filters before but the suzuki x90s filters different when blow it out after a dusty trial. I really dont mind spending out on servicing parts, tho i use slightly cheaper oil and change it more often. Tho i normally buy oil when its on offer. Last lot i bought was down to £12 from £20. Filter was half price aswell. still twice as much then the landy filters.
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PostSubject: Re: Recycling air filters   Sun Oct 25, 2015 1:18 pm

Variation on filter - recycling. I washed my fuel filter.

I'd intended to just give it a substantial squirt of carb cleaner up both orifices, but ONCE AGAIN I couldn't find the wee squirty tube thingy it came with, so I reverted to my carb-cleaning weapon of choice.

Water, detergent, and a hypodermic syringe.

You can't hose down the whole of the supply side filter from the inlet because the pipes long enough to narrow your arc of fire, so I just squirted it in and then shook it around a bit.

I didn't make a determined effort to back-flush it from the engine side because I was mildly concerned that it wasn't built to take pressure from that side, but I did blow through it a bit.

Of course the water doesn't mix with the petrol, and is quite hard to get out again. You also can't directly observe the filter surface like you can with an air filter, but some rust was evident in the outflow.

I'll probably skoosh some ethanol in later on to help chase the water out
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PostSubject: Re: Recycling air filters   Sun Oct 25, 2015 5:00 pm

Not being able to see what my cleaning efforts achieved would deter me from this one. Wouldn't be able to see if the filter material got damaged (perforated or collapsed) either. Are the fuel filters expensive or difficult to get for your car?
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PostSubject: Re: Recycling air filters   Mon Oct 26, 2015 2:39 am

Justwatching wrote:
Are the fuel filters expensive or difficult to get for your car?

Dunno.

IF it was car-specific it might be difficult to get. I'd guess generic ones might be available, though it'd help if the inlet and outlet spigots fitted the fuel hoses.

Ideally I'd get a see-through/take-apart replacement, but I dunno if that'll be possible. Now I've got the original off I can take it shopping with me, for fit.

I'll probably give the fuel tank a drain-and-flush too, since it appears to have a drain plug and its probably never been done.

Just have to score a container big enough to park the petrol in.

While this stuff is probably worth doing, I doubt its relevant to my idling awkwardness since a clogged fuel filter would be expected to have more effect at high revs.

Incidentally I had an alternative thought about air filter cleaning (for the old stylee circular ones). I'm thinking a kind of water feature/hamster wheel, with water dribbling on the inside off-axis, causing it to rotate so part of the filter is continually being back-flushed at low pressure.
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PostSubject: Re: Recycling air filters   Mon Oct 26, 2015 11:52 am

Come to think on't, I know where there are a couple of unguarded Stuart tanks with fairly intact engine installations.

Might be a bit big, but spare capacity shouldn't hurt, should it?
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PostSubject: Re: Recycling air filters   Mon Oct 26, 2015 12:42 pm

You could actually BUY a NOS filter for an M3 :-

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but the ones I have...er...access to are M5's, so only have twin Cadillac V8 engines, and the fuel filters will likely be a bit smaller.
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PostSubject: Re: Recycling air filters   Mon Oct 26, 2015 5:30 pm

edlithgow wrote:
Come to think on't, I know where there are a couple of unguarded Stuart tanks with fairly intact engine installations.

Might be a bit big, but spare capacity shouldn't hurt, should it?

Don't think it would matter. Fitting it to the car and attaching fuel lines would be more problematic.

This seems too much effort for a fuel filter.
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PostSubject: Think Tank   Tue Oct 27, 2015 12:22 am

Justwatching wrote:
edlithgow wrote:
Come to think on't, I know where there are a couple of unguarded Stuart tanks with fairly intact engine installations.

Might be a bit big, but spare capacity shouldn't hurt, should it?

Don't think it would matter. Fitting it to the car and attaching fuel lines would be more problematic.

This seems too much effort for a fuel filter.

Hauling it around would probably increase the fuel consumption enough that you might actually need it.

But it'd be a conversation piece.
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PostSubject: Re: Recycling air filters   Tue Oct 27, 2015 4:29 pm

edlithgow wrote:
But it'd be a conversation piece.

Your whole car is a conversation piece.
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PostSubject: Re: Recycling air filters   Wed Oct 28, 2015 8:06 am

Well, recieved opinion is its a Piece Of Something, right enough.
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