Air Filters-thoughts please

Submitted: Friday, May 26, 2006 at 20:51
ThreadID: 34307 Views:2395 Replies:13 FollowUps:12
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Just toying with the idea of upgrading from the factory filter to K&N/Unifilter systems. Keeping in mind most of mileage will be on blacktop with occasional dirt work when we go away, is it worth the extra cost and maintenance time. Do these type of filters have higher airflow to improve performance? Vehicle is RA Rodeo TD.


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Reply By: Peter 2 - Friday, May 26, 2006 at 20:59

Friday, May 26, 2006 at 20:59
Most tests indicate that they don't filter as well as the paper filters, some reckon they provide more 'go' but no stats to back up seat of the pants.
My experience with oiled foam filters over an extened period was that it did let very fine dust through. Modern vehicles with airflow sensors can have probs with oiled filters too.
How long do you intend to keep the vehicle or are you accessorising it for the second owner ;-))
AnswerID: 174981

Follow Up By: MP - Friday, May 26, 2006 at 21:09

Friday, May 26, 2006 at 21:09
Thanks for the reply Peter 2. I hope to upgrade in about 3 years. Hadn't thought of that. I suppose I should only need to put 2 more filters in it at the most. Would be OK if its the same model with same engine but that's crystal ball stuff.....

FollowupID: 431053

Follow Up By: BenSpoon - Monday, May 29, 2006 at 16:09

Monday, May 29, 2006 at 16:09
Completely agree.

I ran a finer filter oil/foam filter for 2 years and cleaned it out maybe 3-5 times during that. After a while there was a fine dust build up on the inside of the throttle body- I decided to use more oil to fix it, but it became over oiled and ran ritch. I replaced the finer filter with a repco paper one and I now get 40km more per tank.
I have been told that finer filters dont even compare to K&N, but I dont care- Its paper for me from here on.
FollowupID: 431463

Reply By: Peter - Friday, May 26, 2006 at 21:03

Friday, May 26, 2006 at 21:03
Dunno about any advantages of the K&N. I put on in my 4.2 Patrol but have gone back to the original paper type filters. Didn't seem to make any difference to fuel economy but the car did seem to be a bit sluggish. Will probably use it for dusty conditions.
Would I buy another one? Probably not
AnswerID: 174982

Follow Up By: MP - Friday, May 26, 2006 at 21:16

Friday, May 26, 2006 at 21:16
I agree with the dusty conditions. The off road racing fraternity (Finke etc) obviously use them for easy of cleaning. I saw one of these vehicles with a blocked paper element with the element totally sucked in. The V8's certainly want to draw the air. Thanks for the input. Looks like I'll have a bit of extra time tomorrow.

FollowupID: 431055

Reply By: Member - Duncs - Friday, May 26, 2006 at 21:25

Friday, May 26, 2006 at 21:25
I don't know what the set up is on the Rodeo.

I was considering one years ago and my mate who is a very experienced diesel mechanic said not to. They don't stop the fine stuff. He said it may be OK in the first filter but that I should keep the original paper elements for the final filter.

Then again if you are not keeping the car long you probably won't get your money back.

Fit a compressor and blow out the paper element regularly when on a dusty trip. You'll use the compressor for a lot more than that. Footballs, airbeds, hey you might even pump up a tyre every now and then.

AnswerID: 174989

Follow Up By: Scubaroo - Saturday, May 27, 2006 at 12:42

Saturday, May 27, 2006 at 12:42
I tried blowing an air filter with one of those Bushranger clone compressors - ha. what a waste of time. It would have taken twenty minutes to clean it. It seems to pump tyres at comparable speeds to quoted test results, so I don't think my individual compressor is faulty.

You need a shop compressor to get the airflow required to properly clean a paper filter.
FollowupID: 431115

Follow Up By: MP - Sunday, May 28, 2006 at 07:21

Sunday, May 28, 2006 at 07:21
Thanks Duncs. I agree with the compressor. Have both one in the shed (which also works a treat for the 50 party balloons the wife wants me to blow up every now & again) and one in the vehicle. I clean air filters with the compressor from inside out so as not to force dirt in further(my theory anyway). I agree with Scubaroo re tyre compressor - wouldn't have enough oomph. Thinking of buying a cheap air compressor blowing tool- the click on type- to keep in the vehicle. Might be able to use it at fuel stations using their air outlets or fabricate something using a tyre valve so it would go straight on.
FollowupID: 431202

Follow Up By: Member - Duncs - Monday, May 29, 2006 at 10:16

Monday, May 29, 2006 at 10:16
What you need to blow out a filter is a resevoir. My ARB with the little bean can attached does OK. Would it be nice to have a bigger reserve of stored air? Absolutely but I work with what I have and it does jsut fine.

FollowupID: 431402

Reply By: Member - Captain (WA) - Friday, May 26, 2006 at 21:57

Friday, May 26, 2006 at 21:57
Hi MP,

Check out this link then see if you still want to go away from OEM filters :) Best Independent report I have seen on the subject.

Site Link


Its not what you drive, but how you drive it!
LC 200 + AOR Quantum+

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AnswerID: 174995

Follow Up By: 120scruiser (NSW) - Monday, May 29, 2006 at 08:18

Monday, May 29, 2006 at 08:18
Geez captain great minds think alike.
You beat me to it because you rambled on less than me.
FollowupID: 431383

Reply By: 120scruiser (NSW) - Friday, May 26, 2006 at 21:58

Friday, May 26, 2006 at 21:58
High MP.
This link was posted some time ago.
It is a bit of reading but interesting.
Have a read and then make your own mind up.
Site Link
Mixed comments on this site but I wouldn't spend the money.
For the record most of my customers cars get the AC Delco air, oil and fuel filter. We have been using them for about 5 years now and not one return.
AnswerID: 174996

Follow Up By: rash - Saturday, May 27, 2006 at 19:23

Saturday, May 27, 2006 at 19:23
High 120scruiser

Do you know where in W.A. i can get AC Delco air filter
Have a 3.0l t.d nasty comments know

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Follow Up By: Exploder - Saturday, May 27, 2006 at 20:05

Saturday, May 27, 2006 at 20:05
Try Coventry’s, i think thay do AC Delco
FollowupID: 431169

Follow Up By: Muzzgit (WA) - Sunday, May 28, 2006 at 01:31

Sunday, May 28, 2006 at 01:31
Hey cruiser, you being a mechanic, I thought you might like this.

When I first bought my 2000 3.0 GU (64,000 KLM) it had a grey paper element air filter, and after having problems with dust in the AFM while we were going through the north west, Nissan in Port Hedland said that this was not the correct filter and replaced it with a red "waxed" paper filter. (by waxed I mean in appearance, it is actually silicon caoted)

The vehicle has been serviced by the same mechanic that I have used for about 10 years and claims that he always uses genuine imagine my disapointment when I checked my air filter a few weeks back to discover it was the grey dry-paper element. (mechanic is now retired)

So down to Repco I went, asked for an air filter to fit a 3.0 patrol, and the bloke comes out with the grey one, and emphatically states that it is the genuine part (yes it is in a Nissan box). So I drive to Nissan and ask for an air filter for a 3.0 patrol and is red, is silicon coated.

How many 3.0 patrols are going around with the wrong air filter because of this? Not having a crack at you, never met you, BUT...................

FollowupID: 431199

Follow Up By: 120scruiser (NSW) - Monday, May 29, 2006 at 08:16

Monday, May 29, 2006 at 08:16
Dunno about repco's one.
I buy mine from Nissan direct and they are and always have been red. All after market ones are grey or white. After market people reckon its after market companies that make the genuine but who has the proof and thats why I always buy from the dealer.

Coventry do deal in AC Delco and also over hear Holden do.
My listing only goes up to the QD32 engine in the D22 model and there is no listing for it let alone the later ZD30. However my book is only 2002 though so might be worth a phone call.

FollowupID: 431382

Reply By: F4Phantom - Friday, May 26, 2006 at 22:10

Friday, May 26, 2006 at 22:10
here is some info cut and paste

"Jim Conforti (AKA the Land Shark) did some testing:
This was a scientific test, not one done by filter manufacturer X to show that their filters are better than manufacturer Y. The test results are pretty irrefutable as the test lab tests and designs filters where "screw ups" are absolutely NOT allowable (I can't say any more for security. Think "Glow in the Dark").

A scientific test was done on TEST filters where air was loaded with ACCTD (some standardized "test dust" called AC Coarse Test Dust) and sucked through the TEST filter then through an analysis membrane. From the Quantity of dust injected and the amount that gets through the TEST filter and is then captured on the analysis membrane we can calculate the efficiency of the TEST filter in Question.

BMW Stock Filter, Eff. Area of Media: 8.4 sq ft.
K&N Replacement, Eff. Area of Media: 1.6 sq ft.

The filters are the SAME size. They both fit in the STOCK BMW M3 airbox. The difference is that the STOCK filter has 65 pleats 1.5" deep and the K&N only 29 pleats each 0.75" deep.
Now, remember this ratio: " 5.25:1". It's the ratio of the AREA of STOCK to K&N. It's very important and will come into play later.

The STOCK filter efficiency started at 93.4% at 0 loading and increased to 99.2% efficiency as the loading increased to a max tested of 38.8 gm/sq ft of dust.

The K&N filter efficiency started at 85.2% at 0 loading and increased to 98.1% at the max tested loading of 41.38 gm/sq ft.

Now, I hear you. "Jim, that's only a FEW PERCENT". But is it?

Let's look. If we had 100 grams of dust on a new BMW filter we would let through a total of 6.6 grams of dust in. If we used the new K&N filter we get 14.8 grams of dust. That's 224% (TWO HUNDRED TWENTY FOUR PERCENT!!) more dust ingested initially, stock vs. "free flow" and this ratio is pretty much held. Somewhere between 200-300% more dirt gets "ingested" anywhere across loading equivalence. The more INTERESTING thing is when you look at what happens to the DP or Differential Pressure at a constant airflow as you dirty both filters equally with time.

The test used a rate of 75gr of dust per 20 min. Here's where the AREA difference comes MAJORLY into play. See, even though the BMW filter flows a bit less at the SAME loading, it also LOADS UP 5.25 times SLOWER due to it's LARGER effective area. So what happens is that the K&N initially flows better, but as the dirt continues coming in, the K&N eventually flows WORSE while still letting MORE dirt in.

Now, does any of this additional dirt cause problems? I dunno. I suppose we could have a few people do some independent oil analyses on different motors using both K&Ns and Stock filters. Get enough of them, and you'd have a good statistical basis. For me though, it's simple: More DIRT = BAD.

The additional short-term airflow might make sense on a track car. IMHO, it doesn't for the street.

-- Jim Conforti

K&N Response:

It is incorrect. The difference between 99.2% and 98.1% (his results) is 1.1% not 224% as he states!!! ( who didn't go to school, Jim was measuring the amount of dust that goes inside the engine). Furthermore, does he realize that 96% meets OEM standards? K&N has been around for over 30 years and we sell over 2,000,000 units a year. If there were any sort of problem, one would think we would know by now and so would everyone else. One Internet "expert's" opinion is not reason for concern and should be taken loosely at best.

That information is 100% untrue. Don't believe all you read on the Net. Most is opinions not based on any sort of factual evidence. Our filters are tested by an outside, independent laboratory. They have been proven to stop at least 99% of particles on a SAE dust test. This test uses particles as low as the 0 - 5 micron range and goes up to 20 microns.
For comparison, a paper filter also stops 99% on the same test and the OEM minimum standard is 96%. Foam is generally the worst media with a typical efficiency rating of 75 - 85%. To get higher ratings, the foam must be more dense and therefore way more restrictive. The "tack" characteristic of a K&N allows for increase filtration without loss of flow as well. The testing procedure used is SAE J-726 using ISO Test Dust.
This test is the standard of the air filter industry. The test procedure consists of flowing air through the filter at a constant rate (airflow rate is determined by the application) while feeding test dust into the air stream at a rate of 1 gram per cubic meter of air.
As the filter loads with dust the pressure drop across the
filter is increased to maintain the prescribed airflow rate. The test is continued until the pressure drop increases 10" H2O above the initial restriction of the clean element (in this case .78" to 10.78" H2O). At this point the test is terminated. The dirty filter element is then weighed. This weight is compared to the clean element weight to determine the total Dust
Capacity. The amount of dust retained by the filter is divided by the total amount of dust fed during the test to determine the Cumulative Efficiency.

The K&N filter achieved the following results:
- Dust Capacity: 305grams
- K&N Cumulative Efficiency: 99.05 %

Holding the filter to the light is useless, pin holes are normal.
That is what makes a K&N filter. There are actually hundreds of microscopic fibers that cross these holes and when treated with oil, capture and hold the very fine particles. On the same hand, they allow the filter to flow more air than paper or foam. The filter is 4 ply cotton gauze unlike some competitors synthetic material filters. The synthetics do not
have the very small fibers that natural cotton does. Also, the oil can be pulled off of a foam filter contaminating electronic sensors. It will absorb into cotton and stay in the media. In fact, Honda and Toyota only recommend K&N filters when using aftermarket high flow filters as K&N is the only brand of filter the oil does NOT come off of. They will not cover a failed sensor if foam filters were used.
We got started over 30 years ago making filters for motorcycles and off road racers. The filters did so well that these guys wanted them for their cars and trucks. We started making filters for these applications and here we are today. If they did not work, we would not still be here and growing every year.
We now make filters for Chrysler/Mopar, Ford Motorsports, Edelbrock, Rotax Engines, and Harley Davidson. We come as original equipment on the 2000 Ford Mustang Cobra-R. We even made filters for the Apache helicopters used in Desert Storm because of maintenance problems with the original paper design. If they work in these conditions they will work for you.

Rick from (Information emailed by Martin)"
AnswerID: 175001

Reply By: jorgejhandal - Friday, May 26, 2006 at 23:44

Friday, May 26, 2006 at 23:44
I put a k&n filter in my patrol , and at first seemed ok , gave a little performance , but after 2000 kms it seemed about the same as stock and when I checked the filter it was really dirty and dust was around the pipe that goes to the engine, lots of dust had gotten in, also the 50000 km mile, I dont know , cleaning its not true , it got so dirty I had to clean it every 5000kms or sooner.
so dont upgrade its not worth it.

Site Link
AnswerID: 175022

Reply By: Exploder - Saturday, May 27, 2006 at 00:03

Saturday, May 27, 2006 at 00:03
Filter Efficiency:
Top AC Delco> 99.93%
K&N> 96.8
Yeah I think I will risk it over 3%.

The K&N filtering capabilities come from the Oil so obviously the more dirt it collects the less efficient it becomes, so if you are driving in extremely dusty conditions. I.E riding up the ass of a road train on a gravel road for a few hrs it might pay to give it a clean

Have you seen the story of the guy who drove 1,000,000 miles on a K&N filter?

Clearly if you are operating Earth moving equipment that operate in a cloud of dust for 12Hrs a day the K&N is not the best for you. I have run a K&N for 50,000k’s my MAF senior is like 3-inch away from the filter and I have never had a problem, never any dust in the intake tube inspect it every 10,000 clean and re-oil every 25,000 or as necessary, it’s already payed for it self once.

K&N are used on XR6 Turbo XR8 and GT’s from factory.

I use K&N I will recommend K&N and I will bet my engine life on K&N, I will never use a Factory paper filter agene.
AnswerID: 175025

Reply By: Member - Ivan (ACT) - Saturday, May 27, 2006 at 08:00

Saturday, May 27, 2006 at 08:00
Or go the Donaldson - why get your filter dirty, when you can catch it before it gets in there! - and the new TopSpin have a spinning vane which ejects the dirt and crap on the move (rather than catch it like the older style)

Have compared Top Spin with traditional Donaldson with no Donaldson on a trip with 15 cars and the dust was like talcum powder (almost white out conditions)

No Donaldson - filter almost choked with dust
Traditional Donaldson - a couple of bangs on the wheel and dust gone
Top Spin - one bang on the wheel, and the slightest hint of dust.

They are different spec depending on the amount of airflow you want need - and because it is simply a hoseclamp to hold on, you can put it on and off easier than changing your jocks ;-)
AnswerID: 175041

Reply By: Darian (SA) - Saturday, May 27, 2006 at 17:14

Saturday, May 27, 2006 at 17:14
I use a Unifilter on the Jackaroo - 2 reasons....... 1. Genuine filter is a complete $ rip off and there were no alternatives when I went to Unifilter. 2. I was pulling a lot of dust in through thre wheel well with the original setup ... not such an issue now, seeing I've got a snorkel.
Cleaning is a little bit of a chore - washing in turps and re-oiling etc. - I use a spare sleeve and swap them as I go - My Jack is a long term vehicle - if you only have 2/3 years to go, probably forget it.
Can't see any dust getting through - there are 3 seperate oiled sleeves in the system - the outer only getting cleaned frequently.
Air flow would have to be reduced a bit compared to the papers, but not noticable on my 3.0L TD.
They are reported to foul some sensors in some systems (with tiny oil droplets) and though mine has had such a snag, I've met another bloke with the identical snag in the very same vehicle and he has only ever had paper filters.
I like it - I press on.
AnswerID: 175076

Reply By: MP - Sunday, May 28, 2006 at 07:32

Sunday, May 28, 2006 at 07:32
Thanks to all for the response. I think I'll give one more paper filter a go and see how it travels.
AnswerID: 175133

Follow Up By: Muzzgit (WA) - Tuesday, May 30, 2006 at 00:47

Tuesday, May 30, 2006 at 00:47
Sorry I'm so late, but after reading the whole thread it appears that most will agree, you'd be better off with a snorkel, and stick to the standard air filter.
FollowupID: 431606

Reply By: geocacher (djcache) - Sunday, May 28, 2006 at 18:54

Sunday, May 28, 2006 at 18:54
I changed to a Finer Filter a few services ago. I'm happy I did.

I didn't do it for performance I did it so on convoy trips in dusty conditions I can do a filter clean on the go and don't have to carry a spare.

My mechanic uses them, the guys I know riding bikes use them and on the Canning we did a couple of filter cleans in the two weeks we were travelling.

The cartridge for a Bravo/Courier is dear as poison $50+.

I've done a few cleans on mine and the inner foam is still the same color as new. If it were letting any sort of quantity of dust through gradual colour change is a reasonable expectation but there is none.

I'll keep mine thanks and I'd get another when I change vehicle.

AnswerID: 175230

Reply By: Robin - Monday, May 29, 2006 at 08:58

Monday, May 29, 2006 at 08:58
Hi Mark

I'm in the Unifilter/Finer filter camp here, but I read that
you will be sticking with paper.

Many of the facts are reports quoted above are correct as stated
but there are a number of nuances and situations in the field of 4wding that
need to be considered to get best result.

One of these ,particularly with paper and K&N is initial loading
of the filter.

Your paper filter will let a lot more dust through in first
1000km of driving. Many get car serviced and head off to bush.
Bad move , if new paper filter was fitted, get it done a few weeks
early and get some km's into filter on highway first.

For same reason, never take and fit new paper filter in bush.

The oiled foam ones are the only ones that can be adequately
serviced in bush - although its messy, and idea above of carrying
spare outer foam layer is good and practical as it occupies little

If read between the lines of some of the above referenced reports you
might observe that filter efficentcy depends a lot of dust particle

While all will pass standard tests - if you check results for very
fine particles (sub about 4 mircons) you will notice that paper
performance drops off rapidily.

I.E. If your heading into the bulldust then this is were paper is
worst and oil foam is best, and significantly shorter engine life
can result if used in those circumstances, hence use of oiled foam
in long haul transport vehicles subject to dust.

Your main question regarded improved performance, and really
when all filters are in good condition there is little difference
and more importantly , little need anyway as its only at high
rev's where a marginal effect may be observed.

Still I like to have the marginal effect , so on my petrol patrol
I put a voltmeter on the air flow meter, vaccum cleaner down the
air intake chain and got a reading relating to air flow which was
quite repeatable as engine was not running.

The foam filter I use is easy to play with ,and with a little playing
around and slight adjustment I got more air flow into engine than
with even no filter at all.

P.S. Note that some above have been unsucessful in using 12v compressor
to clean air filter.
Previously I have suggested carrying an air transfer hose to use
off spare tyre. Cleaning a paper filter in the bush is another
effective use for same.

Robin Miller
AnswerID: 175305

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