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Looks like a good test. However you must realise that the K&N is only 3.13 PERCENT less effective... in this test.

Then you look at the small percentage of extra POTENTIAL dust passing against the 4.54 VS 6.23 inches of water restriction graph, WHICH by the way is drawn to make the worst restriction look like the least restriction at a glance.

So 4.54 VS 6.23 is 0.164PSI VS 0.2251PSI - which shows that the filter that potentially lets 3.13 percent more dust in has 72.86 percent of the restriction or flows 1.3725 times as easily as the AC Delco unit.

As for the acumulative capacity graph, in a sports car or bike application, to whom is it going to matter that the K&N reaches max restriction when OVER 200g of DIRT IS IN IT????

And the accumulative gain graph puts the whole test in question by showing that a filter that is apparently less efficient in the overall efficiency graph ends up letting less dirt through than a "better" filter. (Note K&N and UNI in both graphs)
 

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air filter study...

Should I understand this graph to mean that the K&N filter has the best air flow, which can translate into better engine performance...all at the expense of a few insignificant extra grains of dust? Or am I underestimating the potential harm that 3% more dirt pollution can do? Thanks all!:)
 

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Snappo, I think that the main problem is that just how harmful dust is, is not explained.

The two most important and informative graphs are the "rate" graphs that show dust loading and resistance to flow. The K&N loads up fast, (but not the fastest) and is always the least restriction. Now they should have explained whether 9.8g/min is considered normal, or is the high extreme of what a filter should have to cope with. That would give perspective. I assume - because it is an ISO test for passing a manufactured component, that it is the worst extreme, which is not where most K&N's operate.

The have the same graph in line form and bar form, and they both show different values, one, the "Initial restriction" bar graph shows the K&N giving 1.3725 times less restriction than AC Delco at 350 CFM, and the "Resistance to flow" line graph lower on the page shows the K&N giving a whopping 2.7 times less restriction at the same 350 CFM. It seems the line graph is the more correct one as at zero cfm the all have zero resistance to that flow. I'm guessing the other graph includes the same jig fixtures resistance to flow which should have been take out to compare just filter resistances.

It's similar to comparing a 5kg pushbike with a 5hp motor attached, to a 180kg motorcycle with a 180hp engine. They should have the same power-to-weight ratio right? Not if you test them with the same rider (analoguous to the jig fixture). If the rider weighs 80kg you suddenly have a motorcycle with a power to weight ratio of 180:260 and a pushbike with a power to weight ratio of 5:85. (0.692HP/kg VS 0.059HP/kg) - one is now 11.73 times better off.

Will the engine of your car provide a constant restriction just like the jig fixture does? Quite likely! It could in fact be MORE of a restriction, BUT for the purpose of comparing FILTERS and only the filters, you want the properties of JUST the filter.

I also note that they simplified the K&N filter efficiency number in the first graph, and how many more times dust it passed than the AC Delco in a paragraph down the page.
 

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air filter study...

Firepath: Excellent analysis! Thank you! I would suggest, however, that one's choice of air filter may be best suited to type of riding, and where. If on the track, I would be least concerned with pollution particulates, and most concerned with minimal air flow resistance, affording a few extra horses. On the street in our local city or town where pollution is most dense, I would personally care to protect my engine by keeping it clean, dry, and running sweet...albeit with a HP or two less. I'm interested in your opinion on this matter:)
 

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Well, after rethinking how much dust was actually introduced to the filters, if the best filter was run for an hour and loaded up with over half a kg of dust, I'm pretty darn certain that the amount of dust the introduced the filters to was on the very, very, very, very high end. The test probably would have taken far too long if they were to do it with closer to in-use levels, so it's understandable, but still very excessive compared to what you're going to encounter on the street. (Keep in mind that most of the time you're not sucking 350CFM through it either, especially on a bike.)

I don't think I've increased the weight of a filter from one of my cars more than 50g after hundreds of hours of use, including going to and leaving from my dusty workplace, and travelling in fairly dense traffic.

Although I'd like things to be as clean as possible, I think the 3 percent extra dust is acceptable for the much easier flow, and if you change your oil and clean or replace your air cleaner filter as often as you're meant to I doubt you'll notice the effect of the extra potential dust over the life of the vehicle.

The same vehicle I talked about above has around 250 000km on it, has had a head gasket bust and leak coolant into some cylinders, and the oil, and more recently had a crack in one combustion face of the head, letting more coolant into number 3 cylinder. I looked at the engine while it was apart, all cylinders were smooth, but number 3 was rough, rings were probably toast too. With just a new head back on it, it doesn't smoke, unless really flogged, and still runs like a train, has done for over a year since. The oil gets black quick, but hey, it's got a quarter of a million ks on it.

My point is, this engine has far worse things wrong with it than a tiny amount more dust could dream of doing, and it's doing quite well for a 17 year old workhorse.

Bottom line - I'd use a K&N for a street car or bike, and in fact I'm quite happy with how little drop in filtering they provide, according to that test. I would of course try to avoid dusty areas, but I'd do that anyway, no matter what the filter.
 
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