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Vigge sent very good links, which everyone should read with care.
"The air filter posses very little restriction at all in this application. As long as an air filter is properly sized for an application, the lost airflow will be very minimal. This means that there is very little if any power to be found from removing the air filter, much less changing the filter type. The K&N did flow better than the Napa Gold in the first test to the tune of 0.02 psi. That is less than 1/3rd the loss in the factory piping, and it is a whopping 0.14% of atmospheric pressure (14.7 psi). If you need the 0.14% better airflow, than the K&N is hands down the best filter." ( source: http://www.bobistheoilguy.com/airfilter/airtest2.htm )
And the quote above concerns only pressure drop caused by filters ( ie. power increase ). What comes to filtration issues, one can examine the following:
"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." ( source: http://www.bmwe34.net/E34main/Upgrade/Air_filter.htm )
Spicer's article ( http://home.usadatanet.net/~jbplock/ISO5011/SPICER.htm ) is based on scientific tests, and draw the following conclusions:
“Now that I am not doing the tests and my objectivity is not necessary, let me explain my motivation. The reason I started this crusade was that I was seeing people spend a lot of money on aftermarket filters based on the word of a salesperson or based on the misleading, incomplete or outright deceiving information printed on boxes and in sales literature. Gentlemen and Ladies, Marketing and the lure of profit is VERY POWERFUL! It is amazing how many people believe that better airflow = more power! Unless you have modifications out the wazoo, a more porous filter will just dirty your oil!"
Racing use differs from normal use because use purpose is different. Bigger airmasses are to be moved through engines. Maintenance or filtration issues are not important in this context at all. It's whole different situation for average Joe in United States.
To me it seems that it's easy to sell snake oil in America. People seems to believe whatever marketing persons say. Next time you'll buy free flow filters please ask some proved test results before your buying decision. This kind of test results are very rare for some reason...
posted by 84.249.15...
, Fri, 24 Mar 2006 07:50:07
, Thu, 23 Mar 2006 22:14:00, Fri, 24 Mar 2006 06:38:14, Fri, 24 Mar 2006 06:29:51
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