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K&N filters[ALL/1998] posted by orson on
Friday, 5 December 1997, at 7:38 p.m.
I've been reading a lot about owners putting K&N filters in their Volvos. I decided not to put a K&N filter because I believe it will compromise the long-term reliability of my vehicle. There are two reasons why I believe this.
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1) I found this on the web. According to the author, this information is from Amsoil, so you have to take it with a grain of salt.
Here's the info I have on air filter performance. Tests were done using
SAE J726C Test Method 5-best --> 1-worst
Oiled foam Paper Oil Bath Oiled Gauze
(AMSOIL, UNI) (K&N)
Large particle efficiency 5 5 5 4
Small particle efficiency 5 4 1 2
Airflow capacity 5 2 3 5
Dust holding capacity 4 2 5 2
Load up characteristic 4 1 5 1
Backfire characteristic 3 2 5 3
Cleanability 4 1 4 3
As you can see, K&Ns are great for airflow, which is what they were
designed for. Their original application was on racing engines, where
airflow is important and ultimate engine life was of little consern. They
are not as good at filtering as paper or oiled foam types.
Ed Hackett edh@maxey.dri.edu The Desert Research Institute
DoD #0200 WMTC BMWRA DIOC Reno, Nevada (702) 673-7380
KotLS KotLE DotD #0003 I'm not really a chemist, I'm just one of
BMW K100RS, Moto Morini Camel them motorsickle sonsabitches. __=o&o>__
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2) My second reason is from a friend who works in Chrysler powertrain. He took an entire one-day seminar on filters. According to what he learned, with a given cross-section (filter size for example) air flow and filter capacity must necessarily be trade-offs. In other words, it is impossible to get better air flow and better filtering at the same time when the air-flow cross sectional area is the same.
I still use Volvo paper air filters.
Re: K&N filters[ALL/1998] posted by Topi on
Saturday, 6 December 1997, at 8:30 p.m.
I bet Amsoil filters are made by UNI Filter.... I've tried both: K@N is a hundred times better than any foam crap! UNI will get dirty fast and doesn't flow but K@N has many "wrinkles" = more surface = longer life. Also, wash a UNI and it's rock hard! Won't flow at all. Doesn't resist gasoline, either, gets hard. UNIs are OK for low price, when clean but when dirty - forget! All Amsoil's claims are false. Still - you're right, paper WILL clean best! I use K@N 'cause they are last 50 000 mls (cleaned at every 7500 mls) and give MORE POWER. Cheap...
Re: K&N filters[ALL/1998] posted by orson on
Sunday, 7 December 1997, at 9:36 a.m.
You say that the UNI foam filter gets dirty fast. I'm not sure what you mean by that, but if you mean that it picks up more dirt, that would seem to correlate with the chart's assertion that foam filters are better at removing dirt (even if they do not flow as well). I also tried a foam filter for a while (Amsoil) and ended up throwing it out because I did not find it too easy to clean and re-oil.
Also, you say that K&N has more "wrinkles" which means it has greater surface area. True, but a foam filter uses it's entire thickness as filtering media and the thickness of foam filters is typically much more than that of a K&N cloth filter. So the total filter "volume" is larger with foam.
None of this, however, conclusively tells us which filter is better a removing dirt. According to what I learned from my Chrysler buddy, the only way to tell is to put the filters on a flow bench. The one that flows better is necessarily worse at removing dirt according to what he learned (again, assuming same air-flow cross section).
As another note, one artifact of this theorem is that if you want maximum protection against dirt, you should never change your air filter! After all, the more dirt it collects, the better it filters. Practically speaking, you still have to change the filter to prevent restricting the air flow to the point where mileage or power is significantly affected.
My intent with the original note was to point out that there is a good possibility that installing a K&N filter in place of paper degrades the cleanliness of the intake air. Perhaps more frequent oil changes or more frequent doses of fuel system cleaner are in order if you install a K&N.
Re: K&N filters[ALL/1998] posted by Peter on
Monday, 8 December 1997, at 1:10 p.m.
I know a chassis dyno guy that maintains that he sees higher HP figures on cars with paper filters. We switched filters on my old low-hp race car and saw no difference. He also says that an used paper filter lowers HP where an used K&N doesn't.
This to me means that well (overly?) oiled K&N filter flows less well than a paper filter and as the oil is sucked away, flows improves. One could reasonably infer that a key factor in how well an oiled filter flows (and filters) is how much oil is on it.
I use a paper filter on my race car. They're cheap to replace and I don't have to get my hands all oily! The primary consideration is not what material the filter is made from, but the area of the filter. The ideal scenario is to have a filter that filters well (and is thereby restrictive) but is large enough that it doesn't matter.
Having said that, I've used a K&N filter on a couple of street cars and upon disassembly at about 120K miles have seen no appreciable cylinder bore wear. And no, I haven't re-oiled every 7500 miles. It may be that new cars are built using materials that are durable enough and tolerances that are tight enough, that within the "filtering range" of both the K&N and a paper filter, engines will be just fine.
In my experience, on a street car the bottleneck is not the filter itself, but the small intake holes or tubes through which air flows into the airbox. Noise requirements being what they are, one can often get a substantial HP increase by making the holes larger or removing the intake tubes. You just have to decide whether you can live with the resultant intake roar...
Re: K&N filters[ALL/1998] posted by Paul Elliott on
Tuesday, 9 December 1997, at 1:24 p.m.
>>And no, I haven't re-oiled every 7500 miles<<
Why would you want to? The instructions which came with my K&N drop in filter say that you can go 50,000 miles before service! It also says that up to a point, the dirtier it gets, the better it filters, without sacrificing flow. Only after about 1/8" of dirt accumulates does it need servicing , again, according to the directions. I've had mine for about 9,000 miles, and have along time to go before it needs servicing. Even at a conservative 30,000 miles, when the stock filter gets replaced as part of Volvo's 30,000 mi service, my K&N just gets cleaned and replaced. That's where the cost savings comes in.
The Ronco Window Filter[ALL/1998] posted by Peter on
Tuesday, 9 December 1997, at 2:43 p.m.
I have a cone type K&N that sits in the engine compartment without an airbox so it gets dirty quickly. I probably SHOULD clean it every 7500 miles. I was trying to illustrate a point.
I've been working on what I think is the next step in filtration technology: the "Window Filter" (pat. pend.). This is a large filter that replaces one's side window or backlight. Then one then simply runs the intake hose for the engine into the passenger compartment (using the existing heating and AC ducting) resulting in a huge airbox with massive filter area!
There are problems: In high HP V-8 conversions, I've noticed that the driver often loses consciousness due to lack of oxygen (a real issue for anybody that would contemplate this type on conversion - they need all the brain cells they can get). I had a fix drawn up, but the damn sketch got sucked off the front seat into the intake manifold last night.
Re: The Ronco Window Filter[ALL/1998] posted by Topi on
Tuesday, 9 December 1997, at 11:09 p.m.
Sounds like "medicine marijuana" is still legal in San Francisco......