Air filter study - very interesting

[Spokane-Pete]

http://home.usadatanet.net/~jbplock/ISO5011/SPICER.htm

 

Especially read the end.

[Dickensheets]

I guess I just blew $40 on the K&N for no reason.

[mattocs]

I have a K&N...i've been thinking about going back to the OEM filter. This makes me want to do it even more.

[n16ht5]

I bought a k&n for my ranger when I was 16, saw that it let in a lot of dust and didn't help my power, went back to paper.... I just get cold air coming into it and i get more power

[Legacy777]

Yeah,

 

I read it a while ago. It's pretty good, and I sort of came to the same conclusion. I felt absolutely no difference between a new paper filter and a K&N. The fact that the K&N flows better when dirty is irrelevent IMO, because I'll just get a new paper filter......

[jamal]

Thanks. I've been getting sick of people telling me their K&N adds 10 horsepower and then getting pissed off when I tell them it doesn't. Now I can make them even more angry with actual proof.

 

 

Here's an oil filter study that's good.

[n16ht5]

http://www.bobistheoilguy.com/airfilter/airtest2.htm

[RallyKeith]

I only have one question about the test. Is 350CFM representative of the duramax diesel's actual flow? A filter of X size when at low flow rate would show much less restriction for the amount of dirt trapped than at higher flow rates. I'm not disagreeing with the results exactly, I'm jus curious. It works just like a restrictor plate, at a low flow you don't know it's there, at higher flow you notice.

 

Keith

[rweddy]

Thanks. I've been getting sick of people telling me their K&N adds 10 horsepower and then getting pissed off when I tell them it doesn't. Now I can make them even more angry with actual proof.

 

 

Here's an oil filter study that's good.

I hate when people tell me this also, it is not worth the added debris they allow into the engine even if you did get 10hp.

[MiniTransAm]

So if I'm reading this correctly, the Delco flows the least out of the box, but lasts the longest and filters more crap.

 

My question is what do those of us do with an intake?? Last I checked, Delco didn't make cone filters.

[Steve530]

I only have one question about the test. Is 350CFM representative of the duramax diesel's actual flow? A filter of X size when at low flow rate would show much less restriction for the amount of dirt trapped than at higher flow rates. I'm not disagreeing with the results exactly, I'm jus curious. It works just like a restrictor plate, at a low flow you don't know it's there, at higher flow you notice.

 

Keith

 

I found the Duramax displacement is 475.9 cu. in.

 

475.9 in^3 * (1ft^3/1728 in^3)= 0.2754 ft^3, which is the amount of air (and fuel) used in 1 revolution.

 

(350 ft^3/minute) / (0.2754 ft^3/ revolution) = 1271 rpm

 

So a duramax diesel engine at 1271 rpm would intake about 350 CFM. My guess is that 1271 rpm is above idle on that enigne and is probably a reasonable test.

 

Did I do the math right?

[jamal]

I found the Duramax displacement is 475.9 cu. in.

 

475.9 in^3 * (1ft^3/1728 in^3)= 0.2754 ft^3, which is the amount of air (and fuel) used in 1 revolution.

 

(350 ft^3/minute) / (0.2754 ft^3/ revolution) = 1271 rpm

 

So a duramax diesel engine at 1271 rpm would intake about 350 CFM. My guess is that 1271 rpm is above idle on that enigne and is probably a reasonable test.

 

Did I do the math right?

 

Well, being turbocharged, the air going into the chamber is pressurized, so it uses more than the volume of the cylinders at atmospheric pressure.

 

Sounds to me that the 350 cfs is just the standard for the test. I think it would be possible to extrapolate the data to a differently sized filter or different flow rates. While you might not be able to determine the exact amount of dirt being trapped by, say, a purolator filter on an EJ22 versus the AC Delco, the comparison between the different filters should still be good, so I can probably say that the AC will still filter more but not flow as well as the purolator.

 

Of course, the real question is "does any of this really matter?"

 

Most of the differences probably aren't that significant.

 

The K&N kind of stands out, though. The amount it filters doesn't seem as proportional to the flow as the others, letting by more dirt for a small gain. Does it adquately filter dirt to keep an engine safe and running for a long time? I think it probably does. I'm not ever going to use one, though.

[Setright]

Well, being a cynical man, always sceptical of "the latest research" and other such heresay, I am inclined to say:

 

BALONEY!

 

Those graphs are clearly designed to put some of the filters in a bad light. Notice how the filtration graph doesn't have the axes starting at zero? The percent wise small difference between AC and K&N is hugely exagerated!

 

Please people, don't be fooled by such blatant manipulation.

 

 

(Same goes for K&N's blurb..)

[Setright]

Reading the numbers, the K&N filters only 3% worse for a flow gain of 27%.

 

 

According to the filtration and restriction graphs.

[RallyKeith]

Well, being a cynical man, always sceptical of "the latest research" and other such heresay, I am inclined to say:

 

BALONEY!

 

Those graphs are clearly designed to put some of the filters in a bad light. Notice how the filtration graph doesn't have the axes starting at zero? The percent wise small difference between AC and K&N is hugely exagerated!

 

Please people, don't be fooled by such blatant manipulation.

 

 

(Same goes for K&N's blurb..)

 

I agree 100% The first thing I learned in the engineering world was that you can make the same numbers have totally different impacts based on how you display them. That is also why I called into question the flow rate.

 

Keith

[bjwirth]

Well, being a cynical man, always sceptical of "the latest research" and other such heresay, I am inclined to say:

 

BALONEY!

 

I briefly looked at this study, and it's impossible to get any conclusion out of it without getting more info. I've done some air filtration expts, and for "state of the art," this notion of weighing filters is crap. and if you look, the numbers don't add up. t's obvious that these folks had an agenda, so it's hard to take this seriously. The same goes for any K&N claim as well.

 

Every time I see a "pretty" graph, I always wonder.

[mattocs]

Anyone want to buy a used K&N off me :-P

[wkoepp]

Anytime someone makes a big point of telling how much this or that expert test would cost to do and how expensive the super testing equipment is, it rings a warning bell in my head. You can put whatever filter you want on your diesel engine but a K&N filter will always go on my subaru and my mazda. Oily filters beat paper filters in California!

[blitz]

With a passive filtration system, there's only two ways to decrease the resistance to flow:

 

1. Increase the media area (larger filter).

2. Make the holes in the media bigger.

 

Finally realize that the factory cams, exhaust system, and port configuration are far and away the biggest determinants of volumetric efficiency, not the paper air filter. Once you've actually got the engine flowing 20-30% more air, then it would be beneficial to get the filter to accomodate the increased flow.

[blitz]

I found the Duramax displacement is 475.9 cu. in.

 

475.9 in^3 * (1ft^3/1728 in^3)= 0.2754 ft^3, which is the amount of air (and fuel) used in 1 revolution.

 

(350 ft^3/minute) / (0.2754 ft^3/ revolution) = 1271 rpm

 

So a duramax diesel engine at 1271 rpm would intake about 350 CFM. My guess is that 1271 rpm is above idle on that enigne and is probably a reasonable test.

 

Did I do the math right?

Since it's a four stroke, it would pump that much air in TWO revolutions, so divide the airflow figure by two.

 

Next, estimate a rough best volumetric efficiency of 85% (includes intercooler and exhaust system/turbo losses). Multiply airflow by .85.

 

Finally like jamal mentions, you'd need to factor in the blower pressure over atmospheric. Assuming .7 bar, multiply the airflow by 1.7 (.8 bar = x 1.8, etc).

 

The resulting figure would be rough, but close enough for rock n roll.

 

Volumetric efficiency is greatest at peak torque. Then with increasing RPM, airflow continues to increase against a falling volumetric efficiency up to the point at which peak HP is reached. Above that, power, torque, and VE all fall off sharply.

[nipper]

Anytime someone makes a big point of telling how much this or that expert test would cost to do and how expensive the super testing equipment is, it rings a warning bell in my head. You can put whatever filter you want on your diesel engine but a K&N filter will always go on my subaru and my mazda. Oily filters beat paper filters in California!

 

Oil filters are the best for very high dust areas, like the desert.

 

nipper

[Steve530]

Since it's a four stroke, it would pump that much air in TWO revolutions, so divide the airflow figure by two...

 

You still end up with a reasonable flow rate for the engine.

[blitz]

You still end up with a reasonable flow rate for the engine.

I have no issues with that, but you asked the question:

 

Did I do the math right?

So I answered it ...at least the rough cuts involved in getting a reasonably close CFM figure.

[bergman05]

I have a math degree, and have reviewed all of the charts (but not the tables). The only downside of the Delco is that at increased air volumes, it is more restrictive. For standard moderate acceleration curves, this would matter very little, if any. The data tells me that Purolator and Wix are the winners.

 

Yes, the charts are biased against K&N in the way that the vertical axis often does not start at zero. To read the charts correctly, ignore the height of the bars, and just focus on the numbers.

thanks for posting the URL to this study!

[Ranger83]

I'm not as smart as all you guys. Years ago when I was racing a Scirocco, I did a performance test with the stock paper filter versus no filter. No performance gain.

 

What I would love to see is the power decrease from the big fat exhaust tips kids are putting on their cars, and the increase in drag from some of the tailgate spoilers.

 

I worked with quite a few OEM engineers and still do. They've done their homework.