Author Topic: Air filters or no?  (Read 19854 times)

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Offline Sumner

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Re: Air filters or no?
« Reply #45 on: August 25, 2014, 04:06:56 PM »
I don't, but it's not totally sealed up underneath. On the compressor we have a 4" by 90% elbow that just sticks through a 4" hole in the bottom under the filter pac. Probably could have put a little stub on the bottom and slid it over it but it is kind of a pain to get on any way and we were just trying to stop the big pieces of Salt from getting in. It seems to work as the Salt just lays on the top filter now.
   Doug  :cheers: :cheers: :cheers:

Thanks, that helps,

Sum

Offline WOODY@DDLLC

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Re: Air filters or no?
« Reply #46 on: August 25, 2014, 04:49:55 PM »
I wish K&N had a CFM rating on their filters.

CFM is in the secret [Vizard] recipe at filter selection: http://www.knfilters.com/filter_facts.htm#MYTHS
All models are wrong, but some are useful! G.E. Box (1967) www.designdreams.biz

Offline Harold Bettes

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Re: Air filters or no?
« Reply #47 on: August 25, 2014, 11:58:03 PM »
Woody and All that like this kind of stuff,

I think you are mistaken about the secret recipe stuff and to whom to attribute same. :roll: The correct guy would be a guy named Bernoulli  :-D and the issue of dynamic pressure. Then if one considers the filtration part (loss of head) perhaps Darcy-Weisbach would be a better inclusion. Of course all those guys came along quite some time before David don't you think? :-o

Over and over again: The use of filtration media does not need to cause much airflow loss if the correct media is chosen along with sufficient area of that media. :lol: 8-)

You can now return to your regularly scheduled programs. :cheers:

Regards to All,
HB2 :-)

 
If it was easy, everybody would be doing it.

As iron sharpens iron, one man sharpens another.

Offline WOODY@DDLLC

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Re: Air filters or no?
« Reply #48 on: August 26, 2014, 09:39:42 AM »
Harold, someone still has to convert all that "chalk on the blackboard" into useful "recipes"!   :-o
Thanks to you and David for that!  :cheers: :cheers:
All models are wrong, but some are useful! G.E. Box (1967) www.designdreams.biz

Offline Milwaukee Midget

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Re: Air filters or no?
« Reply #49 on: August 26, 2014, 10:34:44 AM »
Ah - a close re-read and BINGO - the devil in the details -

We're all talking about air filters, but Harold let slip a distinction in his earlier post -

There is a common misconception that any air filtration system will cost power from restriction to the airflow path into the engine. The filtration system does not need to be a power robbing solution however with most folks wanting the "quick and easy" off-the-shelf answer will probably make the wrong choice in air filtration. :-(

HB2 :-)

And seeing as K&N - or any manufacturer of filters - has little ability to control how their filters are used . . .

I wish K&N had a CFM rating on their filters.

. . . any information they could glean with a flowbench would be dependent on the housing and system the filter was incorporated into.

Woody, I've been checking out your pages on airflow - scoops in particular - and what becomes clear is that intake - regardless of whether or not filters are involved - needs to be looked at as a complete, integrated system.

The evidence Vizard has put forth is that a properly sized and designed filter can produce no restriction, but Woody's work indicates that such a filter would need to be something well integrated to be effective.



"Problems are almost always a sign of progress."  Harold Bettes
Well, I guess we're making a LOT of progress . . .  :roll:

Offline Hot Rod Lincoln

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Re: Air filters or no?
« Reply #50 on: August 26, 2014, 12:05:12 PM »
I wish K&N had a CFM rating on their filters.

CFM is in the secret [Vizard] recipe at filter selection: http://www.knfilters.com/filter_facts.htm#MYTHS

I was just taking a wild-as s guess as to the needed filter size based off CFM requirement. I was just using "round" numbers:
180" x 9,000 rpm/3,456 = 469 cfm

at 20 lbs boost the engine "thinks" it's 2.4 times bigger than it is: 2.4 x 470 cfm = 1,128 cfm.

looking at it another way: if we are making 900hp ( rounded up numbers) with a BSFC of .55 we are burning 495 lbs fuel an hour.  At an AF ratio of 11:1 we would be burning 5,445 lbs air an hour or 91 lbs air per minute. 91lbs/.0807( weight of a cubic foot of air) = 1,124 cf.

So my wild a ss guess was kind of close. We need at least 1,125 cfm to feed 900hp.

A 9" diameter round filter has a circumference of approx. 28"    28" x 5''(H) = 140 x 2 (filters) = 280 sq. in. of filter area to feed 900 hp. 

If I use the K&N formula where A= filter area  and CID x rpm/20,839 =A  I'd get 187" filter area.

180" x 2.4 ( boosted engine) 432" x 9,000 / 20,839 = 187" filter area.  So my filter area of 280" would have a minimum of a 50% over-size factor in it.

I think that all works out ..... ????   :?

Offline Harold Bettes

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Re: Air filters or no?
« Reply #51 on: August 26, 2014, 06:44:55 PM »
Howdy to All that like this kind of stuff,

Indeed the system is the key in all this stuff as many components have to work together. It is the system that should be integrated into a design. Attached is a pic of a roadster that has gone through many iterrations but the air supply system has remained constant. Now the thing runs as a D class (smaller engine). The package shown does include air filtration and adherence to Mr. Bernoulli's directions relative to airflow as a system.

Hope All that go to the upcoming meet have salty  success. :cheers:

Regards to All,
HB2 :-)
If it was easy, everybody would be doing it.

As iron sharpens iron, one man sharpens another.