bdog

I currently have a K&N in the stock box. How does the flow of this compare to the BHAF? What about noise levels?

Alan_Reagan

The BHAF is right at 700 CFM and the K&N is right at 800 CFM depending on which one you have. My BHAF is comparable in sound to the K&N I got rid of. I like the BHAF better because I no longer get oil in my intake system.

rattle_rattle

[quote author=Smoke Dog link=board=4;threadid=7180;start=0#68583 date=1037632429]<br>The BHAF is right at 700 CFM and the K&amp;N is right at 800 CFM depending on which one you have. My BHAF is comparable in sound to the K&amp;N I got rid of. I like the BHAF better because I no longer get oil in my intake system. <br>[/quote]<br>Am I getting this right? Are you saying that the stock air box with a K&amp;N is rated higher flow than a BHAF?

Tom Bolitho

I had the K&amp;N Re0880 on my truck and really liked it until I took a three hour trip. The high pitched whine from the turbo really got to my head. After I changed to the BHAF it cut the top of the turbo whine and made it very liveable now I look forward long trip with the turbo and the straight pipe singing

KC

BHAF, I have had K &amp; N its a good system but cummins says no K &amp; N. Just my .02 worth.<br><br>KC

Alan_Reagan

[quote author=rattle_rattle link=board=4;threadid=7180;start=0#68994 date=1037675616]<br>[quote author=Smoke Dog link=board=4;threadid=7180;start=0#68583 date=1037632429]<br>The BHAF is right at 700 CFM and the K&amp;N is right at 800 CFM depending on which one you have. My BHAF is comparable in sound to the K&amp;N I got rid of. I like the BHAF better because I no longer get oil in my intake system. <br>[/quote]<br>Am I getting this right? Are you saying that the stock air box with a K&amp;N is rated higher flow than a BHAF?<br>[/quote]<br><br>Not quite 800 on the stock box. That's more like 500 (on a good day and depending on whose flow charts you look at). 800+ is on the round filters. Sorry for the confusion. I was comparing round filter to round filter because surface area is the big factor in determining flow rate. That's why I said &quot;depending on which one you have&quot;. <br><br>Now, how much air flow do you need? You have a 5.9L engine which is about 359 cu/in. That means you take in 359 cu/in of air every two revolutions of the engine. So at 2250 RPMs, you are &quot;flowing&quot; 233 CFM. Problem is, these engines are turbocharged so although the volume remains constant, more air has to go through the filter because you are increasing the pressure on the intake. What they need to do is tell us how many lbs/minute these filters flow instead of CFM so we don't have to convert for engines running turbos.

Alan_Reagan

[quote author=Gary - KJ6Q link=board=4;threadid=7180;start=0#70184 date=1037837372]<br>&quot;Now, how much air flow do you need? You have a 5.9L engine which is about 359 cu/in. That means you take in 359 cu/in of air every two revolutions of the engine. So at 2250 RPMs, you are &quot;flowing&quot; 233 CFM.&quot;<br><br>Well, not (necessarily) exactly....<br><br>Displacement at *sea level*, with NO BOOST APPLIED in the Cummins, is 360 cu in or so - BUT, at 14 psi boost, that volume is DOUBLED - and at full boost with one of the Comp-style boost elbows, 30-32 psi boost, equivalent displacement is more than TRIPLED... so, what IS 3 x 360 cu inches... ;D<br><br>Somewhere well over 1000 *equivalent* cubic inches, and ya BETTER have enough air filter capacity to handle it, or YOU will end up sucking yer filter minder WAY down with a new STOCK filter ob yer first serious pull with a Comp, just like I and a few others have done... ;D<br>[/quote]<br><br>At 14 psi boost the volume of the engine doesn't double. Volume remains constant. 360 cubic inches is the volume. What doubles is the weight of the air. In other words, for every two revolutions of the engine, you take in 360 cu/in of air. So it takes twice as much air, compressed into that same volume to get the weight to double. That's where the volume you are talking about doubles. We have to take 720 cu/in of air and put it in 360 cu/in of space. So we really cut the volume of the air in half when we compress. (I know, it's a technicality, but a necessary one to figure out air flow) This isn't a &quot;I know more than you thing&quot;. We are almost saying the same thing. I don't have time right, but the reason I asked the question and am being exact with the answer is that for this little exercise, I'm not taking into account volumetric efficiency of the intercooler or heat factors from different turbos which really change the calculations significantly.<br>At sea level (14.7 lbs/psi ambient, no boost applied) running 2250 rpms the engine would take 17 lbs of air/minute (226 CFM). With 14 lbs of boost applied the engine would take 33 lbs/min (440 CFM). At 30 lbs of boost it will take 52 lbs/min (693 CFM). All of these calculations are for sea level.<br>That's why I asked, how much do you need. <br>Thanks for waking me up Gary. Your rule of thumb (double the air when you double the boost) is a good one to follow. I just wanted to finally let most guys know that a 700-800 CFM filter will probably meet their needs. Have a good one.<br> <br> <br>

Alan_Reagan

Something else you alluded to that needs to be said. It's not just a flow rate of CFM per minute that has to be considered. The other thing is that the flow rate we have is NOT CONSTANT and can spike from a no boost condition (stopped at a light) to 20 plus psi boost in a matter of a few seconds and then return to zero with a sudden lift off the accelerator. With that in mind, I think the heavier construction of the BHAF lends itself to our application. In my 98, I tried a K&amp;N and seemed to suck a lot of oil.

Scotty

Then theres the folks that can have nearly instant boost over 45 psi and if you 'bark' the turbo you will notice that the boost gauge can flip back down to zero [on the pin] or beyond [if theres no stop pin] which means that all the pressure is blowing back out of the filter...does that mean I just purged the filter of all the deposits on the dirty side? ;D<br><br>All the filters have their limits and what I see here is a good reason to have Twin filters [your choice] providing filtration and ample CFM flow. The Scottty Airr TUTU <br><br>I think I need a nap.<br><br>Maybe a staged filtration system with staged turbos.<br><br>eh