At 75 CFM per inch of water, the B085011 is only a 50% improvement over the stock airbox. aren't you inclinded to think bigger?

In case you haven't seen this, hereh is a donaldson filter application search engine. may be something there.

remember AFE is at 300 CFM per inch of water. no doubt it won't flow 1800 at 6 inches (media not linear) but its gonna flow a lot more than a B085011.

 

This is just a starting point until I can see what will physically fit in that area. BTW where did you come up with 75 CFM per 1" of H20. I have found that most Donaldson spec's are at 4.25" of H20. I have e-mailed them to find out what the H20 spec is for the B085011.

50% to me is still far better than an oiled filter.

 

huh. I must have made a mistake 'cuz I can't re-produce the 75 CFM per inch figure The donaldson site puts it at about 46 CFM per inch. 280 CFM at 6" 280/6=46.

here is a donaldson specs lookup chart. lots o fun.

check out the G132000. 1200 CFM at 6" water. thats 200 CFM per inch. now we're talking! kind of expensive though...

 

If I'm reading this right this filter would flow less than stock at the 14" which appears to be what the factory filter is rated at. I took the #'s right off of the side of the DC filter. I don't see how this can be when this filter easily has twice the surface area and is listed on the Donaldson site as an 6BTA 5.9 application. Now I'm really confused.

 

I actually only drive on the street and I live in the Northwest where we don't have dust because of the rain.... Just kidding, No really , I don't drive in the dust.... Should I take the pre-filter off? I was just worried about warranty and stuff but I didn't notice much if any improvement in performance or mileage(de-fueling?)

 

Does anyone know the actual flow of just the factory filter at various levels of H20?

 

If you took your earlier numbers right off the side of the factory filter, then I'd say you got it.

I have been looking for a formula to figure this out. I ran across someone who had this pegged on another, not so well known forum, but can't find it again. So I'm still lost on the big question. How much CFM @ what restriction is enough?

1) According to the Donaldson guy, if I got this straight, it is virtually impossible to create more than 6" H20 equivalent restriction under normal operating conditions unless you sink your truck in the local reservoir. If you have more than 6" H20 equivalent restriction at any horsepower level, you got issues.

2) Add that to Gypsyman's numbers for the stock filter, 675.21 CFM @ 14.05" H20 , and I'm beginning to wonder if we are looking for a rate of flow at an unrealistic level of H20 restriction.

Just for giggles, I looked up the specs for a Detroit Diesel 12V149 making over 800 horsepower with a HUGE turbo. On the specs chart, it has a maximum CFM requirement of 2800 at 8" H20. According to AFE's testing standards, that is 350 CFM at 1" H20. Even with a chipped truck, we should only need about half of that. Our little turbo ain't gonna pull in but so much. Heck, why are they still putting $150 40-inch canister filters on the hood of this Detroit when they could replace it with this little o'l AFE PG7. This just ain't make'n sense.

Sure, 600 CFM @ 1.5" H20 sounds good, but maybe that is why they used 1.5", because it sounds so good compared to everything else at 1.5". Why do we establish 1.5" as our standard for restriction when no one, but AFE, uses it?

I guess I'm just gonna have to go buy a big one and do the o'l filter minder test to satisfy myself. I would think 1000 CFM at 6" H20 might would be overkill for our little huffers.

 

This is exactly what is stated on the side of the factory filter...

"DUST CAP. 450G MAX. AIR FLOW 19.12 M3/MIN. EFF. 99% PRESSURE LOSS @ MAX FLOW 0.035 BAR"

Double check my numbers and interpretations. Let me know if I'm wrong.

Since I already have the pieces, I think I'll vacuum gauge the stock system and then check it against what I fabricate along with an EGT verification.

This is the same filter used for the Powerstroke upgrade offered by Airflow Systems and I believe I read that thier airflow requirement are higher than ours due to rpm and engine size. Is this correct?

Weren't the 2nd gens making monster HP and TQ with just a 405 to 680 CFM BHAF. Maybe a drilled factory box isn't as bad as everyone would have us believe. Has anyone pushed the limits of a drilled factory box with mods or has it just become so common to do an oiled aftermarket air filter and an exhaust system first that we stopped questioning these stock items?

 

I think your numbers are right. at least the cubic meters to cubic feet are right, so I have no reason to question the conversion from Bar to inches of water (no chemistry book in front of me either...).

I think about it this way: The stock filter is about 46 CFM per inch of water and the stock engine exhausts at about 1200 CFM. We know that this combination works, the design point is appropriate, and all of that. We also can apply dougs reality check about volume versus temperature: that 46 CFM of cold air intake itself is suffient to support 1200 CFM of hot air exhaust. But we also know that this design point has very little margin in it -- EGTs can climb with a bone stock truck.

so put that stake in the ground.

Now then, when you bomb, you are trying to go outside the design limits. Using standard formulae, running the 5.9 at 3500 rpm and 1400 degrees EGT will exhaust at about 2000 CFM. So we need about twice the intake flow to support that. Add to that the fact that with additional fueling, retarded timing, turbochargers at their limit of efficiency, etc. we are fighting a very real and nasty EGT problem. That game does not have a design point -- it has a "do as much as you can" mandate.

all right, how to quanitify this approach with numbers: Unless you want to play small potatoes and make only small incremental improvments, you're not going to make any significant difference unless you can double the CFM once again. What good is a 30% improvement or even 50% flow increase. We gotta go for 100% increase. my opinion of course.

So where does that leave us. It leaves us at the following reality:

1. Just to support the extra fueling to the maximum potential of the 5.9, and STILL have an EGT proglem owing to the tight design margin already present, you have to double the filter flow rate from about 50 CFM per inch of water to 100 CFM per inch of water

2. now to attack the EGT problem you have to double it again. or else you're not really making much of a difference. playing with small incremental but not significant improvements.

ergo, we need a filter that can support 200 CFM per inch of water.

one other thing: these oiled filters may not be as linear as dry paper filters. meaning that as the restriction (pressure) increases, the flow rate will probably not follow in direct proportion as it would for a paper filter. so that 300 CFM per inch of water AFE with torque tube-- probably would flow on 1.5 times that much at 2 times the pressure. perhaps 450 CFM at 2" of water I would think.

As for the oiled filters, technology shows that the benefit of oiled filters is that you can get monster flow rates with smaller media and the same filteration. But yea I think the bombing dodge community has grown accustomed to just accepting that without question. They also got accustomed to accepting that it was ok to relax the filtration efficiency in favor of flow, and now that is being questioned as well. So you guys keep at it, and find a paper air cleaner that will fit under the hood and give us 200 CFM per inch of water, and you'll have a solution that will compete with the AFE PG-7, properly oiled, in combination with the torque tube.

 

spec'ing out the flow rates at lower restrictions makes them look worse, not better. thats why all those BHAF numbers look good at first -- they are measured at higher restrictions. The AFE PG-7 with torque tube at 1.5" of water is far more conservative than a paper filter at 6".

I still think we should target 200 CFM per inch of water. that means a paper filter of 1200 CFM at 6" of water. otherwise it won't compete with the PG-7 system with torque tube.

 

Very well put. Time to get the tape measure out again.

 

I just installed my AFE Intake with PG7 and prefilter. The oil was visible on the inside of the filter from the factory. I had 15k on the original paper filter with the filter minder sucked down into the red. After taking a test drive West of Denver on I-70 (really got on it...WOT runs to 90+ and 1300*) I checked the filter minder. It had not budged. I don't know how AK is having this problem. Turbo seamed to spool quicker...but truck seamed to run 50* hotter. Maybe it was the AC.

 

My head hurts from all this water talk, inches, CFM, dry, wet, hot, cold, left, right, up, down, filters, exhaust....argh, argh, argh.

Excedrin, anyone?

 

I was noodling over this and started fooling around with the Ideal Gas Law (PV=nRT). I converted all temperatures from Farenhiet to Kelvin using the formula degrees K=(5/9)*(degreesF+459.67). R is a constant and for the purposes of this discussion, I'm ASSUMING for simplicity sake that n is a constant, although that is NOT perfectly accurate. That leaves V, P, and T as functions of each other. For further simplicity (since I don't have any decent data) I held P (pressure) constant ON BOTH SIDES OF THE TURBO. Below is a table of some of the values from my simple model. T_I = intake temperature (F), T__E=exhaust temp (F), CFM E=exhaust CFM, CFM I=required intake CFM.

T_I T__ E CFM E CFM I
100 1200 1600 540
100 1400 2000 602
120 1200 1600 559
120 1400 2000 623

Note:If the intake temerature is held constant, the required intake CFM goes down as the exhaust temps go up.

Anyway, this is an oversimplified model and substituting decent values for P will help to refine it a lot.

100 Proof

 

Me too........give me a five pound Excedrin and let me gnaw off what I feel I need! Been reading these posts for a few days and almost feel like a lost puppy in tall grass!
Greg