Dave, that is a cool possibility. I now have a benchmark on price haha...

What comes with that set up for rain situations and such? I would not want an open entrance for rain/snow/etc..

 

The "factory filter is restrictive" question was answered by the reference link I gave and by the CFM versus Inches H20 restriction curve that I plotted from the reference link. I also found a "Banks" data point for a 99.5 stock air box and filter which gives a 580 CFM at a 15" H20 restriction which exactly matches the measured CFM data in the reference link. As I'll show with some analyses the 2" H20 higher restriction at maximum CFM for the stock air box setup versus a 6637 filter isn't all that significant in as people here like to say "real world" conditions!

What's really important for EGT control is getting more MAF=Mass Air Flow lb/min because the "thermal mass" of the charge air is determined by its weight and it's the "thermal mass" of the charge air that absorbs the "heat of combustion" and limits the temperature rise in the cylinder. It's just like putting cups of water into a microwave oven and blasting them for a fixed time. The cup containing the most weight of water sees the lowest temperature increase!

Since the MAF going into the air filter inlet is given by MAF={(IAD)(VAF)} lb/min where VAF is the Volume Air Flow ft^3/min=CFM going into the air filter inlet and IAD=Inlet Air Density lb/ft^3 is the air density going into the air filter inlet you see that it's the combination of VAF and IAD that counts for getting more MAF to control EGT!

Now lets examine this part of your question... "the volume of air the 6637 would let through over it would help EGTs, even though it is hotter air"? Now this following assumption isn't actually correct but it does give the maximum possible benefit to the lower restriction 6637 filter. Lets assume that the turbo applies the same 15" H20 suction to both a stock filter and to a 6637 filter. From the graph I gave earlier if you look at 15" H20 and move up vertically you see that the stock filter has a VAF=580 ft^3/min and that the 6637 filter has a VAF=640 ft^3/min which is a 60 CFM advantage for the 6637 filter.

To complete this comparison analysis we need to consider that IAD is given by IAD={(2.70325)(IAP)}/{(IAT+459.67)} lb/ft^3 where IAP=Inlet Air Pressure psi at the air filter inlet and IAT=Inlet Air Temperature F at the air filter inlet. Lets assume a baseline at sea level so that IAP=14.7 psi and that IAT=70 F which gives an IAD={(2.70325)(IAP)}/{(IAT+459.67)}={(2.70325)(14.7)}/{(70+459.67)}=0.075 lb/ft^3. So for an IAT=70 F the stock filter would flow a MAF={(IAD)(VAF)}={(0.075)(580)}=43.5 lb/min and the 6637 filter would flow a MAF={(IAD)(VAF)}={(0.075)(640)}=48.0 lb/min.

Now based on my many years of towing measurements where I saw engine compartment temperatures in excess of 200 F, Tenn's measurements where he saw engine compartment temperatures from 125 F to 145 F, all of my internet searches for engine compartment temperatures which showed maximum values in excess of 200 F, and even that contrived engine compartment temperature data on the Tymar Performance web site which showed a "hot/cold average" of a 45 F increase above ambient, using a 50 F increase above ambient to give an IAT=120 F for the "open element" 6637 filter is far from being a worst case.

This gives an IAD={(2.70325)(IAP)}/{(IAT+459.67)}={(2.70325)(14.7)}/{(120+459.67)}=0.0685 lb/ft^3 and a MAF={(IAD)(VAF)}={(0.0685)(640)}=43.8 lb/min MAF for the "open element" 6637 filter versus a 43.5 lb/min MAF for the stock filter which is a virtual "dead heat" where the "heat pun" is most definitely intended!

Now assume you've been towing a 22K GCW for 3 hours and you're westbound on I-70 just approaching Denver and your altitude is now 5,500 ft so that the IAP=12.0 psi, and that due to 3 hours of "heat soak" the engine compartment temperature has increased from 120 F to 140 F so that the IAT=140 F for the "open element" 6637 filter. When you consider that the AC condenser is 140 F and that the radiator is 190 F and that the only air flowing into the engine compartment flows through those heat exchangers, having a 140 F air temperature in the engine compartment shouldn't be surprising!

This gives an IAD={(2.70325)(IAP)}/{(IAT+459.67)}={(2.70325)(12.0)}/{(140+459.67)}=0.0541 lb/ft^3 for the "open element" 6637 filter and a IAD={(2.70325)(IAP)}/{(IAT+459.67)}={(2.70325)(12.0)}/{(70+459.67)}=0.0612 lb/ft^3 for the stock filter. These IADs give a MAF={(IAD)(VAF)}={(0.0541)(640)}=34.6 lb/min MAF for the "open element" 6637 filter and a MAF={(IAD)(VAF)}={(0.0612)(580)}=35.5 lb/min for the stock filter. So the stock filter is already ahead by an MAF of 0.9 lb/min and we haven't yet started the long tow up to the Eisenhower Tunnel at an altitude of over 11,000 ft!

So you're headed toward the Eisenhower Tunnel, you're at 10,000 ft so that the IAP=10.1 psi, and your radiator fan has been in its full lockup mode for the last several miles indicating that the engine compartment temperature is more than 200 F so that the IAT=200 F. This gives an IAD={(2.70325)(IAP)}/{(IAT+459.67)}={(2.70325)(10.1)}/{(200+459.67)}=0.0414 lb/ft^3 for the "open element" 6637 filter and a IAD={(2.70325)(IAP)}/{(IAT+459.67)}={(2.70325)(10.1)}/{(70+459.67)}=0.0516 lb/ft^3 for the stock filter. These IADs give a MAF={(IAD)(VAF)}={(0.0414)(640)}=26.5 lb/min MAF for the "open element" 6637 filter and a MAF={(IAD)(VAF)}={(0.0516)(580)}=29.9 lb/min for the stock filter. So the stock filter is now ahead by an MAF of 3.4 lb/min!

In the above analyses I use an IAT=70 F=ambient air temperature for the stock filter but that does require at least a basic Zoodad mod. I know for a fact that my version of the Zoodad mod shown below supplies cool ambient "RAM" air to the air filter inlet and that the "RAM air effect" provides a 2" H20 pressure which pushes the air through the filter element and in effect it's like reducing the restriction of the air filter element by 2" H20! To get the full RAM air effect you do need to cut off that piece of grill because I've measured it both ways!

My bottom line conclusion is that if you stay with the stock filter and do my Zoodad mod you'll have the same restriction as for a 6637 filter and this will give the same VAF=640 ft^3/min as for the 6637 filter and you'll also have the cooler IAT and this gives the stock filter an MAF={(IAD)(VAF)}={(0.0516)(640)}=33.0 lb/min when approaching the Eisenhower Tunnel which is 6.5 lb/min more MAF than with the "open element" 6637 filter. So based on this analysis and on my goal for highest reliability when towing heavy in the mountains I know which one I'd pick if I was forced to choose between only these two options!

Did anyone ever wonder why an OEM doesn't just save some money by using a "filter on a stick"? It's because they couldn't possibly meet the city driving loop NOx emissions specification which requires the coolest possible IAT!

 

So your saying I got ripped off with my AFE too... Damn, should have stuck with my stocker...

Anyone have a stock airbox they want to trade for a AFE stage 2?

 

I don't think you got ripped off on that AFE.. I think there are differing views on the 6637 vs. stock..

I'll trade you my stock airbox tho.. if you want..

 

Well if your AFE is the same 7.3L AFE (Part Number 40035) in this link...

The following were measured in accordance with the test: Pressure Drop for Clean Element, Initial Efficiency, and Dust Loading Capacity. See Page 7 for the CFM airflow versus Inches H20 restriction graph for a stock 7.3L FA-1750 filter. http://www.thetruthaboutfilters.com/results/ISO_5011_Test_Results-AEMandAFE_Dry.pdf

...then I'd say yes to the ripped off question because that AFE passed far too much dirt in the "Dust Loading" test. It passed 4.70 grams of dirt compared to only 1.31 grams of dirt for a stock FA-1750! On the bright side at a 12" H20 restriction the AFE flows 950 CFM compared to the 37.5" H20 restriction that's required to get a 950 CFM flow from a stock FA-1750.

 

I received a PM asking about my thoughts on mods for a RAM air inlet on the hood of a PSD and I decided to post them in case anyone else is interested. The VAF=CFM through a RAM air inlet is given by VAF={(AFV)(CSA)} ft^3/min where AFV=Air Flow Velocity ft/min is the velocity of the air flow stream into the RAM air inlet and CSA=Cross Section Area ft^2 is the area of the RAM air inlet that's perpendicular to the air flow stream.

For a 6"x6" RAM air inlet the CSA=0.25 ft^2 and at a 60 MPH=88 ft/sec=5,280 ft/min truck speed the CFM flow through the RAM air inlet is VAF={(AFV)(CSA)}={(5,280)(0.25)}=1,320 ft^3/min which is more than sufficient for meeting the CFM demand of the engine and if you're climbing a steep grade in 2nd gear at 30 MPH this RAM air inlet still gives a 660 CFM flow which is sufficient for most applications. Therefore to be effective a RAM air inlet should have a CSA=0.25 ft^2 or larger.

Now the top of the hood is a low pressure region because the air stream is being forced to flow up and over the windshield so the hood isn't the best location for a RAM air inlet to begin with and putting one there that sticks up into the air stream high enough to be effective will make your PSD look like a "funny car" dragster!

The best place for a RAM air inlet is in the grill where it sees the maximum dynamic air pressure and the incoming air stream is allowed to flow straight into the air box. If you object to the ugly but extremely functional RAM air inlet in the grill of my old F350 then just follow the advice I was given below and build a "beautified" version which will be almost as effective as mine and far more effective than any hood modification!

You can also put the Ram Air funnel on the passenger side to good use by providing cool ambient air to the engine compartment.



Now to achieve the maximum RAM air effect the incoming air flow stream needs to impact the surface of the air filter element at a perpendicular angle. How is this possible for a cylindrical shaped element like the 6637? Since a cylindrical shaped element needs to have a radial incoming air flow stream that's symmetric over 360 degrees you'll never get much of a RAM air effect with a 6637 filter.

Since the 6637 filter never uses all of its large surface area at any one time anyway I think its large size is a disadvantage because it's stuffed so tightly into the PSD engine compartment that there's not enough room for a proper radial incoming air flow stream that's symmetric over 360 degrees around the filter.

This is another suggestion that I never got around to investigating because by then I was shopping for a larger truck.

 

LOL Holy crap Gene!!!! First time I saw that same ambulance grill years ago I thought to myself "I bet someone could make a ram-air setup out of that".

I know of someone that does 3D computer CAD modeling, and another person that is a plastics supplier. Do you have any contacts with someone that does plastic moulding and manufacturing? How about some test equipment? We could be the first to make a true cold air intake setup for the Superduty using a custom ambulance grill!

 

The reason I said "this following assumption isn't actually correct" in the above is because 1) as Tenn's measurements show a 15" H2O restriction is a flat out maximum value that you'll be unlikely to hit with a clean filter and a stock turbo because he only saw a maximum of 12" H2O restriction, 2) most people don't have a real-time restriction gauge like Tenn has and I did so they can't drive and apply the exact amount of throttle that's required to keep the air filter operating at some specific constant Inches H2O restriction value, and 3) to drive this way requires that you vary your MPH speed as road conditions change which isn't how people drive anyway.

A more realistic "real world" way to compare a 6637 filter to a stock FA-1750 filter is to consider the MAF operating points that I previously calculated in another thread on safe maximum BP for a stock turbo and are shown in the graph below and then compare the VAF=CFM versus Inches H2O restriction for each filter at a given MAF value as a function of the IAT=Inlet Air Temperature F at the air filter inlet. If you solve the above MAF equation for VAF you get VAF={MAF}/{IAD} ft^3/min=CFM.

For point #1 the MAF=28.6 lb/min and if the IAT=70 F for both the 6637 filter and the stock FA-1750 filter both filters have a VAF={MAF}/{IAD}={28.6}/{0.075}=381 ft^3/min so both filters will flow the same 381 CFM air flow for the same IAT=70 F and the same MAF=28.6 lb/min.



From the graph below by reading across from a 381 CFM value you see that the 6637 filter flows this 381 CFM at a restriction of about 5.6" H2O whereas a stock FA-1750 filter flows this 381 CFM at a restriction of about 6.3" H2O. So for this "real world" operating point the 6637 filter has a 0.7" H2O lower restriction than for a stock FA-1750 filter and this even assumes the "unrealistic" condition that the engine compartment temperature is equal to the ambient temperature.



For point #2 the MAF=34.8 lb/min and if the IAT=70 F for both the 6637 filter and the stock FA-1750 filter both filters have a VAF={MAF}/{IAD}={34.8}/{0.075}=464 ft^3/min so both filters will flow the same 464 CFM air flow for the same IAT=70 F and the same MAF=34.8 lb/min.

From the restriction graph above you see that the 6637 filter flows this 464 CFM at a restriction of about 7.6" H2O whereas a stock FA-1750 filter flows this 464 CFM at a restriction of about 9.4" H2O. So for this "real world" operating point the 6637 has a 1.8" H2O lower restriction than a stock FA-1750 filter but this advantage assumes the "unrealistic" condition that the engine compartment temperature is equal to the ambient temperature.

Using the above IAD=0.0685 lb/ft^3 for the 6637 filter the MAF=34.8 lb/min given in point #2 requires a VAF={MAF}/{IAD}={34.8}/{0.0685}=508 ft^3/min which is a 44 ft^3/min higher CFM at an IAT=120 F compared to an IAT=70 F and this means the Inches H2O restriction for the 6637 filter increases from 7.6" H2O to 9.4" H2O which is exactly the same restriction the stock FA-1750 filter has for an MAF=34.8 lb/min and an IAT=70 F.

For point #3 the MAF=44.5 lb/min and if the IAT=70 F for both the 6637 filter and the stock FA-1750 filter both filters have a VAF={MAF}/{IAD}={44.5}/{0.075}=593 ft^3/min so both filters will flow the same 593 CFM air flow for the same IAT=70 F and the same MAF=44.5 lb/min.

From the restriction graph above you see that the 6637 filter flows this 593 CFM at a restriction of about 13.2" H2O whereas a stock FA-1750 filter flows this 593 CFM at a restriction of about 15.2" H2O. So for this "real world" operating point the 6637 has a 2.0" H2O lower restriction than a stock FA-1750 filter but this advantage assumes the "unrealistic" condition that the engine compartment temperature is equal to the ambient temperature.

Since operating point #3 corresponds to using a higher HP chip and pulling a heavy load up a steep grade at WOT in 3rd gear I'll use the IAT=140 F for the "open element" 6637 filter that I used in the previous towing analysis which gives an IAD={(2.70325)(IAP)}/{(IAT+459.67)}={(2.70325)(14.7)}/{(140+459.67)}=0.0663 lb/ft^3.

This gives a VAF={MAF}/{IAD}={44.5}/{0.0663}=671 ft^3/min which is a 78 ft^3/min higher CFM at an IAT=140 F compared to an IAT=70 F and this means the Inches H2O restriction for the 6637 filter increases from 13.2" H2O to 15.8" H2O which is a 0.6" H2O higher restriction than for the stock FA-1750 filter at an MAF=44.5 lb/min and an IAT=70 F.

All three of the above operating points run the engine at the maximum safe BP for a stock turbo at the indicated RPM and although they represent realistic "real world" operating conditions when towing a load up a grade most people spend most of their time running down the road empty at 70 MPH where the BP is about 3 psi in 4th gear at 2,000 RPM.

For this above "cursing" condition the MAF is about 18 lb/min and if the IAT=70 F for both the 6637 filter and the stock FA-1750 filter both filters have a VAF={MAF}/{IAD}={18}/{0.075}=240 ft^3/min so both filters will flow the same 240 CFM air flow for the same IAT=70 F and the same MAF=18 lb/min.

From the restriction graph above you see that the 6637 filter flows this 240 CFM at a restriction of about 3.2" H2O whereas a stock FA-1750 filter flows this 240 CFM at a restriction of about 3.4" H2O. So for cursing down the highway the 6637 has a 0.2" H2O lower restriction than a stock FA-1750 filter but this advantage assumes the "unrealistic" condition that the engine compartment temperature is equal to the ambient temperature.

Lets assume the engine compartment temperature is only 20 F hotter than ambient under these cursing conditions so that IAT=90 F for the 6637 filter. This gives an IAD={(2.70325)(IAP)}/{(IAT+459.67)}={(2.70325)(14.7)}/{(90+459.67)}=0.0723 lb/ft^3 so that the VAF={MAF}/{IAD}={18}/{0.0723}=249 ft^3/min and this increases the restriction of the 6637 filter to 3.5" H2O which is a 0.1" H2O higher restriction than for a stock FA-1750 filter!

Also consider that if you keep the stock air box or upgrade to an AIS air box and do the RAM air mod you'll get an effective 2" H2O reduction in air filter restriction at 70 MPH as well as having the benefit of the cooler IAT.