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Another small addition. The parasitic drag and rotational power loss from the Heavy Duty Hayden fan clutch and 19" fan comes to 14.8 HP unengaged and 32.6 HP fully engaged. Running the alternator to power the two Windstar fans at 37.5 amps comes to 1.25 HP. FYI.
. Running the alternator to power the two Windstar fans at 37.5 amps comes to 1.25 HP. FYI.
Well that 37 amps draw for those fans will kill my charging system! As I have EFI on my 460 the total power draw will be over 150 amps out of the alternator! Also with that dual AC compressor setup, the alternator belt(which also runs the 2nd AC compressor and smog pump) does wear out much faster than normal.
I am doing away with that 2nd AC compressor, just have to get the factory dual AC pipes from the junkyard and replumb the rear in. I just hope the FS10 AC compressor will handle both chassis and coach AC units.
The rear AC compressor I have is a Seltech TM15 9.0Cid 6 cylinder while the factory AC compressor is the FS10 10.0Cid 10 cylinder. I never could find the HP rating of them.
The most important issue is surface area, larger cools better.
True, as far as it goes, but there is more to it. Airflow is a huge factor. Two different radiators with equal surface areas and different airflows will perform differently. That is why this next statement is dangerously false, even though it's taken as gospel by many:
Originally Posted by jimandnena
Triple rows cool better than double rows.
Triple rows do not necessarily have more surface area. Again, there is more to it. Mere row count does not translate directly to surface area.
Radiator design is a lot more complicated than just "more rows = more cooling".
Thought I'd add an update, detailing progress on incorporating the Dorman 620-131 replacement fan assembly for the factory Windstar Dual Electric Fan into my E350 with the 460/7.5L big block.
As I indicated previously, the 620-131 shroud is slightly wider than the 460 radiator core (0.3125") but is significantly shorter than the core by 3.725". The 460 shroud for the mechanical clutch fan is 32.5" wide and 22.4375" high, incorporating the shroud mounting points and some complex clearances around the radiator hoses and the power steering gear. Interestingly, the 460 OEM shroud, at the edge of the fan opening, projects the same distance from the radiator core as the Windstar 620-131 replacement as measured to the back of the fan motors. I therefore decided to merge or meld the 620-131 into the OEM 460 shroud in order to give me full shrouded air flow coverage with the electric fans.
To accomplish this, I purchased a used (78-88) E350 460 radiator shroud for $30. Note that the F-series shrouds for the 460 are completely different and won't fit the E-series. The vans use a very large down flow radiator while the F-series used a crossflow unit (I believe). After studying the possible interferences (power steering unit in particular) I placed the Dorman assembly centered in the horizontal dimension and aligned to the very top of the radiator core projected to the 460 shroud. Using a radial arm saw, I cut out a 29.5"x17.4" segment from the OEM 460 shroud. I then fitted (Dremel sanding drum) the 460 shroud over and onto the Dorman assembly making certain that the face of the Dorman shroud was aligned with the face of the OEM 460 shroud and therefore with the radiator core.
I mechanically fixed the Dorman shroud to the 460 unit using stainless pop rivets and stainless corner brackets. The complex bracket angles needed were made with the judicious rap of a heavy weight hammer. I used two 1" right angle aluminum channels to form the air seal for the bottom section of the 460 shroud to the 620-131 unit.
The OEM shroud seems to be made with a fiberglas impregnated polypropylene plastic, while the Dorman shroud was fabricated from a polyamide (Nylon-66). Both of these materials are notorious for being impervious to most plastic sealants and epoxy fillers. I wanted to provide an airtight shroud and therefore needed to seal the interfaces between the two shroud segments. Fortunately, JB Weld Plastic Bonder #50133 is formulated to form a 3770 psi tensile strength bond to polypropylenes and polyimides, so I used this bonder as a sealant to fill all gaps remaining between the shrouds. Mechanical rigidity and placement provided by the riveted brackets and the whole structure stiffened with the sealant/bonder. The only materials used for enclosing the air volume were components from the OEM shroud, the Dorman structure, the aluminum channel, the stainless brackets/rivets and the bonder.
To make certain that the original Dorman shroud area drew air from the previously uncovered 29.1875"x3.725" area of the 460 core, I removed the lower edge of the Dorman shroud, leaving a few spacer supports with a Dremel cutting wheel as can be seen in the enclosed photo labeled Full Interior View. The edge material was removed giving a flat surface on the Dorman shroud (difficult to see) right to the bottom edge.
Face on view of the inside of the co-merged shrouds showing the alignment of the Dorman shroud within the OEM 460 unit.
Exterior View of the final e-fan shroud showing the alignment of the Dorman unit to the OEM 460 shroud.
Detail of the closure of the original clutch fan opening with segments of the original shroud material.
Lower Driver's side showing molded power steering gear clearance.
Pass side bottom showing shroud alignment.
Top pass side showing the fabrication, sealing and alignment of the shroud components.
Driver's side top edge showing alignment of components.
Driver's side edge of composite shroud showing clearance area for the power steering unit.
Just some final observations at this stage. After careful measurements, the complete swept area of the two Dorman fans less the area blocked by the fan motors is 284.31 sq. in. The equivalent area of the mechanical clutch fan is 234.25 sq. in. The electric fans are directly drawing 21% more surface area than the clutch fan. Interestingly, the driver's side fan counter rotates relative to the passenger side fan. Mounting the shroud on an open jig with full power applied made a tornado in the workshop. My best aerometer measurement of air flow in the workshop at full power was 5280 cfm! I'm looking forward to the final result when the shroud is installed. I'll try to report temperatures and handheld CFM readings after the system is completed.
My apologies for the length, but I hope this will help someone else.
Wirelessengineer, you're right, there was no torque on the assembly when I had it crudely mounted in the workshop! The windstorm coming out of the unit seemed very strongly directed to the center. Had trouble holding onto the aerometer if I got too close to the fan inlet. Actually used a screen to protect my hand!
That counter-rotation is a good thing has been known since WWII. The P-38 Lightning (and other planes) had counter rotating props for that reason.
The Brits ordered a bunch of them for their use, but they decided to cheap out and have them without the counter rotating gearbox, so both props rotated int the same direction. They were shipped over, and the first time they tried to take off (in formation in a big, huge ceremony with lots of VIPs in attendance), they ran off the runway from the torque. They literally could not be flown that way.
Just another observation about the differences between the Windstar dual electric fan shroud configuration relative to the OEM 460 E350 mechanical fan shroud. One can see from the posted photos that the Dorman/Windstar fans completely fill the shroud openings. No edge gap between the fan blade tips and the shroud opening. On the other hand the mechanical fan shroud opening is 22.18" in diameter. My measured diameter of the 19" mechanical fan is 19.5" for both the 5-blade and the 7-blade version. This gives a 1.34" gap between the mechanical fan blade tip and the shroud opening. Some of this may be for mechanical clearance for engine displacement under normal driving conditions. There is also a turbulent flow gap requirement mentioned in several engineering studies. However, the Windstar/Dorman OEM shroud has no such allowances for the electric fans which operate over the some of the same rpm ranges as the mechanical fan.
In my installation, I will be bonding to the mounting surface of the shroud a Nomex gasket seal so that all air drawn by the electric fans will pull through the radiator core. The OEM E350 460 mechanical shroud has several 0.25"+ gaps around the mounting surface to let heated air from inside the engine compartment to enter the shroud, thereby reducing the effective pressure differential across the radiator. In the fabrication of the melded 460 fan shroud with the Windstar/Dorman shroud, all gaps were sealed with JB Weld as the sealant.
Keep the engine driven fan, I did this last year when I replaced my radiator, worked great around town, drove to the mountains, it could not keep it cool, it worked that fan till it seized up, vans have hot engine bays due to restriction of air flow. I run a 6 blade flex fan now, it draws in more air than stock, will find out this summer how good it is, but mine sold before they added a fan shroud.
Keep the engine driven fan, I did this last year when I replaced my radiator, worked great around town, drove to the mountains, it could not keep it cool, it worked that fan till it seized up,
I'm not clear on what you are saying, maples. Are you saying you installed electric fans, and they didn't get the job done in the mountains?
Yep, it was fantastic around town, but in October, temps in the 70's outside, it was not able to keep it cool under load of the long pull up the mountain, I have no trailer, no AC, no power steering to lug the engine, and mine is just a long wheelbase with a 302. I was sold by all the comments and others doing it, so I found a speed shop, bought one they trust and run on their race car, they even guarantee it, they replaced it like advertised, but it ain't going back, I fabricated a shroud from diamond plate aluminum to force it to draw through the entire radiator, not tied directly to the cores. I'll stick with an engine driven fan, I need to make a shroud for it to increase pull. I think they work so well on cars because all of the room for air, vans are just to cramp, you can't move the air through fast enough to get the heat out, if only there was a way to add ducting.
Maples01, you have raised several very important points with your experience and direct observation of cooling problems on a long and continuous grade. This issue also applies to any towing loads which require additional power. Those issues bring up the correlated questions of 1.What CFM capability of a non-stock fan configuration is needed to adequately cool and engine with "X" horsepower with radiator of "Y" area and "Z" thickness (more generally, what is the BTU/min capacity of a radiator and CFM combination? 2. What is the actual CFM capability of the factory clutch fan engaged and slipping? 3.What is the true CFM capability of aftermarket electric fans despite the hyperbolic advertising claims? 4.What is the impact of high speed air (60+ mph cruising speed) entering the radiator and then encountering an electric fan generating a lower flow rate? and 5. What is the use of having a high CFM fan in an engine compartment that can't exhaust the air from the radiator? I'll try to address each in turn for the record and those with the patience to read on.
1. I have attempted for years to get any hard numbers addressing this question from production and engineering people as well as hobbyists like myself with absolutely no success! I have encountered numerous internet statements ranging from "I heard that it takes 3000 CFM to cool a 250 HP engine" to "there lots of handbooks and computer programs to give you that number but it won't help" to "there are lots of numbers depending on frontal surface area, fin density, tube thickness and material, tube spacing, radiator composition, water pump flow rate, ...". The only good answer is find a setup that works and try to duplicate it.
In this case, as you have suggested, the OEM configuration of fan/clutch performance must be reproduced.
2. This reproduction requires that we have a measured level of OEM fan clutch performance. This too is incredibly elusive. I have found (through the library resource of the internet) comments ranging from 10,000 cfm at speed to 2,000 cfm at idle. Always these numbers are given by hearsay (I have heard, they say, ...) never with attribution or published work or from a factory document. But, going back to my files, I actually have one set of compelling data to recall!
According to my notes a surprising dyno test was reported in Sport Trucks Magazine, Nov. Issue, 2000. The authors used a Chevy 454 engine with several different fans installed in a free box configuration, with OEM engine shroud using a screen mesh to model a radiator and a set of pitot tubes before and after the box to determine air flow. The experimenters then measured air flow, reported CFM for several engine speeds and included the measured HP loss for each fan combination relative to the engine power w/o fan. The results were very interesting. The bare fan (Chevy 18.5" OEM) gave 1680 cfm @800 rpm, 2355 cfm @ 1600 and cost 40.8 HP loss. The OEM fan mounted to non-locked clutch gave 1104 cfm@800, 1400 cfm @ 1600, 2103 cfm @ 3500 rpm and cost 19.3 HP. The OEM fan with locked clutch gave 1580 cfm @ 800, 2205 @ 1600, 3686 cfm @ 3500 rpm and cost 35.6 HP. Finally, the Flex 17" fan gave 1420 cfm @ 800, 1814 @ 1600, 2815 @ 3500 rpm and cost 20.2 HP. The point I'd make here is that the unlocked clutch/fan assembly generated 2103 cfm at 3500 and the locked version made 3686. This is important because these values are well within the range of quality electric fan modules. Also, by design, the clutch units slip to a constant speed between 3,000 and 3,500 rpm. In other words, they will not generate any higher cfm than they do at the 3,000 rpm level.
Now it can be said that these were not Ford fans, nor Ford shrouds, but they are literally all the data I have found over the years. However, I recently had occasion to search out 7-blade 19.5 inch truck fans of both Chevy and Ford design and manufacture. The Chevy fan blades were 25% wider than the Ford and the blade pitch was 36 degrees for the Chevy and 30 for the Ford. By the equations of fan operation, the Chevy fan moves more air than the Ford per revolution. So to equal the OEM fan performance under the most strenuous conditions, we need a fan delivering 3,500 CFM or more! If their Flex 17" sample was equivalent to yours, then your 302 needs 2,815 cfm to meet your cooling needs under mountain stress.
Addressing Question 3! The true CFM capability of electrical fans can be confusing as well. For free stand measurements (stand-alone fan, no radiator nearby) pay no attention to the advertised CFM claims, just look at the current reported. A quality electrical fan will deliver between 100 and 120 CFM per ampere of current used. So if the Continental Mark VIII 18" shrouded fan is reported to draw 40 amps on high speed, then it is pulling between 4,000 and 4,800 CFM. The Dorman Fans, that I'm using in this report, draw 37.5 amps (together) and measure 4,403 CFM at high speed for 117 CFM/amp. I have found OEM electric fans and their replacements to be a higher quality/price than Derale or Spal, and eBay fans might well not be considered for such a critical function. 10 amp fans said to deliver 2,500 cfm are BS+!
The next point to be made is that the true drawing power of an electric fan drops significantly as it approaches the radiator core. If you place the fan 1" to 2" from the radiator core, a good estimate of the net CFM capability would be to reduce the free air value by 30%. So the Dorman fans, mounted against the radiator should give 3,000 CFM at high speed. When the snow melts and I can access the beast, I and my trusty anemometer will measure and report the air flow at the face of the radiator with the OEM fan clutch system and the Dorman setup!
Question 4. It is generally claimed that above 35 mph, no fan is needed (suggesting that this measured flow velocity is equal to the BTU/min thermal demands of the engine operating at about 20% HP capacity). Most hobbyists assume that this is exactly the velocity of the air going through the radiator. Not so! Aerodynamic measurements have well established at the actual velocity through the radiator is about 40% of the vehicle speed. So 35 mph generates air through the radiator at about 15 mph! 60 mph becomes 24 mph. In other words, the actual velocity inside the engine compartment is rather modest. The real question comes down to the pressure differential being established by the fan pumping air out from behind the radiator and the pressure at the face of the radiator. Under certain flow conditions the fan can stall (while moving) blocking air from moving through the radiator. Now these engineering conditions are the provenance of the Ford engineers who designed these things and as long as we stay within reasonable boundaries these modifications should be fine. From the measurements I cited above, the OEM unlocked fan/clutch system is pulling 2,000+ CFM at cruising speed and a well behaved electric fan should be off at that point without a thermal crisis.
The point has been implied that a fully sealed shroud would impede airflow through the radiator assembly. By personal measurement, the area of the opening available with the two Dorman fans at rest is 7% larger than that of the OEM mechanical fan with shroud at rest. It has been well established that the electric fans are spun by incoming air under these conditions and under spinning conditions, the electric fan opening is 18% larger than the OEM system. Nonetheless, at the first sign of a problem, I'll cut holes and add flaps!
I really enjoyed the fan shootout as well. Watch these guys while the wife has another dose of "Orange is the New Black"! Unfortunately, they didn't do any CFM measurements!
