[DeTomaso] Stock fan output vs. Flex-a-lite

[Dave Doddek]

You only need the fans while at idle and slow speed.  If you get the car to
cool with only fans and no shroud, then all the better.  Puller fans are
also better because it is easier for a fan to draw a vacuum through the
radiator than to push pressure.  

Dave "Use suckers and a shroud" D

At 11:28 PM 12/2/2006 -0800, you wrote:
>FWIW.....I spent some time at SEMA talking with after-market radiator and
fan suppliers concerning overheating issues I have with my 5.0 Mustang when
driving ORR at speeds above 125mph. There was a lot of conflicting
information/opinions, but one of the comments that made sense to me was
that pusher fans are pushing cool air, while sucker fans are sucking warm
air. Cool air is easier/more efficient to push than warm air is to pull.
>
>mikeldrew at aol.com wrote:  
>Jack wrote:
>
>We've also found sucker-fans (behind the rad rather than pushers from 
>the front) to be much more efficient than
>pushers, and another efficiency increase comes when suckers are 
>combined with a
>full shroud that forces air flow through the entire rad core, not just 
>two spots
>directly in front of or behind the fans.
>
>>>>It's worth mentioning that this shroud has both advantages and 
>disadvantages. It improves the efficiency of the fans at lower speeds, 
>but can radically decrease the effectiveness of the radiator at higher 
>speeds, because it causes a restriction--the relatively small openings 
>prevent air from flowing through and out of the radiator at elevated 
>speeds.
>
>Johnny Woods found this out when he installed the Flex-A-Lite unit on 
>his Pantera. He routinely drives around France at 150 mph, and he 
>found that at triple-digit speeds, his car would start to overheat, but 
>it ran fine below 100 mph, which is a classic symptom of an airflow 
>problem. He wound up cutting the shroud apart and making an elaborate 
>series of trap doors/flaps, which blow open when the pressure inside 
>the shroud is greater than that on the outside. At lower speeds, when 
>the fan is spinning, it is creating vacuum which sucks the trap doors 
>closed. In fact, he may have gotten the idea from me, as this is an 
>OEM arrangement used by VW on all their water-cooled cars, and I 
>described the mechanism in use on my Sciroccos to him when he asked me 
>about his problem.
>
>If you aren't in the habit of cruising at 100+, then it's probably 
>never going to be an issue for you, and you can probably get away with, 
>and in fact be quite happy with the Flex-A-Lite suckers. Having said 
>that, the non-shrouded Spal fans that Wilkinson sells work extremely 
>well too, and flow enough air to render a shroud unnecessary. Take 
>your pick.
>
>Installing a fan setup with the shroud in front of the radiator is the 
>stupidest thing I've ever heard of--yet Flex-A-Lite markets some of 
>their fans thusly.
>
>Another point Jack made bears repeating--many fan manufacturers sell 
>their fans with a cheesy mounting kit that relies on custom zip-ties 
>that pass through the radiator core, to secure it to the radiator. 
>This is NOT a good idea, and more than one Pantera owner has found out 
>the hard way that road vibration etc. will cause the fans to move 
>around on the radiator, and the zip ties act like little saws, slowly 
>cutting the radiator apart until it leaks. IF you can find no better 
>way to secure it, get a small-diameter aluminum or brass tube, 
>carefully feed it through the fins, and then pass the zip ties through 
>the tube. That MIGHT prevent a leak--but in my view it's no substitute 
>for a proper mounting system, which utilizes brackets which are 
>brazed/welded/whatevered to the radiator frame itself, without actually 
>touching the fragile core. To me, that alone justifies the added 
>expense of buying a package from a Pantera vendor, rather than saving a 
>few bucks and ordering the ingredients from Summit etc.
>
>Cheers!
>
>Mike
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