Flex-a-lite's Duramax Electric Fans

[More Power]

Flex-a-lite has changed the ad copy for their Duramax dual electric fan, which I applaud. In the beginning, they pushed the 6000 CFM and power/torque gain the Duramax produced when not turning the engine driven fan - and that was about it...

Those in the know, know that the Duramax 9-blade 21" fan is capable of moving more than 10,000 CFM when the engine is turning 3,000 rpm. No 6,000 CFM electric fan can compete with the factory fan when the going gets tough (i.e. towing uphill). We also know that electric cooling fans require juice from the alternator - pulling a few tens of amps. Alternators are approximately 80-85% efficient when hot. The factory GM alternator in your Duramax powered truck is rated for 105 amps. At 85% efficiency, your alternator is capable of producing a max of about 89 amps. What we don't know at this point is, what is a typical electrical load - at night and while towing a trailer? Is there enough excess electrical capacity to safely and reliably power a pair of electric cooling fans?

Flex-a-Lite's current ad copy says:

Flex-a-lite has recently introduced its Chevy/GMC electric fan that helps to free up additional horsepower by eliminating the stock fan and clutch assembly. Flex-a-lite's Duramax fan pulls up to 6,000 CFM while drawing 28-36 amps. This helps keep high-horsepower diesels cool on hot days during towing and traffic, and improves (lowers) air conditioning temperatures. Depending upon engine temperature, the variable speed control module will operate the twin 15-inch fans independently between 60 and 100 percent. Flex-a-lite dyno tests show gains of 27 horsepower and 34 lb-ft of torque at the rear wheels. The electric fan is not recommended for combined gross weights of more than 18,000 pounds. www.flex-a-lite.com

Now, I am a "fan" of electric fans - for light-duty driving or light towing, for extremely cold environments, for performance trucks, and/or for fuel efficiency while driving unloaded. If your driving fits into any of these categories, an electric fan set like that offered by Flex-a-lite could be a good idea - as would a second alternator, depending on your truck's electrical loads. However, for heavy-duty towing, I feel the stock engine driven fan remains the best choice.

On a related subject, while at SEMA, I noticed that the new 6.7L Dodge Cummins and the new 6.4L Powerstroke both use an engine driven fan and electric fan clutch. They look similar to those produced by Horton. The clutch engages electrically, based on many engine and related systems temperatures.
Jim

[mcwhitsitt]

Thanks for the input Jim and others. I was about to spend over $600 for the flexLites. I have an 05, 3500 2WD with 102,000 and 4" exhaust, Banks air and Dr. Performance module. I pull a 34' 5th wheel weighing in at about 12,500+. I have plenty of power but do see some high temps here in Texas while driving in Hill Country. I was hoping to see a drop in those temps but this is obviously not the route to take. I have ordered the air scoop which attaches to the Banks air box to try and get away from the hot air in the engine compartment. Don't really know what else to do. Any suggestions?

[Mark Rinker]

These would probably work for me in the winter. Snowplowing.

Their recommendation of max 18K# gross combined makes no allowance for wind drag.

The front of a big 5'r, or oversize boat will pull the Duramax into a condition requiring the fan very quickly.

Ground speed, terrain, outside air temps all have alot to do with it too...