New cooling upgrade option??

[bl78ljb]

Well, I know that electric fans have been discussed here before as being insufficient for our diesels. However, I was just looking at something on the flex-a-lite website (www.flex-a-lite.com) and noticed that they now have cooling fans for diesels. Listed for Chevy / GM is for Duramax applications with a CFM rating of 6000. In talking with the tech at Flex-a-lite it appears the fan for the 90's trucks (which also now list the 6.5L as an acceptable application with a 5500 CFM rating and no longer states "not for diesel applications" as it did before) is the same size as the Duramax application and can likely be used on our trucks as well with the higher CFM application. However, I don't know what the CFM rating on our stock mechanical fans is, nor the rating on the D-max fans. So, in deferring to the experts what do you think about this possibility - granted more expensive than a typical fan upgrade, but you get more room and more control over the fans such as with AC and cold weather operation.

[More Power]

The 21" 9-blade Duramax fan pulls 10,000+ CFM at 3000 engine RPM - or about half that CFM at 1500 rpm.

This subject comes up occasionally, especially since Flex-a-Lite began advertising their fan setup.

If your 6.5 is simply a people mover or light hauler, electric cooling fans might help produce a measurable power and fuel economy increase.

If you tow moderate to heavy trailers, the higher rated engine-driven fan would likely be a better choice.

In addition, towing a big trailer at night (all those extra lights + electric brakes) and with the truck's A/C on would tax the factory 105 amp alternator - if you're running electric cooling fans. A second alternator or a higher capacity single would be a wise addition for those using electric cooling fans.

Jim

[bl78ljb]

Jim,
Do you know what the CFM rating of the stock 6.5 fan is? The reason I was looking is because I have noticed the temp gauge rises when I am towing so the information you have given is very helpful. My biggest concern was low RPM in town towing which is where I have noticed the stock fan doesn't quite cut it.

[More Power]

Jim,
Do you know what the CFM rating of the stock 6.5 fan is? The reason I was looking is because I have noticed the temp gauge rises when I am towing so the information you have given is very helpful. My biggest concern was low RPM in town towing which is where I have noticed the stock fan doesn't quite cut it.


I don't have the air flow rate for the different steel-bladed fans used on the 6.5. The newest stock 20" 9-blade steel fan is recommended by some.

What's not commonly known is that an uprated 6.5 (215 hp / 440 lb-ft)was tested and engineered to become an optional engine in the 1999 and newer GMT-800 body style trucks. But, GM changed their minds, and pulled the 6.5 option when the new trucks were released. The screw-on fan-clutch hub and a composite 21" 9-blade fan that were intended for this installation was a part of the factory cooling package. In fact, one of those early water pumps and fans are what we used in our own 6.5 project in late 1998 (they were removed from GM test engines). It's not a coincidence that the Duramax fan bolts onto the 1997 and newer 6.5 fan-clutch. They were designed to.

Correct fan-clutch operation is vital to proper cooling. I prefer to see it cut in at 200/205 engine temp or certainly before 210. Running 180 degree t-stats can sometimes allow the fan-clutch to engage a little sooner, because hot coolant begins cycling through the radiator sooner. It's the temperature of the air in front of the fan-clutch (working on the thermostatic coil) that causes it to engage. If you're not hearing the fan begin to roar by 210, you'll need to solve that problem before moving on.

Jim

[bl78ljb]

Not towing the truck barely hits 200F, but when I was towing I did hear the fan kick on, though I cannot remember at what temp. If the d-max fan fits is there a certain year or all years, as this might warrant a trip to the local bone yard. Also does anyone know the specs of the factory pusher fan or if an aftermarket pusher works just as well as I have seen some of the 6.5 trucks with one - don't know if it was an option or came with a certain package or GVWR but that might help at low speeds.

Thanks