Cooling fan "upgrade"?

[2tough2park]

One of the major changes to the LMM engine configuration was the changeover to a factory electic cooling fan setup. At least that's what I read. It was done for fuel economy and other various reasons so they say. So I ask: could this be retrofitted on LBZ, LLY, etc? There's been rumblings in the past of people wanting to do that which is why I bring it up. Some had said there was no electric fan setup that could move enough air to cool a Duramax. Well, apparently, now there is. So...opinions? I'm willing to try it out.

[More Power]

GM had initially indicated they would be using an electrically engaged fan-clutch for the LLY, but they kept the viscous version for whatever reason.

AM General showed their newest 6.5L diesel engine at a recent SAE conference. This engine was equipped with an electric fan clutch. The newest 6.5's shared the same style fan-clutch and hub attachment with the Duramax - though the calibration may be somewhat different. Point is, even if GM doesn't eventually produce a compatible electric fan-clutch, perhaps the AMG version will be. :)

Jim

[rob from bc canada]

Big difference between electric fan and electric fan-clutch.

The former runs off the battery, saving power while already straining to go up hill, the second merely uses electricity to engage a belt-driven fan.

In the long run (long grades towing?) an electric fan might actually use more power, becuase it first has to use the engine to run the alternator to produce the electricity, and then use the electricty to run the fans, more steps, one would expect more inefficiency.

On the other hand, a multiple fan setup, as many cars now have, you pull only the amount of air needed, and don't waste power running a fan at higher RPM's than needed.

[2tough2park]

Yes I meant full electric fan setup. I remember old posts from those wanting to ditch the belt driven fan setup altogether. Funny you should mention about power draw. While the belt driven setup drags the engine down when the clutch engages increasing fuel consumption. A full electric fan setup cause more drag on the alternator causing the same scenerio. I guess it's all in the details about electric fan programming(LMM's ecm controls the fans directly) to help reduce drag on the motor. hahahha derned if you do derned if you don't.
Personally, I'd rather have the full electric setup myself. My LBZ now runs the fan on cold start when the fan clutch is cold. Even if it's 80 degrees outside, it'll engage in the morning for a few minutes. I'd bet it would be as effective or more during those long idle times like the traffic I sit in everyday especially with the A/C running.

[More Power]

We've talked about the electric fan option several times before, but it is worth repeating.

If you don't tow with your Duramax, a Flex-a-Lite dual fan setup might be a good idea from a fuel economy standpoint. This dual fan pair is advertised as being able to pull a max of 6,000 CFM. Your factory stock 9-blade 21" lightweight composite fan is capable of pulling more than 10,000 CFM at 3,000 RPM. The stock fan is what I'd want for pulling in the hot summer heat. :)

If going all electric, a dual alternator option might make things more reliable.

Jim

[2tough2park]

Now I know we all don't sit in Santa Monica freeway traffic all day every day(but dam it feels like it up here sometimes), but if the stocker pulles 10k cfm at 3000rpm, that's all well and good. But what about the times I'm not at 3000rpm? I know all this is figured into the design and engineering from the getgo, but I'm just sayin'.

[D_R_C]

Ford uses the elect controled viscous fan clutch,that was about the only thing that worked well on the 6.0.
Borg warner mfg the elect viscous fan clutch for Ford.
Hayden Elect has a 17" 2 speed 1500/2100 cfm that I tested for them last summer,I`m sure it is on the market by now.
It worked ok in aiding the A/C cooling about 8 degrees temp drop out of the vents,mostly driving around town in the heat,engine temp drop was not even noticable.
I also tested a heavy duty elect viscous fan clutch for Hayden which did kick in sooner a little more aggresive and the engine ran about 10 degrees cooler all around.
Ford runs the heavy duty on ambulance equip set-ups.
I don`t think there is a electric fan available that would cool a diesel especially towing,by itself without the fan clutch as the main cooling source.

[More Power]

But what about the times I'm not at 3000rpm? I know all this is figured into the design and engineering from the getgo, but I'm just sayin'.

Well, if your engine is turning 2000 rpm with an engaged fan-clutch, the stock fan could be pulling about 6,600 CFM.

Sounds like you're leaning toward the Flex-a-Lite. Let us know how it goes. :)

Jim

[40grit]

while I'm not picking elec over stock, I have a few questions/ ideas

Has anyone figured out at what speed the truck moving thru the air overcomes the CFM the stock fan is capable of pulling? It would seem that even though the stock fan is capable of 10K cfm (with no restrictions such as the intercooler or anything else, same way the electrics are rated) at 3000rpm, who drives like that? the electric can pull 6600 cfm from idle thru redline, but all of this is limited by how much air will physically fit thru the grill area when sitting still versus the forced air effect of the truck moving...

You could also wire a switch to have the elec stay on no matter what while towing, while the stock needs the engine to heat up high enough to engage the visco-clutch. so the elec could have a sizeable "lead" on cooling down the engine while chugging along at 10 mph up some huge hill.

but I'm more interested if anyone has done math and airflow calc to figure out at what speed all this becomes irrelevant as the truck moving thru the air starts to force more air thru the grill area than either stock or electric is capable of doing. should be a straight forward calc, square inches of grill area versus feet of movement thru the air at various mph...

It would seem both the electric and the stock are only for those really hot days while sitting in traffic or chugging up hills at real slow speed with heavy loads and from what little I know now the electric would have some advantage due to being able to turn it on and off( or in auto temp control) at will with a switch in the cab where as with the stocker, you are stuck with whenever the General decides your fan should turn on...

although right now, my fan does engage for the first 1/2 hour of each drive in the morning due to visco-fluid settling during the night. GM considers this "acceptable", but I'm still fighting with them over it...it's a sizable load on the engine when it fully engages when cold, makes the truck sound like it's prop-powered in the morning. I would like to change it out so it only works when it's supposed to when hot, but I'm not going to buy another visco-clutch and have this happen again, with only 3500 miles on the truck, it'll going to be their problem to fix...

[Mountainman]

All of this has been gone over (every point) and tested and is presently in production and it is not Flex-O-Lite. Google coolmyduramax and you will be amazed.

[More Power]

Electric fan clutches would be a better choice - in my opinion, if someone feels the need for more control over fan engagement. This way, you'll get more CFM (with the large engine-driven fan) than an electric fan pair, and no strain on the stock alternator.

The new Dodge and I think Ford use an electric fan clutch. The Duramax was supposed to get one with the LLY....

I'm surprised the entrepreneurs out there haven't jumped at the electric fan-clutch...

Jim

[gmdieseldan]

Hi Lets use both electric fan clutch & electric fans at the same time. Set the electric fan clutch at a higher temp before it comes on.

[Dakster]

Got news for you all. The LMM is just as loud, and until I read the prop powered comment, I couldn't describe it as accurately. That fits it just right. The truck sounds like a prop plane for the first few minutes of drive time and then it quiets out significantly. It is only loud when the RPMS are up, which I guess its why I didn't notice as much until today when I jumped in and took off. I usually remote start and let it run for a few minutes before I leave... Cools the truck off and lets me load the kids in.

It is a little annoying, but at least I know the fan and clutch is working!

[killerbee]

Has anyone figured out at what speed the truck moving thru the air overcomes the CFM the stock fan is capable of pulling? ...

approximately 160-200 mph. But they are additive at all times, FWIW.

for clarity, there is not an electric fan option that can pull over 6000 cfm through this restrictive 3 layer cooling module. There never will be either. That would require fans that could move 18,000 cfm in free air (this is how fans are rated). That is not practical with our electrical system.

The electric IS more efficient, however, from the perspective of BTU's per parasitic HP loss. That is mainly because our thermoviscous fan is overdriven by a smaller fan pulley than existed on the LB7. Upsize the fan pulley, and you can restore the fan drive ratio to sane values, and keep it looking stock. But for high loads, an electric option is mute if it can't cool enough.

A loud fan is an innefficient fan. Noise is waste energy also, but it is also a measure of turbulence and energy conversion.

The electro-viscous fan, when it becomes a reality will have all the same problems, it will just be smarter. The main issues with the stock fan, is the IAT increase loop, where fan engagement creates IAT creep, and high speed fan stall/air flow loss associated with overspeed, and a bunch of parasitic HP loss. With all this comes a reduction in actual airflow.

From an age old document (http://members.cox.net/beekiller/GMC%20Light%20Duty/White%20Paper%20on%20LLY%20overheating%20issues%20 related%20to%20airflow%20deficiencies.doc)

It is also important to understand that the fan clutch is a mechanism that operates on the principles of viscous slip, similar to a torque converter. Silicone fluid is the slip media. As a Newtonian fluid, its viscosity reduces, or thins with temperature increase. At the same time, this slip creates frictional heat. The hotter the clutch becomes, due to slip heat and poor airflow, the worse it will perform in slip, i.e., it will turn slower. If it turns slower, the air flowing across will be even hotter yet, a basic heat exchange concept. This was another potential negative feedback phenomenon. At full lockup, performance might be expected to decrease with hotter ensuing temps or higher engine RPM causing more slip heat. Add further to the complexity, that the clutch itself is dependent on heat exchange to stay cool. The fins on the clutch are tasked with offloading heat from viscous slip operation. Excess heat in the clutch reduces viscous coupling, lowering fan speed, but more importantly, that heat is a parasitic power loss that. Mechanical energy conversion to heat, up to 15 HP worth of heat.