[killerbee]

I can't stand it any more. It has been 2 years since I suggested that the increased fan drive ratio on the LLY is culpable in the increased overheat arena. I have never tested the research on a test mule.

Background: based on my sieve of a memory, the FDR went from 1.29 LB7 to 1.48. FDR is just the ratio of the crank pulley dia to the fan pulley dia. In the LLY, the FDR was changed and the change was obvious in noise level. The reasoning to consider with the change, is that the fan now operates outside it's optimum zone, with several side affects to its increased speed. Higher noise, less air flow, higher parasitic drag, bigger centrifugal effect, reducing the axial nature of the fan design, possible over exertion of the viscous clutch resulting in further loss of energy in excess heat conversion (the clutch has cooling fins). Excess heat in the clutch is a conversion of crank work to heat production in the clutch. etc etc, blah blah. IOW, 20 HP more drag with less actual airflow.

Agree, don't agree...not important. Let's test this one out. A new LB7 fan pulley (pn 97226289) is under $400 new, perhaps less than $30 if someone can find a yard with one. I am asking for you guys to find one or 10 and try it out. The belt is the same IIRC. Anyone who can find these used, PM me, I'll buy it .

And please don't bring up electric fan conversions, I'd like this thread to stay open.

 

[TheBac]

So why didnt you just go to the local junkyard and rob an LB7 of its fan pulley?

 

[killerbee]

If anyone can find an LLY and LB7 fan pulley, I will model and machine some duplicates.

We can go from there. I am not sure how difficult that will be, but I am willing to give it a try.

Tom, i think my yard roaming days are over.

 

[TheBac]

Ah, darn. Yardin' can be fun, too. You never know what you'll find.
I just figured that would be the easiest way to find one.

 

[4wheeln]

The local Boneyards in the Phoenix area are mainly networked now. While there are a few "u-pick-it", most can be called and they will have it pulled for you for pickup. I get alot of Jeep items and parts for experimenting on other vehicles. This is considerably cheaper then modeling and machining. As far as time, a phone call and then pick it up later sometime while I am out and about.

;-)
4wheen

 

[killerbee]

"modeling and machining", because if my reasoning holds water, i will probably manufacture a version. That's what I was getting at. Maybe I will make some calls. i just have a feeling there aren't a lot of duramaxes in the boneyard with good front end parts.

 

[killerbee]

The LB7 is 97226289
LLY is 97309640

If they are used on another motor, that would make it easier to find.

 

[4wheeln]

I know that they can cross reference factory numbers so you should be able to give those numbers. They can quote a price on the phone also. My experience with the online ordering / questionaire is that they do not respond. Phone works best.

My experience is that 2 years and older is best for success on getting parts. Less then 2 years is hit and miss. So I would expect success for an LB7 and an 04 LLY. Doesn't hurt to try ;-) Also an existing unit makes it easier to prep up a production run if you are going that route.

;-)
4wheeln

 

[4wheeln]

"modeling and machining", because if my reasoning holds water, i will probably manufacture a version. That's what I was getting at. Maybe I will make some calls. i just have a feeling there aren't a lot of duramaxes in the boneyard with good front end parts.

I had someone make me a 16% smaller waterpump pulley for my highly modified jeep. I needed more air across the rad at idle. The vehicle in motion was fine. Ths also allowed me to have a faster water exchange through the head. (I know that the waterpumps are gear driven for these diesels so not the same)

I went with aluminum for the pulley but found that the belt mixed with running in the sand dunes was eating at the belt section of the pulley. (excessive wear) I have had it sent out to be chromed on the belt area only to eliminate the wear issue.

;-)
4wheeln

 

[killerbee]

2 more pieces of the puzzle.

1. parasitic power loss increases with the cube of the rpm increase.

HP2=HP1 (rpm2/rpm1)^3. it is the rpm of the fan that applies. So a 20%increase in rpm (1.20 factor) results in a parasitic drag increase of 72.8%, or 1.20^3. If the LB7 drag loss was 30 HP, then the LLY is 52 HP.

2. Fan tip speed must be kept under 14,000 fpm for optimization, under 16,000 fpm (180 mph) to avoid operation near stall. Do the math on a 21" fan with a 4600 rpm speed, over 25,000 fpm. We have the added complication of not being direct drive, instead viscous slip drive. Imagine the amount of heat converted from rotational work in the clutch.

 

[okauto]

I'm very interested in getting a little more airflow thru this massive stack, and in eliminating some of the roar from the overdriven fan. Has anyone switched to the larger, slower fan pulley to see if there is any result either positive or negative. Maybe doing that and adding a switched pusher electric fan in front of the stack to aid the flow would give me enough extra capacity to get by. I've done everything else except one of the mega cooling alternatives.

 

[killerbee]

These are no commonly available in yards, unfortunately.

If I can get my hands on one, I will look at testing, and building them.

Another idea was some kind of press fit sleeve.

 

[stevebos]

We have the added complication of not being direct drive, instead viscous slip drive.

Has anyone tinkered with an electromagnetic fan clutch; ie: the Horton MagForce or the Linnig clutches? I beleive they provide direct drive when engaged. :idea:

http://fulfill.pgicompanies.com/sqlimages/horton/pdf/22777.pdf

http://www.conceptsnrec.com/products/linnig.htm

 

[chloeourdog]

Hi Steve,

If one could provide a partial engage (ie: controlled speed) then this would be similar to a larger pully (which would allow the fan to spin at a speed it would pull the most air effeciently). Some car manufaturers used to have a variable speed clutch on A/C compressors that would provide better economy but still provide decent cooling. Some of the original Dodge Avengers had this (I remember a friend test-driving it and he hit the A/C button - it went from amber to green to off). I would think the fan would still need to turn when the A/C is on and/or whenever the ECT went above a certain temperature.

-Mark

 

[killerbee]

I'm very interested in getting a little more airflow thru this massive stack, and in eliminating some of the roar from the overdriven fan. Has anyone switched to the larger, slower fan pulley to see if there is any result either positive or negative. Maybe doing that and adding a switched pusher electric fan in front of the stack to aid the flow would give me enough extra capacity to get by. I've done everything else except one of the mega cooling alternatives.

with your mods, including the CAI, have you monitored the IAT when towing?

 

[killerbee]

The viscous design, is suppose to be a way to avoid fan tip stall through a wide range of rpm. It begs the question, what happens if you try to spin the whole assembly faster?

I like the direct drive concept, but it does not suit the vehicle well IMO, since we drive through a wide range of engine speed. Plus air condition plays a big role on optimum fan speed. Cold dense air vs hot dry thin air at altitude.

I think the Dodge now uses an electro-viscous, EV, clutch now. It uses logic solid state to enable and disable. I do not know if it modulates fan speed or not, through other than the usual slip mechanics. Viscous slip heat, in over abundance should, in theory, reduce the air moved per HP of required shaft.

I have been towing in the past, and wondered "why doesn't this fan sound like it did 10 minutes ago?" If the clutch is too hot, then the fan could be slowing, and getting quieter.

Just some off-the-cuff thoughts, untested.

Slowing it down, may well be improvement, especially if you have a stock intake..

 

[okauto]

with your mods, including the CAI, have you monitored the IAT when towing?

No, but my CAI draws air from directly behind the passenger side driving lamp in the front bumper so I am assuming it has to be close to ambient. From all the posts on these sites I understand the LLY's cannot pull as advertised without having the temp go uncontrolled. So I have never pushed mine hard enough to get "overheat" warnings, but the loud cycling fan is really annoying. With all my mods you would think there would be enough air being directed through the stack at hiway speeds, and cooler air going into the intake, and a larger catless exhaust to rid the engine of heat to eliminate the fan completely, but it hasn't. It pulls well, but I know I'd have to back out of it while pulling my 30' camp trailer up any long hills to control the heat. As it is, I've noticed even at 70 mph towing on flat ground that my oil pressure drops about 10 psi from the influence of the added heat.

 

[killerbee]

When your fan cycles on, your IAT rises. Having a fender sourced CAI is very helpful, but it does not fully isolate this problem. After the truck is warm, go to the front and place your hand on the space between the hood and pax headlight, feel that hot air? When the fan engages, even at 60 mph, that air is making way to the intake.

This happens with the newer 06 intake as well.

The oil presssure drop is a byproduct of increased temperature. The TD-EOC takes care of that. The fan should be nearly, if not completely non-existant after installing it.

 

[stevebos]

I've been day-dreaming how to control the OEM fan speed electronically, hence my question regarding electromagnetic fan clutches.

Since then, I've learned two things:


1. The LBZ is equipped with an electro-viscous fan clutch.

http://www.thedieselp*g*.com/features/2006MY.htm


2. The electro-viscous fan clutch found on the 2002 Trailblazer provides infinitely variable speed.

http://www.motor.com/MAGAZINE/Pdf/112003_09.pdf


Assuming the above is true, and if the LBZ clutch is capable of providing infinitely variable speed, what are your thoughts about retrofit of the LBZ clutch to the LLY? If the LLY ECM does not have the capability to control an electro-viscous fan clutch, is it possible to design a clutch controller?

 

[chloeourdog]

Hi Steve,

Which a temperature probe placed in the coolant flow or behind the stack (air flow) one could use a Pulse Width Modulation Controller to generate the correct amount of voltage/current to modulate the electro-viscous fan clutch. One could potentially use the ECT sensor output to do the same. The circuitry is available to do this (I believe TXChristopher uses something similar to control his electric fans using coolant temperature to dictate when the fans operate and what speed they operate - I think he also uses the AC compressor signal to command one of his fans on. His method of control appears to be very reliable and predictible.)

I wonder if we have the clearance to install such a clutch with our current fan setup.


On a different note, for simplicity, could one add a thick piece of rubber to the current fan pully to increase its' diameter to decrease fan speed somewhat - not sure what the difference in diameter is between the LB7 fan pully and our LLY one?