Blue fan clutch mod...Thread has gone to hell, read at your own risk

[Tools R Us]

the more I look at the 2 clutches the more I'm thinking that the newer style clutch might pass more oil when it's on.

Look at the larger relief around the secondary holes (boot and diagonal rectangle) of the two.

As the clutch spins that relief fills with oil and when it is aligned with the holes on the opposing side the oil passes through in preparation to be sheared around the outer edge where the real power is transferred. At higher rpms the time for that to happen will be less than at idle and the larger relief might increase the % of drive during those times and possibly throughout the clutches operation.

You would hope that the new design is an improvement? Mainly posted it so that we are aware of it, the temp adjustment mod calibration would be different.

I saw all of those ridges and wimped out, only put 10K cst in it. The difference is very noticeable, at idle I can feel good airflow at the grill and loads of hot air blows out the fender wells. When it's first started it makes a nice roar, when it's "off" I can stop it no problem and spin the fan backwards, when it's "on" I couldn't stop it with a welding glove on and I gave it a good try, pain was involved.

 

[cruiserdan]

when it's "on" I couldn't stop it with a welding glove on and I gave it a good try, pain was involved.

Don't jack up yer sandwich clamps until after you finish that other spacer....

 

[Tools R Us]

Don't jack up yer sandwich clamps until after you finish that other spacer....

Spacer? .....

 

[landtank]

At idle I can hear the air entering the grill as well. I should probably do the welding glove thing but I don't have a glove and no real motivation to find one for the task. (read wimp)

The real trouble I'm having, is getting my head around how much of that outer area is actually in play. While heavier oil will increase the shearing for any given amount, if the lighter oil flows better and increases the surface area used then maybe that is a better option.

 

[DaveyBoy]

The real trouble I'm having, is getting my head around how much of that outer area is actually in play. While heavier oil will increase the shearing for any given amount, if the lighter oil flows better and increases the surface area used then maybe that is a better option.

Wouldn't the 3000cst be better for New England weather,
ie: cold winters? Just a thought.

 

[Cattledog]

Hey Rick,

As the viscosity of the oil is increased the force necessary to shear the oil will increase assuming no temperature increase... You will get more drive force to the fan blades from the "thicker" oil of equal volume in the hub.

I agree with your original idea that the clutch was "adjusted" from the factory for mpg not cooling.... I will be "fixing" my blue hub as soon as I "fix" my temp guage.

 

[Cattledog]

Wouldn't the 3000cst be better for New England weather,
ie: cold winters? Just a thought.

Why? The clutch will only engage if the bimetal spring reaches the correct temp. Winter should not matter.

 

[Tools R Us]

At idle I can hear the air entering the grill as well. I should probably do the welding glove thing but I don't have a glove and no real motivation to find one for the task. (read wimp).

By putting my hand on the grill I can feel airflow about the same as it was at the condenser before. From running a hand over the condenser there is strong even airflow across the whole surface. Between the A/T cooler and condenser I can feel the heat being sucked from the cooler, good airflow across the face of it, the A/T cooler was almost a dead air area at idle before.

These results are very early, I only have a trip home (midnight) and back (7:30AM) 28mi total and only at about 100F. The real test will be this weekend, taking her to the mountains to beat her on the rocks.

The real trouble I'm having, is getting my head around how much of that outer area is actually in play. While heavier oil will increase the shearing for any given amount, if the lighter oil flows better and increases the surface area used then maybe that is a better option.

The shearing area is the grooved area, from trying to clean back there with compressed air, I would guess that there are shearing grooves on the backside. From laying the valve plate over the hub I am guessing that they only come into play when the valve is mostly or all of the way open? The only way I can see that fluid would get back there is through the hub holes.

 

[Tools R Us]

Wouldn't the 3000cst be better for New England weather,
ie: cold winters? Just a thought.

I think it's more of a question of your needs, how much you heat load your truck. Rick has had good results with the 3000 cst, so a valve tweak may work. If you do rock wheeling where you power brake or tight slow wheeling that add big heat loads to the engine and trans you may want a thicker fluid. Probably don't need 10K cst but it's mixable, so adding a tube of 10K cst to what's already there would net ~4000 cst giving you a conservative upgrade? Removing 18 ml and adding two tubes would net ~6500 cst.

Why? The clutch will only engage if the bimetal spring reaches the correct temp. Winter should not matter.

True, but may not be needed and with the thicker fluid it will roar longer in cold weather before the fluid is pumped into the reservoir.

 

[cruiserdan]

Kevin do you think it possible to "over-drive" the blade to the extent where it may contact the radiator (in a blown truck)?

 

[SUMOTOY]

Kevin do you think it possible to "over-drive" the blade to the extent where it may contact the radiator (in a blown truck)?

Absolutely, btdt.

I also agree with CD, a thicker fluid will cause the blade to spin faster, specifically, the only way to increase the efficiency of a engine driven fan design for a specific rpm (idle for instance) is to decrease the slip of the clutch, or change the pitch of the blade. If you decrease the slip, under 'coupling' you have increased the speed. I'd be very wary of this thicker fluid change if you run your truck to redline.

I also propose that the engine driven fan blades on the 80 is 'pitched' for a specific and narrow rpm band. You can increase the efficiency of it at low rpm by increasing the viscosity of the fluid, but you will trade off efficiency somewhere else in the rpm band.

Another nice feature of electric fans = blade pitch and rpm are a constant, as is cfm.

Scott Justusson

 

[semlin]

the objective here is to get effective cooling while sacrificing minimal gas mileage/power.

We have three ways to adjust the clutch

1. change the temp at which it opens
2. change the amount of oil
3. change the viscosity of the oil

Item one changes responsiveness, while items 2 and 3 change performance. It's not clear to me what is different between topping up a clutch with 3000 cst rather than replacing to the factory level with say 10,000 cst. I would think that unless we understand that relationship, switching to 10,000 cst makes sense primarily if filling it with 3000 cst does not do the trick. Am i missing some other benefit?

 

[Tools R Us]

Kevin do you think it possible to "over-drive" the blade to the extent where it may contact the radiator (in a blown truck)?

The answer would have to be with the 10K cst fluid I don't think so. With the clutch cold and roaring I snap revved it as hard as I dared, then held it at a high rev and only got about 1/4" of flex? Your fan has shorter blades that will pull less air, so all things equal should flex less, but it maybe less stiff, so careful testing will be the only way to tell.

 

[landtank]

Kevin, just to make sure we're together on this. I'm not refering to those grooves that are running around the face of the plate in a 3/8" band. I'm talking about shearing at the outer edge. That area where the oil is sheared against the housing itself and the edge of the drive plate. Where the teeth of a saw blade would be.

 

[Tools R Us]

1. change the temp at which it opens

This changes the temp where the clutch comes on, set it at a lower temp and the clutch comes on sooner and runs longer, has to cool the system more before it turns off.

2. change the amount of oil

The only advantage that I see here is having more fluid in circulation it's less stressed and may not breakdown? There is probably little or no direct performance benefit, but may have a long term durability benefit.

3. change the viscosity of the oil

This will change the torque transfer and RPM of the fan, making for small to large changes in CFM depending on the viscosity used. Also the thicker fluids are harder to over shear, making them more durable.

There is no reason that any or all of these can't be combined to tune the cooling for your driving needs.

 

[Tools R Us]

Kevin, just to make sure we're together on this. I'm not refering to those grooves that are running around the face of the plate in a 3/8" band. I'm talking about shearing at the outer edge. That area where the oil is sheared against the housing itself and the edge of the drive plate. Where the teeth of a saw blade would be.

The saw teeth on the edge are the pump that returns the fluid to the reservoir through the holes in the edge of the valve plate.

 

[landtank]

The saw teeth on the edge are the pump that returns the fluid to the reservoir through the holes in the edge of the valve plate.

Yes, and that is where all the the drive is created

 

[SUMOTOY]

The answer would have to be with the 10K cst fluid I don't think so. With the clutch cold and roaring I snap revved it as hard as I dared, then held it at a high rev and only got about 1/4" of flex? Your fan has shorter blades that will pull less air, so all things equal should flex less, but it maybe less stiff, so careful testing will be the only way to tell.

Shorter blades doesn't necessarily mean less air, it's the shape of the blade that will dictate that. In fact, if the blades were optimized for flow, they will flex more. Remember too, A supercharger has a .75in spacer that moves the fan that much closer to the radiator. I suspect when this is done, the fan sits further in the shroud, reducing the turbulence in the shroud, and causing the fan blades to move toward the radiator.

I measured and reported all this several months ago. I ate 3 fans before I decided to clip what I had. The flex is pretty dramatic ~3in IIRC. What I found was the heavier fluid and/or the high rpms (4500+) caused blades to eat the radiator core.

The theory was postulized that the stock fan shroud was the problem. I removed it, still had interference fan flex. Which also appeared to give me an indication that the shroud wasn't really needed to pull air. Also giving me the indication that the fan would have flexed more, had the radiator not impeded that with interference. BTW, I ran with 2 blades clipped from Steamboat, then ended up clipping more when the below happened...

Scott Justusson
Found it!
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Posted 2-23-06 - SUMOTOY

haven't had a chance to digest all my measures yet, but I believe from what I have found so far, you might just be lucky Dan, or you just don't redline the truck like I do. Here's the measures I took post mortum.

NEW STOCK FJ80 FAN WITH TRD SPACER
TRD SPACER FOR SC - .75in
Stock blade tip to radiator (12 o'clock position) = 1.125in
Depth of 5000rpm Ring cut in Radiator Core = .50in
Diameter of Stock Blade = 18.50
Diameter of Radiator Core Ring Damage = 17.125
Blade Radius deformation at 5000rpm = 1.375in
Blade Depth deformation at 5000rpm = 1.125 + .50 = 1.625in

REFERENCE:
TRD RINGED FAN AND TRD SPACER
Ring to Radiator (12 o'clock position) = 1.125
Blade deformation at 5000rpm = 0

Now, with this data, let's delete the Spacer

NO SPACER
Stock blade to Radiator = 1.125 + .75 = 1.875in
Depth of deformation at 5000rpm = 1.625
Clearance Blade to Radiator at 5000rpm = .250


Let's round the numbers to accomodate vortex, luck, fan placement in shroud, etc. A stock fan blade on a stock truck has approx 1/2in clearance to the radiator core at 5000rpm.

My Conclusion:
TRD specifies the ringed fan so that the Radius Deformation and Depth Deformation = 0. So, with a TRD spacer, the Fan>Radiator clearance is 1.125 at 5000rpm, and without the TRD spacer the Fan>Radiator Clearance is 1.875in at 5000rpm

Dan, I don't have the specifics on the fan you are recommending, but I really doubt that *any* non ringed fan will have 'more' clearance under load than the ringed fan TRD specifies. With .75in spacer your critical dimension is 1.125in at 12 o'clock.

I'm much more comfortable with a Ringed Fan keeping the blades without deformation away from my radiator. I'd come to this conclusion with or without Spacer > with or without supercharger.

Maybe you can find something I am missing here. I'm with Phil, what's the fan blade tip to Radiator Clearance on the 65020? Given the blade depth deformation number, I'm not sure I'd want the stock fan on a stock truck.

Scott Justusson
6 blades of 8 now trimmed off my new stock fan...

 

[semlin]

2. change the amount of oil

The only advantage that I see here is having more fluid in circulation it's less stressed and may not breakdown? There is probably little or no direct performance benefit, but may have a long term durability benefit.

isn't more oil going to mean less turbulence and more pressure in the reservoir so that more oil leaves the reservoir at a given temperature leading to a greater degree of lockup? There is obviously a minimum amount of oil required to drive the pump so it must have some significance and i think landtank's experience is that with more oil he got more cooling so I would postulate that increasing the amount of oil increases the amount of oil leaving the reservoir at a given temperature and that in turn increases the degree of lock up, at least for a while, beyond factory levels. Presumably Toyota chose that level for some optimized goal but it may not have been our goal.

one concern about 10,000 cst oil would be that higher viscosity oil will not flow as well so less oil will leave the reservoir as the holes open. This could mean that at the early stages the clutch locks up less or more slowly at 10,000 cst than at 3000 cst oil at a given temperature. For this reason, I am thinking that
a full reservoir of 3000 cst might make more sense than a factory fill reservoir of 10,000 cst, while a full reservoir of 10,000 cst might not provide significant noticeable benefits over 3000 cst because it would chiefly outperform the 3000 cst at "wide open" higher temps and might even let the engine get hotter before it kicked in effectively. Given landtank's results with a full reservoir of 3000 cst where he does not approach higher temps, I am of the "if it ain't broke" point of view and skeptical about the utility of 10,000 cst until someone provides some data points.

 

[Tools R Us]

Shorter blades doesn't necessarily mean less air, it's the shape of the blade that will dictate that.

Blade cord and pitch are important in blade design, with those things relatively equal a larger diameter fan is always more powerful. Fans make the majority of their power about 2/3 of the way out on their blades, the larger the diameter the larger the sweet spot and swept area. One large fan is almost always more powerful and efficient than multiple smaller ones.

In fact, if the blades were optimized for flow, they will flex more.

It has nothing to do with "optimized for flow" unless the blade is designed to flex. It's about materials selection, I have seen very big, nicely optimized carbon fiber fans that don't flex at all.

Remember too, A supercharger has a .75in spacer that moves the fan that much closer to the radiator. I suspect when this is done, the fan sits further in the shroud, reducing the turbulence in the shroud, and causing the fan blades to move toward the radiator.

Moving the blade into the shroud increases the turbulence in the shroud, reducing the efficiency and power of the fan, causing the blades to flex less.

I measured and reported all this several months ago. I ate 3 fans before I decided to clip what I had. The flex is pretty dramatic ~3in IIRC. What I found was the heavier fluid and/or the high rpms (4500+) caused blades to eat the radiator core.

With or without the fan shroud and what viscosity do you change out to in your clutch? The stock fan is only ~2" from the face radiator, closer to the lower tank, so if it were flexing 3" at 4500 rpm most all of us would be eating radiators.

The theory was postulized that the stock fan shroud was the problem. I removed it, still had interference fan flex. Which also appeared to give me an indication that the shroud wasn't really needed to pull air. Also giving me the indication that the fan would have flexed more, had the radiator not impeded that with interference. BTW, I ran with 2 blades clipped from Steamboat, then ended up clipping more when the below happened...

Radiator fans are actually classified as shrouded blowers in the fan world. The fan is designed with big cord and pitch to allow it to work throughout a large RPM range. The shroud is to limit the air that the fan sees to the air that is needed to do the work. By removing the shroud the fan is uncontrolled, it will pull from wherever is easiest. It will move much higher CFM, flex more, take a bunch more horsepower, with most of the air being pumped in a circle from the front to the backside of the fan. Wasting a bunch of power mixing up the air under the hood and doing very little to cool the system.