I have reviewed the threads on radiator fans, and have done some preliminary studies on the 3 busted ones I now own. It would appear that many theories abound on which fan is better and why, not sure many of them reflect current theory and practice with regard to their application. I am going to specifically address the SC application, because it appears that the spacer required on the clutch thermo makes blade placement and load flex critical.
First off, I'm fairly new to this board, but have extensive cooling management experience in turbocharged applications. Included in that is a 7500rpm stock VC ringed fan application in the 20valve turbo cars (many tweeked run in excess of 8000prm). Hence, I came to the conclusion years ago, that a ringed fan beats a 'free floater' type any day.
The 3 fans I have in my shop are 1 trimmed stocker, 1 to be trimmed (new) stocker, and the TRD (CD "old v6 app") unit supplied with the Supercharger.
Myth #1
The number of fan blades means more airflow. With the same size fan blades of two free floaters, it's more likely that the one with more blades moves more air at a lower rpm, than the one with less blades. Fan blades are wings with high pressure zones and low pressure zones, which should also be considered 'barriers' at some speed (we don't have any data 'yet' as to what speed that is).
Myth #2
A ringed fan moves less air than a non ringed fan. The ring itself really shouldn't matter IMO/E. In fact, if you look at the early v6 design, toyota did more than most manufacturers in designing a reverse velocity stack into the ring, impressive to me (even audi doesn't do that). This means that there is a diverter nozzle at the end of the blade tips which funnels high pressure air (pre fan) into a low pressure zone (post fan). Given 2 fans of equal diameter, the blade design and count, not necessarily the ring presence, will dictate airflow for any given rpm.
Myth #3
'Free floating' fans are better than ringed fans. The key to consistency of airflow is the shape of the wing. I can take a brand new factory fan and deform the blades with very little effort. Change the shape of a wing, it will change the characteristics of airflow, usually, not for the better. I could drop a brick on the ringed fan and those blades won't budge. If Toyota's goal was to reduce blade flex to optimize it's wing properties: The ringed fan meets that goal with extreme prejudice, the 'free floater' fails with very little pressure. Optimize the diverter nozzle design into the ring, airflow should actually be better vs a free floater type.
Myth #4
Fans need to address all engine speeds. Interesting to note that the boys at Land Rover did some interesting tests on radiator and airflow. The conclusions of that testing summarized that above ~45mph, a rover fan won't 'draw' more air. IOW, the cores themselves prevent air flows (hi to low pressure zones pre and post core respectively) beyond a certain point (this can be calculated just like a IC core flow). After that point a shroud and a fan can become more of a hinderance to airflow than without the presence of either. This can happen because of a speed vortex in the fan design (i.e. too many blades vs rpm), or because after 45mph, the best low pressure zone behind a radiator is just nothing behind it.
What to do? I suppose some complicated tests might be in order (Scamper and Gumby were on that thread), or we could prioritize the fit for use (practical engineering). I'm a practical engineer, and failure analysis kind of guy. I see a couple of issues with the threads to date. I know that the 80 series has some phenomenal cooling capacity, so the 'ultimate' fan really isn't necessary. I know that because I drove over 100 track miles and 1200 road miles with no fan or shroud, and some 6 radiator cores blocked off, and my temps never waivered from normal. So, my primary goal is my target: Give me a fan that doesn't deform at high rpm.
The design of the blades between the free floater stocker and the TRD (early v6) are all but identical, in shape and design. That indicates to me that the ringed fan has some distinct advantages, especially at high rpm, where the free floater is known to fail. If you can't deform a blade, flow will be optimized up to vortex or rad flow limit. I suppose we could theorize that the free floating fan design is 'meant' to deform in a good way to allow better flow at higher rpm. Problem, fan blade designs don't appear to be any different. I personally think it's cheaper to build a free floater.
The tests conducted to date, and the resulting conclusions lack some validity IMO. I would expect to find a vortex within a fan blade design, because, just like a turbo, air velocity and pressure is highest at the outer tip of the blades (compressor or turbine theory). Looking at a ringed fan and a freefloater of the same blade design, I find it almost impossible to believe that one could find a difference in 'vortex testing' between the two. For a specific rpm, maybe, but somewhere in that testing of rpm vs vortex (in fact contrary to the posts, the 8 blade fan should 'vortex' sooner in the rpm range), the 7 blade fan will outperform the 8 blade.
Ringed or not, the fan blade designs on both the early and late style are identical, and quite well engineered. Most aftermarket fan blades aren't wing shaped, and many actually 's' curve the blades to reduce noise (which also reduces airflow significantly). Given the threads to date show that we are speaking of less than 5mm clearance between fan models, I'm thinking the beefier ringed fan is desired over the non ringed variety. This design should yield better airflow over a wider rpm due to less deformity of the bade, and a better inverted nozzle design inherent in the ring. So, until we get further data to the contrary, I propose we are really 'only' speaking to the clearance issue of the fan to the shroud/core, not really a performance issue.
I think TRD spec'd the correct fan for the application, but maybe forgot that the shroud needs to be replaced, modified or removed.
Hope this generates some food for thought. I also have read up on the thermostat opinions as well, and can share a lot of real world data on this too (Stock thermostats - oil and water on all turbo audis - including race cars). I'll refrain for now, since I can barely keep up with responses on a single thread...
Scott Justusson
FZJ80 kazuma
modded and field balanced 8blade stocker for now...
First off, I'm fairly new to this board, but have extensive cooling management experience in turbocharged applications. Included in that is a 7500rpm stock VC ringed fan application in the 20valve turbo cars (many tweeked run in excess of 8000prm). Hence, I came to the conclusion years ago, that a ringed fan beats a 'free floater' type any day.
The 3 fans I have in my shop are 1 trimmed stocker, 1 to be trimmed (new) stocker, and the TRD (CD "old v6 app") unit supplied with the Supercharger.
Myth #1
The number of fan blades means more airflow. With the same size fan blades of two free floaters, it's more likely that the one with more blades moves more air at a lower rpm, than the one with less blades. Fan blades are wings with high pressure zones and low pressure zones, which should also be considered 'barriers' at some speed (we don't have any data 'yet' as to what speed that is).
Myth #2
A ringed fan moves less air than a non ringed fan. The ring itself really shouldn't matter IMO/E. In fact, if you look at the early v6 design, toyota did more than most manufacturers in designing a reverse velocity stack into the ring, impressive to me (even audi doesn't do that). This means that there is a diverter nozzle at the end of the blade tips which funnels high pressure air (pre fan) into a low pressure zone (post fan). Given 2 fans of equal diameter, the blade design and count, not necessarily the ring presence, will dictate airflow for any given rpm.
Myth #3
'Free floating' fans are better than ringed fans. The key to consistency of airflow is the shape of the wing. I can take a brand new factory fan and deform the blades with very little effort. Change the shape of a wing, it will change the characteristics of airflow, usually, not for the better. I could drop a brick on the ringed fan and those blades won't budge. If Toyota's goal was to reduce blade flex to optimize it's wing properties: The ringed fan meets that goal with extreme prejudice, the 'free floater' fails with very little pressure. Optimize the diverter nozzle design into the ring, airflow should actually be better vs a free floater type.
Myth #4
Fans need to address all engine speeds. Interesting to note that the boys at Land Rover did some interesting tests on radiator and airflow. The conclusions of that testing summarized that above ~45mph, a rover fan won't 'draw' more air. IOW, the cores themselves prevent air flows (hi to low pressure zones pre and post core respectively) beyond a certain point (this can be calculated just like a IC core flow). After that point a shroud and a fan can become more of a hinderance to airflow than without the presence of either. This can happen because of a speed vortex in the fan design (i.e. too many blades vs rpm), or because after 45mph, the best low pressure zone behind a radiator is just nothing behind it.
What to do? I suppose some complicated tests might be in order (Scamper and Gumby were on that thread), or we could prioritize the fit for use (practical engineering). I'm a practical engineer, and failure analysis kind of guy. I see a couple of issues with the threads to date. I know that the 80 series has some phenomenal cooling capacity, so the 'ultimate' fan really isn't necessary. I know that because I drove over 100 track miles and 1200 road miles with no fan or shroud, and some 6 radiator cores blocked off, and my temps never waivered from normal. So, my primary goal is my target: Give me a fan that doesn't deform at high rpm.
The design of the blades between the free floater stocker and the TRD (early v6) are all but identical, in shape and design. That indicates to me that the ringed fan has some distinct advantages, especially at high rpm, where the free floater is known to fail. If you can't deform a blade, flow will be optimized up to vortex or rad flow limit. I suppose we could theorize that the free floating fan design is 'meant' to deform in a good way to allow better flow at higher rpm. Problem, fan blade designs don't appear to be any different. I personally think it's cheaper to build a free floater.
The tests conducted to date, and the resulting conclusions lack some validity IMO. I would expect to find a vortex within a fan blade design, because, just like a turbo, air velocity and pressure is highest at the outer tip of the blades (compressor or turbine theory). Looking at a ringed fan and a freefloater of the same blade design, I find it almost impossible to believe that one could find a difference in 'vortex testing' between the two. For a specific rpm, maybe, but somewhere in that testing of rpm vs vortex (in fact contrary to the posts, the 8 blade fan should 'vortex' sooner in the rpm range), the 7 blade fan will outperform the 8 blade.
Ringed or not, the fan blade designs on both the early and late style are identical, and quite well engineered. Most aftermarket fan blades aren't wing shaped, and many actually 's' curve the blades to reduce noise (which also reduces airflow significantly). Given the threads to date show that we are speaking of less than 5mm clearance between fan models, I'm thinking the beefier ringed fan is desired over the non ringed variety. This design should yield better airflow over a wider rpm due to less deformity of the bade, and a better inverted nozzle design inherent in the ring. So, until we get further data to the contrary, I propose we are really 'only' speaking to the clearance issue of the fan to the shroud/core, not really a performance issue.
I think TRD spec'd the correct fan for the application, but maybe forgot that the shroud needs to be replaced, modified or removed.
Hope this generates some food for thought. I also have read up on the thermostat opinions as well, and can share a lot of real world data on this too (Stock thermostats - oil and water on all turbo audis - including race cars). I'll refrain for now, since I can barely keep up with responses on a single thread...
Scott Justusson
FZJ80 kazuma
modded and field balanced 8blade stocker for now...
