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Which fan pulls more air, the 9 blade plastic fan or the 6 blade aluminum fan (shown in the wsm)? Are there different years that these different designs were installed?
Really depends on the conditions, as each operates as-needed.
Main fans are all clutch driven up to 85, then electric driven.
I also think cars up to 85 only had an elec pusher fan, if they only had AC to help keep the coils cool.
I mean, at a given rpm, which moves more air? There are 3 sets of two blades separated by a space on the aluminum fan where as the plastic fan has 9 blades somewhat equally spaced.
The clutch fan works off of temperatures seen from the radiator, its slipping or not..and everywhere in between.
HP is being spent on moving air or not, and everything in between.
The pusher, only works with the AC on (sometimes based on R12 temp), and then secondarily based on radiator temp, and also on air intake temp (85-86)...so not even comparable to the AL fan at all. Its a helper fan, at best, depending which system wants help.
But ok, which moves more air? The AL fan, at high temps when the clutch is fully locked...at not at _some_ level of slip.
Just to clarify a bit - there are 2 different belt driven fan types that were used with the viscous clutch. Early cars were 6 blade aluminum, later cars (up to 86) were 9 blade plastic (my 84 Euro has the 9 blade plastic belt driven fan with viscous clutch). I am not sure what year the switch was from 6 blade aluminum to 9 blade plastic (PET lists same part number 928 106 137 01 for 78 - 86).
In addition to the belt driven fan, there is also a pusher fan in front of the A/C condenser (of various shapes and sizes over the years), but I don't think the pusher is the subject of Walt's question.
I think he is wondering which of the 2 belt driven fan versions push more air at a given RPM (such as on a test rig).
I'm literally snacking on popcorn as I read this....really!
However, these "which one is better" threads are such a "hoot" to follow, on a Forum where everyone thinks that whatever they did is the 110% perfect solution, regardless of reality.
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
I'm actually eating Cracker Jacks. But sensed some confusion by cross-pollinating belt driven and pusher fan comparisons, and tried to clear up the question at hand. So, the basic question is which of the 2 belt driven fan types push more air, all other variables equal?
I don't really care, as my "factory installed 9 blade plastic belt driven by viscous clutch" fan works just fine in my car, for which it was originally intended, and I suspect that if a particular car originally had the 6 blade aluminum fan, it too works just fine.
I'm literally snacking on popcorn as I read this....really!
However, these "which one is better" threads are such a "hoot" to follow, on a Forum where everyone thinks that whatever they did is the 110% perfect solution, regardless of reality.
Just to clarify a bit - there are 2 different belt driven fan types that were used with the viscous clutch. Early cars were 6 blade aluminum, later cars (up to 86) were 9 blade plastic (my 84 Euro has the 9 blade plastic belt driven fan with viscous clutch). I am not sure what year the switch was from 6 blade aluminum to 9 blade plastic (PET lists same part number 928 106 137 01 for 78 - 86).
In addition to the belt driven fan, there is also a pusher fan in front of the A/C condenser (of various shapes and sizes over the years), but I don't think the pusher is the subject of Walt's question.
I think he is wondering which of the 2 belt driven fan versions push more air at a given RPM (such as on a test rig).
Does it matter when there wasnt a flow issue to begin with, because there is no "flow" number behind a temp activated clutch..it moves "enough" as needed.
This was likely, I think, a materials cost issue in the change...hence the same part number.
Does it matter when there wasnt a flow issue to begin with, because there is no "flow" number behind a temp activated clutch..it moves "enough" as needed.
This was likely, I think, a materials cost issue in the change...hence the same part number.
Agree with both points.
My participation here was to seek clarity in the OP question, and basic curiosity as to if the different designs have any know performance differences. I'm not seeking to solve a problem I don't have.
Speedtoys, I want some of what you are having. You dont seem to lock on to the point of the question. To clarify another posters comment, it was a question of volumetric efficiency, not hoping what I did was 110% better.
SO, even though there is no "given rpm" if the respective fans were bolted to a direct drive test rig at the same rpm, which one would flow more air? Can we make the assumption that the pitch is identical? Can we assume that the factory calculated the same or more flow with more blades and heavier materials for some reason? The aluminum fan is lighter than the steel and plastic version as a point of fact.
Thank you BRB-83-911SC. You make me realize that I do speak and write in English after all.
07-24-2018, 01:20 PM
Fan performance
