Cooling fan shootout - Engine Masters

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ClassicRob
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Cooling fan shootout - Engine Masters

Post by ClassicRob »

Thinking on about this vintage build I have going on and the thought of cooling the iron headed SBC started the mental cooling committee.
Researching this subject has left me unfulfilled to say the least. To break it down, the stock non clutch fixed steel fans are taking about 30hp from the engine. The next worst one was the plastic fan, which had a more aggressive fan blade pitch and it took nearly 25hp from the small block. The next one was one of the slim aluminum fans with the raked look, and it didn't do all that well either. Surprisingly the winner THEY cast was a stock fan with a thermal fan clutch. They ran the test with it but they did it with the thermal spring basically "off" which doesn't really simulate what a normal operating temp fan clutch would see.

You can watch the episode here: https://drivemag.com/video/cooling-fan- ... ters-ep-20

I know they make an RPM sensitive fan clutch (fluid filled?) that doesn't actuate the fan when the RPM's go up but I have never used one of these.


My question is simple, what are some of you guys using for your cooling fan set-up?
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Re: Cooling fan shootout - Engine Masters

Post by Rick! »

Running a fan to create airflow thru a radiator takes engine power, period.
30hp seems a bit much for an SBC but it's a data point.
You think running a fan clutch is somehow not realistic. Why?
Mopar used fan clutches on their stuff forever.
What part of not using 1HP more than what is absolutely necessary is "not real world"?
I'm not aware of any fan drives, viscous, non viscous, electric over viscous or just plain electric on-off that only respond to rpm.
Heat, whether from the radiator airflow, oil temp, CAC temp, IAT temp and coolant temp are what is used to control fan speed on higher end units.
Complicated ones use an ECU or borrow space in the engine ECU to control the amount of engagement depending on feedback.
You have mentioned you don't want an electric fan so there must be a reason or some obscure nostalgia class you're preparing for.
You're not going to get a lower parasitic draw than a plain jane thermostatic spring viscous fan drive with a stock steel bladed fan if you require the engine to spin it.
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Re: Cooling fan shootout - Engine Masters

Post by lefty o »

if you arent running electric fans, a fan with a clutch is the only way to fly. not only do oe clutch fans generally eat less horsepower, but they also cool better too.
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Re: Cooling fan shootout - Engine Masters

Post by ClassicRob »

Rick! wrote: Wed May 05, 2021 7:34 pm Running a fan to create airflow thru a radiator takes engine power, period.
30hp seems a bit much for an SBC but it's a data point.
You think running a fan clutch is somehow not realistic. Why?
Mopar used fan clutches on their stuff forever.
What part of not using 1HP more than what is absolutely necessary is "not real world"?
I'm not aware of any fan drives, viscous, non viscous, electric over viscous or just plain electric on-off that only respond to rpm.
Heat, whether from the radiator airflow, oil temp, CAC temp, IAT temp and coolant temp are what is used to control fan speed on higher end units.
Complicated ones use an ECU or borrow space in the engine ECU to control the amount of engagement depending on feedback.
You have mentioned you don't want an electric fan so there must be a reason or some obscure nostalgia class you're preparing for.
You're not going to get a lower parasitic draw than a plain jane thermostatic spring viscous fan drive with a stock steel bladed fan if you require the engine to spin it.
I don’t think the test was realistic because when a fan clutch is cold, it’s not engaged. It could be realistic in the sense you’ve cooled your car down before a pass. But I was curious about the real world loss.

Complicated ones? Complex is more like it. Modern cooling systems use an engine coolant temp sensor and radiator temp sensor. They also use a heated thermostat. Fan speeds can also be controlled with up to 3 relays. Low. Low-Med. and high.

I’m not interested in any of that and to be honest, my past vehicles with an electric fan always ran too loud and I hated hearing it over the car. These were typical thermostatic controlled on/off deals that you can adjust with a potentiometer.

I’m mostly just curious to see if you mechanical guys are running a clutch, or a flex deal.
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Re: Cooling fan shootout - Engine Masters

Post by panic »

Best CFM air movement per HP drag:
1. largest diameter blades that fit the shroud
2. turning the slowest speed
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Re: Cooling fan shootout - Engine Masters

Post by rfoll »

On a similar thread, someone suggested that the clutch fan is helped by the air pushing through the radiator, lessening the parasitic loss.
So much to do, so little time...
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Re: Cooling fan shootout - Engine Masters

Post by lefty o »

rfoll wrote: Wed May 05, 2021 9:24 pm On a similar thread, someone suggested that the clutch fan is helped by the air pushing through the radiator, lessening the parasitic loss.
dont forget a properly fitting fan shroud.
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Re: Cooling fan shootout - Engine Masters

Post by PackardV8 »

rfoll wrote: Wed May 05, 2021 9:24 pm On a similar thread, someone suggested that the clutch fan is helped by the air pushing through the radiator, lessening the parasitic loss.
Yes, No, Maybe. Fans are there to create a low pressure area behind the radiator to assist speed generated air pressure.

FWIW, in a vehicle I knew well, removing the engine driven fan raised the 65 MPH cruise coolant temperature 10 - 15 degrees. The theory that highway speed air pressure is enough depends totally on all the elements of styling, air flow, fan shrouding, engine compartment space and underbody design, to name a few.
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Re: Cooling fan shootout - Engine Masters

Post by BOOT »

Carcraft & I think another mag(other mag had more detailed dyno pulls if I rem right) did this test way back and the info is basically the same. Many of their shows are recycled mag test, some with a modern twist.

I based my setup on the mag article I had and their current test backs it up. Basically with my current pulley underdrive my plastic fan sees just bout 4000rpm MAX and when you looked at the dyno data they all lost bout 10HP or so +/- with their prob greater than 1:1 pulley ratio. The article I attached shows all bout the same ave hp for 3500-5000rpm except no-fan, e-fan, and one clutch. Think I rem them all being pretty close at 4k when I watched the video.
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Re: Cooling fan shootout - Engine Masters

Post by Steve K »

I have a dual fan Be Cool set up with an aluminum rad in my 79 Camaro with a tunnel Ram 427 SBC that makes over 600 hp and looks like a tricked out 305. It never gets hotter than 180 deg
79 Cmaro, 427 sbc, Tunnel Ram Dual Quad with Eddy carbs, AFR 210 Race Ready heads, 263-272 @.50 Comp solid roller cam, 4.10's and a faceplated Tremec TKO 600.
65 Beaumont 406 tunnel ram faceplated TKO600
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Re: Cooling fan shootout - Engine Masters

Post by ClassicRob »

BOOT wrote: Wed May 05, 2021 9:55 pm Carcraft & I think another mag(other mag had more detailed dyno pulls if I rem right) did this test way back and the info is basically the same. Many of their shows are recycled mag test, some with a modern twist.

I based my setup on the mag article I had and their current test backs it up. Basically with my current pulley underdrive my plastic fan sees just bout 4000rpm MAX and when you looked at the dyno data they all lost bout 10HP or so +/- with their prob greater than 1:1 pulley ratio. The article I attached shows all bout the same ave hp for 3500-5000rpm except no-fan, e-fan, and one clutch. Think I rem them all being pretty close at 4k when I watched the video.
Crazy to think the flex fan is supposed to be a gift from the cooling gods yet it’s literally the worst option next to a fixed fan of any type. Think of how many hot rods there are out there running these things, yet the data looks the same on every test. Flex fans are power hungry!
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Re: Cooling fan shootout - Engine Masters

Post by ClassicRob »

Which begs the question, what RPM can a fan clutch safely sustain?
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Re: Cooling fan shootout - Engine Masters

Post by lefty o »

ClassicRob wrote: Wed May 05, 2021 10:36 pm Which begs the question, what RPM can a fan clutch safely sustain?
ive spun them to 8000, but regularily shift at 7000.
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Re: Cooling fan shootout - Engine Masters

Post by barnym17 »

I would use a clutch fan, but get a good one that is thermostatically controlled as oem design. Not a cheapie replacement clutch as they eliminate the thermostatic control and simply use a preset slippage amount.
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Re: Cooling fan shootout - Engine Masters

Post by bobmc »

what is being tested by running the clutch fan cold? you need to know the drain when it's hot also, and how fast the controller responds to temp change, from a vintage perspective start with a fan from Vega aluminum engine
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