Cooling fan shootout - Engine Masters

[lc-gtr-1969]

That belt is 1/2 or 5/8 inch wide. How much power goes to propelling the mower vs. turning the blades?

Come on people, look at the 5 HP electric motor on your shop air compressor, do you see two 5/8" belts? A 3/8" V belt is not going to deliver anywhere close to 30 HP and last 50,000 miles.

If you do not believe the data, an if you have access to a dyno- why don't you spend 30 minutes to run up a car and remove the mech. fan and post before and after data? I am sure plenty would be interested.

See, this is what happens when you don't read the whole thread and just jump right in with a kneejerk reaction instead of applying you maff skilzz. 1 HP = 746 Watts. 30 HP = 22371 Watts / 12 V = 1,864.25 Amps. A large electric fan assembly listed in Summit which has two fans/motors is rated at 50 amps. 50A x 12V = 600 Watts 1 HP = 746 Watts. It is ridiculous to think a fan driven by a single 3/8" belt is absorbing 30 HP.

I'm sorry, but am I the only one who thinks that 30 HP to turn a fan is absurd? So, I would need to take a very powerful 30 HP electric motor that spins the fan up to speed (either directly or by gearing it up) to move the same amount of air as the same fan being spun by an engine? Does that seem reasonable to anyone?

Not reasonable at all, 30 HP is just nuts, yellow journalism. 30 HP = 22371 Watts / 12 V = 1,864.25 Amps. Who wants to try again?

Once upon a time on a chassis dyno on a hot summer day with a 355 SBC short-track car that had no fan at all it started getting warmer than ideal with just a 110V squirrel cage fan blowing at it so we put one of those molded black plastic fans on it about 12"-14" diameter and it did not change the RWHP at all but it did cool the engine just fine so we left it on and made a shroud out of one of the shop's Rubbermaid trash cans that serendipitously was the perfect size, length and diameter, when cut short and attached with tranny cooler zip ties through the heater core and the lip of the trash can.

Just FYI, I did read the whole thread and you have made a large assumption of a knee jerk reaction.

So, where is your own data? Not theoretical data but real test data. I am genuinely curious.

I follow the engine masters program and they appear to run very well planned scientific tests, but if someone was willing to spend the time with real world actual testing, it would be great to either prove or disprove the theory.

And no, it's not 'maffs skilzz' that will tell you the answer because you have too many variables values placed upon assumptions. You do not know the parasitic drag from the belt, fan blades, bearings etc, but have rather presumed it (unless I am mistaken). You may be correct but when you are plucking frictional drag values out of thin air, it leaves people, quite rightly, skeptical.

Run the data on a dyno, same oil temps same air temps and post back here... I think it would be very interesting.

[Tuner]

How many time can I tell you we put a 14" plastic fan on a 355 SBC short track car on a chassis dyno and it didn't change the RWHP at all. The fan belonged to the dyno owner so we removed it when done and made another pull and same result, no change in RWHP at all. Don't ask me why, you make up a reason why, but it had no effect on RWHP at all and it did cool the engine.

Do you know anything about snowmobiles or golf carts? Do you really think a 3/8" fan belt can transmit 30 HP?

[dannobee]

I guess that settles it then. You don't believe us that it takes 30hp to run some fans at high engine speeds, and we don't believe you that you've found a perpetual motion fan that can cool down a race engine without using any power.

[Tuner]

And I don't believe you have much actual experience with the same engines run on engine dynos and chassis dynos, the same engine run on each, first one and then the other.

My example above was a manual transmission car, so no confusion in the chassis dyno smoke and mirror parlor trick about how much is lost in the torque converter and it had plenty of tire, 10" Hoosier asphalt slicks, so no slippage there.

Search this and other forums for bafflement about why there is so much difference between engine and chassis dnyo HP. Correction factors are meaningless, the HP at the tire just is what it is.

The fan did not change the measured power on the chassis dyno at all, when put on or taken off, zip, none. If you don't like that, try it yourself some time.

[Circlotron]

How many time can I tell you we put a 14" plastic fan on a 355 SBC short track car on a chassis dyno and it didn't change the RWHP at all. The fan belonged to the dyno owner so we removed it when done and made another pull and same result, no change in RWHP at all. Don't ask me why, you make up a reason why, but it had no effect on RWHP at all and it did cool the engine.

Maybe the cooler engine made as much extra power as the fan absorbed?

[lc-gtr-1969]

Tuner- it is plausible that your test showed no power loss to a fan, but basic research methodology required one to consider confounding variables- or factors that could influence the data without being obvious. It is always something that needs to be considered in R&D.

Here is a quick video;
https://www.youtube.com/watch?v=rCsH6ta3r40

Low revving pickup made just under 5hp by removing the fan, with the results shown across the rev range.

[Tuner]

Tuner- it is plausible that your test showed no power loss to a fan, but basic research methodology required one to consider confounding variables- or factors that could influence the data without being obvious. It is always something that needs to be considered in R&D.

Here is a quick video;
https://www.youtube.com/watch?v=rCsH6ta3r40

Low revving pickup made just under 5hp by removing the fan, with the results shown across the rev range.

Did you actually watch that vid? Did you notice at the end where the "expert" said the 4 HP loss measured at the tire would be 8 or 10 HP at the engine?

Who actually thinks from engine to chassis dyno there is a loss of 50% HP?

To do this right it is necessary to remove and replace the fan a few times to see what repeats.

An engine will gain at least 4 HP just from getting the oil temp over 240 F.

[lc-gtr-1969]

In all honesty, I get the impression we could find 100s of tests that show losses with using an engine fan, but you will ignore the data. There's no science in that.

It is common sense and simple physics that the greater the parasitic drag on an engine, the more hp is loss to overcome this drag.

Is turning a mechanical fan a parasitic drag? Yes. Does running an electric fan increase parasitic drag? Yes (through alternator load)- however, the rpm of the electric fan is stabilised where the mechanical is relative to rpm, whilst also is typically a more inefficient design (from a drag perspective), albeit a more efficient design when it comes to moving air. Nonetheless, the extra parasitic load from the mechanical fan is plausible to result in a degree of hp loss. Categorically denying this is just nonsense- especially when there is a plethora of data available.

[n2omike]

In all honesty, I get the impression we could find 100s of tests that show losses with using an engine fan, but you will ignore the data. There's no science in that.

It is common sense and simple physics that the greater the parasitic drag on an engine, the more hp is loss to overcome this drag.

Is turning a mechanical fan a parasitic drag? Yes. Does running an electric fan increase parasitic drag? Yes (through alternator load)- however, the rpm of the electric fan is stabilised where the mechanical is relative to rpm, whilst also is typically a more inefficient design (from a drag perspective), albeit a more efficient design when it comes to moving air. Nonetheless, the extra parasitic load from the mechanical fan is plausible to result in a degree of hp loss. Categorically denying this is just nonsense- especially when there is a plethora of data available.

Exactly. If you want the most power to the rear wheels, you use an electric fan. Parasitic losses go up significantly with RPM. Engine driven fans are designed to pull ample air at near idle engine speeds. Revving them up to 5k+ RPM creates incredible drag. Electric fans are designed to consume a set amount of power to move ample air, and do not go into the 'retard zone' of parasitic drag by spinning 5X as fast as needed like the engine driven units. Losses from electric fans can be easily calculated by their amp draw. Power (Watts) = Volts x Amps.... and 1 HP = 746 Watts.

This all being said, I remember when I was street racing with an engine driven fan... and would loosen the fan belt as much as possible. The fan and water pump still seemed to spin fast enough for short term use while reducing losses as much as possible.

[Tuner]

Car Craft, May 2000, p50-51. Fan dyno test.

No fan 496hp
Black Magic fan, running 494hp
plastic fan 460hp
flex fan 466hp
hi-perf flex fan 476hp
6-blade rigid fan 449hp
non-thermal clutch fan 485hp
4-blade rigid fan 473hp
HD thermal clutch fan 476hp
thermal clutch fan 487hp

[GuysMonteSS]

I would like to know how much parasitic loss there is with a clutch fan that is just freewheeling and not engaged.
From my own experience with my car,I can hear when the fan engages.
But,this very seldom happens,and never when going down the road.
Is there horsepower loss when not engaged ??
Guy

[NewbVetteGuy]

In all honesty, I get the impression we could find 100s of tests that show losses with using an engine fan, but you will ignore the data. There's no science in that.

It is common sense and simple physics that the greater the parasitic drag on an engine, the more hp is loss to overcome this drag.

Is turning a mechanical fan a parasitic drag? Yes. Does running an electric fan increase parasitic drag? Yes (through alternator load)- however, the rpm of the electric fan is stabilised where the mechanical is relative to rpm, whilst also is typically a more inefficient design (from a drag perspective), albeit a more efficient design when it comes to moving air. Nonetheless, the extra parasitic load from the mechanical fan is plausible to result in a degree of hp loss. Categorically denying this is just nonsense- especially when there is a plethora of data available.

Exactly. If you want the most power to the rear wheels, you use an electric fan. Parasitic losses go up significantly with RPM. Engine driven fans are designed to pull ample air at near idle engine speeds. Revving them up to 5k+ RPM creates incredible drag. Electric fans are designed to consume a set amount of power to move ample air, and do not go into the 'retard zone' of parasitic drag by spinning 5X as fast as needed like the engine driven units. Losses from electric fans can be easily calculated by their amp draw. Power (Watts) = Volts x Amps.... and 1 HP = 746 Watts.

This all being said, I remember when I was street racing with an engine driven fan... and would loosen the fan belt as much as possible. The fan and water pump still seemed to spin fast enough for short term use while reducing losses as much as possible.

Run that same electric fan (which is usually significantly lighter and smaller in diameter than an engine-driven fan, in addition to running at much lower max RPM) with a modern dynamic control strategy such that the fan shuts off after 40 mph -then from 40 mph+ your parasitic loss is ZERO. How many watts are consumed across the entire 1/4 mile pass vs. the mechanical fan?


Adam

[NewbVetteGuy]

No fan 496hp
Black Magic fan, running 494hp
thermal clutch fan 487hp
non-thermal clutch fan 485hp
HD thermal clutch fan 476hp
hi-perf flex fan 476hp
4-blade rigid fan 473hp
flex fan 466hp
plastic fan 460hp
6-blade rigid fan 449hp


Reordered from least loss to greatest loss.
Good find.

Adam

[ClassAct]

Car Craft, May 2000, p50-51. Fan dyno test.

No fan 496hp
Black Magic fan, running 494hp
plastic fan 460hp
flex fan 466hp
hi-perf flex fan 476hp
6-blade rigid fan 449hp
non-thermal clutch fan 485hp
4-blade rigid fan 473hp
HD thermal clutch fan 476hp
thermal clutch fan 487hp

What is the “Black Magic” fan? Never heard of that.

[Rick!]

Car Craft, May 2000, p50-51. Fan dyno test.

No fan 496hp
Black Magic fan, running 494hp
plastic fan 460hp
flex fan 466hp
hi-perf flex fan 476hp
6-blade rigid fan 449hp
non-thermal clutch fan 485hp
4-blade rigid fan 473hp
HD thermal clutch fan 476hp
thermal clutch fan 487hp

What is the “Black Magic” fan? Never heard of that.

It appears to be a Flex a Lite electric fan.

To the one poster that related to the power draw of the fan to v³, here is a link to the fan laws.
Turns out that Power draw is related to (new RPM/old RPM)³.
It also turns out that Power draw is related to (new Diameter/old Diameter)⁵