Don Terrill’s Speed-Talk

I see that this Car Craft dyno test I posted

Tuner wrote: ↑Wed May 12, 2021 1:51 pm 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

.... and NewbVetteGuy thoughtfully arranged in order by HP loss

NewbVetteGuy wrote: ↑Wed May 12, 2021 4:57 pm 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

is the same Car Craft dyno test in the post BOOT made on the first page
viewtopic.php?p=893784#p893784

Other than difference in dynos and dyno operator techniques, such as dyno setting for control of specific acceleration rate and correction factors, what accounts for the large disparity between the two dyno tests in maximum HP loss of the factory solid six blade steel fan, 30 HP in the OP video and almost 50 HP in the magazine article?

Simple math. One engine is at higher rpm, and fan power used is a cube function of rpm ratio (said delta earlier but meant ratio, I used the wrong word - sorry). The pull without the rad was 22 hp down, 5000 rpm, and convert that to 6200 rpm and it's 42 hp down. Pretty close to the 46 in the old CC article, and with all the variables that's pretty close. Obviously the cube of the rpm ratio is a huge factor - we don't know the actual fan rpm and it's a different engine.

And of course there might be some pulley slippage. Gotta agree it's pretty hard to stomach the belt being able to transmit that much power (who knows how long it can) but the math and physics is good, and it all makes sense. No question a mechanical fan at high rpm eats a lot of power - you don't even need to test to know that.

I have not run a mechanical fan on a performance car ever. Daily driver is a different story.

Good you mention ratio, how about the pulley diameter ratios? Looks like a lot of overdrive to me in both tests and significantly more so in the magazine article test (at least visually).

Why didn't they try some "Magic Billet" underdrive pulley action, or would that make it more difficult to sell electric fans?

BTW, the short track car example I mentioned where we saw no power loss at all with the plastic fan on the chassis dyno had a small diameter "underdrive" billet crank pulley.

Since in the obvious effort to sell electric fans we are doing spurious dyno testing of fans for performance cars with more pulley overdrive than a rational person would use on their performance car, why don't we do an actual useful dyno test of how much RPM causes a fan to fly apart. How much overdrive can the fan stand before it launches a blade or two and kills someone.

Because simple high RPM is the only necessity we could save wear and tear on the dyno mule by using an electric motor but that wouldn't be as dramatic.

If you haven't seen a few fans lose a blade or two in your lifetime you need to get out more.

https://buffalonews.com/news/danger-in- ... 27204.html
An engine-cooling device known as the flex fan has killed or maimed at least 80 people across the country since it was introduced in General Motors pickup trucks manufactured in the 1970s.

The fatalities and injuries occurred when blades broke off while the engines were running, hurtling jagged pieces toward people who were either working on the engines or standing nearby.

The victims have included a 15-year-old Florida boy who bled to death, a California man injured when a fan blade became embedded in his upper body, and an Alden man who lost an eye to the flying metal.

GM insists that the blades, installed in about 2.6 million of its pickup trucks from 1973 to 1979, are safe. But a Buffalo News investigation of the fan blade accidents turned up many people who believe otherwise, including several victims, consumer safety proponents, mechanics and an expert on fan engineering.

https://www.nytimes.com/1977/09/02/arch ... -ford.html

Beating this dead horse...

Electric fans are installed on ALL new cars because they are more efficient. Period.
Engine driven fans provide ample airflow at IDLE SPEEDS. Spinning them faster causes them to consume FAR more power than necessary.
It truly is that simple.
If you want to get max power to the rear wheels, an electric fan is what you use.

If you want to pulley an engine driven fan (and water pump) to where it turns at a fraction of engine speed in order to keep it from robbing too much power, then the car will likely overheat at idle in traffic... and will STILL consume more power than an electric when the engine is at full song.

Can a V-belt transmit 30 hp? Yes. Hit a stump/dirt/rock with your belt driven lawnmower, and watch it stall the engine... and they don't even have the belts all that tight.

electric fans are certainly more efficient when sized correctly. The OEM ones are way more powerful than the aftermarket ones which are toys in comparison.

Most new cars have engines mounted across the frame...A mechanical fan would be impractical...Not to say that electric fans are not an improvement...Do new PU trucks have electric fans?

Truckedup wrote: ↑Mon May 17, 2021 6:11 pm Most new cars have engines mounted across the frame...A mechanical fan would be impractical...Not to say that electric fans are not an improvement...Do new PU trucks have electric fans?

GM switched to electric fans on most of their trucks about 15 years ago.

Truckedup wrote: ↑Mon May 17, 2021 6:11 pm Most new cars have engines mounted across the frame...A mechanical fan would be impractical...Not to say that electric fans are not an improvement...Do new PU trucks have electric fans?

My Ecodiesel has an electric fan, pretty large diameter, along with shutters to decrease drag thru the radiator.
Coolant runs 210-215, oil runs up to 234 when towing 5000bs, 216ish without towing.

Former Taurus fans and controllers used to be popular items for some hot rodders, maybe not so much anymore since Ford killed the breed.

n2omike wrote: ↑Mon May 17, 2021 11:38 am Beating this dead horse...

Electric fans are installed on ALL new cars because they are more efficient. Period.
Engine driven fans provide ample airflow at IDLE SPEEDS. Spinning them faster causes them to consume FAR more power than necessary.
It truly is that simple.
If you want to get max power to the rear wheels, an electric fan is what you use.

If you want to pulley an engine driven fan (and water pump) to where it turns at a fraction of engine speed in order to keep it from robbing too much power, then the car will likely overheat at idle in traffic... and will STILL consume more power than an electric when the engine is at full song.
Can a V-belt transmit 30 hp? Yes. Hit a stump/dirt/rock with your belt driven lawnmower, and watch it stall the engine... and they don't even have the belts all that tight.

Sure enough beat a dead horse, and the dead horse is intentionally skewed dyno tests to lure the gullible into buying black magic à la mode, whatever whichever advertiser desires hyped, whether it is fans, cams, rocker arms, headers, intake manifolds or carburetors vs. EFI.

Except for a truck with low engine RPM, nobody in their right mind would use 50% overdrive on the water pump and fan on a performance vehicle.

Tuner wrote: ↑Mon May 17, 2021 9:15 pm

n2omike wrote: ↑Mon May 17, 2021 11:38 am Beating this dead horse...

Electric fans are installed on ALL new cars because they are more efficient. Period.
Engine driven fans provide ample airflow at IDLE SPEEDS. Spinning them faster causes them to consume FAR more power than necessary.
It truly is that simple.
If you want to get max power to the rear wheels, an electric fan is what you use.

If you want to pulley an engine driven fan (and water pump) to where it turns at a fraction of engine speed in order to keep it from robbing too much power, then the car will likely overheat at idle in traffic... and will STILL consume more power than an electric when the engine is at full song.
Can a V-belt transmit 30 hp? Yes. Hit a stump/dirt/rock with your belt driven lawnmower, and watch it stall the engine... and they don't even have the belts all that tight.

Sure enough beat a dead horse, and the dead horse is intentionally skewed dyno tests to lure the gullible into buying black magic à la mode, whatever whichever advertiser desires hyped, whether it is fans, cams, rocker arms, headers, intake manifolds or carburetors vs. EFI.

Except for a truck with low engine RPM, nobody in their right mind would use 50% overdrive on the water pump and fan on a performance vehicle.

I run a 50% underdrive pulley on my car at times. Last year when I put the 2nd set of Vortec heads on my 406 I was running my 30% pulley and the car ran 11.02 off the trailer, went back to the pits and put the 50% pulley on the car cooled it off a bit and ran 10.92 with no other changes so the smaller pulley does work and have always picked up at least a tenth with it.

n2omike wrote: ↑Mon May 17, 2021 11:38 am Beating this dead horse...

Electric fans are installed on ALL new cars because they are more efficient. Period.
Engine driven fans provide ample airflow at IDLE SPEEDS. Spinning them faster causes them to consume FAR more power than necessary.
It truly is that simple.
If you want to get max power to the rear wheels, an electric fan is what you use.

If you want to pulley an engine driven fan (and water pump) to where it turns at a fraction of engine speed in order to keep it from robbing too much power, then the car will likely overheat at idle in traffic... and will STILL consume more power than an electric when the engine is at full song.

Can a V-belt transmit 30 hp? Yes. Hit a stump/dirt/rock with your belt driven lawnmower, and watch it stall the engine... and they don't even have the belts all that tight.

My sentiments exactly. Well put.

Truckedup wrote: ↑Mon May 17, 2021 6:11 pm Most new cars have engines mounted across the frame...A mechanical fan would be impractical...

First gen Minis had the radiator at the left side of the engine bay with the belt-driven fan blowing through it and into the wheel well, but they were an exception. The less electrics on an old English car the better! Electric fan makes lots of sense for east-west engines.

Has the equivalent of the viscous fan coupler been used on the water pump pulley?