fan clutch or solid drive extension

[high perf mopar]

will be addressing carb perculation issues tomorrow with 3 phenolic spacers and insulation for fuel lines,

starting looking at my fan clutch,its a new unit,can feel the drag while turning,7 blade factory fan 3/4's of the way into the shroud,would i be better to remove the clutch and install a solid drive fan spacer for better cooling?i know that in high RPM applications the clutch spares HP,,but i have alot of HP to spare..car is not raced,just amusement on back country roads,short burst's of tire smoking fun.cooling and air flow is more important.

does anybody use this system,hard drive fan?,any downsides to this? my thinking is it should draw/push alot more air....thoughts?

[cudabob496]

A big aluminum radiator with an electric fan is the way to go. Better cooling, and lose 25 pounds.

However, spinning a fan up to 6000 rpm (or whatever the rpm is with the pulleys), with no slippage, seems to be a major
hp drag, with no beneficial cooling, since the car going fast provides a lot of air
through the radiator.

At 6000 rpm, a non slip fan may be a 40hp loss.

[Strawdawg]

Most electric fans don't come close to pulling the air that a mechanical fan does with a proper  shroud.  Of the aftermarket fans, the Spal pulls a lot of air give a good head pressure.  The Lincoln, Taurus, and HHR fans all have a good reputation for moving serious cfm.

They also can pull some serious amperage with most of the good ones pulling over 30 amps at kick on.  need a good alternator.

How much hp a mechanical fan pulls depends on the blade design and the rpm if there is no slippage involved.  15 hp would be on the high end from most tests I have seen and 5-10 would be more likely.

40 hp must have been the prop on a Piper Cub! 

I would use a clutch fan with a proper factory shroud.  Many of these fancy electric fans with aluminum shrouds are killed by the shallow shroud design that forces the air to make a near 90 deg turn on the outer parts of the core.

[high perf mopar]

A big aluminum radiator with an electric fan is the way to go. Better cooling, and lose 25 pounds.

However, spinning a fan up to 6000 rpm (or whatever the rpm is with the pulleys), with no slippage, seems to be a major
hp drag, with no beneficial cooling, since the car going fast provides a lot of air
through the radiator.

At 6000 rpm, a non slip fan may be a 40hp loss.

yes,i realize that but.at lower speeds,lower RPM's,which is where i live most of the time,except freeway use,im wondering if it would be beneficial to switch to the hard drive?no race trak here..i guess it would be a cheap experiment to see.

just was wondering if anybody has done it...and to what effect...i once had to throw a $1000.00 be-cool aluminum rad unit with dual fans to cool a 482 inch p%ssed off hemi to live on the street,,,barely .

[high perf mopar]

Most electric fans don't come close to pulling the air that a mechanical fan does with a proper  shroud.  Of the aftermarket fans, the Spal pulls a lot of air give a good head pressure.  The Lincoln, Taurus, and HHR fans all have a good reputation for moving serious cfm.

They also can pull some serious amperage with most of the good ones pulling over 30 amps at kick on.  need a good alternator.

How much hp a mechanical fan pulls depends on the blade design and the rpm if there is no slippage involved.  15 hp would be on the high end from most tests I have seen and 5-10 would be more likely.

40 hp must have been the prop on a Piper Cub! 

I would use a clutch fan with a proper factory shroud.  Many of these fancy electric fans with aluminum shrouds are killed by the shallow shroud design that forces the air to make a near 90 deg turn on the outer parts of the core.

im already using the proper clutch fan and shroud...the question still stands,,,has anybody tried it without the clutch..temps?

[Chryco Psycho]

it will cool better with the clutch fan 

[cudabob496]

Most electric fans don't come close to pulling the air that a mechanical fan does with a proper  shroud.  Of the aftermarket fans, the Spal pulls a lot of air give a good head pressure.  The Lincoln, Taurus, and HHR fans all have a good reputation for moving serious cfm.

They also can pull some serious amperage with most of the good ones pulling over 30 amps at kick on.  need a good alternator.

How much hp a mechanical fan pulls depends on the blade design and the rpm if there is no slippage involved.  15 hp would be on the high end from most tests I have seen and 5-10 would be more likely.

40 hp must have been the prop on a Piper Cub! 

I would use a clutch fan with a proper factory shroud.  Many of these fancy electric fans with aluminum shrouds are killed by the shallow shroud design that forces the air to make a near 90 deg turn on the outer parts of the core.

Well, I agree that a mechanical fan is a must for a copper brass radiator, and they can pull a lot of air, but my 13 amp 2100cfm electric cools 600 hp fine, with an aluminum radiator.

A solid shaft fan spinning at 6000 rpm seems pretty scary to me. Would have thought it would be up around 40hp loss, but it was just a guess. Guess I was envisioning the big heavy Mopar clutch fan I have sitting on a shelf in the garage, at 6000rpm (minus pulley ratios).

The 15 hp loss seems reasonable if it was a clutch fan.

[cudabob496]

found this. Looks like a solid mount fan at 4500 rpm loses 40 hp.


http://www.carnut.com/ramblin/dyno.html

[72cudamaan]

Thermal clutch would work better. Only fully engages when it's needed. And increased drag from the alternator
is constant with the electric fans.

[mopar jack]

Never understood fan power loss on a dyno. In the real world at 4500 rpm you are flying down the road and the fan is doing a lot less work as air is being forced through the radiator. Ma mopar used a big fan with an agressive pitch and a clutch to cool their biggest land yahts.

[Strawdawg]

Well, I agree that a mechanical fan is a must for a copper brass radiator, and they can pull a lot of air, but my 13 amp 2100cfm electric cools 600 hp fine, with an aluminum radiator.

A solid shaft fan spinning at 6000 rpm seems pretty scary to me. Would have thought it would be up around 40hp loss, but it was just a guess. Guess I was envisioning the big heavy Mopar clutch fan I have sitting on a shelf in the garage, at 6000rpm (minus pulley ratios).

The 15 hp loss seems reasonable if it was a clutch fan.

Bet your 13 amp 2100 cfm will not come close to 2100 when measured pulling thru the head pressure created by a big radiator.  If it did, you would be pulling a lot more than 13 amps 

Advertised amperage and cfm are subject to a lot of interpretation in the ad wars.

Unless they quote the number of inches of water for the numbers they advertise, it means very little.

[Strawdawg]

im already using the proper clutch fan and shroud...the question still stands,,,has anybody tried it without the clutch..temps?

Take the clutch off and replace it with a spacer to keep the fan located at the same place in the shroud and report your results   Cheap and easy

The key is a properly functioning clutch and they don't fail too often.  If it does not spin too easily, it should be working.

[73EStroker]

  with Strawdog. You still have to top up the electric reservoir by driving the alternator and that takes hp. As it has already been stated, as a retrofit on our cars,  electric fans cannot do what a stock clutch fan will do. Comparing a modern car is not an even comparison as the manufacturers design the shape of their front ends with cooling in mind so there is an efficiency increase factor there so less air required = better gas mileage.
I would heed what CP and others said - that was use a clutch fan. I have zero issues with mine over the last 4 seasons.

[cudabob496]

Never understood fan power loss on a dyno. In the real world at 4500 rpm you are flying down the road and the fan is doing a lot less work as air is being forced through the radiator. Ma mopar used a big fan with an agressive pitch and a clutch to cool their biggest land yahts.

Pretty sure the air coming through my radiator tries to force the fan in the opposite direction it would normally turn.

[cudabob496]

An alternator draw of 57 amps is equivalent to using one horsepower.