Simple,

A mechanical fan is using the energy directly from the motor. However, an electrical fan gets its energy after having been converted to electricity from kinetic energy.

Every time you have a step like that you lose efficiency.

 

I won't debate the point that a mechanical fan is more effecient. But the mechanical set up on the F150 draws more power to run than the PPI twin electric fan. The Fans draw <1hp each when running so they take 2 hp to run. The mechanical fan draws from about 5 to 20 HP depending on rpm.

Reference for HP draw per amp:
http://pkys.com/Alternators.htm

Reference for HP draw of Mechanical fan:
http://www.mercurycapri.com/technica...ing/csiat.html

JMC

 

I won't debate the point that a mechanical fan is more effecient. But the mechanical set up on the F150 draws more power to run than the PPI twin electric fan. The Fans draw <1hp each when running so they take 2 hp to run. The mechanical fan draws from about 5 to 20 HP depending on rpm.

Reference for HP draw per amp:
http://pkys.com/Alternators.htm

Reference for HP draw of Mechanical fan:
http://www.mercurycapri.com/technica...ing/csiat.html

JMC

 

Certainly, if the F150 stock fans won't completely freewheel then you will definitely be able to get some improvement in HP, gas mileage, since that means even cold they are producing a drag.

I was purely assuming that they were similar to the mechanical fans I had on my Nova.

 

Mark,

Can your "Nova" fan be adapted to the truck? A mechanical fan is a lot safer than an electric one. There are two reasons I went to e fans. Compared to the OEM set up it frees up HP and beacuse when I play in the water I can turn them off so they don't chew a hole in the rad.

JMC

 

I doubt it. My Nova is a chebby and probably uses a different bolt pattern.

Either which way, the current fan in my F150 keeps it cool so I have no desire to change things.

People saying that electric fans increased their HP or their ETs is just a pet peeve of mine. There are enough valid reasons to run an electric fan (just as you desire to run the electric fan so you can turn it off), I just don't count HP gains as one of them.

The only exception to that is when you race on the track and turn it off during the race then immediately turn it back on when done.

 

I think the reaons for why one would want the electrical instead of the mechanical fans need to be addressed.

If one was looking for outright horsepower gains then the electric is probably not the way to go in the $/hp arena. They could easily do a lot better with supercharging, nitrous and a plethora of other avenues.

I personally want the fans for two reasons. First is that I want to insure that the truck isn't going to overheat when I'm somewhere in Texas in the middle of 110 deg summer pulling my TT. Second is that I want to help my POS air conditioner that doesn't work worth crap in traffic while the mechanical fan is freewheeling.

If I get an extra horsepower or two then that is a bonus that I'll be happy to have but it isn't what I'll be buying for. Getting into a pissing contest over a couple of horsepower is simply a waste of time.

 

the big reason I went with an electric fan on my Mustang was so I could run it between rounds and really control my engine temps. It saves some HP, as witnessed in about a billion different dyno tests, but I was less concerned with the few HP gain than with temp consistency at the track.

Incidently, I think I have $20 in my entire Mark 8 dual speed fan setup from the jy, and it moves more air than most aftermarket fans.

 

RobKong hates me.

 

Where are you in 110 degree weather in Texas? I've lived here all my life and never seen temps anywhere close to that level except maybe in far West Texas (really 100 is more like it) where there's no traffic, so you'll always be moving and it doesn't matter if you have electric fans or stock. Either way your moving hot air through the rad.

 

Are you following me?

 

I wished I could have found a Mark VIII fan, that would have been great!

Generally, I always thought you are better off with a small pusher fan in front of your A/C condensor, if thats your problem.

 

Are you saying that the mechanical fan hanging off of the water pump pulley doesn't use any horsepower?? Sorry, but I am kind of confused. If you switch to electric fans and the engine revs easier and faster, doesn't that mean that power has been freed up? Doesn't removing the mechanical fan also indirectly remove rotational mass hangng off the crankshaft?

 

I noticed no differences between my ETs before and after removing my mechanical fan. I'm certain there was a small difference, as the clutch fan cannot be perfect, but it was imperceptible to me. I can also tell no difference in how quickly my engine revs.

The same sentiment is expressed on the drag racing listserv I'm on.

 

Mark,

How many HP does your Nova produce?

10-20 HP on a 500+Hp engine is not noticable. One thing I have learned is that the BUT-O-METER is not very Precise. Your ETs are a better indicator of any gains. 10-20 hp on my 5000 lbs truck is not impressive. The difference I felt was in the ability to spin my 33 inch tires when rolling in 1st gear.

I don't think that any gains from e-fans are made from the removal of the weight of the fan/clutch but from the decreased wind resistance of the spinning blade. Example: Flexolite blades. As the rmps mount the blade flexes and the resistance decreases. Mt truck revs to 6500 rpm. At those revs the fan has a lot of drag. The e-fans help with the power at those revs. I also no longer have to worry about launching a blade through the hood.

JMC

PS I think I will take a close look at the claims of the e-fan manufacturers. They claim a 15-25 ? Hp gain but it might be at peak and not throughout the full power band. That would make sense becasue the faster you spin the fan the more wind resistance there is.