Blow Harder, Cool Better, Go Faster
By Kevin Whipps
Who wants something as boring as electric fans? You do, for two very good reasons: they lessen parasitic drag and free up space under the hood. Read on past the jump for details, and get ready to pull out your checkbook.
That bulky fan on your motor doesn’t turn by itself. Every time it starts up it’s robbing horsepower from your ride. That’s called parasitic drag. By removing the belt driven fan and installing electric fans, you can can retain that power for pushing the car, not fans – as much as 10-15 horses on a large V8.
Belt-driven fans are engine bay hogs, too. Want to squeeze a big block in that Pinto? You’re gonna run out of room quickly, and you need some way to cool your motor. Without all the pulleys and drive shafts, electric fans fit in tighter spaces than belt driven fans, giving you the extra space you need for tough swaps.
An extra plus: they often cool better, too, moving more air than a single big fan.
Ready to buy yet? If so, you’re in luck. SPAL USA has released a new series of electric fans designed to move air more efficiently in high static pressure conditions – like under your hood when you’re flying low. SPAL builds all of their fans in house instead of outsourcing it to every Tom, Dick and Harry with an injection molding machine, so they’ve got a better edge on quality. And their fan motors are sealed and balanced, too.
More horsepower, more space, and better cooling. That’s hard to beat.
SPAL USA [Corporate Site]
November 28th, 2007 at 12:38 pm
I can definitely see the advantage in not having belts run every which way and reducing space necessary at the front end, esp when putting in bigger blocks in smaller cars, but does anyone know what kind of parasitic power loss we’re talking about here? It just doesn’t seem it would be that significant.
November 28th, 2007 at 1:08 pm
the power loss can be significant - say 5 percent or more. the belt driven fans suffer from friction, as well as a heavy metal fan. they also have the problem of being in use constantly, even when they aren’t needed. you will notice that almost all modern cars use electric fans.
November 28th, 2007 at 5:23 pm
That’s a good point about them being run constantly. An electric counterpart would likely help me get up those cold mountain climbs in the dead of winter.
November 30th, 2007 at 11:20 pm
There are other advantages to electric fans:
We’ve measured a 7HP gain at 5500RPM on the engines we specialize in by removing the stock crankshaft driven fan. These are large 14″ plastic fans, bolted via a hub extension to the front of the crankshaft. I consider 7HP fairly significant given that these engines produce less than 150HP in their stock form.
Electric fans run “as needed”… which is precisely what you want a cooling fan to do.
Packaging of electric fans is a little easier than that of mechanical fans. A mechanical fan that must be attached ot the crank has to be located behind the radiator (draw through) and should be shrouded for max efficiency. However, in space limited applications, an electric fan in front of the radiator (push through) is a better option from a packaging point of view.
The only reason to stick with a stock mechanical fan is if you’re competing in a stock show class and you’ll be docked points for having the mechanical fan. From every other aspect though, the electric fan is superior in every way.
Fans in general are designed for an optimum RPM. Blade pitch and fan diameter determine this. Most stock crank driven fans are most efficient below 2000RPM. An electric driven fan runs at a single operating RPM, meaning that it is always turning at an RPM close or at the intended design RPM for that blade pattern.