There was a thread a while back discussing efan drag vs mechanical fan drag. The general conclusion seemed to be that the efan would take just as much power to turn, and would be dragging the alternator as much or more than the stock fan.

I've spent the past few days working on my stock fan (bad clutches on it, and then a bad replacement clutch - third one seems to be working). It seems to me that at high RPM, that fan is going to draw a LOT of power. Even with the clutch slipping as designed, there's still going to be an awful lot of power drained by that fan spinning. And the faster the engine spins, the more power is going to be taken (either spinning the fan or slipping the clutch).

An efan, on the other hand, is going to draw a constant amount of power. As the engine speed goes up, this drain will be less and less, percentagewise.

So, to answer the question, has anyone tried running a dyno with the stock fan, and then again with it removed? If nobody's actually tried this, I may have to do some experiments and see if I can generate some numbers.

-=Russ=-

 

I've got an electric fan that I installed with a simple toggle switch. I only have to turn it on if I'm going slower than 15-25 mph for more than a minute or two. Any speed over that and the air passing through takes care of the cooling. So my fan doesn't take any power to turn at all 99% of the time.

 

Why do you think that? You can't just make that claim without some theory or info to back it up.
No, that's wrong. Since the fan speed is no longer increasing, the amount of power it's using remains the same too.

That's asking for a melted engine. The chances of you forgetting to turn it on one day are too high. When one overheat can trash the engine, why risk it? It's not like thermoswitches are expensive.

 

I suggest the original poster search for electric fan threads. This has all been covered before, in great detail.

 

*blinks* I need to stop posting late at night. I swear, that made sense to me when I posted it.

SORRY!

-=Russ=-

 

I've read in varoius places that different mechanical fans pull 5-15 HP.

Ours only pull hard when the radiator heat activates the fan clutch.
An E-fan should work the same - no worries.

For an E-fan to move the same amount of air, they need to draw approximately the same power.
Most don't move as much air, so yes, they don't use quite as much power.

If you really must count on that ~10 HP for a short (14 sec) period, Use an E-fan with a temporary cut-out switch.
Or even better, an alternator cut-out switch.
Flip it off when you pre-satge, flip it back on when you lift & slow down.

 

I have a Fiero fan that has not been installed....I plan to dynotune with the stock fan first and after I remove all emissions I will dyno with the efan........we'll see.

 

Can you possibly try running with the stock fan & efan in the same configuration? They shouldn't collide, and even though running the stock fan without a shroud would be not exactly the same as running it in the shroud, it should be close enough to see if it makes a difference.

-=Russ=-

 

I live out in the country so I don't slow down too much. When I do its the first thing I start thinking about so I keep an eye on my temp guage. I bought a thermo switch from Autozone that came with a relay and everything but I couldn't get it to work. I know the relay was working because my toggle switch was ran through it where the A/C override goes. I think the actual sensor might have been broken, but whatever I just decided to run it how I have it.

 

Aaron is right, this topic has been beat to death already in other threads