electric fan v/s motor driven

[Brock]

I've heard that using an electric fan instead of the motor driven will increase horsepower...Actually I think the theory is it decreases the horsepower lost to resistance created by the motor having to turn the fan. Either way there is supposed to be a gain in HP. Has anyone heard of this? If so how much HP do you think would be gained? (350 c.i. SBC +.030)

[Wasted Income]

You're on teh right path. An electric fan will free up some hp from parasitic losses, and will only come on when needed (via a thermostat). I'm pretty sure HotRod or some other car rag did a test on this not too long ago. I think the ballpark was 5-7 more hp by going to an electric fan vs. a NON clutched fan.

This will put an increased load on your charging system and the alternator will be slightly more parasitic to create the extra electrical power.

[Brock]

Actually I'm gonna use this set-up on my dirt-track car...no alternator, gonna run it off a seperate battery with a simple on/off switch

[69C10@16]

..........

no

..........

alternator????????

[Brock]

2 batteries...one for the motor and one for the fan. Not to mention I can arrange them to provide weight where needed

[Scott68-93-97]

clutch fans rob nothing until it gets hot enough then they can rob like the flex ones do which is around 20hp they did a test a year or so ago in chevy high performance so an electric fan does free up a little power but when on your alternator will have a little more draw on the motor but not enough to notice.

[crazy longhorn]

There is no such thing as "free lunch", when it comes to horse power. I run a dual elect fan setup on my longhorn, & it works great.....but it never runs wide open for more than about a 1/4 mile at a time(once in a while) On your dirt car, you will twist it what 6500-7000,burp it , then twist it back up down the next straight......how many laps? I can keep my streeter cool on a on a 2700 cfm fan setup, but it will take a lot of fan to cool that dirt track car running wide open for several laps.....I wont say cant.....cause if you are anything like this crazy old fart, the answer will be "watch me do it"! best of luck, crazyL

[piecesparts]

The average is around 5 to 7 horses freed up for the engine to apply elsewhere. You could also see an increase in fuel economy (I did on my trucks -- about a mile per gallon) and you will see a smoother running engine with that load removed. My DD warms up faster in the winter, also.

[Brock]

Sounds to me like there are advantages all around, more HP and better gas milage. I'll definitly look into going that route when/if I ever get the '68 going.

I turn around 5500rpm in my car at the end of the straight. my nephew popped his engine at 6400 (you could put your fist in the cylinder chamber through the side) so I try to not go that high. We run 7 green flag laps. it might take 25 laps to get those 7 in (caution laps don't count, and I don't think the flag guy counts too good...sometimes it seems longer/shorter). I don't know the CFM of the fan(s) actually there are two. I'm planning on wiring them through switches where I can turn them on and off as needed based on temp. Here's what the fans look like

[ChevyC102007]

Ok I can understand the HP/ mileage increase of the electric fans. But IMO if ya wanted to decrease even more parasiti power loss wouldnt it make sense to also run an electric water pump? Or under/overdrive pulleys? I guess Im not understanding just stopping at the electric fan solution. Im sure Ill get flamed for this post and I dont mean to step all over the original post but its just my opinion.

[piecesparts]

Originally Posted by ChevyC102007

Ok I can understand the HP/ mileage increase of the electric fans. But IMO if ya wanted to decrease even more parasiti power loss wouldnt it make sense to also run an electric water pump? Or under/overdrive pulleys? I guess Im not understanding just stopping at the electric fan solution. Im sure Ill get flamed for this post and I dont mean to step all over the original post but its just my opinion.

There is a breakover point on parasitic items. You have to consider the amount of increase of electrical use you would have and the extra drag you would have on the 140 amp alternator needed for the electrical load. The alternator is ONLY cutting a magnetic field, but the field is resultant of the load needed to cover ALL of the items used. The electric water pump would be great and many drag cars and some show cars use them, but there is a relability factor here. Can you get one on the road to Tulsa or Victorville, when you break one? At least most of the local parts stores carry the belt driven ones.