Flex fan
- Thread starter bill cook
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I seen a video on line that had a 350 Chevy on the dyno. They tried all types of fans and the worst power loss was 30 hp and it was a mechanical fan. The electric fan used up 4 hp. I do not remember the link.
That is 14 HP nearly FREEWHEELING. Fulling locked up (behind a Hot radiator) its a lot more than than that. When my 2+2 was having high speed overheating issues and we were still using a clutching fan, the car sounded like a P-51 Mustang going by. It was probably more like 50 HP @ 5500 RPM than 14 HP.
Replacing the clutching fan with a dual electric fan helped a lot. The extra 50 or so HP needed to run the fan made the motor run even hotter.
We added a 6" deep core support air dam to increase flow through the radiator and blocked off the upper grill to reduce front end lift.
Front end lift is a major driver of very high speed overheating on a G-body as it pressurizes the back side of the radiator, reducing flow through the radiator. The intercooled Turbos are the worst for this, because the actually pipe air to the wrong side of the radiator.
What are those off of? Do they actually last?+
= less than $40 for a "controller".
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A temp switch grounds the 86/85 circuit on the relay and turns on the fan. Both should be good for 100's of thousands of cycles. If the relays fails, unplug it and plug in another. They are only $4.
A temp switch grounds the 86/85 circuit on the relay and turns on the fan. Both should be good for 100's of thousands of cycles. If the relays fails, unplug it and plug in another. They are only $4.
I actually had a temp switch fail, twice. It's been good so far. I teed a female spade into the relay trigger, and have a male screwed to the firewall. That way, I can run the fans manually without the thermo switch.
Since the control amps are low, you can easily run a backup ground from an in car switch to the to the thermoswitch wire, just in case... or just ground it a piece of bailing wire or coat hanger you keep in the trunk and wrap around something metal under the hood in an emergency (really just in case). If the fans are wired to "run" + they will come on with the key, but the car won't overheat until the temp switch is fixed.
It looks like nobody has yet given you a clear, direct answer to your question. The short answer is yes, this has been measured... and an electric fan typically draws 1 HP or less compared to the same engine with the same alternator spinning but not powering the fan. Here are two pages from a relevant Car Craft dyno test answering this exact question:
As you can see, going from no alternator to an unloaded alternator cost 1.0 horsepower, and then powering the electric fan only required an additional 0.6 horsepower in drag. Alternators are extremely efficient at making electricity.
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