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Old 06-26-2008, 09:20 PM   This thread is in the EcoModder Project Library | #1 (permalink)
EcoModding Apprentice
Join Date: May 2008
Location: South Dakota
Posts: 117

GMC Sonoma - '94 GMC Sonoma
90 day: 36.97 mpg (US)
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Electric vs. belt driven cooling fan

I just got done replacing the belt driven cooling fan on my GMC Sonoma with an electric fan, for the purpose of trying to save fuel. But after doing this I figured out a way to measure (guesstimate actually) the amount of fuel savings I might expect.

The electric fan draws 6 amps at 14 volts (84 watts). If one horsepower is 745 watts then the electric fan uses 0.11 horsepower. My electric fan seems to blow about as much air as the original mechanical fan. This suggests that the original fan was probably using about the same amount of power, which would be about 1% of the total cruising speed power used by the vehicle if cruising power used is around 11 HP.

Note, almost no energy is consumed by my electric fan because it is almost never running. In other words, this pickup rarely needs a fan at all under the conditions which I use it. So this is saying that I have removed the 0.11 horsepower robbing mechanical fan, with almost zero added energy deficit of the new fan.

I realize my method of measuring the energy expense of the original belt driven fan is a bit crude but I could not think of any better way to calculate it.

My question is, what are the opinions of others on how much fuel might be saved using an electric fan vs. mechanical, and how did you come up with your figures?

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