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Old 06-26-2008, 10:06 PM   #5 (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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Originally Posted by ttoyoda View Post
... here is a link that says 16 to 41 hp used for big trucks.
Thanks for the link.

Gee, if a truck fan consumes a minimum of 16 HP then my little pickup fan may consume a whole 1 HP perhaps instead of the 0.11 HP I was calculating. But, I wonder if my clutch actually ever engaged. The reason is, as I mentioned earlier, I have driven around a few days without any fan at all and had no temp problem at all. My new electric fan only comes on near the end of the 1/2 mile hill I must climb in 1st gear to get to my house. Otherwise the normal driving airspeed provides adequate airflow.

I drive a school bus and I can feel the loss of power when its fan clutch engages. It is not real pronounced but it is definite.

Measuring manifold vacuum as you suggest would be a good idea but it is too much work to remove and reinstall fans so I guess I will pass.

One thing that I thought of that might be beneficial is that the electric fan may allow the engine to warm up faster when first started since it does not blow any cold air over the motor, since it is off until needed. The mechanical fan blew air constantly, even though it has a fluid clutch, and that must have had some cooling affect on a motor that is trying to get warmed up.

Thanks for the input.

Last edited by Gregte; 06-26-2008 at 10:15 PM..
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