Forum Discussion
Ron_Gratz
Jul 19, 2015Explorer
marcsbigfoot20b27 wrote:
AIRFLOW. Creeping up a hill at 35 you will have terribly low airflow to cool your radiator, transmission, AC, intercooler (if you have one) etc.
Now suddenly your fan kicks on and has to scream and rob another 20 hp to keep things cool enough (barely). Going 55-65 your airflow is (I didn't look up the math) maybe triple to quadruple.
A combination weight of 15000# and frontal area of 85 sq ft moving up a 6% grade at 60 mph will require about
90
hp to overcome aerodynamic drag, about 150 hp due to rate of climb,and about 25 hp to overcome rolling resistance
.The same weight and frontal area moving up the 6% grade at 40 mph will require about
40
hp to overcome aerodynamic drag, about 100 hp due to rate of climb,and about 15 hp to overcome rolling resistance
.If going up the hill at 60 mph requires
265
hp, and going up the hill at 40 mph requires155
hp, the higher speed will require an addition of about110
hp.If the non-boosted airflow through the radiator at 40 mph is not sufficient for proper cooling, the fans will provide necessary increased airflow -- and the fans will not be consuming
110
hp.The OP stated he was going about 40 mph at the top of the grade and "the trans never really got hot, just a tad over 200."
Doesn't sound to me as though he had a cooling problem.
Edited,
in red
, to correct for using speed in ft/sec instead of mph for calculating aerodynamic drag, and to include power required to overcome rolling resistance.Ron
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