Fan drive ratio
I can't stand it any more. It has been 2 years since I suggested that the increased fan drive ratio on the LLY is culpable in the increased overheat arena. I have never tested the research on a test mule.
Background: based on my sieve of a memory, the FDR went from 1.29 LB7 to 1.48. FDR is just the ratio of the crank pulley dia to the fan pulley dia. In the LLY, the FDR was changed and the change was obvious in noise level. The reasoning to consider with the change, is that the fan now operates outside it's optimum zone, with several side affects to its increased speed. Higher noise, less air flow, higher parasitic drag, bigger centrifugal effect, reducing the axial nature of the fan design, possible over exertion of the viscous clutch resulting in further loss of energy in excess heat conversion (the clutch has cooling fins). Excess heat in the clutch is a conversion of crank work to heat production in the clutch. etc etc, blah blah. IOW, 20 HP more drag with less actual airflow.
Agree, don't agree...not important. Let's test this one out. A new LB7 fan pulley (pn 97226289) is under $400 new, perhaps less than $30 if someone can find a yard with one. I am asking for you guys to find one or 10 and try it out. The belt is the same IIRC. Anyone who can find these used, PM me, I'll buy it .
And please don't bring up electric fan conversions, I'd like this thread to stay open.
Vehicle Systems Engineer/Professional Tuner
04.5 GMC 2500HD SRW LLY
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