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Ziggster · 10-23-2019, 04:53 PM

Yes, lots of variables at work simultaneously. You can expect a one degree increase in coolant temp for every degree increase in air inlet temp to radiator everything else being equal. Engine cooling systems for military vehicles are typically designed around max engine load (most heat rejected into coolant) at lowest vehicle speed. This is referred to as a drawbar pull test. For passenger vehicles this would equate to climbing a constant grade at Gross Combination Weight Rating with AC system engaged. Not a typical scenario for most. At idle, engine reject heat is minimal, but airflow through the radiator is then entirely dependent on the system cooling fan(s). There is also the issue of removing the hot air out from the engine compartment as quickly and efficiently as possible.
More blades is better, but there are diminishing returns. You could add auxillary electric fan(s) and stage them based on coolant temp. You could also use a thermostatic clutch attached to the fan to reduce unnecessary noise, power draw.

10-23-2019, 04:53 PM	#17
Ziggster Senior Member Join Date: Aug 2018 Location: Ottawa, ON Posts: 854	Re: factory fan cfm Yes, lots of variables at work simultaneously. You can expect a one degree increase in coolant temp for every degree increase in air inlet temp to radiator everything else being equal. Engine cooling systems for military vehicles are typically designed around max engine load (most heat rejected into coolant) at lowest vehicle speed. This is referred to as a drawbar pull test. For passenger vehicles this would equate to climbing a constant grade at Gross Combination Weight Rating with AC system engaged. Not a typical scenario for most. At idle, engine reject heat is minimal, but airflow through the radiator is then entirely dependent on the system cooling fan(s). There is also the issue of removing the hot air out from the engine compartment as quickly and efficiently as possible. More blades is better, but there are diminishing returns. You could add auxillary electric fan(s) and stage them based on coolant temp. You could also use a thermostatic clutch attached to the fan to reduce unnecessary noise, power draw.