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Nigel_S · 11-21-2014, 07:47 AM

With the grill fully blocked and no airflow through the radiator and going up a steep hill the engine will overheat fairly quickly but on the flat with gentle driving it can take 15 minutes (maybe the full journey) before needing any air for cooling. It seems widely accepted that there is an aerodynamic advantage to keeping the grill fully blocked until cooling air is needed.

Question - When the radiator does need some air for cooling, where is the best place to get it?

I could open a flap in the grill but that increases the amount of air flowing under the car and that appears to be bad for fuel economy.

Alternatively I could use the radiator cooling fan to suck air from behind the front splitter through the radiator. That way the air that ends up under the car is air that was already under the car so maybe has no overall effect on fuel consumption, except for the 10-30W (depending on air temperature) of power needed for the fan. A few guesses suggests that keeping the grill blocked might save a KW of engine power so using a few 10s of W for the fan may give a good return...

Has anyone tried sourcing the cooling air from anywhere but the grill? Are there any figures available for the results? Any knowledge if it is a good or bad idea?

11-21-2014, 07:47 AM	#1 (permalink)
Nigel_S EcoModding Lurker Join Date: Nov 2014 Location: UK Posts: 42 Thanks: 0 Thanked 12 Times in 12 Posts	Full Grill Block - Where best to get air for cooling? With the grill fully blocked and no airflow through the radiator and going up a steep hill the engine will overheat fairly quickly but on the flat with gentle driving it can take 15 minutes (maybe the full journey) before needing any air for cooling. It seems widely accepted that there is an aerodynamic advantage to keeping the grill fully blocked until cooling air is needed. Question - When the radiator does need some air for cooling, where is the best place to get it? I could open a flap in the grill but that increases the amount of air flowing under the car and that appears to be bad for fuel economy. Alternatively I could use the radiator cooling fan to suck air from behind the front splitter through the radiator. That way the air that ends up under the car is air that was already under the car so maybe has no overall effect on fuel consumption, except for the 10-30W (depending on air temperature) of power needed for the fan. A few guesses suggests that keeping the grill blocked might save a KW of engine power so using a few 10s of W for the fan may give a good return... Has anyone tried sourcing the cooling air from anywhere but the grill? Are there any figures available for the results? Any knowledge if it is a good or bad idea?