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- Apr 30, 2021
Hmmm, but is there anywhere for convective airflow that isn't drawing past or through a significant source of heat? At standstill air is really only filtering up past a hot engine or getting drawn through a hot radiator. The DS has one of the most "sealed in" engine bays I've encountered in an older water cooled car. The amount of heat generated by one or two 90W thermo fan motors isn't much considering (depending on the DS model) it is sharing the engine compartment with a heat source generating up to 100,000W of energy. If this source of heat (the fan motor/s) is/are located at the very top of the engine bay on the underside of the bonnet, wouldn't that positioning therefore aid convection?If you had significant louvres, at standstill normal convective flow would be adequate.
I don't think there is any need to add fans, which add energy into the air, just let the hot air that is there, out.
I believe one of Citroen's last mods to "improve" the cooling system of the DS was to add a supplementary electric radiator fan?
How about using the aluminium bonnet as a heat sink, strip the underside of padding/paint and give it a very thin coat of primerless flat black, weld fins lengthways down the bonnet on the topside and polish the whole upper surface so it doesn't absorb heat from the sun. Look the ducks guts on a silver car! I was going to say weld the fins on like chevrons, but I don't think these would flow as well as straiģht ones.
I had a slightly modified P6 Rover many, many years ago, these cars also suffer from a tightly packed engine bay. It was the later series with the "power bulges" pressed into the aluminium bonnet. As I already had the bonnet stripped I thought I would polish the bulges and mask them off before I painted it, just for something different. Interestingly when the car was hot, the polished parts of the bonnet were relatively cool to touch, whereas the adjacent black paint got bloody hot. The entire underside of the bonnet was painted satin black. You can see the polished bulges in the photo, either side of the "hood ornament".
Sorry about the quality, it is a digital photo of a old "real" photograph.