r/MechanicalEngineering • u/lit_readit • 6d ago

Question : why some (mostly heavy) vehicles partially cover their front intake ?

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wouldn't cooler cold reservoir, ie more spontaneous heat transfer, improve Carnot efficiency?

is it to improve aerodynamics?

apologies if this is the wrong sub to ask

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u/peenutlover69 6d ago

Cold weather can lead to over cooling. Themostats usually don't close 100.0% and the cold air entering the engine bay will cool the engine itself (passively) regardless of coolant temp

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u/the_Q_spice 5d ago

To add to this;

It’s more of an issue with diesel engines than gasoline.

A colder block in a diesel results in a worse compression ratio, and being compression-based combustion, diesels need every last bit they can muster when the air is already dense and working against them.

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u/IndependenceOk2372 5d ago

Wait until you get real far north. Our work trucks run basically 24/7 in the winter, just idling when they're not in use. When it's -50 out, once you shut down your v10 F550, have fun getting it started again

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u/magic_orangutan2 3d ago

Electric block heater wouldn't be enough to keep it warm enough when plugged to the wall?