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Old 05-04-2020, 05:51 PM
Autoputzer Autoputzer is offline
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Location: NW Floriduh
Join Date: Mar 2014
Posts: 10,227
Mein Auto: 2014 535i + 2018 X3 30i
Small, powerful, turbocharged engines create a lot of heat. The catalytic converters are up there too, close to the engine.

BMW engine compartments are sealed up relatively tight, for efficient cooling and aerodynamics. All the air coming into the engine compartment goes through the radiator and heat exchangers, and they're blocked by computer controlled shutters. The EU emissions and fuel consumption tests have a sequence of a warm start-up, simulating a relatively short shopping trip. The warmer the engine stays during that short shut-off, the better it does in the test. So, BMW's software probably closes the shutters when the car is shut off, unless the cooling system needs to run to cool the coolant some after shut-off.

Engines now have a plastic cover over them. It performs two functions: aesthetics, and sound suppression (especially with direct injection that has noisy injectors). But, those covers also retain engine heat.

Finally, it varies how much insulation BMW puts on the bottom of the hoods. My F10 535i has insulation there, but Frau Putzer's G01 X3 30i doesn't.

I check my tire pressures early in the mornings, after the cars have been sitting overnight. I adjust the pressures to one PSI increments on the tire pressure gauge. I've found that that the front tires are still slightly warmer than the back ones even after the car has been sitting for over ten hours. If I've driven the car the night before, I now leave the hood open overnight, so that the car and front tires cool down completely by morning.
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