And on top of all that, I’m sure bmw has this issue addressed anyways with plenty of vents moving the hot air out where the hood and windsheild come together.
newman:
heat rises.
having an intake manifold physically connected to a hot engine block and over an heat source is not a good idea for IATs.
i have seen many many turbos mounted far closer to hoods that have no thermal insulation with no ill effects. Next time you drive your car, make a HARD run, and then put your hand 2 inches away from the turbo. Unless you’re a huge pussy, you can probably hold it there indefinitely. Air is an amazing thermal insulator (double pane windows?). Now keep in mind that you can be horribly burned by steam at 212F… Now replace your hand with plastic that at more than double that is completely stable. If the plastic was mounted to the turbo, it would be a different story, but it’s not.
the plastic that is covering the turbos is probably a grade of ULTEM which has a thermal stability well over 500 degrees Fahrenheit. The radiant heat from the turbos will never EVER get that hot.
i would be willing to bet that average underhood temperatures will be lower with the turbos placed there. The heat is concentrated to the TOP center of the hood which allows for hot air to escape far more readily than if the turbos were jammed underneath the engine and next to the strut towers.