raised bonnets

[belalegosi]

^^^
he's talkin about the expansion and compression (hot n cold) properties of the glass.

[Alpha_2nr]

ome racecar drivers raise the bonnets not for heat scavenging actually, but for cooler intake charges (yup, believe it...it's an entry point, NOT an exit point

You're right! That area between the windshield and the bonnet has lots of "eddy currents" from fast moving air that hits the windsheild. Thus its difficult for air to leave the engine bay in this area, but its alot easier for it to enter. Some of those old muscle cars (Chevelle SS for example) back in the day actual tried to utilise this air in what we know as "Cowl Induction"






The cowl induction hoods shown above allow air to enter through the "bulges" near the top (by the windshield area)

Comments: 1970 saw the introduction of the most powerful Chevelle SS of all time. Responding to the lifting of GM's ban on engines larger than 400 cid in midsize cars, Chevrolet responded by dropping in a new 454 cubic engine into its Chevelle SS. The entry level 454 was known as the LS5 and packed 360bhp. The top engine choice was the LS6 version with 450bhp. Optional on both the 396 and 454 was a new cowl-induction hood, which had a rear facing flapper near the base of the windshield to feed air into the engine