Didn’t see any other threads addressing this, but it’s a detail that really bothers me…
On my 68 Dodge Dart Hemi, I have the exposed supercharger hood. When driving, the butterfly valves on the supercharger do not actuate with throttle position (like they should). They open/close with the same timing as shifting which is not correct.
Not sure if there are other cars affected but I would imagine this behavior holds true for any exposed supercharger setup.
Not to mention what happens when you drive a supercharged car on the rev limit, it would not stay on the limit very long opening and closing the way it does in game hehe 
The fact you can have an exposed supercharger on a car that has no supercharger bothers me more lol
Ya this one kinda gets to me too. It’s one of those things that I know I should ignore because it’s just a game but man does it annoy me
Pretty sure it’s possible to have a mock up blower purely for looks, similar to what the stunt cars in films use if they’re supposed to have a supercharger/blower combo.
I’ve never analyzed this too much for all these reasons. I use this hoo because it provides weight saving measures and the other two hoods are two of the most ugly objects ever programmed into a Forza game. Just my two cents.
If I looked too closely this might bother me and then I’d be tempted not to use it - like the ugly rear wing on hatchbacks…
I don’t use it 'cause it messes with the areo