Maybe the gap is to use the airflow to help suck air through the exit of the horizontally mounted heat exchanger located on the bottom of the front underbody.
The lower front of the M5 uses a bit of a different design. I guess the heat exchanger on the M4 sits lower than on the M4 and therefore necessitates the different underbody design. Don’t go driving over any tall curbing in the M5; it could result in a call for a tow truck and a very expensive repair.
The M5 looks to have three main muffler sections. Look way to the left and you can see more gigantic fins on the rear diff cover for cooling. The rear fins on the bottom of the rear bumper? I’d guess they are more for looks than anything. You know, carbon fiber makes it all better.
Yup, the roof is carbon fiber. On a side note, notice how all the hoods are closed on all the other cars. I’m one of the few jerks going around and popping the hoods on the cars so that I can look at the engine. I mean, I like to see what makes the car go instead of just the exterior looks. I guess I’m just old school. I do close the hoods when I’m done and try to not leave fingerprints.
I didn’t look specifically, but notice the center lower bumper opening is partitioned. The lower opening air looks to direct air solely to the horizontally mounted heat exchanger which dumps out the bottom of the car. The M4 doesn’t have this feature, hence perhaps the difference in the chin spoiler and undertray designs. The solid black plastic thing in the middle is probably radar for the adaptive cruise control, emergency braking, all those modern driver aid things.
The 2018 M5 gets an upgrade pushing out 600hp. The turbos are I the middle of the V; each turbo is fed air by a massive airbox and filter to minimize pressure drop.