As I understand things; the better the exhaust scavenging; the higher the compression one can run due to a cooler exhaust valve (and chamber) and less hot exhaust gas in the new mix.
(But there also seems to be temperature limit here where vaporization does not occur enough, leading to misfire..?)
Anyway; Perhaps using (and filling) the area of maximum vacuum behind the car to better extract the exhaust (and minimize the vacuum)is of interest to you?
ie: Kill 2 birds with one stone by vacuuming the exhaust out some and filling the vacuum behind every car with exhaust.
There is only one, badly translated, paper on the subject of where best to exhaust exhaust, that seems to point to an exhaust exit just below dead center in the vertical rear as optimal.
The position changes if you prefer downforce.
Taking a 2nd look at this now I NB that the original low position doesn't look bad at all and saves weight, so this is likely just 'nice to know'.
Anyway; The discussion is here:
https://ecomodder.com/forum/showthre...tml#post695293
While I'm at it;
here's some original thinking/theory on ameliorating the vacuum at the front of the roof with the high pressure air under the bonnet, using the A pillars as air ducts:
https://ecomodder.com/forum/showthre...ard-41539.html
As a mod this would involve opening the A pillars, as ducts, to the engine compartment air, an aero designed duct more or less above the sun visors and aerodynamically designed slots in the roof in just the right places.
That makes it something for rally teams etc, with an aero research budget, to think about and experiment with, but an interesting idea/theory IMHO as it should cut down on the cooling air going/lifting under the car AND the lift/vacuum above the front of the roof.
I certainly wouldn't start hacking away at a perfectly good, water tight car roof panel on the off chance I'd get this right on the 1st try!
I just thought you might find the idea interesting due to all the heat you need to get rid of.
The 1st post there (and paper) on directing the under hood cooling air backward rather than just letting it flow downward is also worth a look IMHO.