It seems to me that the aerodynamic picture of an F1 car would also have to account for all the air getting sucked into the engine and blown out the exhaust, no?
Similarly, a lot of the tricky aerodynamic effects in F1 come off the tyres (tyre squirt etc.) so without modelling those you're not getting a great view of the bigger picture.
In a similar vein I remember reading that one of the reasons for the CFD restrictions was because the bigger teams were starting to spend a lot of money modelling the aerodynamics of the tyres as they oscillated in corners (because F1 tyres have a relatively high sidewall they deform a lot through corners, then if a wheel lifts a little e.g. bouncing over a curb, then the whole tyre starts oscillating laterally.) Sounds very interesting but a bit of a CFD nightmare!
I wonder if this is one of the reasons why they will switch to bigger rims in 2022. The explanation given was that the wheels would look more like those of road cars; making the cars more relatable to prospective car buyers I guess. Anyway, if you can reduce the side wobbling with larger rims then teams have it easier to meet the cost cap without having to spend money there.
Another justification I've heard for the larger rims is that the current, smaller rims make it difficult to make any meaningful adjustments to the car's suspension. Ideally, suspension adjustments will become a bigger part of the setup for each race, which could help differentiate teams that are able to get the ideal settings for each track.
That certainly was the case in the past with the whole 'blown diffuser' situation which led to cars' engine maps being specifically created to allow lots of volume of air through the exhausts even when they weren't generating much power to take advantage of this - listen to the exhaust sound in mid corner of this era F1 car and you'll hear what I mean (I think it was around 2011 and Red Bull were the best at it, but I think many did it to a degree).
