Indeed; the way to do a FADEC is well established.
The huge issue is that car engines are not heat dissipation limited. They are water-cooled and have massive radiators, so you can run them stochiometric at almost all power settings if you want to.
For them, FADEC is perfect. It also helps to meet the emission regs etc etc.
Aircraft engines are made with thin metal sections are and air cooled. Only about half the heat goes into the oil; the other half has to be dumped into the airflow and that isn't terribly efficient. So the constraints are very different, and much cruder.