>> Flat-out means at full RPM, which is not a thermal decision. It is a limit based on cylinder size and flame speed. Any higher and the fire is still burning w

>> Flat-out means at full RPM, which is not a thermal decision. It is a limit based on cylinder size and flame speed. Any higher and the fire is still burning when the exhaust valve opens. Partially -with some engines, the limit is valve float, or cam shape (which is why electronically operated valves are becoming a thing), with some it is thermal. With pro-level drag race cars, producing 7000+ Hp / 5+MW, some of the more key considerations are how much fuel can be pumped into the cylinders. But they turn over only something like 900 revolutions each race run and need to be torn down between each run. The point is that ICE engine design is a massive balancing act between inertia of parts, internal friction, strength of parts, fuel, and thermal. Thermal may not be the main driver of every engine design, but if you claim thermal is irrelevant and not a limiting factor, you're just plain wrong. In many types of road races from F1 to Le Mans, merely picking up a small sheet of plastic or paper on the radiator intake will be a cause to pit almost immediately because the thermal management is designed to handle the requirements.