Peter,
The answer to this question is RPM. The answer is also a lot closer to home than you think !!!!
All the Group A touring cars in Australia now use the serpentine belt set up because the v belts had a tendancy to invert at revs above 7000. This is not a hard and fast number as the tension of the belts and the diameter of the associated pulleys also must be taken into account. At Roaring Forties we always use serpentine belts for high reving engines 6500 rpm PLUS.
This leads me on to another pet subject of mine which is pulley size and in particular the coolant pump pulley size. The standard size pulley is designed to be used in a standard family car / truck at the NORMAL engine speeds. If the engine is used in a sports aplication than the engine revs are usually much higher and therefore the impeller speed in therefore much higher. A thing called cavitation occurs where small air bubbles appear on the trailing edge of the impeller blades. This air will be transfered around the coolant system and usually accumulates in the radiator. There are at least two fixes for this, make sure that the radiator has a self bleeding facility and design the pulleys to match their application (stop producing the bubbles). Because our cars are used in many applications we have taken both into account and a road car can be used for track work with engine rev limitations. Motor car engineering is a much more complicated science than many people understand and all cars should be fully engineered. It is not acceptable in my mind that a mid engined car should have to stop and cool down just because the driver has been unlucky enough to be stopped at two red lights in a few hundred meters.
The A/C should be operating at full bore, the car parked outside a friendly coffee shop in searing heat and the car not to miss a beat. Normal cars have to pass a SOAK test to prove their ability to run and then restart in very high temperatures. Most of these tests are conducted in the deserts of Australia or Navada, USA. Our cars should pass the same tests.
Ron thanks for a great forum , you are to be congratulated on all your hard work bringing all these people together.
Best wishes, Robert