Is my cooling system operating normal?
I have a hard time grasping the cavitation argument. How much time does an engine spend at high rpms (where cavitation would be an issue) under normal street driving conditions? I'll take the high flow pump any day over the low flow pump - even with over driven pulleys.
It's not just the highest rpm rating though, although even temporarily spinning a pump designed to max out at 6k all the way up to 8,400 could have catastrophic results even without cavitation, just like over-revving your engine. If the pump is trying to shove too much water through the systems small passages the resistance in the system goes up and the actual flow rate goes down. You can get a pressure difference across the pump, and if the intake pressure drops too much it will cavitate the pump even at low rpm. The speed of the pump is only one factor, with enough pressure differential you can cavitate the pump at idle speeds. Not gonna see something that extreme in this application, but in firefighting pumps it comes up frequently with poorly performing hydrants. That's not quite apples to apples because there can also be a volume difference at a level you wouldn't see in a closed system like the cooling system for these cars.
It's a complicated subject, and if it was as simple as just running the high volume pump with the overdriven pulley to get better cooling don't you think the factory would have saved the money on designing two different water pumps and pulley sets?
Exactly. There's a ton of factors that go into this, none of which we'll really have the specifications to run the actual numbers on. Even if you got all the pump numbers the resistance in the cooling system and rate of return would have to be known, and you'd have to measure that, because there is most definitely a maximum GPM for the flow through the system, and trying to pump more GPM through the system than it can handle just causes turbulence, increases resistance, and results in a lower actual flow rate.
That's another thing that comes up in firefighting. For example, a 175 GPM nozzle on an 1 3/4" hose. You attach that to a 1,000 GPM pump, but, past a certain point all that happens is the pressure in the line goes up and the pump works harder, you don't get more GPM out of the nozzle. In fact, you actually get LESS flow out of the nozzle. Assuming the line doesn't burst and the poor bastard on the line manages to hold on still. If you want to flow more, you need a bigger line and nozzle, not try to force more through the smaller line because that simply doesn't work.
You can run either pump at nominal speeds, the thermostat will regulate the flow to achieve the chosen temp .
You're giving WAY too much credit to the thermostat. Yes, they do regulate flow because they're not always fully open or closed, but, if you actually check the temperature range from fully open to fully closed it's not that wide of a range. If it's actually hot outside your thermostat is wide open more than it's not, and usually all of these cooling discussions are about operating temps in hot weather, not what's happening on a cold day when the thermostat might hang out at a spot where its barely open.