charles.harbert wrote:

Paul, it isn't likely that your dealing with discharge cavitation which is much
harder to induce IMHO. It would be hard to believe that Mazda could do such a
poor job of engineering. When we raced boats we were always dealing with prop
cavitation. A huge amt of energy went into prop design to make it efficient a
extremely high rpms (15K+). In essence (according to what I've read and been
told), cavitation is created by a vacuum on the back side of the impeller
causing water to boil (vaporize) at low temp. You know that you can make water
boil at very low temps by drawing a  vacuum. When the prop or impeller moves
thru water at very high speed, it is difficult for the water to stay attached to
the backside of the prop, you create a vacuum which causes water to boil,
otherwise known as cavitation. Classic case is very high flow rates (at high
pump spd) that can't be met by the inflow capacity needed by the pump.

On race cars (Nascar) that turn very high rpms continuously, they end up slowing
down the pump (and the flow) to avoid cavitation, but they do add bigger
radiators to get the cooling that they need. The other way is to increase the
inlet flow capability and pump inlet diameter. Remember that flow is directly
related to pressure. What's the inlet pressure to the pump??? The pressure
differential is very important.

 
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