Water Pump
- Thread starter Broncitis
- Start date
yes you can, most water pump pulleys are the same, you might find a random one somewhere where it's bigger, I used to have a 250 water pump pulley making the WP spin slower as it's bigger diameter, mike sells the smaller ones billit made of course. his should work to spin faster the WP
Yes and no.
The pump isn't pumping air directly (unless you are low on coolant). What is happening is that the pump is spinning so fast that the low pressure side of the impeller gets so low that the coolant actually flash boils (boiling temp goes down with pressure drop) locally, creating air bubbles that then collapse. That collapse is cavitation. The real problem with cavitation is that it leads to increased wear on the impeller blades, and also a lose in pumping efficiency.
Another thing to consider, is that just because you increase the pump shaft velocity, it does not necessarily mean you will be pumping more fluid. Every pump has an efficiency curve based on many factors, like the blade design, inlet restrictions, outlet restrictions, Net Positive Head, etc. If you spin the pump too fast, the impeller will move out of it's efficient zone and all that will happen is you will increase the power demand of the pump, increase the heat generated in the pump, and increase it's wear and tear, all while losing efficiency and likely not increasing fluid flow significantly.
But then again, I'm not a fan of reworking water pumps on engines. If the car is running warm, look for the cause, not a bandaid. Flushing the system, new hoses, new radiator (or recore), etc. Even timing and engine tune effect the cooling system.
The pump isn't pumping air directly (unless you are low on coolant). What is happening is that the pump is spinning so fast that the low pressure side of the impeller gets so low that the coolant actually flash boils (boiling temp goes down with pressure drop) locally, creating air bubbles that then collapse. That collapse is cavitation. The real problem with cavitation is that it leads to increased wear on the impeller blades, and also a lose in pumping efficiency.
Another thing to consider, is that just because you increase the pump shaft velocity, it does not necessarily mean you will be pumping more fluid. Every pump has an efficiency curve based on many factors, like the blade design, inlet restrictions, outlet restrictions, Net Positive Head, etc. If you spin the pump too fast, the impeller will move out of it's efficient zone and all that will happen is you will increase the power demand of the pump, increase the heat generated in the pump, and increase it's wear and tear, all while losing efficiency and likely not increasing fluid flow significantly.
But then again, I'm not a fan of reworking water pumps on engines. If the car is running warm, look for the cause, not a bandaid. Flushing the system, new hoses, new radiator (or recore), etc. Even timing and engine tune effect the cooling system.
66 Fastback
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Yes, a smaller pump pulley will result in a faster rpm on the pump and more flow. According to the pump affinity laws, the flow is proportional to the rpm of the pump. A down side of the rpm increase is the horsepower consumption is proportional to the cube of the speed.
With regards to cavitation, I think as long as the pump is kept within an rpm range that is reasonable, you will not encounter cavitation. I think where you see cavitation in automotive water pumps is when you take it outside of its operating envelope. Say a racer builds and engine with a stock water pump that spins the engine at 7000 rpm. Several factors would then contribute to a pump cavitating. The engine rpm increases the Net positive suction head required to not cavitate at the elevated rpm. Translated, the pump will flash boil the liquid easier as Slade mentioned. The race engine is also developing more power and dumping more heat into the coolant. So the cooling system is operating at a higher temperatue and closer to the boiling point.
Keep in mind that in normal driving, we aren't bouncing off the red line and generating max horsepower like race cars, so I think any pump speed changes you ar able to make with pulley changes will be well within the operating envelope.
Doug
With regards to cavitation, I think as long as the pump is kept within an rpm range that is reasonable, you will not encounter cavitation. I think where you see cavitation in automotive water pumps is when you take it outside of its operating envelope. Say a racer builds and engine with a stock water pump that spins the engine at 7000 rpm. Several factors would then contribute to a pump cavitating. The engine rpm increases the Net positive suction head required to not cavitate at the elevated rpm. Translated, the pump will flash boil the liquid easier as Slade mentioned. The race engine is also developing more power and dumping more heat into the coolant. So the cooling system is operating at a higher temperatue and closer to the boiling point.
Keep in mind that in normal driving, we aren't bouncing off the red line and generating max horsepower like race cars, so I think any pump speed changes you ar able to make with pulley changes will be well within the operating envelope.
Doug