1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Water pump cavitation likelihood?

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Old 06-23-05, 07:34 PM
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Firing on all rotor faces

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Arrow Water pump cavitation likelihood?

I have always wondered that if you go around removing the air pump, and a/c compressor, does the chance for water pump cavitation become dangerous or is it exaggerated?

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Old 06-23-05, 07:38 PM
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I doubt it'd change at all - the engine is still spinning at the same RPM, just not having energy drawn away from it by turning non-critical devices.

Cavitation is what happens when the blads spin so fast in the housing from high RPM operation that air bubbles form around the blades and it prevents coolant from being pumped. Keep the RPM below about 6k and you won't ever have a problem, A/C, A/P, or not.

If you're really concerned about it, or drive at high RPM >6k+, then you can get some 'underdrive' pulleys which are larger than stock and will decrease their RPM considerably. This also affects the rotational speed of your alternator, though, so expect some dim lights at idle speed. HTH,
Old 06-23-05, 09:19 PM
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Originally Posted by LongDuck
I doubt it'd change at all - the engine is still spinning at the same RPM, just not having energy drawn away from it by turning non-critical devices.

Cavitation is what happens when the blads spin so fast in the housing from high RPM operation that air bubbles form around the blades and it prevents coolant from being pumped. Keep the RPM below about 6k and you won't ever have a problem, A/C, A/P, or not.

If you're really concerned about it, or drive at high RPM >6k+, then you can get some 'underdrive' pulleys which are larger than stock and will decrease their RPM considerably. This also affects the rotational speed of your alternator, though, so expect some dim lights at idle speed. HTH,
All true. 7K and above = cavitation. If using a larger diameter alternator drive pulley to slow down the alternator at high rpms, going with a higher amperage alternator (ex: from a 2nd gen) should fix the dimmer lights at idle issue... I think.
Old 06-23-05, 09:23 PM
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Firing on all rotor faces

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Thanks for the thorough relies guys
Old 06-23-05, 09:42 PM
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Cavitation can also occur if you have air bubbles trapped in the cooling system. If you heat gauge is erratic you have bubbles, so get rid of them.

B
Old 06-24-05, 04:22 PM
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Originally Posted by LongDuck
If you're really concerned about it, or drive at high RPM >6k+, then you can get some 'underdrive' pulleys which are larger than stock and will decrease their RPM considerably. This also affects the rotational speed of your alternator, though, so expect some dim lights at idle speed. HTH,
Yes this works, I run the MazdaComp pulley's. Also changing the factory pump with an aftermaket pump helps. The aftermarket (I forget the brand GMB or something) has smaller vanes, actually works better at higher RPM, anyway it's what the racers use.
Old 06-24-05, 04:46 PM
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evan's NPG+ makes it so u don't have cavitation period, since it is a waterless system
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