Standard water pumps have 7 impeller vanes and AC pumps have 8.
I opted for 8 since my car generally runs at lower RPM's I figured the extra vane would help the flow at lower speeds.
Actually, cars with AC used 6 vanes, non ac cars used 8 vanes.
The water pump pulley on AC cars are smaller, which spin the pump faster.
Using a 8 vane pump, with an AC pulley can push the water to fast, which causes cavitation.
