The picture of the stock-looking impeller with the vanes machined to a smaller diameter is interesting. That is the classic way of reducing the output of a pump. A pump manufacturer will tailor a pump to fit a customer's spec by cutting the vanes back like that. The flow varies directly as the outside diameter, the pressure as the square of the diameter and the power consumed as the cube of the diameter. So it looks like the rebuilder made a conscious decision to reduce the output of the pump from stock. I wonder why - perhaps they figured the OEM pump output was unnecessarily high, and they could cut back on power demand ... but why would they care, unless they were building it for racers? Scaling from photo, cut-back is about 20% of diameter, so flow would be down 20% and power required would be halved.
Malcolm
|