The present invention provides the art with a scroll machine which has a
plurality of built-in volume ratios along with their respective design
pressure ratios. The incorporation of more than one built-in volume ratio
allows a single compressor to be optimized for more than one operating
condition. The operating envelope for the compressor will determine which
of the various built-in volume ratios is going to be selected. Each
volume ratio includes a discharge passage extending between one of the
pockets of the scroll machine and the discharge chamber. All but the
highest volume ration utilize a valve controlling the flow through the
discharge passage.