A scroll compressor is provided with a passage for providing both an unloader function and an economizer injection function. This common passage communicates with separate ports. The ports that are exclusively used for by-pass unloading operation are open only during by-pass unloading operation, but blocked off by a check valve during vapor injection operation. The other, normally smaller vapor injection ports are open for both vapor injection and by-pass unloading operation. By utilizing these two sets of ports, a smaller total port area is provided for vapor injection operation and a much larger total open port area for by-pass operation. The different open port areas for by-pass unloading operation and vapor injection operation allows optimization of compressor operation at both of those regimes of operation.