A vapor compression system comprising: a compressor; a heat rejection heat exchanger coupled to the compressor to receive refrigerant compressed by the compressor; an ejector comprising; a motive flow inlet, a secondary flow inlet, an ejector outlet, a motive flow nozzle having an outlet, a primary flowpath from the motive flow inlet through the motive flow nozzle to the ejector outlet, a secondary flowpath from the secondary flow inlet to the ejector outlet, merging with the primary flowpath at the motive nozzle outlet, a control needle (200; 300; 400) shiftable along a range of motion between a first condition and a second condition and seated against the motive flow nozzle in the second condition, wherein the needle comprises: a main shaft, a tip, a first portion (220; 320) converging toward the tip, and a shoulder portion (214; 314; 422) between the first portion and the main shaft and seated against the motive flow nozzle in the second condition and converging toward the tip at a greater angle (θ l; θ 1-2) than an angle (θ 2; θ 2-2) of the first portion; a heat absorption heat exchanger; and a separator having: an inlet coupled to the outlet of the ejector to receive refrigerant from the ejector, a gas outlet, and a liquid outlet. a compressor; a heat rejection heat exchanger coupled to the compressor to receive refrigerant compressed by the compressor; an ejector comprising; a motive flow inlet, a secondary flow inlet, an ejector outlet, a motive flow nozzle having an outlet, a primary flowpath from the motive flow inlet through the motive flow nozzle to the ejector outlet, a secondary flowpath from the secondary flow inlet to the ejector outlet, merging with the primary flowpath at the motive nozzle outlet, a control needle (200; 300; 400) shiftable along a range of motion between a first condition and a second condition and seated against the motive flow nozzle in the second condition, a motive flow inlet, a secondary flow inlet, an ejector outlet, a motive flow nozzle having an outlet, a primary flowpath from the motive flow inlet through the motive flow nozzle to the ejector outlet, a secondary flowpath from the secondary flow inlet to the ejector outlet, merging with the primary flowpath at the motive nozzle outlet, a control needle (200; 300; 400) shiftable along a range of motion between a first condition and a second condition and seated against the motive flow nozzle in the second condition, wherein the needle comprises: a main shaft, a tip, a first portion (220; 320) converging toward the tip, and a shoulder portion (214; 314; 422) between the first portion and the main shaft and seated against the motive flow nozzle in the second condition and converging toward the tip at a greater angle (θ l; θ 1-2) than an angle (θ 2; θ 2-2) of the first portion; a main shaft, a tip, a first portion (220; 320) converging toward the tip, and a shoulder portion (214; 314; 422) between the first portion and the main shaft and seated against the motive flow nozzle in the second condition and converging toward the tip at a greater angle (θ l; θ 1-2) than an angle (θ 2; θ 2-2) of the first portion; a heat absorption heat exchanger; and a separator having: an inlet coupled to the outlet of the ejector to receive refrigerant from the ejector, a gas outlet, and a liquid outlet. an inlet coupled to the outlet of the ejector to receive refrigerant from the ejector, a gas outlet, and a liquid outlet.