$$Q = 13.2 \times d^2 \times (P + 14.7)$$
Example: You have 1 liter of total volume and a suction flow rate of 100 L/min (1.66 L/sec). $$t = \frac11.66 \times 2.3 \approx 1.4 \text seconds$$ vacuum ejector calculation
Have a specific application? Drop the specs (part size, material, cycle time) in the comments, and we will run the numbers for you. $$Q = 13