Present-day oxygen abundance vs. M_∗ as predicted by models with normal wind. All the models contain 7 bursts and the same burst sequence (ϵ = 0.2,n = 7,t = 1/3/5/7/9/11/13,d = 0.1 for each burst), and the total infall mass varies from M_inf = 10⁸ to 10¹⁰ M_⊙. The upper panel shows results on a short infall timescale (τ = 1 Gyr), whereas the lower one shows results with a long timescale (τ = 10 Gyr). The predicted M − Z relation with different strengths of normal wind are shown by black lines: solid, dash-dotted, long-dashed, short-dashed, and dotted black lines are for λ_m = 0,0.2,0.5,1,3, respectively. Models with same M_inf are connected by blue lines. An increasing wind efficiency to less massive galaxies is shown by a solid red line. Observational data are shown by open cyan circles (BCDs) and open cyan triangles (dIrrs), the solid cyan line is the best fit of all the data, as in Fig. 1.