Present-day oxygen abundance vs. M_∗ as predicted by models with metal-enhanced wind (w_H,He = 0.1). All the models contain 7 bursts and the same SFH (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 predicted M − Z relation with different strength of metal-enhanced wind are shown by different lines: dash-dotted, long-dashed, short-dashed, and dotted black lines are for λ_mw = 0,0.2,1,3 respective. Models with the same M_inf are connected by blue lines. An increasing wind efficiency to less massive galaxies is shown by a solid red line, which can fit the data very well. 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.