This study belongs to a broader project that examines the efficacy of rhythm instruction to enhance Spanish/Catalan engineering undergraduates’ comprehensibility and fluency in English. To this end, a ten-week pronunciation module was designed and embedded within a technical English course. 42 students participated in the experiment: half of them received explicit rhythm instruction (experimental group), and half of them did not (control group). All the subjects were recorded before and after treatment. Ten sentences were analyzed acoustically, and measures of VarcoV and %V were obtained, as these have been considered better measures of rhythm in second language research. Previous studies showed that VarcoV values tended to increase after treatment for the experiential group, adopting a more stress-timed rhythm, whereas the control group showed several inconsistencies. This paper will present the results obtained when measuring %V, and how these complement previous findings. Results revealed that the experimental group tended to decrease their %V values, while the control group appeared to increase them. Besides, the comparison of the effect sizes of each group’s differences in performance showed more and larger signs of improvement for the experimental group. These findings further support that rhythm instruction can be beneficial to enhance ESP students’ prosody.