The following images in Figure 19 show the effect of a butterfly throttle body in (A) as compared to a clear barrel in (D). it also shows the effect of optimizing the throttle plate aerodynamically to reduce the effect of impeding air flow, and with more optimization, the presence of the butterfly valve can still approach that of an open barrel, shown by sharpening the plate in (B) and trimming down the shaft holding the plate (C) .