For optimal exhaust efficiency you need a wider exhaust diameter at higher rpm as compared to lower rpm and that is exactly what the EXUP system does: it reduces the diameter at lower rpm.

• 最佳排气效率，您需要一个更广泛的排气直径在更高的转速为每分钟转速比较低，而且正是EXUP系统不：它降低了直径在较低的转速。