The helix-angel of intake ports is educed and valve set is a new design, the exhaust ports adopt the approximate circle shape cross-section as the exhaust pipe.

• 进气道减小了螺旋角度并对气阀座进行了重新设计,排气道采用了与排气管相匹配的近似圆形截面并进行了光滑过渡。