{latex}
\large
$$
D_{orificemanifold}  = \root 4 \of {{{(1 - Q_{manifoldratio} )d_{pipe} ^4 } \over {\left[ {\left( {K_{total}  + f{{L_l } \over {d_{pipe} }}} \right)} \right]Pi_{VenaContractaOrifice} ^2 n_{orifice} ^2 }}} 
$$

{latex}