Note that these flexible SS mesh exhaust pipe sections are actually
corrugated bellows convolutions with a flexible external mesh to safeguard
the weaker interior from damage, denting ... penetration. Much of the flex is
established by the corrugations which bend more readily than smooth tube, but
the wall thickness is also significantly reduced as well. The high interior
surface area and effective roughness increase the heat injected into this
segment and reduce the flow. Porsche flexible joints often have an inner pipe
to reduce the scattering problem for gas flow. The net effect is no problem
on a well cooled exhaust with modest heat loads, and local burn through on
short rear engine systems like ...

Frank Grunthaner