Normal smooth wall flow with interFLEX (with inliner)
Low turbulence = low back pressure (only 1.6 mbar pressure loss at full engine load)
Adding turbulence due to the open waves of the flexible pipe (without inliner)
High turbulence = high back pressure
(here 8 mbar pressure loss at full motor load)
Frequent damage to the inner braid:
Constriction of braided hose after tearing off the wires in the entrance area