Exhaust system to open air — everything from the header back. Header-back systems are generally produced as aftermarket performance systems for cars without turbochargers. The Turbo-back (or turbo back) is the part of the exhaust system from the outlet of a turbocharger to the final vent to open air. Turbo-back systems are generally produced as aftermarket performance systems for cars with turbochargers. Some turbo-back (and header-back) systems replace stock catalytic converters with others having less flow restriction. Some systems (including in former time all systems) (sometimes nowadays called catless or de-cat) eliminate the catalytic converter. It is illegal and is against Federal
Exhaust mixer increasing thrust. The exhaust thrust from a jet engine is equal to exhaust mass flow times exhaust velocity, i.e., "Thrust = ṁv", while the energy to make that thrust is given by "Energy" = 1/2"mv". A mixer helps reduce the fastest exhaust velocities from the core of the engine, while making the average exhaust velocity faster, producing more thrust with the same energy. Mixing efficiency is defined in a number of ways, but simply, compares the actual thrust gain (due to mixing) to that of the ideal case. Annular mixers have a low pressure loss, but a low mixing efficiency.