Exhaust valve type
Built-in
The built-in exhaust valves are part of the turbine cover. The transmission devices of the exhaust valves are generally fixed on the compressor cover with a metal bracket. The built-in exhaust valve generally uses a tongue valve. The built-in valve is widely used because of its low cost, but it is not suitable for use in high-horsepower engines. A built-in valve that is too small often causes pressure creep or pressure swing, which is generally manifested as a fluctuating or uncoordinated power curve.
External
The separate exhaust valve discharges the exhaust gas directly into the atmosphere without recovering the exhaust gas through the exhaust device at the end of the engine. This can prevent the turbulence of the exhaust gas flow and reduce the total back pressure of the exhaust system. Separate exhaust valve exhaust pipes are generally called "screamer pipes", because the exhaust gas that has not been silenced will produce huge noise.
The built-in exhaust valve generally cannot be directly discharged into the atmosphere because the built-in valve port and the turbine outlet wind deflector are not in the same chassis. Occasionally, the under-hung exhaust pipe of a turbocharger with an exhaust valve is called "separate" because it integrates two pipes, one of which only serves as an exhaust valve. It is worth noting that it is difficult to truly distinguish the exhaust gas flow of the turbine and the exhaust valve. Therefore, the built-in exhaust valve is rarely equipped with an external exhaust pipe.
