Turbine Housing TypeSelectt3, 0.83 a/r, single scroll turbine housing with internal wastegatet4, 1.45 a/r, twin scroll turbine housing (requires external wastegate)t4, 1.05 a/r, twin scroll turbine housing (requires external wastegate)t4, 0.92 a/r, twin scroll turbine housing with pneumatic internal wastegatet3, 0.83 a/r, single scroll turbine housing with pneumatic internal wastegate