Exhaust risers Turbocharger 1-3-5 Exhaust risers Exhaust wastegate valve Controller Tailpipe 1-3-5 Tailpipe 2-4-6 Turbocharger 2-4-6 Oil outlet port controller Butterfly Piston Power cylinder drain port Oil inlet port Seal Figure 3-15.  Waste gate control of exhaust. 3-10 If the waste gate is completely closed, all the exhaust gases  are “backed up” and forced through the turbine wheel. If the  waste gate is partially closed, a corresponding amount of  exhaust gas is directed to the turbine. The exhaust gasses, thus  waste gate regulates the amount of exhaust gases directed to  the turbine. The waste gate controls the volume of the exhaust  gas that is directed onto the turbine and thereby regulates  the speed of the rotor (turbine and impeller).  [Figure 3-15]  Figure 3-14.  Exhaust gas turbine assembly. 