PURPOSE: To suppress engine exhaustion pressure within a prescribed permissible range in a wide-range driving area without any response by connecting piping for introducing outside air to a branch part of an exhaust gas suction pipe provided nearby the exhaust gas pipe of the engine.

CONSTITUTION: In engine full-load driving, all of exhaust gas from the exhaust port part B of the engine 3 to be tested is introduced to the exhaust gas suction pipe 7 through an exhaust gas flexible pipe 5 and an exhaust gas through nozzle 6 to enable induction processing by an exhaust gas blower 8. At this time, the pressure of the branch part C is at high as the pressure in the intake port D of a suction pipe 12 and no engine exhaust gas is blown out of the intake port D through the suction pipe 12. A manual by-pass dumper 11 is provided to a by-pass pipe 10 provided right in front of the suction side of the exhaust gas blower 8 of the exhaust gas suction pipe 7 and the opening degree of the by-pass dumper 11 is so adjusted that the pressure of the branch part C is negative within the prescribed value range, thereby adjusting the exhaust gas induction amount.