Method of regulating the flow rate of EGR gas through short and long EGR routes of a turbocharged i.c. engine

The flow rate of EGR gas through short and long EGR routes 50, 60 of a turbocharged i.c. engine is regulated by a method comprising (a) determining a first setpoint value S1 for the total amount of exhaust gas requested into the intake manifold 10; (b) determining a second setpoint value S2 for a parameter representative of the relationship between the total amount of exhaust gas requested into the intake manifold and the amounts from the short and long EGR routes 50, 60; (c) applying the set-point values S1, S2 to a control routine for adjusting the means 52, 62, 63 which regulate the flow rate through the EGR routes 50, 60; (d) determining a third setpoint value S3 for the temperature in the intake manifold 10; (e) determining the actual intake manifold temperature A3; (f) calculating the error E3 between the actual temperature A3 and the third setpoint value S3; and (g) using the error E3 for generating a correction index I to apply to the second setpoint value S2 in order to minimize the error E3.