An exhaust line has upstream and downstream blocks for processing exhaust gases. An injection section is arranged between an upstream face defined by the upstream block and a downstream face defined by the downstream block and includes a circulation channel for the exhaust gas flow extending from the upstream face to the downstream face. The channel includes a central line having a determined length between the upstream and downstream faces. The injection section includes a reagent injector capable of injecting a reagent into the injection section. The injection section has a first cup inside the circulation channel in the flow path such that the average path of exhaust gas jets is higher by at least 20% in relation to the predetermined length. A second cup is arranged inside the circulation channel between the upstream face and the first cup. The reagent is done between the first cup and the second cup.