An aftertreatment system may include an exhaust pipe and a mixing pipe. The exhaust pipe may receive exhaust gas from an engine and may include a first portion defining a first longitudinal axis and a second portion defining a second longitudinal axis that is angled relative to the first axis. The mixing pipe may be disposed in the exhaust pipe and may include a tubular portion and a collar extending radially outward from the tubular portion. The tubular portion may include a plurality of openings and a plurality of deflectors. The plurality of openings may extend through inner and outer diametrical surfaces of the tubular portion. Each of the plurality of deflectors may be disposed adjacent a corresponding one of the plurality of openings.