A closely-coupled exhaust aftertreatment system for an engine having twin turbochargers includes a first exhaust conduit comprising a first valve operable between first and second positions, the first promoting flow within the first conduit to an oxidation catalyst (OC), the second promoting flow within a second conduit; a third conduit is fluidly coupled to the OC outlet and includes a second valve operable between first and second positions, the first promoting flow within the third exhaust conduit to a particulate filter (PF), the second promoting flow through a fourth conduit to an inlet in the second conduit. A first turbocharger is coupled to the second exhaust conduit downstream of the inlet; an SCR catalyst is downstream of the first turbocharger to receive the flow therefrom and upstream of the PF to provide the flow thereto. A second turbocharger is coupled to the third exhaust conduit downstream of the second valve.