A gas turbine engine comprises a core engine housing. A nacelle is positioned radially outwardly of the core engine housing. An outer bypass housing is positioned outwardly of the nacelle. There is at least one accessory to be cooled positioned in a chamber radially between the core engine housing and the nacelle. A manifold delivers cooling air into the chamber, and extends ng circumferentially about a central axis of the core engine. The nacelle has an asymmetric flow cross-section across a circumferential extent.