Method of installing a longitudinally offset multi-layer mat in an exhaust gas aftertreatment or acoustic device

A method is provided for installing a multi-layer mat (24) in an exhaust gas aftertreatment or acoustic device. The method includes the steps of wrapping the mat (24) around an inner surface of the device along the same plane for at least a complete wrap around the inner surface; subsequently wrapping the mat (24) around the already completed wrap such that each of the successive wraps of the mat (24) are offset a constant distance from the plane of the previous wrap; a final wrap of the mat (24) wherein the mat is wrapped along a final plane for at least a complete wrap around the catalyst; and installing the mat (24) in the device (18) after the wrapping steps.