Engine piston channel for optimum air scavenging

A piston channel (16) is provided for a piston (12) of an air scavenging internal combustion engine (10). The channel (16) extends radially inward partially around a circumference of a piston body. An edge wall (18) of the channel (16) is sloped towards a wrist pin aperture (19) in the piston (12) to improve purging efficiency of a transfer duct.