A Kramer graph is a specific multiple-line 2D geometric symbolic representation of the characteristics of intake, scavenging and exhaust components in a two-stroke cycle engine.
They are typically used to visualize the opening time versus area and/ or lift of the following components: These representations are used to describe corresponding changes in crankshaft angle and port-area.
A Kramer graph plots the relation of the open area of various ports with respect to the angle of the crankshaft in a two-stroke engine.
So that upon completion of the cycle (one revolution of 360°) there has been no net change in state of the system; i.e. the device returns to the starting position and area which is zero.
Kramer graphs are named after Dutch engineer Hans Kramer, who is considered to have been the first to use this type of graph in a publication on the effect of port shape and area on two-stroke cycle engine performance.