Kramer graph

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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:

They do not show the specific configuration of ports like in a port-map, which enables it to illustrate a more useful visualization of port area distribution,

This could be useful because different types of port configurations could have the same opening time and area.

In these graphs the X-axis represents the crankshaft angle (θ) in degrees, and the left Y-axis represents the open area in any square unit of measure such as cm². To discern the different types of ports each type is given a designated color.

For example (commonly used):

  • Blue - Intake system
  • Green - Scavenging system
  • Red - Exhaust system
  • Purple - Inlet valve


Kramer graphs are named after Dutch engineer H. 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.