Kramer graph

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:

• Intake port / valve
• Scavenging port / valve
• Exhaust port / valve
• Reed inlet valve
• Rotary inlet valve

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.