Effect of spark-timing regularity on the knock of engine performance
A 1938 NASA technical report on engine testing, issued by the NASA Technical Reports Server, presenting measured engineering data rather than illustration for a general audience. Its single picture is a line graph of inlet-air pressure in inches of mercury absolute against spark advance in degrees before top center, with curves for indicated mean effective pressure and inlet pressure for two test runs, marked A and B, plotted on a grid and captioned as Figure 3. A designer might take from it a clean, sparse technical chart style with dashed and solid line pairs, labelled axes, and small circular and cross data markers.
