"This report presents some results obtained during an investigation to determine the relative characteristics for several methods of control of an overcompressed engine using gasoline and operating under sea-level conditions. For this work, a special single cylinder test engine, 5-inch bore by 7-inch stroke, and designed for ready adjustment of compression ratio, valve timing and valve lift while running, was used. This engine has been fully described in NACA-TR-250. Tests were made at an engine speed of 1,400 R. P. M. for compression ratios ranging from 4.0 to 7.6" (p. 329).

"Apparatus for recording photographically the start, growth, and cut-off of oil sprays from injection valves has been developed at the Langley Memorial Aeronautical Laboratory. The apparatus consists of a high-tension transformer by means of which a bank of condensers is charged to a high voltage. The controlled discharge of these condensers in sequence, at a rate of several thousand per second, produces electric sparks of sufficient intensity to illuminate the moving spray for photographing. The sprays are injected from various types of valves into a chamber containing gases at pressures up to 600 pounds per square inch" (p. 361).