This paper presents details of the development of, and experimental results from, an internal combustion engine dynamic cylinder heat transfer control device for use on single-cylinder research engines. This device replicates the varying temperature profile and heat transfer distribution circumferentially around a cylinder in a multicylinder engine. This circumferential temperature distribution varies around a cylinder because of the location of, or lack of coolant passages around the cylinders, and varies from cylinder to cylinder as a result of the flow of the coolant through these passages as it accumulates thermal energy and increases in temperature. This temperature distribution is important because it directly affects the NO emissions from each cylinder, as will be seen in the experimental results. Single-cylinder research engines do not replicate these varying cylinder temperature profiles, and as a result the emission measurements from these research engines may not be representative of what would occur in a multi-cylinder engine. This technology allows engineers to simulate and directly measure the causal relationships between engine coolant passage design, resulting cylinder temperature profiles, and the resulting emissions from individual cylinders. These results can significantly help engine designers understand the trade-offs they make in such designs, their effects on engine emissions, and perhaps design a better engine.