You can learn a lot about the inner working of an engine from physical tests — how it heats up, how it cools down, how it behaves during acceleration, and so on. Looking at the test cell data from the dynamometer, Tony Willcox, Pinnacle Engines' director of simulation and controls, can gauge the engine's average performance characteristics such as torque, power, fuel flow, and emissions. He can examine crank-angle-resolved data to analyze cylinder and port pressures, rotation speed, and piston position during a series of combustion events. But Willcox and the simulation team at Pinnacle are also interested in what they cannot see or measure. To extract every last joule of energy from the fuel, they need to peel off the engine cover and look inside to quantify and improve each source of energy loss from spark to exhaust. And that's where they run into the limitations of physical tests. "Optical engine technologies exist that enable some visibility into the cylinder," he remarked, "but they present their own sets of challenges: for example, their configurations are limited, and it's very expensive to implement them."

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