The development of modern engine mechanical systems and electronic control systems has been advanced significantly over the last few years by increased use of engine modeling. A key requirement for improved modeling will be more accurate verification of the prototype engine performance to that predicted by the model. As percentage gains in engine power, fuel economy, and emissions become incrementally smaller, accurate measurements of these parameters are more critical. In addition, as engine testing in the dyno cell moves more toward transient operating conditions which more accurately represent actual driving conditions, measurement speed of the engine and ECM performance must increase tenfold or more to fully characterize transient behavior. This paper will illustrate these points with examples of engine development problems accompanied by descriptions of the key data system requirements such as sampling speed, measurement accuracy, and triggering flexibility.