In order to approach the Carnot efficiency in modern diesel engines that see variable loads and high speeds, programmable electrically controlled fuel injections are required. Traditional solenoid based transducers are binary and cannot achieve this programmability while newer piezoelectric transducers are susceptible to performance degradation due to high pressures and temperatures. This paper presents the experimental characterization of a programmable diesel fuel injector transducer designed by Great Plains Diesel Technologies, L.C. to address the limitations of existing technology. This transducer employs a little-known magnetostrictive alloy to position its needle. In contrast to piezoelectric ceramics, quantum mechanics endows this alloy with the indestructible property of magnetostriction, the ability to strain proportional to a magnetic field. This allows it to be fast and infinitely adjustable (or, “programmable”) without degradation. A fuel injector based on this alloy has the inherent durability to survive on an engine while maximizing performance. In the tested prototype, the magnetostrictive rod is surrounded by a coil excited by a current pulse to energize the alloy. The prestress needed to achieve maximum performance is provided by the pressurized diesel fuel.This paper presents the results of a series of tests run to determine the effect of the amplitude of the excitation current and the prestress provided by the pressurized fuel, and to characterize the amplitude and speed of the transducer output displacement and its proportionality.