Magnetostrictive and piezoceramic materials combine specific energy with speed, enabling fast and powerful but compact transducers. These materials, used in US Navy sonar for decades, elastically strain under the influence of a magnetic or electric field. Piezoceramics become active when electrically poled. Poling being artificial, the ceramic loses its piezoelectric properties under overstress, overstrain, overvoltage, or overheating, conditions present in a diesel engine that limit injector performance. In contrast, a magnetostrictive alloy of terbium, dysprosium, and iron will not permanently degrade under the same conditions, enabling an injector to be pushed to the highest possible speed. Quantum mechanics dictate that the non-bonding 4f electron cloud of the terbium atom be oblate, not spherical, an inherent property that connects magnetic and elastic influences.