The term POWERFUL AUTO ENGINE can be summarized by three crossword solutions: HEMI, VSIX, and VTEN. HEMI stands for 'hemispherical combustion chamber, ' a type of engine design that is known for its power and efficiency. VSIX stands for 'variable-speed six-cylinder, ' a type of engine that uses variable valve timing to increase power output. Finally, VTEN stands for 'variable-torque ten-cylinder, ' a type of engine that combines the power of a V8 with the fuel efficiency of a V6. All three of these engines are powerful and efficient, making them ideal for powering powerful auto engines.