Data from the first seven power tests of a lightweight, self-excited MHD generator system are presented. Among the achievements of these tests were: 1) highest power from a diagonally connected MHD generator in the United States (4.8 MW, gross), 2) fastest self-excitation time for an MHD generator (0.4 s), and 3) highest specific power for a combustion-driven MHD generator in the United States on the basis of gross or net power per unit system mass. The tests show evidence of strong MHD interaction processes, including magnetoaerothermal effects, as expected from the design calculations. Solution of the intricate problems presented by these processes for each size of this family of MHD generators is necessary before the ultimate performance of these systems is realized. The software for obtaining these solutions has been validated, and some results are discussed in this paper.