This paper presents experimental results for a low-NOx aero gas turbine combustor, in particular, a third-generation swirl-venturi lean direct injection (SV-LDI-3) combustor concept called V4. The purpose of testing was three-fold. First, to evaluate the combustor against the 80% NOx reduction goal set by NASA’s AATT project. Second, to compare V4 to a previous SV-LDI-3 combustor concept called V3, especially at low power conditions. Third, to examine the accuracy of a type of correlation equation frequently used by engine systems analysis groups to estimate NOx emissions. All three testing goals were met. For the first testing goal, with an estimated NOx reduction of 85%–90%, SV-LDI-3 V4 surpassed the AATT goal. For the second goal, however, V4 did not perform better than V3 at low power conditions. For the third goal, it was found that a major assumption of the correlation equations — a simple dependence on combustor inlet pressure — did not hold.