Characterization of a three-dimensional Mach 2 scramjet combustor with aspect ratio one has been conducted in order to provide baseline performance data. The maximum combustion performance was achieved at an equivalence ratio of 0.25 due to poor mixing. Subsequent fuel injection studies investigated transverse and ramped parallel mixing schemes in a Mach 2 duct. It was shown ramped injection required too high of flow blockage to be practical for efficient mixing. From these studies a new Fin-Guided fuel injection technique was established. Substantial improvement in mixing performance was observed through pressure traces, Schlieren and Mie-scattering. With the use of Fin-Guided Injection the fuel penetration height was increased by 100~120% and the flow losses associated with jet-induced shocks were reduced by 13~30% over injection without a fin. The results open up the possibility of further increasing performance by optimizing the fin height and the fuel injection angle behind the fin.