A parametric investigation on high pressure diesel spray combustion characteristics was performed using a constant volume bomb, in such a way as to cover a wide range of chamber conditions, for 100, 210, and 320 MPa injection pressure. Ignition delay and position were found to be scarcely affected by injection pressure. High values of gas temperature and density produce faster ignition and move the ignition location closer to the injector nozzle. The duration of the combustion process was found to be a function of both injection pressure and chamber conditions. In particular, injection pressure increments shorten the combustion time, featuring a monotonic effect. Chamber temperature variations did not produce monotonic effects on combustion times. In fact, a minimum was found in the low- medium temperature range for all the conditions tested. In this respect, for each injection pressure, a fast combustion region on a gas pressure-temperature map can be defined, whose extent increases as the injection pressure increases.