This paper addresses both the generation of various injection rate shapes using the accumulator type electronic injector, and their effects on engine combustion and sound level performance as recorded by a 500,000 sample-per-second PC board Engine Analyzer. An advanced hydro-electronic unit injector has been developed by BKM to offer a wide range of readily adjustable injection rate shapes to match a particular engine combustion configuration. The system is adaptable to both fixed (passive) rate shaping and active on-line optimization with electronically adjustable injection timing, fuel quantity, and injection rate. The effects of a range of injection rate shapes on fuel economy, exhaust emission, heat release rate, and noise level are readily available and properly documented within a few minutes of the engine running. Difficulties and errors in instrumentation and test variables can be diagnosed during the run and corrected before the operating condition is varied for the next test run. The test engine is a commercial engine normally equipped with a jerk type pump-line-nozzle (PLN) system. A baseline is run first and the injection system is subsequently replaced with the Servojet system with a G-4 electronic unit injector. The test engine is installed in a test cell with an eddy-current dynamometer and a computerized data acquisition system outputting torque, f/A, rpm, bmep, smoke, NOx, CO and bsfc on a computer printout. A PEI 504 Engine Analyzer with sample and hold features is used to simultaneously record the cylinder pressure and injection accumulator pressure. From these two sensings, fuel injection characteristics are compared with heat release rate, ignition delay, premix combustion index, noise level, and several other engine performance and emission parameters.