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A phenomenon exists in diesel or compression ignition engine powertrains with torsionally flexible couplings where the powertrain sometimes cannot accelerate through a torsional resonance such as during engine start-up. This phenomenon is sometimes referred to as resonance stall, resonance hang-up, or a jackhammer start. The current theory is that the hysteretic damping of an elastomeric coupling is dissipating input energy from the engine, thereby prohibiting the system from accelerating through the resonance. This theory comes about because the elastomeric coupling, with its hysteretic damping, heats up during resonance and is obviously dissipating energy. By conducting a theoretical study of the energy balances of vibration for a powertrain model and by carefully considering field observations, this paper will show that energy dissipated by the torsionally flexible coupling does not come at the expense of the mean or working torque that was input by the engine.

This paper presents a simple method of estimating steady-state diesel engine disturbance amplitudes that can be used in rigid-body, low frequency vibration modeling to predict the performance of an engine's isolation suspension and its components. The internal disturbances occurring at each cylinder and crank throw are determined and combined to provide the net disturbances for several common four-stroke diesel engine configurations. The method utilizes a simplified Fourier decomposition of diesel combustion and the predominant inertia disturbances from within the engine. With a few pieces of information from the engine maker, actual disturbance amplitudes and phases can be estimated. Conditions and simplifying assumptions are discussed. The estimated disturbance amplitudes can also be used in torsional vibration modeling of the drivetrain.