Engine Idle Combustion Stability Evaluation Using Calibration Parameters

Vehicle idle quality has become an increasing quality concern for automobile manufacturers because of its impact on customer satisfaction. As demand for better fuel economy increases, automobile manufacturers are continuously looking for any benefits from different driving conditions. One area is lowering the idle speed at both drive and neutral idles. This typically has adverse impact on vehicle idle quality for the two reasons. First, lowering the idle speed generally degrades the engine combustion stability, which typically increases the excitation forces (0.5^th, 1.0^th, 1.5^th, etc combustion torques). Second, lowering idle speed will cause modal alignment issues (i.e. combustion and inertia forces align with Powertrain rigid body modes, body modes, etc.). NVH development engineers have been requesting for an easy and quick way to measure engine combustion stability, which can help them to understand the contributions to their idle quality issues from different factors and evaluate the count measures for the fixing.