Evaluation of Idle Combustion Stability Using Flywheel Acceleration

Vehicle idle quality has become an increasing quality concern for car manufacturers because of its impact on customer satisfaction. To get better fuel economy the overall trend is to reduce idle speed at both drive and neutral idles. This typically has adverse impact on vehicle idle quality. Lowering the idle rpm generally degrades the engine combustion stability and also makes the engine driving forces more likely to align with vehicle sensitivities (Powertrain rigid body modes, body modes, etc.). To better understand the contribution to the idle quality from different factors and carry out well-planned improvement measures, a quick and easy way to assess engine combustion stability is required.