GM Global Propulsion Systems Division constantly strives to optimize engine combustion for best fuel economy, power, drivability and emissions. Good metrics are required to make consistent engine design and calibration tradeoff decisions. A key metric in tradeoff decisions is combustion stability which has an integral relationship with fuel efficiency, emissions, drivability, and probability of Misfire. Coefficient of Variation of Indicated Mean Effective Pressure (COV of IMEP) is a widely used metric to quantify combustion variation and stability. However, COV of IMEP is not always a consistent metric when trying to set optimum stability limits for efficiency, emissions or probability of misfire. To augment COV, Lowest Normalized Value or LNV of IMEP and Pressure ratio have been used, but also are not as consistent of an indicator as desired.
Instead of basing combustion stability metrics on Gaussian statistics with Normal Distributions, a combustion stability metric should instead take into account levels of asymmetry in the distribution.
Students on this team will develop a new, more consistent combustion stability metric that takes into account existing, asymmetrically-distributed engine measurement data.
Check back in September for student IP/NDA agreement forms.