Calibration of engine management systems requires considerable engineering resources during the development of modern engines. Traditional calibration methods use a combination of engine dynamometer and vehicle testing, but pressure to reduce powertrain development cost and time is driving development of more advanced calibration techniques. In addition, future engines will feature new technology, such as variable valve actuation, that is necessary to improve fuel economy, performance, and emissions. This introduces a greater level of system complexity and greatly increases test requirements to achieve successful calibrations.
To address these problems, new simulation tools and procedures have been developed within Delphi to rapidly generate optimized calibration maps. The objective of the work is to reduce calibration effort while fully realizing the potential benefit from advanced engine technology. The procedure utilizes GT Power engine simulation software and engine models validated through limited dynamometer testing.
A front end to GT Power was written to automatically call GT Power executables and produce the calibration dataset. Several methods were used to accelerate the simulation process. Calibrations are optimized using an additional software tool that includes a weighted-optimization scheme. User-defined constraints may be applied during optimization for cam phaser position, combustion dilute limits, exhaust temperature or any other variable defined in the engine model. The overall procedure includes vehicle simulation using ADVISOR to estimate fuel economy and emissions for the drive cycle.
This paper describes the simulation tools and procedures, and presents calibration results for a modern V6 engine equipped with two-step VVA and intake cam phasing. Preferred two-step switching schedules and cam phaser position maps are presented.