Intake camshaft retard beyond that necessary for reliable cold start-ability is shown to improve part-load fuel economy. By retarding the intake camshaft timing, engine pumping losses can be reduced and fuel economy significantly improved. At high engine speeds, additional intake cam retard may also improve full-load torque and power.
To achieve these benefits, an intake camshaft phaser with intermediate lock pin position (ILP) and increased phaser authority was developed. ILP is necessary to reliably start at the intermediate phase position for cold temperatures, while providing increased phaser retard under warm conditions. The phaser also provides sufficient intake advance to maximize low-speed torque and provides good scavenging for boosted engine applications.
Design and development of the intermediate locking phaser system is described. The pros and cons of various methods of accomplishing locking and unlocking a phaser are illustrated. An AMESim model of the phaser was developed and Robust Engineering methods were applied.
Engine simulation and dynamometer testing was performed to determine system benefits. Control algorithms were developed and an enhanced engine management system was demonstrated in a vehicle.
