In order to improve fuel economy and available power, a knock detector system has been developed which controls the maximum charge pressure in the Saab 2-litre Otto Cycle Turbo engine.
Compared to ignition retard knock control, the charge pressure control offers advantages in tolerance to variations in fuel octane number, full throttle fuel economy, hot spot auto ignition control, exhaust gas temperature and sensitivity to electrical noise and interference.
Further, the system allows a significant temporary increase in available engine power when accelerating in normal traffic conditions.
The turbocharger wastegate setting for maximum charge pressure is achieved through an integrated electronic system. The charge pressure knock control system is to a great extent “fail-safe”.