2016 Volvo S90 - Power Pulse
The PowerPulse system works by drawing fresh air directly from the air box and compressing it into a two-liter tank. If the driver presses hard on the accelerator at low speeds or even at launch, the compressed air from the tank will be blown through a valve directed at the turbo.
With conventional wastegated turbochargers or fixed geometry turbochargers (FGT), a turbine flow area cannot be adjusted during operation.
Knocking is abnormal combustion in which the air-fuel mixture ignites prematurely due to exposure to high temperature and pressure, creating an unwanted high-frequency noise. When the compression ratio is increased, the temperature at compression top dead center (TDC) also rises, increasing the probability of knocking.