All-New Jaguar XJ

COMBUSTION EFFICIENCY

A new commonrail fuel-injection system delivers up to five injections on each cycle at a pressure of 2000bar (as shown in the video to the right).

Each injector tip is perforated by seven holes through which finely atomised fuel is sprayed into the cylinders. The high-pressure injection increases power, improves economy and reduces both CO2 and particulate emissions. New third-generation high-speed piezo injectors allow up to five precise injection events during each combustion cycle, minimising engine combustion noise.

Piezo crystal 'packs' operate each injector by expanding when an electric current is passed through them. They react virtually instantaneously but can make a distinctive click when fired, which can add to engine noise at idle. The crystals in Jaguar's new injectors are fitted nearer the tip meaning they are mounted deeper inside the engine providing better sound insulation.

Another new feature of the third-generation fuel-injection system is the metering mode. Traditional diesel commonrail fuel pumps oversupply the injectors, with the surplus being returned to the fuel tank. During this process, fuel temperature increases and cooling it again consumes considerable amounts of energy. In metering mode, the pump delivers fuel to the injectors only at the rate required. Consequentially, there is no rise in fuel temperature or wasted energy.

« BACK