Jaguar’s long-awaited high-performance X-type diesel has finally been unveiled. It’s powered by a 153bhp 2.2-litre four-cylinder engine, which produces 266lb ft of torque from just 1800rpm. The new engine, also used in the Ford Mondeo features an ‘overboost’ facility ideal for overtaking manoeuvres, which kicks in under hard acceleration to deliver 295lb ft of torque for a brief period. The car also gets a new six-speed manual transmission. The new model, which is distinguished by a bodykit, goes on sale in September. Jaguar says that the car will be one of the quickest four-pot diesels on the market, with the ability to sprint from 50-75mph in fourth gear in 6.7sec and hit 60mph in 8.5sec. CO2 emissions have been held down to 159g/km for the saloon and 164g/km for the estate. The engine is based on Jaguar’s existing 2.0-litre turbodiesel, but with a number of engineering changes. Both the 2.0- and 2.2-litre units get a new, electronically controlled variable-vane turbocharger and a revised common-rail fuel injection system. Jaguar says lightweight conrods aid ‘extremely low levels of vibration’. Jaguar engineers say that meeting Euro4 emission levels can lead to greater noise, vibration and harshness in the warm-up phase, so they developed a new acoustic trim to line the engine bay and even the undertray is tuned to absorb certain frequencies during start-up. New driveshafts have been designed to match the 2.2’s extra torque. The long-striding sixth gear means the engine will be turning over at just 2000rpm at 70mph.