The majority of the changes are mechanical. The D4 receives two engines from Jaguar Land Rover’s ‘Gen III’ range. The TDV6 Gen III is a 3-litre development of the 2.7-litre engine used in the D3. The new version features advanced twin-sequential turbochargers where a Variable geometry turbocharger is used at low engine speeds, with a second standard turbo is brought online at higher engine speeds. This system provides greater output than the older engine (now 241 bhp (180 kW) and 600 N·m (440 lb·ft) whilst reducing CO2 emissions by 10%. The Gen III version of the V8 petrol engine (available in markets outside the UK and Europe such as North America, Russia and Australia) is now a 5-litre unit with Direct Petrol Injection developing 385 bhp (287 kW) and 520 N·m (380 lb·ft).
The Discovery 4 was unveiled in the summer of 2009 and went on sale in the United Kingdom on the 1st September that year. A Commercial van variant was released in the UK at the same time using the 2.7 engine and offered in GS and XS trim levels. In the Republic of Ireland a Commercial van was offered from 1st January 2010 based on the XE 2.7 manual and HSE 3.0 auto engines.
For the 2011 model year announced late 2010, the 2.7 engine was dropped (supplies had run out!) and two versions of the 3.0 litre engine were made available – one called the TDV6 and one called the SDV6 (the latter offering 245bhp). Van variants for the Republic of Ireland were now built and converted in the UK before being shipped to Ireland.
