
Under the hood, the 4.4-liter V8 diesel has been tuned by Cosworth to produce 500 hp (373 kW / 507 PS) - an impressive gain of 191 hp (142 kW / 194 PS).
Source:
worldcarfans Tuning
https://www.tuning-links.com/news_1022_Project+Kahn+unveils+the+Range+Rover+RS500.html