Ford introduced a new in-line 4-cylinder 2.3L DOHC 16-valve engine in its European D-class Scorpio vehicle. The engine is based on the proven 2.0L-DOHC engine with 8 or 16 valves. The new engine replaces the 2.0L DOHC 8-valve version.Primary focus of the development of this new 2.3L engine was on the noise and vibration improvement, both for the engine and for the vehicle interior noise. One measure to achieve this target was the application of balance shafts.In this paper, the development of the new engine will be described from the design stage to the production version. It will focus on the design of the balance shaft housing and all relevant engine NVH features. The various stages of the design and detailed optimization are explained. The NVH prediction by CAE methods is verified with experimental results. The influence of optimized components like the oil pan, front cover and the chain tensioner on the noise behavior will be discussed. Finally, test bed and vehicle measurements are presented.In the final version, the overall noise level of the new 2.3L engine is reduced by up to 4 dBA compared to the 2.0L engine, that means a 60 % noise improvement. With the concept of balance shafts a benefit of almost 70 % on the second engine order level at the engine mounts is achieved. In comparison to the state-of-the-art (i.e. range of similar engines) the new engine is very close to being „best-in-class” in the noise behavior.