Volvo designed the SI6 (“short inline 6”) straight-6 automobile engine for use in 2007 models. An evolution of the company’s long-used straight-5 Volvo Modular engine, which itself is an evolution of the Volvo B6304 straight
six engine, the SI6 can be mounted transversely for front wheel drive or all wheel drive applications. Despite the added cylinder and displacement, the engine remains compact, and is in fact 1 mm (0.039 in) shorter than the
previous straight-5. The engine was initially offered in two displacements — a 3.0 L turbocharged version and a 3.2 L naturally aspirated version. Both offered variable cam timing, though only the turbo version varies both the
intake and exhaust valves. On top of the variable cam timing used on the intake cam of the naturally aspirated engine it also had variable valve lift by using Cam Profile Switching (CPS).
Production of the Volvo SI6 began at the Ford Bridgend Engine Plant in Wales in May 2006. It was assumed that the engines would be used in European Ford and Jaguar products as well as Volvos.