Ten years after the first 928 was launched, Porsche unveiled the 928S4. This had a 5.0-litre engine with four valves per cylinder and twin overhead camshafts per cylinder bank. Power rose to 320bhp.
The updated car looked more modern, thanks to smoother and flusher front and rear bumpers and lights, while there was a large black rear spoiler.
Intriguingly, the S4 had an ‘intelligent’ cooling system for the engine. This consisted of horizontal louvres between the front intake and the radiator; these were computer controlled and their angle changed according to coolant temperature. The idea being that the louvres were kept closed as much as possible to ensure the best aerodynamic efficiency; the Cd increased from 0.34 to 0.36 when they were open.