The unrelenting progress of diesel engines shows no sign of flagging. Witness BMW’s brilliant new twin-turbo 535d. Ignore the capacity implications of the 535d badge and the still-3.0-litre in-line six reclaims the title of the world’s fastest-accelerating diesel car from Audi’s A8 4.0 TDi.
Not only that, it introduces new levels of responsiveness, an even broader powerband and the highest specific output – a staggering 90bhp per litre – of any current production diesel.
The 535d is so powerful it outguns even the 255bhp 3.9-litre V8 currently offered only in the left-hand-drive 740d. Understandably, the V8 is due to be enlarged for next year’s revised 7-series. The new six uses twin turbos of differing sizes.
A small turbo operates alone from idle to 1500rpm, when it’s joined by the big turbo for a short second stage, before the larger blower takes over from 2500rpm to the maximum 5000rpm. So the new BMW unit is entirely different from Jaguar’s 2.7-litre diesel, which effectively operates as two three-cylinder engines, each with its own identically-sized turbo.