If you like the 330d, the 535d will blow your mind. Now, it hasn't got a 3.5L-its displacement is the same size as the 330d's-but it comes with two turbos arranged inline, sequentially. It's the same system adopted by the Porsche 959 almost two decades ago, but it's still fresh thinking in this field.
At low speed, a small turbocharger handles the workload; at medium speeds, some of the intake air is diverted to the larger turbo; and at high speeds, it takes over completely. Now that sounds like an electronics nightmare in the making, but this car works so well that others will copy the design.
The crankcase has to withstand 2.85 bar of pressure, more with mods, but this car will likely go for hundreds of thousands of miles, if properly maintained. Some of Europe's less developed nations have long been populated by 1980s diesel-powered taxis that have gone round the clock more often than the minute hand on a Seiko.
The results are astonishing for an executive diesel saloon. With 272 bhp and 412 lb-ft of torque, this car can break traction for fun. It only comes with an auto box at the moment, as BMW say there's just too much torque for its manual boxes to handle, which of course begs questions about the longevity of the Hartge 330d.
And the really mad thing is that spending 500 with Superchips can boost this machine to 319 bhp and a plain stupid 466 lb-ft of torque. That gives it the real world mid-range power of anything, bar the most expensive Mercedes AMGs, for about half the price and, at 34.4 mpg on a combined cycle, more than twice the economy. If BMW can be tempted to bring this stunning car to these shores, it will be a sensation. The future, it seems, is dark.