It's an exciting twist to turbocharging just as this previous bad boy feature threatened to become boring.
Philip King road tests and reviews the new BMW X6 M50d with specs, fuel economy and verdict.
When too much turbocharging is barely enough, BMW has the answer.
And if you think of a turbocharged car as a ram-raid waiting to happen or a one-way ticket into accident statistics for an acned yoof who doesn't know the front of his cap from the back, then take a look at some new car brochures.
With a price of $157,000, it's $30k more than the next most expensive diesel, the X40d, and about $30k less than the petrol X6 M. Among performance SUVs, the X6 M50d has few diesel rivals beyond that Audi Q7 V12. Its real competition comes from petrol models such as the Mercedes ML63 AMG or Porsche Cayenne GTS.
The M550d is ruled out for Australia because it's only made in left-hand drive. But the same engine does come here under the bonnet of the facelifted X6 SUV in a model dubbed M50d.
This wagon spearheads a BMW initiative called M Performance, which is a sort of halfway house between regular models and the highly tuned cars produced by its M division. M Performance cars go down the same assembly line as standard cars, instead of being whisked away for full-strength M treatment. But M waves a wand over the chassis.
It needs to, because the hero ingredient is the aforementioned 280kW diesel and its party trick is not one turbocharger or even two. It has three. This is also the most powerful six-cylinder diesel you can buy. The M50d adds to the three petrol and two diesel engines already available for the X6.
This model heralds a facelift for the X6, which brings restyling so subtle as to be undetectable and some new options, including LED lights. Particular to the M50d are a power-bulge bonnet and black tailpipes. This engine and a similar makeover will soon be available in the X5.
The M50d's unique choir of three turbochargers join in progressively as revs rise. Just above idle, a small high-pressure turbo spins up to give an initial boost. At 1500rpm, it's joined downstream by a larger air pump that maintains maximum torque into the mid-range.
Then at 2700rpm, an additional route opens to channel exhaust gas to another small turbo, which in turn also feeds the large turbo as well. The software that controls this must be dauntingly complex, because from behind the wheel all you feel is a sheer avalanche of torque.
It propels this 2.2 tonne, 4.9m long coupe-on-stilts to 100km/h in a mere 5.3s. That's quicker than Audi's Q7 V12 and not a whole lot slower than an X6 M. At the same time, it uses just 7.7 litres per 100km. A road leg with the Territory's 130km/h speed limit showed the M50d is every bit as quick off the mark as expected.
It revealed little about the chassis tuning, however, and actually exposed some disadvantages. These stem mainly from the standard 20-inch wheels with low-profile run-flat rubber, which generate a fair bit of noise and result in a ride that's jarring at times while uneven tarmac causes kickback through the wheel.
However, on the racetrack the dynamic virtues of the car came to the fore. Its all-wheel drive system preferences the rear wheels, dividing torque 40:60 under normal circumstances. But it can divert 100 per cent of power to fronts or rears if required.
This X6 also gets something called Dynamic Performance Control, which can redirect power between the rear wheels to counter understeer or oversteer. With active dampers and an active anti-roll system, the X6 M50d handles Hidden Valley's corners with the gentle grace of a circus elephant and you can feel it redirecting the torque as required.
On the straight it powers away without any strain, revving to 5400rpm and reaching 200km/h-plus before brakes are required to rein it in. There's 740Nm of torque on hand to punch out of corners -- if the electronic stability control allows -- and brakes that stand up well to abuse lap after lap.
For some, the M50d will be just another illustration of how pointless a large, impractical SUV can be. For me, it's an exciting twist to turbocharging just as this previous bad boy feature threatened to become boring. If it heralds a new age of performance diesels, bring it on.
BMW X6 M50d
Price: $157,000 plus on-road costs
Engine: 3.0-litre turbocharged straight-six diesel, 280kW/740Nm
Transmission: eight-speed automatic, all-wheel drive
Porsche Cayenne V6 - compare this car
Engine: 3-litre, V6 turbo-diesel, 176kW/550Nm
Transmission: 8-spd dual-clutch auto, all-wheel drive
Body: 4-door sedan
Thirst: 7.2l/100km, CO2 189g/km
Range Rover Sport - compare this car
Engine: 3-litre, V6 turbo-diesel, 180kW/600Nm
Transmission: 6-spd auto, all-wheel drive
Body: 4-door wagon
Thirst: 9.2L/100km, CO2 243g/km