BMW’s X6 is a strange brew. A four-door fastback-cum-SUV-cum-Sandton status symbol. When we first wrote about it five years ago, we headlined the story: “X-actly what is this?”
Today, though, we’re not going to delve too deep into the why and wherefore of Beemer’s self-proclaimed “Sports Activity Coupé”. No, this road test is more about what lies beneath its bulging bonnet; and while a 3-litre turbodiesel BMW is in no way unusual – one with turbos in triplicate surely is.
BMW has done high-performance diesels before, and they’ve been impressive. But this one, badged with the brand’s celebrated “M” logo, builds a bridge to a new type of performance engine. One with three turbos forcing air down its six throats. One with less kilowatts than the most powerful car in BMW’s range (the 412kW/680Nm M5), but with way more torque. Let’s call it mega-diesel.
MEGA DIESEL
The idea here is not only huge power but huge efficiency as well, and the combination of 280kW/740Nm, together with a claimed consumption average of 7.7l/100km, gives this triple-turbodiesel one of the best output versus drinkage ratios in the world, says BMW.
Actually, editor Droppa coined the phrase “mega-diesel” when he took this very vehicle, the X6 M50d, on a pan-European adventure earlier this year. Over unrestricted autobahn and snowy mountain passes, he averaged just 10 litres per 100km diesel consumption (not exactly 7.7 but impressive nonetheless), which seems ludicrously low for a car that claims to be able to shunt from 0-100km/h in only 5.3 seconds. He had confirmed the frugality half of the equation, but until it was launched on South African soil, we’d have to wait for performance particulars.
Well, that time has come and we’ve got the data for you. BMW claims 0-100km/h happens in 5.3 seconds. At Gauteng altitude we got 5.9, with a quarter-mile best of 14.2 seconds. Not shabby for a two-ton diesel SUV, and makes it the second-quickest diesel SUV we’ve ever tested, just pipped by Audi’s V12 TDI Q7 of a few years ago.
There’s a tiny trace of turbolag, that, if anything, exaggerates the torrential boost moments later. It leaps forward with a feel much like other big turbodiesel SUVs, but where those start to taper off as the tacho’s needle sweeps to higher revs, this triple-turbo surges right through to redline. As per most diesel engines, max revs come relatively lowly (here at about 5500rpm), but there’s no lapse in the torque spread right up until that point.
A GOOD ROAR
From inside there’s a nice roar too; one that you might not have thought originated from an engine that runs on compression alone – but, just like some other current Beemers, much of the aural excitement comes from the car’s speakers. BMW says it’s an “authentic reproduction” of actual engine noise, but from the outside it sounds more like a hurricane forced through a drain pipe. It’s loud, but pretty much characterless.
The X6, like the X5 it’s based on, sits high up and features all-wheel drive. But in these applications (this triple-turbodiesel comes in the X5 too) almost all offroad ability has been set aside and replaced with ways of improving handling on tar. The suspension systems are very similar to what you get in X5 and X6Ms, with self-levelling air rides that offer little give in the corners. Not to mention 20” alloys and low-profile tyres.
Mounting rubbers for the body, transmission, engine and suspension mounts are also more rigid than in normal X6s, and you can always feel it. Not that the M50d models are uncomfortable; they’re just not as comfortable as lesser (softer) models.
SO WHY THREE TURBOS?
It’s a complicated answer, but here goes. There are two small turbos and one big one feeding this straight six. Small turbos spin up quicker, so at low revs there’s less lag. In this case one of the small turbos boosts until higher revs, and then the big one takes over. Most of the time it runs as a bi-turbo, but if extra load is detected, such as under foot-flat acceleration, the second small turbo will be called up for duty as well – again, only until the big guy takes the reins. Capice?
It’s an interesting concept that seems to work well, even if I’ve heard much cynicism from folks questioning its longevity. Fair enough, three turbos could equal three times the chance of turbo failure. But we’re not able to predict the future, and besides, BMW will watch your back with its standard two-year/unlimited kilometre warranty.
VERDICT
Think of the X6 and X5 M50d as diesel-powered versions of BMW’s insane flagships with the same bodies – the X6M and X5M. Of course those petrol-powered bi-turbo beasts (with 408kW and 680Nm) are much quicker than their diesel counterparts, but they’re also more than R400 000 more expensive. The X6M50d is priced at R1 097 000, and the X5 with the same engine is R991 000. -Star Motoring