LA MOTOR SHOW: New BMW X5 and X6 Ms

More urge, less fuel for BMW M's hot and hefty SUV twins

It wasn't that long ago that anything bursting through the standing kilometre sprint in less than 23 seconds could safely be assumed to be a svelte, two-door supercar. Usually a German or Italian one.

As of next month's Los Angeles motor show, though, that will have to be reconsidered because new BMW's X5 M and X6 M twins will make their debuts there, and they manage 22.6 seconds for the metric blast.

And they do it without being svelte in any way, with the X5-based version frightening off elephants at 2270kg and the X6 M just 5kg lighter. The only slight sliver of a saving grace for carrying that much weight is that everything has been uprated from the standard models for the extra speed expected of an M model. Exactly 95kg worth of uprating over the standard 50i models.

A large part of the straight-line urge of the X5 M and X6 M, which sees both M models blast to 100km/h in only 4.2 seconds, comes from the revisions to the thumping 4.4-litre, twin-turbocharged V8 petrol engine.

Yes, there is a half-step M550d xDrive version of both the X5 and the X6, with its tri-turbo straight six, but for a full-house M badge, you have to have the petrol V8.

And why not? It's slightly more powerful (four per cent) than it was in the old model, with the power figure eked out to 423kW at 6000rpm, but there's 70Nm more torque to take it up to 750Nm from just 2200rpm. That torque figure, which is a 10 per cent improvement, stays on until 5000rpm, while the power peak also sticks around for 500 revs after it hits.

The hot-vee V8 uses cross-bank manifolds and a pair of twin-scroll turbochargers, combined with 200 bar of fuel-injection pressure from the direct injection system. The bottom end has a forged crankshaft and a closed-deck crankcase that allowed M to raise the cylinder pressures.

It's a wet-stump engine, still, but M claims it has designed the oil scavenge and delivery systems to cope with the 1.2g of cornering forces it expects at the Nurburgring's Nordschleife. BMW also claims the new hot and cold air radiators deliver a big boost to the consistency of performances across the cars' potential operating ranges.

Both cars are all-wheel drive, via an electronically controlled multi-plate clutch system, and both have the all-wheel drive systems tweaked to deliver a rear-biased driving feel. It constantly adjusts the drive depending on everything from slip to grip and can move 100 per cent of the torque to the front and then send it all back to the rear wheels in the blink of an eye.

One of the bigger upgrades from the 2009 X5 M and X6 M is the arrival of an eight-speed, torque converter hydraulic automatic transmission.

Besides enabling start-stop, its wider spread of gear ratios allowed BMW to deliver some economy-specific plans, stretching the range of the 85-litre fuel tank out to a claimed 765km, which is 26 per cent farther than the old versions.

M claims an NEDC combined fuel economy figure of 11.1L/100km, with a CO2 emissions figure of 258g/km, both of which are at least 20 per cent better than the outgoing models.

But the transmission has more tricks up its sleeve than just better economy. It has tricks up to and including a launch control system, where the driver just plucks Sport mode, stands on the brake pedal then squeezes down firmly on the throttle. The computer then figures out the best available launch revs and the driver sidesteps the brake and off you go, with M claiming it will smash out 4.2-second sprints to 100km/h every time.

It can be left in Drive or the transmission selector can be used as a manual sequential shifter or, should that all prove too difficult, the gears can be changed via the steering wheel-mounted shift paddles.

It also allows for a Low Speed Assistant to let the driver run in traffic jams without bothering with the pedals, thanks to the radar cruise control and some software magic. There are also Eco, Comfort and Sport modes to change the gearshift patterns and speeds.

The noise is there, too, with M adding its usual electronically controlled exhaust flaps to intensify the V8-ness of the sound at the push of a button.

Both models have received a very welcome addition in the braking system, with six-piston fixed calipers now clamping the cross-drilled, vented discs. M claims it delivers 50 per cent more brake lining surface than before, though it sticks with a single-piston floating caliper for the rear end.

Those new brakes are surrounded by a new set of 20-inch alloy wheels clad in Pirelli PZero rubber, but they're different sizes front and rear. The front tyres measure 285/40 R20 while the rear end uses 325/35 R20.

There is an optional 21-inch wheel and tyre set (which has traditionally garnered a lot of support amongst the X5 M and X6 M set), with an upgrade to Michelin Pilot Super Sport UHP rubber all around the car, with a 285/35 R21 version on the front axle and 325/30 R21s on the back.

All of this is suspended on both cars by a double wishbone front suspension, with M's modifications largely focused on the top wishbone, stiffer wheel bearings and the car's elasto-kinematics. It rides only 10mm lower than the standard versions, but the suspension is firmer and runs on air suspension and has a self-leveling rear end as standard equipment.

It's helmed by an electro-mechanical power-steering system that M claims saves it 0.3L/100km alone and uses no fuel at all when the car is running straight ahead.

All of this chassis hardware and software funnels through the upgraded Dynamic Stability Control that now allows the driver greater freedom, all the way up to a drifting mode. No, seriously, M claims it allows the driver to drift its two-tonne Tessie.

It will, in the M Dynamic Mode, allow the X5 M and X6 M to drift in either under or oversteer, but will let the car slide even further by letting the driver turn the DSC system off completely. It's never completely gone, though, because it still intervenes in extreme situations to prevent rollovers.

With 195mm of ground clearance, neither car will bother the hard-core off-road set, though BMW claims a 2970kg braked trailer weight for the X5 M and 2950kg for the X6 version.

The X6 is, at 4909mm, 29mm longer than the more conservative looking X5 M. It's all a matter of millimetres elsewhere, too, because the X6 M's 1989mm width is 4mm broader than the X5 M's and its 1689mm height is 65mm lower than the X5 M's. Both cars share a 2933mm wheelbase.

As before, both cars have had significant visual tuning to make sure the extra power and potential isn't lost on those occupying the same roads.

They both have four large air intakes up front, they both use side gills and air breathers behind the front wheels and they both use four exhaust tips and a rear spoiler to emanate menace.

They both use M-specific interiors, including a stand-alone instrument cluster (with shift lights, a gear indicator and a rev band), aluminium on the gear lever and the shift paddles.

Both models get knee pads on the centre console to ward off bruises in hard cornering and both get an aluminium M footrest for the driver.

The standard equipment list runs to things like three automatically dimming mirrors, climate control, parking distance control, adaptive LED headlights and BMW's latest navigation system.

Both range-topping M SUVs are due on sale in Australia next May.

LA MOTOR SHOW: New BMW X5 and X6 Ms

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