BMW X5 M v Porsche Cayenne Turbo 2010 Comparison

Supercar performance combined with SUV packaging: a match made in heaven or genetic engineering gone mad?

It's hard to fathom today, but there was a time not so long ago when BMW and Porsche would never have dreamed of building a four-wheel-drive family wagon, let alone a high-performance version.

And yet, each brand now has exactly that sort of vehicle – and they are vying for the title of the world's fastest SUV.

Though the $180,000 BMW X5 M and the $240,000 Porsche Cayenne Turbo represent the top of the SUV performance tree now, BMW and Porsche have been working up to this point for the better part of the past decade.

In 2002, Porsche released the Cayenne, a vehicle it promised would rewrite the rulebook on four-wheel drives. As history would show, the original Cayenne sold beyond Porsche's expectations (almost double the forecast rate in fact) but it was flawed in some key areas including weight (2.5-tonnes!) and handling. Indeed, despite the Porsche badge, and a gallant first effort, the original Cayenne ended up heaping kudos on the BMW X5 of the day.

Now with the all-new Cayenne Turbo just released locally and the BMW X5M released late last year, it's time for a rematch.

Here's how they stack up.

'How dare the proud M badge adorn a four-wheel-drive!' they gasped. 'And it's an automatic,' they sighed. Wonder what they make of the turtle-shaped BMW X6 M.

Incidentally, we chose to compare the X5 M (not the X6 M) with the Porsche Cayenne Turbo so that it was five-seater against five-seater, wagon against wagon comparison. For what it's worth, the performance and vital statistics of both BMWs are identical according to the manufacturer's claims (including weight!).

The only differences (apart from the X6 M missing a fifth seating position) are that, compared to the X5 M, the X6 M is 2.5cm longer, 1.1cm narrower, and 8cm lower. That's it.

It turns out BMW has been warming customers to the idea of an M-badged 4WD for some time now. The X5 4.6is released in 2002 was a pretty potent machine. With 255kW and 480Nm, it managed to propel the X5 from 0-100km/h time of 6.5 seconds. Then in 2004, BMW upped the ante with a 4.8-litre version of the same X5 called, fittingly, the X5 4.8is. Thanks to its 265kW and 490Nm V8 it was able to trim the 0-100km/h time to 6.1 seconds.

This was fast for a softroader, but still not worthy of the proud M badge. Perhaps that's because BMW knew all along what the second generation X5 would spawn: the X5 M.

The X5 M released in late 2009 is powered by a smaller 4.4-litre V8 – but BMW decided to hang a couple of turbochargers off it. In fact the two turbochargers are nestled in the vee of the engine, up close and personal with the catalytic converters, to reduce lag and improve efficiency.

The result is astounding: 408kW and 680Nm. And that translates to a 0-100km/h time of 4.7 seconds. This is the stuff Porsche 911s are usually made of and would easily dust any HSV or FPV. Not bad for a family trickster!

While the X5 M has a heap more power and torque than before, weight has only increased by about 50kg compared with its predecessor.

The power delivery is nothing short of phenomenal, with zero lag and a massive shove in the back any time you stab the throttle.

As with other M cars, it has a bunch of switches and dials that unleash the full wrath of the beast. In M mode the automatic gearbox's shifts are more abrupt and it even has a launch control mode to guarantee a perfect start. Just don't do too many back-to-back. The transmission doesn't like it.

The X5 M perseveres with a six-speed torque converter auto (while other brands either switch to twin clutch or robotised manuals, or eight-speed torque converter autos). But it works well. The alloy shift paddles are cool to the touch and feel precise. And with such a spread of torque (peak torque is spread across 1500-5650rpm) it easily handles the six-speed auto.

Traction is instant, as you might expect, thanks to an all-wheel-drive system that features a 40:60, front:rear split.

And the brakes are superb. The 395mm front discs and 385mm rear discs (yes, they're almost as big as the front!) are the biggest brakes ever fitted to a BMW – and bigger than those fitted to the Porsche!

The steering is direct, the suspension is firm without being uncomfortable and the grip from the 20-inch Bridgestone tyres is brilliant.

Unless you put a stopwatch on this pair, you'd struggle to pick the difference. But alas, we did mark them against the clock – to satisfy our curiosity more than anything. And we also got their tyres a little dirty, just to see if they really are all-purpose performance cars.

There is no suggestion that either company was looking over the other's shoulder and copying their homework; if anything it shows that both brands have truly extracted the absolute maximum out of their machines. But how is it so? How can two companies come up with the same result, using different algorithms to get there?

While the BMW uses a twin-turbo 4.4-litre V8 with six-speed auto to shift 2305kg, the Porsche uses a twin-turbo 4.8-litre V8 with eight-speed auto to move its 2245kg. The Porsche has less power (368kW to the BMW's 408kW) but more torque (700Nm to the BMW's 680Nm).

So we ran them down the drag strip. The Cayenne did a 4.7 second 0-100km/h time on the way to a 12.9 second time for the 400m dash, while the BMW X5 M did 4.8 second 0-100km/h on the way to a 13.0 for the 400 metre dash. Call it hair-splitting, but that's how they ended up. 

The differences don't end there. The Porsche has slightly smaller brakes than the X5 M (390mm front discs, 370mm rears) but massive 410mm carbon-ceramic discs (with yellow calipers) are optional. We're yet to sample the Porsche's carbon brakes on a Cayenne but it's safe to say there is nothing wrong with the standard red caliper, steel disc arrangement.

The Cayenne Turbo comes standard with adjustable air suspension; conventional suspension is not an option. This means the Porsche has three main suspension settings – comfort, normal, and sport – and the BMW steel spring set up has one setting (the one it left the factory with).

The Cayenne also has a fourth offroad suspension setting. Once idle or at low speeds it'll rise as if it's on stilts at the press of a button to help clear an obstacle or take a creek crossing without inhaling. Handy if you'd ever be inclined to get your $240,000 Porsche scratched or soggy.

I'm generally not a fan of air-suspension, and there's a belief among some chassis engineers that there is only one correct suspension setting for a vehicle. The X5 M is a good example of this – it works a treat. Indeed, while air suspension can iron out the bumps on a rippled road, it's less competent at handling jolts over expansion joins. The best example of an admission of this is the new Jaguar XJ limousine which uses conventional suspension up front and air suspension on the rear.

The Cayenne Turbo, in this instance riding on 20-inch Michelin Pilot Sport tyres, is better than previous iterations of Porsche's air suspension set-up. Perhaps that's because it has less weight to deal with now, with the Cayenne having shed 250kg across the range.

You can definitely notice the difference between this set-up and the old Cayenne's air suspension. It's much more refined. I found myself leaving it in comfort or normal most of the time. Sport mode tightens things up in corners but it's firm over bumps and feels like you're being shaken awake.

The eight-speed auto shifts well and because the ratios are so closely stacked together, you barely notice the gearchanges. It's especially good when kicking down a gear; it has a knack of finding the perfect ratio to get you moving.

No wonder the 80-120km/h time is so impressive: 3.1 seconds for the Porsche and 4.3 for the BMW. That's a substantial margin…

We also ran this pair around a test track – and the Cayenne won that argument, too. The extra ratios helped it find the right gear and the slightly lighter, lower body seemed to help handling. Compared to X5 M the Cayenne is 60kg lighter, 0.5cm shorter, 5.5cm narrower – and 6.2cm lower. The Michelin Pilot tyres were also likely a factor.

Oddly, driving around town, the Cayenne Turbo doesn't feel as quick as the BMW. That's probably because the gearshifts are so quick and seamless. But at least it sounds sensational, with a deep, German V8 burble.

The BMW X5 M, meanwhile, sounds like a four-cylinder rally car. A powerful one, but a four-cylinder no less. It must be something to do with the engine's firing order. Only when the X5 M is on full noise does it start to sound appealing, but still not like a V8. On full noise it sounds a bit like the muffler from an XR6 Turbo.

The sound of the BMW X5 M exhaust low in the rev range is a bit like a drain starting to make a choking noise.

Before our time ended with the BMW and the Porsche, we took them carefully offroad. Interestingly, neither company makes bold claims about these vehicles off the beaten track. Every photo in the brochure is in the city or on a freeway or racetrack. It's as if both brands have conveniently ignored the fact that both these vehicles did start life as 4WDs after all.

No wonder, really. Their underbodies have plastic shields designed to cool brakes and improve airflow at high speeds, not act as a bash plate to protect vital components.

Both had a stunning amount of grip on gravel, despite driving on high speed tarmac tyres. But ultimately, the Cayenne could get into and out of more difficult situations because it has better approach and departure angles. Press the button and watch the Cayenne raise its skirt, and it'll go even further.

So at least in that sense, Porsche should be commended for have a broader 'bandwidth' of ability. Even if most Cayenne owners will never use it.

THE VERDICT
In case you haven't guessed by now, both these vehicles are epic machines. That may sound like a cop-out in a back-to-back test, but when you consider the engineering nous that has gone into both of these vehicles, it is little wonder choosing between them is difficult.

For the record, I would happily live with either of these vehicles. If your budget stretches to $180,000 you're taking the BMW -- which has the better suspension set-up for my taste. But if you can afford to make the $60,000 leap to the $240,000 Cayenne Turbo, it is worth every cent.

Not only does the interior look a million dollars better, it is quicker, more agile and covers a greater spectrum in its abilities.

There is quite simply no other vehicle in the world that has the Cayenne Turbo's spread of capability. It can outrun a sportscar, outmaneuovre a sports sedan, and it can tackle the great outdoors when you're tired of playing in the urban jungle. All with five people and luggage on board if necessary.

It is no longer a laughing stock.

The original Cayenne wasn't exactly a failure, but it wasn't brilliant either. Clearly Porsche has learned a lot over the past six years – and it has put all that knowledge into its all-new, second generation vehicle.

You could say the new Cayenne is the vehicle Porsche should have built in the first place. But the engineers had to build the first one to figure out what they did wrong…

Read the latest Carsales Network news and reviews on your mobile, iPhone or PDA at the carsales mobile site