ArcaMax

Some perspective: The X5 M's engine produces about 70-75 percent of the output of a current Nextel Cup stocker's all-out race V8 - but without the race car's shake/rattle n' roll. It'll hit almost 190 MPH on top. Which is about 75 percent of the top-end of a Nextel Cup car geared for the Daytona 500.

But unlike a Nextel Cup stocker, the X5 M is street legal, emissions-compliant and will definitely last longer than a 200 mile race (though maybe it won't make it 200 miles on a single tank; read on).

Even more jaw-drop-worthy, it corners. The sensation of being that high up - while going this fast through an apex - is a sensation your body and mind will initially have trouble reconciling. Like a too-good-looking blind date, you wonder - What's the catch? When is the other shoe is going to drop? It never does.

Some more perspective: A Porsche 911 is just 51.3 inches high at the roofline and has about 5.5 inches of ground clearance. The X5 M stands 67.6 inches high and its skirts are 8.1 inches off the pavement.

Yet the X5 can trace a 911-esque line through the esses. It is like watching a five-foot-five guy score 20 points in an NBA championship.

The Cayenne Turbo is comparably adroit in the curves - but can't keep up with the M in a straight up drag race. Plus it costs more. A lot more.

The Benz ML63 and Range Rover Sport, meanwhile, are much more "trucky" than either the M or the Cayenne - both featuring more in the way off-road capability (including Low range gearing and more ground clearance). But this inevitably compromises what they're capable of laterally, on road. They both have higher-than-you'd expect capabilities in that respect. But neither of them feel remotely 911-esque. The X5 M does.

AT THE CURB

The X5 is the biggest of the four, but a bit less space efficient than some of its rivals. The BMW's back seats, for instance, have less legroom (36.6 inches) than in the Benz (38.4inches ) despite the X5 M's being 3.6 inches longer overall (192.7 inches vs. 189.1 for the ML63 AMG).

On the other hand, the BMW has significantly more cargo capacity (76.7 cubic feet in total) than either the Cayenne (62.2 cubic feet) or the Range Rover Sport (62.9 cubic feet) and only a little bit less than the ML63 AMG (80.3 cubes) and is the only one of the four with a standard two-piece tailgate. The lower section folds out and down while the upper section opens - conventionally - up. When the lower section is folded down, you get what amounts to a bed extender - about a foot more load floor. This is handy whether to sit on during a tailgate party or for hauling stuff home. With the lower section locked in the up position - and the upper section open - you have a handy little dam to keep cargo in the X5 that might tend to slide out if not tied down adequately in other SUVs.

Car People can spot the M version of the X5 at a glance. It is the only X5 with four exhaust tips, a pair of front fender air extractors (functional, not cosmetic) and subtle wheelwell extenders (necessary to keep the 21 inch wheels/tires scooched within the bodywork). But to most people, it's just another - yawn - crossover SUV. A clearly expensive one, without doubt. But few among the uninitiated are remotely conscious of the 911-thrashing capabilities discreetly tucked within that unassuming shell. This is a beautiful thing - because it makes it much more feasible to thrash 911s. Or rather to drive regularly on public roads as if you were in a 911… and get away with it.

Out in the wild, effective predators are ambush predators. They make use of camouflage. You do not see them coming ... until you feel the fangs sinking deep into the back of your neck. And by then of course it is much too late to do anything about it. You are doomed.

The X5 M fits that bill. The 911 - magnificent though it may be - does not.

Neither does the Cayenne Turbo, for that matter. Because it looks like a 911 fattened up. The Porsche profile is unmistakable and when another driver sees thatface in the rearview, he knows what to expect - and that puts you at a disadvantage, even against much lesser machinery. That Prius up ahead? He can simply block you in, out of spite. Then, all the horsepower in the world is as useful as a thong at the Vatican.

It's a never-ending treat to drive the X5 in heavy traffic - to thread the needle in heavy traffic - which you can do much more easily, with near-impunity, not just because of all that power but also because you can use all that power. They almost never see you coming. Same goes for The Law.

THE REST

The M gets a different shifter than regular X5s. It's a little stubby toggle thing that's fully drive-by-wire and so lacks tactile feedback. It's functionally faultless but something more mechanically engaging would be more appropriate here, probably.

On the other hand, the M's exhaust system - which features a pressure release system under wide-open-throttle - makes up for that. It's similar to the set-up that's available optionally in the AMG-tuned version of the Benz GLA (reviewed here). It works like the old-school exhaust cut-outs that muscle cars back in the late '60s sometimes had - but it's fully automated. No need to pull a cable to bypass the mufflers. Under WOT, pressure is released via vacuum-actuated flapper doors - accompanied by a sound that rips the air like a mini sonic boom. This happens at the crescendo of each WOT upshift, so as many as eight times in sequence. Your neighbors will feel like the sky boss in Top Gun when Maverick's Tomcat did an unauthorized flyby, both afterburners lit. There goes the coffee...

The M's traction/stability control also has more libertine programming. While straight-line burnouts are not allowed, you can smoke 'em sideways a bit, if you like.

Gas mileage is about as relevant a consideration here as the fertility of nursing home residents. When you are interested in 500-plus hp twice-turbo'd V8s and top speeds approaching 200 MPH you are not, by definition, much interested in how much it costs to feed it.

However, you might be interested in how often you'll need to feed it. Even with a pretty large (22.4 gallon) fuel tank, the X5 M can drain it dry in 200 miles. Less, if you're really working at it. EPA rates the BMW as being capable of 14 city, 19 highway (vs. 14/21 for the Cayenne Turbo, 13/17 for the ML63 AMG and 17/23 for the "class best" RR Sport SVR) which maybe it is. If that's what you're trying for.

But isn't that like trying to keep an ice cream cone from melting as opposed to just eating the thing? EP (me) rates it at about 8 MPG. A larger tank would be great.

THE BOTTOM LINE

I'm always looking for a way to end-run the system, to get away with everything they're trying to shut down and suck the life out of. The X5 M is like one of those horse needle things they use to revive someone technically dead with a shot of epinephrine straight into the heart. If you haven't got a pulse, this will restore it. If you want to feel alive again, this will do it.

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www.ericpetersautos.com or EPeters952@aol.com for comments.