by Phil Berg
Competition from Mercedes suggested that BMW wouldn’t let its two-year-old V-8 X5 4.4i sport-utility remain an only child very long before a hot-rod model joined it. On sale this winter is a 340-horsepower hot-rod version called X5 4.6is that boasts the launch capability of a sport sedan: 0 to 60 mph in a claimed 6.2 seconds. Volume will be limited for this hot-rod model, not by production constraints, but rather by a price tag of $66,845, nearly $17,000 more than the 4.4i, and about the same as Mercedes’ ML55 AMG sport-utility.
After a rousing drive, we think BMW is correct in predicting the X5 4.6is will be worth it only to a small group of buyers with specific needs. BMW says those needs include a high driving position and ease of loading stuff into the tall body. Both Mercedes and BMW continue to develop their SUVs for pavement and dirt, though Mercedes maintains its M-Class is capable off-road, while BMW says dirt roads are as rough as they expect an X5's environment to get.
In addition to a beefed-up new V-8, the X5 4.6is' transmission and suspension have been thoroughly revised for less compromised sporty pavement driving. Almost the entire options list except for the navigation system has been loaded onto the 4.6is, too. Inflatable head protection is added to the rear side airbags, and a big navigation screen on a swing-out panel like you'll find on some Mercedes models clears more room on the already large instrument panel. Add fender flares and paint that’s otherwise exclusive to the M sport sedans and roadsters in BMW’s lineup, and you can see what most of the high price is paying for.
The 4.6-liter engine is a bored and stroked version of the muscular 4.4-liter DOHC 32-valve V-8, with compression boosted from 10.2:1 to 10.5:1, and it retains the VANOS variable valve timing system and Motronic engine control. The redline goes up from 6200 to 7000 rpm, and the horsepower peak comes higher, at 5700 rpm versus 5400 rpm. Peak torque goes up 26 lb-ft to 350, but it comes higher up the tach, too, from 3600 rpm to 3700. The tach, and the rest of the gauges, match those of the M5, with small LED indicators that lower the redline until the engine is thoroughly warmed up. The tweaked engine requires a break-in period of 6000 miles before it reaches optimal potential, BMW says.
2002 BMW X5
More hot-rod tricks follow in the ZF five-speed automatic, which has a torque converter with a higher stall speed, allowing the engine to spool up quicker at launch. The five-speed is also tuned to shift at higher rpm, and the final gearing is lower, at 3.91:1 instead of 3.64:1 in the 4.4i. At 82 mph in fifth gear, the new V-8 turns at a relatively quiet 3000 rpm.
We flogged our 4.6is down a few wide-open country lanes, and although the 4.6is’ exhaust actually sounded quieter than we’re used to in a 4.4i, the new model revved noticeably quicker. From a stop the 4.6is leaps forward compared to a 4.4i, but the sensation feels less rapid than it does in a similarly powerful Mercedes AMG ML55. Still, BMW claims a quicker time to 60 mph. Despite the power increase in the BMW, you don’t forget that the X5 4.6is weighs the same 4800 pounds of the slower 4.4i, which is a lot of inertia for any engine to overcome.
All that mass is well controlled by the suspension, which is firmer than you'll find on the 4.4i. What you first notice in the 4.6is is the steering is remarkably similar in feel to that of a 750iL, crisp and linear, and almost uncomfortably light for a car this heavy. The 4.6is gets vehicle speed-sensitive steering assist, while the lower-line models continue to use engine speed-sensitive assist. Because of the light steering, you can’t tell you’re turning big fat sticky 20-inch 275/40 tires (315/35 in the rear). Every bit of the tires’ capability is used in braking, too, since the front calipers are upgraded to dual piston units, which squeeze huge 14-inch vented rotors. Braking is powerful, and feels more rapid than any other SUV’s, including the ML55.
The 4.6is’ accelerating and braking prowess proves that this big, tall wagon can cover backroads at the same speeds you’d reserve for an M5 sedan. So does the cornering ability. At nearly 100 mph on steady sweepers, we noticed our 4.6is wanted to understeer slightly, but when we lifted the throttle the back end rotated outward just a bit. Same guy, we figure, must have tuned the M5. In reality, the standard Dynamic Stability Control kept us from making any false moves, and when we switched the DSC off, the rear-torque-biased four-wheel-drive contributed to balanced power delivery.
All of this behavior, plus the high-level price, makes us think the top-performing X5 should have been called an MX, but the purists at BMW likely won the argument that the M cars are those bred for the track, not the trail. That is in spite of BMW hinting and suggesting and looking very much like they’ll call you stupid if you think about taking the 4.6is off road.
The long list of items normally called extras include power adjustable rear seat backrests. Curiously, there’s also a hill descent control like you’ll find on a Range Rover, which is, of course, meant to go off-road. The price of the hot-rod power is truly miserable fuel economy — 12 mpg. That figure leaves you feeling guilty that the considerable money that created the fashionable interior and gadgets should have been channeled into a lighter body and chassis. In its purest form, hot-rodding never meant just beefing up a motor; it also meant throwing out excess weight through careful trimming, cutting and lightening.
The X5, like all SUVs, would benefit from the complete treatment.
2002 BMW X5 4.6is
Price as tested: $66,485
Engine: 4.6-liter V-8, 340 hp
Drivetrain: Five-speed automatic transmission, all-wheel drive
Length x width x height: 183.7 x 73.7 x 67.2 in
Wheelbase: 111.0 in
Curb weight: 4824 lb
EPA City/Hwy: 12/17 mpg
Safety equipment: Dual front airbags, side curtain airbags, four-wheel anti-lock brakes, Dynamic Stability Control
Major standard equipment: Power windows/locks/mirrors, air conditioning, AM/FM/CD player, sport suspension, 20-inch wheels
Warranty: Four years/50,000 miles
in your area