From the Archive: Combining the virtues of the 325is with the added security and performance of full-time all-wheel drive, the 325iX is the BMW for all seasons.
From the March 1988 issue of Car and Driver.
Only a few years ago, American BMW enthusiasts—as distinguished from the baby-boomer Bimmer buyers who were flocking to the marque for all the wrong reasons—had all but given up hope of ever again seeing performance-oriented BMWs. The Bavarians were keeping all their best hardware on the far side of the Atlantic and, in their U.S.-bound cars, emphasizing luxury and fuel efficiency. That has changed. In the past year BMW of North America has unveiled 11 new models, nearly all designed to appeal to the hard-core faithful. The two latest additions are the 12-cylinder 750iL, which we’ll review next month, and the 325iX—which you won’t have to wait another second for.
Combining the virtues of the 325is with the added security and performance of full-time four-wheel drive, the 325iX is the BMW for all seasons. Except for its driveline, the iX is virtually identical to the rear-drive 325is—which, like all the other
3- series sedans, wears a slightly revised wrapper for 1988. Sharing the is’s deep front air dam and small rear spoiler, the iX adds only a few exterior distinctions: body-colored rocker-panel extensions, more pronounced wheel-opening flares, and 205/55VR-15 tires on 7.0-inch wheels, in place of 195/65VR-14s on 6.5-inch wheels. The iX also sits 0.8 inch higher than the 325is.
The interior differences between the iX and the is models are even more subtle. The comfortable, supportive seats are the same. The M-Technic steering wheel and the clear, well-located instruments are the same. The tasteful trim and the eight-speaker stereo are the same. The only significant difference in the iX is a small bulge on the driver’s side of the transmission tunnel. It makes room for the transfer case, and it’s the only hint in the cockpit of any new hardware underneath.
Under the hood, the 325i.X gets the same silk-smooth 168-hp 2.5-liter inline-six engine as the i and is 3-series models, mated to a buttery Getrag 260 five-speed transmission. (An automatic is not available in the U.S. edition of the iX.) Otherwise, the driveline of the iX is all new. The engine feeds its power through the transmission to a planetary center differential, which splits the torque between a conventional driveshaft to the rear wheels and a roller chain that transfers power laterally to another driveshaft. This second driveshaft runs alongside the transmission to the front differential, which is bolted to the left side of the oil pan. The front differential drives the left half-shaft directly but uses a transfer shaft, which runs through the oil pan, to drive the right half-shaft. To minimize torque steer, the half-shafts are of equal length.
On the move in the 325iX, you detect only a few subtle clues to the new pieces below. The engine springs to life with the familiar BMW resonance, and engaging the clutch in the iX feels no different from starting off in the 325is. When you accelerate, though, an unfamiliar whine alerts you to the presence of extra gears. And when you tum through a tight, low-speed corner, you feel a trace of 4wd-windup scrub at full lock.
As you gather speed and head off toward your favorite two-lane challenges, the iX maintains the feel and handling poise of the 325is. Its acceleration through the gears seems about the same, thanks to a slightly shorter final-drive ratio (3.91 versus 3.73:1), and the brakes are just as reassuringly effective.
Our test-track figures support these impressions. Our 2988-pound 325iX test car accelerated from zero to 60 in 7 .8 seconds and through the quarter-mile in 15.9 seconds at 86 mph—only 0.4 second slower to 60, and 0.3 second and 2 mph slower in the quarter, than the 2823-pound 325is we tested last August. The extra weight of the iX also showed up on the skidpad, despite its larger wheels and tires: it turned in a figure of 0.78 g, versus 0.81 g for the 325is. In top speed, the extra weight and mechanical drag of the 4wd driveline make little difference: our iX achieved 126 mph, versus 128 for the 325is. Surprisingly, the iX decisively outbraked the 325is: its 171-foot stopping distance from 70 mph was 13 feet shorter. (The 325is is also equipped with ABS.)
The objective figures reveal little, however, about the soul of the iX. As you become more familiar with it, your speed increases and you brake later and later into corners. Accelerating out of a turn, the iX hugs the road tightly, putting its power down with aplomb and balance. As you feel the front wheels gripping the pavement, you can flick the tail out a bit by pressing your right foot down, or induce a similar attitude by lifting. You have to steer the wheel a little more than you do in the is, since the throttle provokes less reaction in the twisties, but the transitions are always smooth and precise. The traditional seat-of-the-pants BMW feel tells you exactly what’s going on between the tires and the pavement.
The special beauty of the 325iX is that it behaves almost as well on slick surfaces. When you encounter snow or ice in the iX, you naturally slow down. But soon you learn that you can drive just as hard on a slippery road as you can on a dry one, at least in a straight line. In fast, slick corners the iX slowly mushes outward, but it remains neutral and controllable; easing off the throttle merely reduces the rate at which it shifts. And you seldom sense the hardware working underneath you. If you pay close attention, you can feel the front and rear wheels gripping independently at the limit, but the distribution and transmission of torque are so smooth that the overall balance is never upset. Of course, no car can defy the laws of physics; but the 325iX is so neutral, smooth, and capable that you can drive it much closer to its limits than you can most other cars.
Through deep snow, too, the iX tracks as if the roads were dry. Starting out on an icy incline or a split-traction surface is no problem, either. Only if you snap the throttle open in first or second under these conditions will you feel the driveline hard at work. First you feel a twitch from the rear, as the rear viscous coupling alternately favors the left and right tires. Then, as more power is fed forward, the open front differential may let one of the front wheels spin. The slight yaw that results, however, is easy to correct with the steering wheel. Any expectation of drama ends in disappointment. The 325iX simply acts as if everything you throw at it is business as usual.
The iX also yaws slightly if you brake hard on a slick or split-traction surface. But the low-traction ABS program keeps the car straight and stops it quickly.
BMW has taken its time developing the 325iX, but the result is well worth the wait. The iX is ideal for the driver who wants a BMW but isn’t prepared to deal with rear-wheel drive in the winter. Let others deal with it: you can arrive fresh and unflustered at your favorite wintry destination in a 325iX, and pass everyone else en route. And you’re unlikely to see your double along the way, for only 2000 four-wheel-drive Bimmers will be available here this year. At a base price of $32,800—a premium of $4400 over the 325is—the iX isn’t cheap. But then neither is skating off the road.
The BMW 325iX isn’t just for the Biff-and-Buffy crowd. A tremendously capable car, it’s always eager to entertain and enthrall. Whether scything through switchbacks or scaling snowy mountain roads, the iX accomplishes your mission with an ease reflected in your confident, knowing smile. What your smile knows is that few cars can keep up with an all-weather blitzen-Bimmer.
Beneath the Bimmer iX lies a four-wheel-drive system that we found smooth and sound. As in any mechanical object, there are reasons for this.
BMW chose a torque split for the center differential of 37 percent front, 63 percent rear, for several reasons. For one, under full throttle in first gear, 37 percent of the iX’s weight rests on its front wheels, 63 percent on its rears; distributing torque in the same proportion maximizes traction when it’s needed most. In addition, the engineers felt that a substantial rearward torque bias would maintain traditional BMW handling characteristics.
There are no manual differential locks in the 325iX. Instead, BMW has incorporated ZF-manufactured viscous couplings in its center and rear differentials. The center differential maintains its 37/63 torque split as long as there is no speed difference between the front and rear axles. If a difference develops, the coupling tightens, sending more torque to the axle with greater traction. The rear differential works in the same way, arbitrating between the rear wheels. Unlike manual differential locks, the iX’s viscous couplings never require the driver to take his attention off a slick road.
As you may know, mechanical differential locks, when activated, defeat anti-lock braking; the iX’s viscous couplings do not. Even so, BMW developed a modified version of the Bosch ABS system for the 325iX. The new system employs an acceleration sensor, mounted on the body of the car, and programming that compares the deceleration of the wheels with that of the body. On dry pavement the ABS works as usual, except that maximum brake pressure can be delayed by up to 0.3 second, reducing any tail-yawing tendency when traction is uneven. On a slick surface, if the wheels start to decelerate much faster than the body, the ABS switches to a low-friction program. The computer can also open the throttle butterfly to reduce engine braking, which sometimes also causes wheels to lock.
Packaging all of these new components in the front half of a 3-series BMW required numerous design changes. The front struts have been relocated, resulting in less caster, an 0.5-inch-wider track, and a 0.1-inch-longer wheelbase. The front anti-roll bar is now forward of the struts. The steering rack is repositioned, too, to eliminate bump steer. Naturally, the engineers had to alter the front substructure to accommodate the new and repositioned pieces. The various modifications contribute 140 pounds of the iX’s 2988- pound curb weight.
The good news is that the system contributes even more to the iX’s worth as an all-seasons runner. —Nicholas Bissoon-Dath
Help me! I just came back from driving the 325iX, and my face is stretched all out of shape. No, it’s not from the g-forces—though they are ample. It’s just that I can’t stop smiling.
Four-wheel drive and good power-to-weight ratios are nothing new, but the iX combines them in a way that seems to extract no penalties. Now, I know that our own Csaba Csere will wave his finger at me and admonish, "Rich, there are penalties: extra weight and cost."
Okay, okay, but none of that seems relevant when I’m waltzing the iX down a back road. It feels terrific, and that’s all my senses want to know. The bonus is its ability to feel terrific the year around. Why should a high-performance car tum into a low-performance liability whenever the Ivory flakes fall?
My face is beginning to resume its normal shape now, but I haven’t quit enjoying the memory of driving this all-weather bullet. If we didn’t have to give it back to BMW, neither rain nor snow nor sleet nor gloom of night could keep this reporter from the swift completion of his appointed rounds. —Rich Ceppos
I’m not an unalloyed fan of four-wheel drive. Sure, I like the security when the friction coefficient of the roads approaches that of a banana peel on linoleum, but I don’t like the added weight, complication, and cost. The negatives can outweigh the benefits.
I’m happy to report that this is not the case with the BMW 325iX. Although our performance tests reveal that the heavier new model is a few ticks slower than the 325is, its shorter gearing makes it feel almost as energetic. Its wider wheels and tires provide similar compensation in the comers, so the iX handles as nimbly and precisely as its rear-drive brother in the dry. And in the wet, you can apply full power as you pull out of your driveway without worrying about doing a doughnut in front of your neighbors.
Only you can decide whether those benefits are worth $4400. I can promise you, though, that the iX imposes virtually no other compromises in exchange for its traction.
As far as every other upmarket power broker is concerned, BMW’s flood of power-mad machines has turned into the Teutonic plague. But it’s what BMW is doing with its power that’s important. All told, the 325iX gives horsepower just about the best home it’s ever had.
The 325iX was clearly not created in a dozone for dolts living in the bozone. With exquisite traction and balance, this car fires out to face anything, savoring and rewarding your every move. Every subjective message to your three Fs—fingers, feet, and fanny—is golden. Despite Audi’s head start, BMW has built the best 4wd package yet. This car just about has it all. Better yet, it does it all with all its heart. Heart is what we’re talking about with the 325iX, wherein "X" marks the heart.
I believe, at last, that 4wd may be the answer. Of course, I, as one who is never satisfied, would also love to see this power-delivery system in BMW’s even more potent and miraculous M3. That would be better than penicillin: there would be no catching the Teutonic plague at all. —Larry Griffin
1988 BMW 325iX
Vehicle Type: front-engine, all-wheel-drive, 5-passenger, 2-door coupe
Base/As Tested: $33,270/$34,115
Options: metallic paint, $375.
SOHC inline-6, iron block and aluminum head, port fuel injection
Displacement: 152 in3, 2494 cm3
Power: 168 hp @ 5800 rpm
Torque: 164 lb-ft @ 4300 rpm
Suspension, F/R: struts/semi-trailing arm
Brakes, F/R: 10.2-in vented disc/10.2-in disc
Tires: Pirelli P600, 205/55VR-15
Wheelbase: 101.3 in
Length: 175.2 in
Width: 65.4 in
Height: 55.1 in
Passenger Volume: 82 ft3
Cargo Volume: 13 ft3
Curb Weight: 2988 lb
C/D TEST RESULTS
60 mph: 7.8 sec
1/4-Mile: 15.9 sec @ 86 mph
100 mph: 23.9 sec
Top Gear, 30–50 mph: 12.1 sec
Top Gear, 50–70 mph: 13.4 sec
Top Speed: 126 mph
Braking, 70–0 mph: 171 ft
Roadholding, 300-ft Skidpad: 0.78 g
C/D FUEL ECONOMY
Observed: 22 mpg
EPA FUEL ECONOMY
City/Highway: 17/23 mpg
C/D TESTING EXPLAINED
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