Our incessant bleating about BMW’s lamentable deviation from its “ultimate driving machine” ethos appears to have at long last spurred some action. The niche M5 drives pretty ultimately, and now the chassis development team for the crucial G20-generation 3 Series sedan seems equally determined to return the iconic Dreier to the top of its highly competitive heap.
So eager is the team to get this right and shut down the haters that a select few of the loudest complainers were invited to the Nurburgring for an intense day of public road and closed ’Ring driving of early 2.0-liter turbo prototype cars. Note, these versions were equipped with the M Sport package, and there’s still time to tune and tweak some of the final calibrations before the new 330i goes on sale early next year.
A quick summary of the key changes: Examine the undercarriage, and you won’t notice anything radically new, and yet every part is significantly revised—geometry, elastokinematics (bushings and bump-stops), spring and damping rates, and damper internals. Of course, the most crucial chassis component is the body structure itself; it’s stiffened by 25 percent in overall torsion, and the areas where the front and rear suspensions mount are about 50 percent more rigid.
The switch to aluminum for most of the front body structure contributes to an overall weight reduction of 120 pounds, which improves agility by lowering the polar moment of inertia, and helps deliver a 50:50 weight distribution (measured with full fluids, 300 pounds of front-seat passengers, and 31 pounds in the trunk). The center of gravity on all 3 Series models drops by 0.4 inch (the sport suspension drops the body another 0.4 inch), and the track widens by 1.2 inch.
That added rigidity around the suspension mounts better resists vibration, so the suspension bushings can be stiffened to deliver more road-feel to the steering rack (for the first time on a BMW, the sport suspension gets unique bushings). Front and rear suspension geometry is revised to lower the roll centers slightly and to make the rear more neutral. With improved front grip, we’re promised, the result is reduced understeer and increased agility.
The front struts feature new internal hydraulic rebound stops that dramatically increase the damping force in both directions near the top of the travel (the old internal rebound springs stored energy as the body rose and released it on the way back down, skewing the effective damping rates). The rear shocks include a similar function operating at the bottom end of travel, where a second, smaller piston enters a narrower cylinder that increases the damping rate by 50 percent. This improves body-motion control when the vehicle is heavily loaded and when it traverses bigger dips and bumps. The base and sport suspensions both utilize this technology, using different damping rates. (The optional adaptive sport dampers do this and more using external bypass spool valves.)
The base steering rack uses a fixed ratio, and sport suspensions get a variable rate with a more gradual (less noticeable) quickening of the ratio at higher steering angles. And—hallelujah!—the utterly unpredictable and truly hateful Active Steering has been banished to a special circle of hell (at least for the G20).
BMW did not share the specific spring and damping figures with us, but base car tuning is very slightly stiffer, and the sport suspenders are about 12 percent stiffer than the outgoing sport setup, meaning the gap between base and sport roughly doubles in this generation. The anti-roll bars have been tweaked very slightly to maintain similar control working in conjunction with the new spring rates and geometric roll axis. Tires remain the same size but are re-engineered for less rolling resistance and noise transmission.
In the braking department, both base and sport models get four-piston front and two-piston rear fixed calipers, but the sport models boast larger-diameter discs and caliper pistons front and rear, with a unique booster and proportioning valves to match. The last piece of the dynamic handling puzzle is the sport suspension’s electronically controlled limited-slip diff, which is entirely controlled by the chassis computers and works just like the ones in M cars, but with two fewer clutch plates.
My first drive is in an electric power steering–equipped development prototype with BMW steering guru Mischa Bachmann riding shotgun. As I steer through the twisty lanes, he taps away on a laptop altering various parameters, like an optometrist working a refractor. “Do you like this one, or is this better?”
Bachmann starts me out with his leading calibration for “comfort” steering,—light on center, effort builds naturally off center, and there’s never any sensation of effort being added for sportiness’ sake. I like it. He lets me sample higher steering effort levels and various damping rate profiles (these affect how quickly you can steer the car and how it returns to center). By comparison with the baseline’s low, natural effort, all seem worse. Other journalists at the event preferred some of Mischa’s tweaks. But what do they know? Do any emulate the feel of a Porsche Boxster or E39 5 Series? No. Mischa’s setup is superbly precise, utterly predictable, and makes the car do exactly what I ask of it. Bravo. It still lacks the feel of those benchmark cars—because it’s so darned hard for road forces to fight their way past the torque of an electric motor twisting a second pinion on the steering rack, which then flows up the main pinion and shaft to the steering wheel rim.
Next we set out on an hour-plus route used by the development team. It offers a brilliant mix of twisty, hilly, and straight country roads with widely varying surfaces, village roads, and unrestricted autobahn stretches. Application driving dynamics boss Jos van As notes that the test cars are the “worst case for ride”—sport suspension and lowest-profile run-flat tires. Yet body motion control is impeccable, and the vehicle absorbs the sharpest impacts with trademark vintage-BMW suppleness. I can only imagine how cosseting the base car on taller sidewalls will feel. Even when those bumps occur in the tightest of corners, they’re absorbed without deviating from the driving line. The e-LSD axle can be felt helping dig the car out of the tightest corners when the throttle is open. In a few hard hairpin corners that clearly involve steering-ratio variation, the effort and motion feel entirely natural. And at 155 mph on the autobahn, the solid on-center feel inspires confidence.
The time arrives for two hot laps of the Nurburgring behind van As in an M2 serving as my driving-line coach. The new 3 feels right at home here—no surprise, given that it’s logged thousands of miles, 12.9 of them at a time, on this 73-turn circuit. A bit more surprising is how quickly this chassis makes a ’Ring virgin like myself feel comfortable probing eight- and nine-tenths of this chassis’ limits, maintaining small-slip-angle drifts and trusting the brakes to do their thing harder and later in the turns. (I did detect a bit of brake vibration at the end of one long braking zone, however.) The steering totally disappears here, drawing no attention to itself.
The session ends. I struggle to think of constructive feedback for the chassis team. My criticisms are all for other 3 Series engineers. The transmission’s sport-mode tuning needs a lot of work. It was forever grabbing high gears at the wrong time and it too seldom downshifted appropriately while slowing for a corner. The shift paddles and manual-gate shifter work great, except the thin red line in the cluster that blinks at redline is too faint to get my attention. I’d also love to see some improvement in the sound of the engine/exhaust at lower revs. It sounds great at full boil, but it’s still plagued by that dieselish clatter at idle and low cruising speeds. (The only other news we received during this chassis-focused trip about the 2.0-liter turbo engine is that it will gain about 7 hp and 37 lb-ft of torque.)
Over dinner we chat about benchmarks, and I ask whether the Alfa Romeo Giulia warranted special attention. “It is a great car, but it is not a BMW,” says chassis integration guy Robert Rothmiller. In his team’s experience, Rothmiller finds that although the Alfa’s ultimate capabilities may be impressive, that car makes its driver work harder than a BMW driver should have to in achieving them. So will this be the ultimate-driving 3 Series? The essential elements seem to be here—provided Mischa doesn’t act on those other journalists’ steering recommendations and ruin his years of development work.
The post 2019 BMW 330i Prototype Review: The Ultimat3? appeared first on Motor Trend.
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