1985 BMW 635CSi Is Perfectly Imperfect

From the February 1985 issue of Car and Driver.

In many ways, the 635CSi is a superlative car. It produces prodigious speed, thanks to its new 3.4-liter engine. It exhibits much better handling than BMW’s early 6-series coupes. It is put together with rare care. Its ergonomics are generally excellent. And now it has Bosch ABS anti-lock braking equipment for help during emergency stops. All told, the 635CSi is a very accom­plished piece of work.

On the other hand, it’s not perfect.

BMW’s glassy coupe has been around for eight years. The 635 remains a very clean design, but flush glass and head­lights, integral drip channels, and aerody­namic wheels do not yet grace its charms. The speed it makes is due to muscle, not aerodynamic slickness. This year, the 635CSi does appear more determined, thanks to a body-colored air dam that houses two fog lights.

The rolling stock has also been upgrad­ed to handle the larger engine. Fat Michelin TRX tires, size 220/55VR-390, are mounted on 6.5-by-15.4-inch alloy wheels (a move from 70-series tires on 6.5-by-14-inch wheels). We found that the new combination is worth 0.79 g on the skidpad, a clear improvement in adhesion. The engineers have also tuned the driveline for a more aggressive attack on the competition. Unfortunately, the 635’s Getrag 260 five-speed gearbox is plagued with notchiness, and second gear balks when cold. BMW long ago dumped smoother-shifting, weaker-synchroed ZF gearboxes in favor of the notchier Getrags. This transmission asks for a heavy hand on the lever, and even the 635’s clutch de­mands extra attention for smooth shifts. (For minimal disruption, a ZF four-speed automatic is optional, for $795.) Lighter shifting is available with Detroit’s five-speed, high-output V-8s, which deliver much more torque than the big BMW.

Still, we’re talking 3.4-liter, high-rev­ving, seven-league boots here. BMW has punched out the 3.2-liter’s bore from 89 to 92 mm, and the torque has increased from 195 to 214 pound-feet. This single­-overhead-cam six is old, but it remains atop the pack in basic design. Its aluminum hemispherical head is fed by Bosch Motronic fuel injection. Crossflow intake and exhaust ports handle the breathing, and a new, adaptive Lambda-sensor control sets the fuel-air mixture more precisely through a wider range of operation. To allow maxi­mum spark advance at all times, BMW has not yet resorted to a knock sensor, and the 3.4-liter motor’s compression ratio remains a relatively low 8.0:1. The added dis­placement has bumped up the horsepower only from 181 to 182. Tuned instead for midrange response, the big six’s power peaks at 5400 rpm, 600 rpm earlier than in the 3.2-liter. A 3.45:1 final-drive replaces the 633’s taller 3.25 gear, boosting the throttle response throughout the rpm range, but a rev limiter clips the power smartly at 6200 rpm.

Additional power or no, stepping hard on the throttle will hang the 635’s tail out with ease. BMWs were once known for hanging out their tails for altogether differ­ent reasons. Lift-throttle oversteer whipped the cars sideways if you suddenly backed out of the throttle when cornering hard. Their semi-trailing-arm independent rear suspensions provided supple adhe­sion over poor roads, but criticisms leveled against their ultimate instability finally mo­tivated BMW into a partial redesign: the semi-trailing arms were angled less so they would steer the rear wheels less when the throttle was closed, and compound outboard pivots, called Trac Links, lowered the rear roll-center height and reduced jacking effects during cornering. Even ear­lier, BMW had built a MacPherson-strut front suspension with double pivots that improved steering feel and response. When it put both these fixes into its cars, they became at once nimble and stable. The 6-series got this good stuff during the 1983 model year, and it has felt terrific ever since.

Best of all, at long last (praise be!), ABS braking arrives on the American market. It is standard equipment on all 3.4-liter 5-, 6-, and 7-series BMWs (as well as assorted Mercedes-Benzes), albeit twenty years af­ter Bosch started development and seven years after Euro-market BMWs got it. Remarkably, ABS detects the imminent lock­ing of any of the four 11.2-inch discs and immediately reduces the hydraulic pres­sure to that brake, releasing it to turn, whereupon the pressure immediately pumps up again for maximum braking. The cycle continues until the pedal effort is relaxed or the car stops. The result is maxi­mum braking with no loss of steering or stability. The driver has only to stand on the brake pedal and steer.

ABS will not save you if the situation is too far gone, but BMW says it will stop the car ten to fifteen percent shorter on dry pavement and 25 to 40 percent shorter in rain, snow, and ice, a whale of a payoff from a system that weighs less than 40 pounds. ABS employs individual wheel-speed sen­sors, an electronic control unit, and a hy­draulic control unit that’s integral with an electrically driven hydraulic power assist. A quick-footed driver might pump the brakes four times per second. ABS pumps each front brake separately and both rear brakes together up to fifteen times per second. What you feel is a pulsing through the ped­al. The 635 exhibits a softer pulsing than ABS-equipped Benzes we’ve tried, per­haps because of differences in software or hardware, or both. In every case, however, the stopping ability is nothing less than sensational. ABS monitors itself, provides a status light, and automatically cuts off if something goes awry. And ABS is only there when you need it: the pedal normally feels like any other in even the hardest driv­ing. Our standard dry-pavement stop from 70 mph needed only 189 feet in the new 635CSi, although a number of non-ABS cars do as well or better, at least in a straight, dry line.

As with any high-performance car, prop­er support in the driving position would be a great help during the hard acceleration, braking, and cornering that the 635CSi en­courages. If you’re broad across the beam and opposed to exercise at the wheel, you may love these seats. But if you’re skinny everywhere except the wallet, you may not love them. They are wide, flat, and slick with leather. No fabric is available in the 635, nor are any of the lumbar and bolster adjustments that are stuffed into nickel-­and-dime Japanese and American GT cars. Roominess up front is so-so, and the two rear cuplets are ridiculously tight, but, hey, this is a GT coupe by BMW’s definition; the company offers roomier sedans, in­cluding the lighter and even faster 535i, for sport delivered in boxes. Thanks to a total of twenty(!) console buttons with complex graphics, dedicated occupants can power the 635CSi’s seats into almost any position, but BMW should swallow its pride and copy the simple Mercedes 3-D controls, de­signed in the shape of a seat.

The 635 has power everything, plenty of storage, and a carpeted, tool-kitted trunk. The electronic stereo seems plenty compe­tent but sounds choked by its smallish speakers. The air-conditioning system is not a set-and-forget climate control, but it’s very adaptable, thanks to good flow, fine controls, and four vent levels. The other­wise sensational black-leathered steering wheel is handicapped by small horn buttons but enlivened by a dab of BMW Motorsport colors. In BMW analog tradi­tion, the 160-mph speedo, the 7000-rpm tach, the fuel and temp gauges, and the in­stantaneous-mpg scale are crisply legible. The wraparound dashboard is both exotic and practical. The cruise control is flawless. A nine-function dash computer handles ev­erything from day tripping to tripping up would-be thieves. And everything is put to­gether as if lives depended on the coupe’s solidity.

A good thing it is, for the 635CSi is a quick car, if not blinding in acceleration. Its ripe torque, short final-drive, and early rev limiter conspire to produce both wheel hop off the line and a time-consuming shift to third gear at only 59 mph. The result is a 0-to-60 time of 8.2 seconds, a half-second slower than the last 633CSi we tested. The quarter-mile performance of 16.0 seconds at 85 mph matches the 633 in elapsed time but is 1 mph slower in trap speed. Top speed, however, is up from 124 to 132 mph, and real-world driving demonstrates considerably more poke, even though this particular car is 95 pounds heavier than the 633. The engine feels great, but many cars, including the new American VW GTI, the Honda CRX, the Porsche 928, and the Eu­ropean-spec 635CSi, have compression ra­tios of 10.0:1. With a measly 8.0:1 in this 635, and much less than one horsepower per cubic inch of displacement, we can’t help feeling that something is missing. Lately, it seems as if BMW’s efforts to block the gray-market importation of higher-per­formance European models have exceed­ed its interest in building state-of-the-art machinery for the American market. A mandate should be sent to the engineering department: send more torque and more horsepower to the U.S.

In BMW’s defense, the 635CSi is so well balanced that it is capable of easily return­ing hair-raising average speeds without ever standing an occupant’s hair on end. For a car of its size and weight, the 635 is quite the gymnast—and, for our money, the best-handling BMW since the M1. It is poised (if occasionally porpoisy and undershocked) when called to heavy duty, and it’s stable over endless stretches of deep throttle. Feed it hard and fast with the strong inputs it calls for, and it rushes back for more.

But don’t face off this $42,000 BMW with the $25,000 Corvette (which appeals to a different crowd but is also much faster), and be careful around IROC-Zs, Trans Ams, Mustang GTs, Merkurs, and sixteen­-valve Saabs. And for God’s sake, don’t get mowed down by the 32-valve, monster­-motor Porsche 928 (which does appeal to this crowd, costs less than $10,000 more, and is 100 hp stronger). Just use the 635CSi as any fast car is used in Europe: as a light plane. Quick and to the point.