By now you've seen BMW's new 6 Series, internally coded the E63 (coupe) and E64 (convertible). Owing to size, price, and content, hardcore Bimmerheads are debating whether the new 6 more closely follows the 8 Series (1991-1997) than the old 6 Series. But while they do that, we are on the cusp of a monumental introduction: the new M6, powered by a firebreathing V10 engine that more closely resembles a Formula 1 design than a street engine.
The E24 6 Series was BMW's biggest Jekyll and Hyde car, with vastly different personalities from year to year and from market to market. While it was a luxury performance coupe here in America, certain versions were clearly performance luxury coupes in Europe, near-160-mph autobahn stormers with close-ratio manual gearboxes-and no cup holders. Still others were veritable strippers in Europe, such as the 1976-77 630CS, with a single Solex four-barrel carburetor, four-speed gearbox, and 195/70-14 tires.
Moreover, the M6, as it is known in the United States, was called the M635CSi in Europe, where production of the much hotter European version began much earlier. Now that the new M6 is upon us, we thought it was time to take a look back at the old M6, both the North American and European versions.
The Truth:1984-1989 M635CSiThe 286-bhp European-version M635CSi started to hit the streets in spring 1984 for the equivalent of about $31,450. Europeans were already used to a very strong 218-hp 635CSi. Don't scoff at those numbers though-we're talking about cars that weighed about 3,200 pounds. Compare that with today's M6. It may have 507 bhp, but it also weighs 3,762 pounds, and it is fairly easy to get more than 300 hp from an M635CSi-it just takes a set of Schrick camshafts. An owner from the BMW Car Club of America's National Capitol Chapter once described this car as "The Truth."
The M88 engine derived from the same dohc, 24-valve, 3.5-liter mill that originally powered the 3.0CSL in the 1970s, and later BMW's M1 supercar. The fuel injection system was modernized to Bosch ML Jetronic and later Motronic, which afforded far greater street drivability and fuel economy. The system used one throttle body per cylinder for outstanding throttle response and mixture delivery. With factory tube headers and a non-catalyst exhaust system, the M88 spun a Getrag 280 sport overdrive five-speed manual gearbox and a 3.73 limited-slip differential. The diff was actually a 7 Series part, requiring the M635CSi's body to be heavily massaged at the rear floor area. (Note that some very early production M635CSis were equipped with a close-ratio five-speed gearbox and a much higher differential, the 3.07 limited-slip unit common in the European 635CSi.) The factory exhaust system was spot-on in terms of sound and performance. This car would rattle your house just idling in the driveway.
The M88 engine itself is a high-rpm power engine without much low-end torque. It's a screamer, and the sounds and power curve are tremendously gratifying at speed. That speed is zero to 60 in 15.1 seconds and 158 mph at full song. But there's a lot more to the M635CSi than the powertrain.
Underpinning the M635CSi were firmer, shorter coil springs than U.S. versions, coupled with Bilstein shocks and larger 25- and16-mm sway bars (an 18mm rear bar was also available). Binders were 300x30mm vented front rotors with four-piston calipers and 284 x10mm solid rear rotors with single-piston floating calipers. ABS was standard as of 1984. The suspension and brakes were essentially performance tuned upgrades, which is what many BMW enthusiasts put on their cars in the States. Wheels and tires are the only areas where BMW faltered. Recall this was the era of the dreaded Michelin TRX tire and wheel combination, a horrible idea that BMW stuck with for a long time. TRX tires required a special metric-sized wheel which could not be used to mount normal tires. If you have TRX wheels, you have to buy TRX tires or else buy new wheels to use with normal tires.
Outside, the M635CSi used a large front air dam and rear spoiler. The frontal treatment was updated as of June 1987 and there were actually four different rear spoilers. The most common of the four was a large black wing that was quite effective at producing downforce. BMW's sport striping was popular in Europe during the 1970s and 1980s, and the M635CSi was often adorned with duel large black or silver side strips extending the length of the upper body line. Of course, the smaller European-specification bumpers blended perfectly into the E24 design, unlike the gigantic aluminum affairs used on American-spec cars.
The E24 interior was a study in Teutonic functionality and no-nonsense design we came to know and love, and which BMW continued to use until recently. The dashboard was angled heavily toward the driver and included nearly full instrumentation with an electronic "check control" system to monitor operating fluid levels and lighting. All controls and instruments were lighted orange at night, same as contemporary Bimmers. Storage bins abounded, and the car was ergonomically perfect for almost every driver. Genuine Recaro sport seats could be ordered in a variety of cloth, vinyl, and leather upholstery, including buffalo hide. The back seat was equally cockpit-like, with deep cradling bucket seats, headrests, and a center armrest housing a small cooler. The cooler temperature was maintained by the air conditioning system, which included vents for the rear seat passengers. The rear parcel shelf housed storage compartments, one of which often contained something most cars carry in Germany: a comprehensive first aid kit. Not just Band-Aids and antiseptic in this one; we're talking tourniquets and giant gauze bandages for your messier autobahn mishaps.
Today, the nicest thing about the M635CSi is quite a few of them are here in the States. It was very popular to personally import these cars from Germany and other European countries where, after three or four years, they were just another used car. Here, they were the hottest BMW we could get our hands on. It was a lot less expensive to buy and import an M635CSi than it was to buy a U.S. 633CSi or 635CSi and performance tune it-until the government got involved. Car manufacturers were obviously less than pleased at the emergence of what they called a "gray market," and before too long importing non-conforming cars to the U.S. was banned. Only recently has importation opened up again, but mainly for cars 25 years old or older. Certifying newer cars is usually incredibly expensive and sometimes impossible.