Summary

From 1980 to 1986, BMW offered a special turbocharged version of its flagship 7-Series sedan called the 745i. The turbocharged six-cylinder engine was supposed to be a more economical substitute for a 4.5-liter V-12 BMW developed in the 1970s, but its fuel consumption was still high, and it performed best at very high speeds. There was also a rare South African version with the normally aspirated (non-turbocharged) 24-valve six-cylinder engine from the M635CSi coupe. The 745i was not officially exported to the U.S. and sold in relatively small numbers. It was discontinued in 1986 and replaced by the 750i and 750iL, which had a non-turbocharged V-12 engine instead of the turbocharged six.

Improvements

To their credit, BMW engineers were obviously aware of the limitations of both the E23 7-Series generally and the 745i in particular, and mitigation was not long in coming. At the 1981 Frankfurt show, less than a year and a half after launch, the company announced that the turbocharged engine had received a variety of detail changes aimed at improving fuel economy, in particular a half-point higher compression ratio (7.5 rather than 7.0:1).

These refinements reduced fuel consumption by about 10 percent, although the results were not so much “more economical” as “incrementally less profligate.” AMS reported a test average of 12.0 mpg (19.5 km/L) with the latest 745i, which was still harrowing by European standards. Their test of a 1982 Mercedes-Benz 500SEL, which also incorporated various changes aimed at reducing fuel consumption (known in Stuttgart as the Energiekonzept, or “Energy Concept”), managed 20.1 mpg (11.7 L/100 km) overall, although the Mercedes sacrificed a bit of power and some acceleration in the process.

Although BMW reported no changes to the power or torque output of the revised M102 engine, the more economical 745i was also quicker than before: 0–62 mph (0–100 km/h) in as little as 7.2 seconds and 0–100 mph (0–160 km/h) in 17.4 seconds, again per AMS. Taking full advantage of this extra performance required manually holding the automatic’s lower gears, which was not ideal (the transmission didn’t always respond swiftly to manual selections, which risked encountering the injection system’s 6,300 rpm fuel cutoff), but it gave the 745i impressive performance for 1982.

These improvements, alas, were not free. Base price of the 745i had risen to DM 56,150, and a limited-slip differential, which had initially been standard on West German cars, was now an extra 683 marks. Adding the TRX package (DM 1,281), sunroof, power seats, metallic paint, headlamp washer system, and newly available cruise control brought the price to a hefty DM 63,738, enough at that time to buy a 323i sedan and a 520i. Even this price did not include air conditioning, which was rarely standard on European executive cars of this era. Automatic climate-controlled air conditioning had been optional on the 745i since launch — for an extra 3,830 marks, thank you very much — but by 1982, there was also a conventional manual system, offered for a mere DM 3,215.

Despite the turbocharged 7er’s high price and unseemly drinking problem, BMW had built 6,193 turbocharged 745i sedans by the end of 1982, a modest but respectable total obviously constrained by the lack of North American or RHD exports. By comparison, Mercedes-Benz built 29,234 500SE and 500SEL sedans in the same period, although the Mercedes was much more widely available.

The lack of a RHD 745i was especially galling for BMW South Africa, which in this era was doing good business selling locally assembled 7-Series sedans to some of that nation’s worst people. The E23 7-Series was then a favorite choice of senior officials of South Africa’s apartheid government, including prime minister P.W. Botha, whom The Guardian later described as “one of the most evil men of the 20th century” (a ranking with much stiff competition, to be sure). Rather than deprive these worthies of the opportunity to own the company’s flagship model, BMW South Africa contrived its own locally built and engineered RHD 745i, powered not by a turbocharged engine, but rather by the latest M88/3 version of the DOHC 24-valve engine from the BMW M1, the same version subsequently used in the M5 sedan and E24 M635CSi coupe. (There was no attempt to rationalize the “745i” badge, which was probably just as well.)

With 290 hp DIN (213 kW) and an available five-speed gearbox (although many likely had the optional ZF 4HP22 automatic), the South African 745i was faster than the turbocharged car — the factory claimed 0–100 km/h (0–62 mph) in 7.0 seconds and a top speed of 240 km/h (149 mph) — and somewhat harder-edged. With a lofty price tag of 65,000 rand plus VAT — then the equivalent of around DM 150,000 in West Germany, although many features that were optional in Germany were standard fit on the South African cars, including automatic air conditioning — the 24-valve 745i was strictly for the few, and, presumably, the white. (AMS, in an embarrassing example of the cultural insensitivity that too often characterizes buff books, pictured the South African 745i with a Black chauffeur behind the wheel while wondering longingly whether such a car might eventually be available in Germany.) Production was very limited, amounting to no more than 209 cars between 1983 and 1986.

A Facelift and the M106 Turbo Engine

For 1983, BMW gave the entire E23 line another round of significant revisions intended to keep the 7-Series viable until its replacement, which wouldn’t be for at least three more years. The 7er had actually gone through a weight-reduction program shortly before the 745i debuted; the latest changes trimmed a bit more weight while tidying up the dated aerodynamics with a lower grille and ugly black filler panels in the A-pillars. This improved the drag coefficient from 0.44 to a still-lackluster 0.41, which was as much as the BMW board deemed they could afford on a flagship model whose basic tooling and development costs hadn’t yet been fully amortized.

From a driver’s standpoint, a more worthwhile change was a revised rear suspension with the semi-trailing arms angled at 13 rather than 20 degrees, which, combined with a stiffer front anti-roll bar, promised to reduce acceleration squat, camber change, and the propensity for hanging out the tail on a trailing throttle. This it did, although the difference was one of degree rather than general trajectory, particularly on wet or slippery roads.

Across most of the line, the three-speed ZF 3HP22 automatic was also replaced by the four-speed 4HP22, with a lockup torque converter, 0.73:1 overdrive top gear, and an array of different automatic and manual modes. It was electronically controlled and integrated with the Bosch Motronic system, which automatically retarded the spark timing during gear changes for greater smoothness.

This new transmission became standard on the updated 745i, which arrived in mid-1983, sporting not only the new automatic, but also a new turbocharged engine, designated M106. The M106 was based on the M30B34 engine in the 735i and displaced the same 3,430 cc (209.3 cu. in.). (Had BMW been serious about the FIA equivalency factor, the new engine would have been considered the equivalent of 4,802 cc (293.0 cu. in.), making the car a 748i, but the “745i” designation remained.)

The M106 had higher compression, now 8.0 rather than 7.5:1, and a Bosch Motronic II digital engine computer rather than the simpler L-Jetronic system of the M102. On the M106 engine, the Motronic system managed boost pressure as well as fuel delivery and ignition timing, taking input from two knock sensors in the cylinder head and from pressure sensors in the compressor outlet and the intake manifold aft of the throttle butterfly. The previous return air system was deleted, and the Motronic system now managed the wastegate to control boost pressure based on a series of preprogrammed digital maps. Knock was controlled by retarding the ignition timing, opening the wastegate valve to reduce boost, or both.

We were unable to obtain copies of contemporary German technical papers describing the new boost control system in detail, and the BMW press kit’s technical description is vague on several points, but it appears that the M106 had a more effective intercooler — it was now said to reduce charge temperature by up to 131 degrees rather than 104 degrees Fahrenheit (55 rather than 40 degrees Celsius) — and that peak boost pressure was functionally lower than before; peak turbine speed was said to have been reduced by over 30,000 rpm. This allowed leaner mixture settings and more spark advance for better fuel economy, but meant that the M106 was no more powerful than the M102 despite its higher compression and larger displacement. BMW claimed the same 252 PS (185 kW) and 280 lb-ft (380 N-m) of torque as before, albeit at slightly lower RPM (now 4,900 and 2,200 rpm respectively).

Since the new 745i was about 80 lb (37 kg) lighter than before and had greater low-end torque, one might expect it to be quicker than its predecessor, but even BMW admitted it was not. The factory now claimed 0–62 mph (0–100 km/h) in 7.9 seconds and the standing kilometer (0.63 miles) in 28.2 seconds, compared to 7.8 and 28.3 seconds, respectively, for the original low-compression M102 car. An early AMS test car with the new engine could manage no better than 0–62 mph (0–100 km/h) in 8.7 seconds and the standing kilometer in 29.2 seconds, due mainly to traction problems that made it difficult to get a good launch; the 3.4-liter car took 1.3 seconds longer than its predecessor to reach 37 mph (60 km/h) and couldn’t make up the difference at higher speeds. Cars tested by both AMS and AR a year or so later did better, managing to equal or better the factory acceleration claims, but this only underscored the fact that there had not been any progress in this area since 1980. The second AMS test car did beat the factory’s claimed 141 mph (227 km/h) top speed, reaching nearly 144 mph (231 km/h), an achievement that probably reflected the lower numerical axle ratio (reduced on four-speed cars from 3.07 to 2.93:1) and slightly lower drag.

The more immediate point of the exercise was to reduce fuel consumption by a further 9 percent, making the latest 745i nearly 20 percent more efficient than the original edition. It still wasn’t very good in absolute terms — between 13.4 and 14.1 mpg (16.7 to 17.5 L/100 km) overall in AMS and Automobil-Revue tests — and it was still worse than the 500SE. Moreover, achieving even these unimpressive figures required enduring the finicky behavior of the 4HP22 transmission’s Economy mode, in which the automatic was reluctant to downshift without a full-throttle kickdown and tended to hunt annoyingly between third and fourth. The overdrive fourth gear was also of little help at higher Autobahn speeds; top speed had to be achieved in third because the transmission would not stay in fourth gear at full throttle even if a 4–3 downshift risked hitting the fuel cutoff.

In other respects, the latest 745i was a cautious step forward. A rear anti-roll bar and hydro-pneumatic self-leveling struts were now standard, and the 13-degree semi-trailing arms reduced the likelihood of kicking the tail out abruptly when the boost came on. Wind noise was better muffled, and eliminating the return air valve served to mitigate the earlier car’s vertiginous lack of engine braking.

“Vertiginous” was nonetheless an apt word for the escalation of the 745i sedan’s base price, which rose from DM 63,204 in mid-1983 to DM 65,700 by January 1984; by the end of the line in mid-1986, it was a lofty DM 73,100. From 1984, there was a new 745i Executive trim level, with additional standard equipment, walnut wood trim, and buffalo leather upholstery. This started at DM 83,760 in 1984, rising to 90,900 in 1985, when it was joined by an even pricier Highline grade that slathered the cabin in soft Nappa leather. In factory list price terms, the 745i Highline was the second-most expensive contemporary BMW model (after the M635CSi coupe), starting at DM 94,350 in 1985 and DM 96,750 in 1986. Although that was enough to buy three E30 320i sedans, these prices still didn’t include air conditioning, which could push the retail price above 100,000 marks.

(Author’s Note: If you’d like to get an approximate sense of what these West German prices represented in contemporary U.S. dollars, Werner Antweiler of the University of British Columbia Sauder School of Business maintains a Pacific Exchange Rate Service that has tables of historical exchange rates for different currencies from 1950 on, based on International Monetary Fund data. Because the relative value of the Deutschmark fluctuated so much during this period (the rates presented for 1972 on are annual averages) and didn’t necessarily have any direct relationship to the prices of German products sold in other markets, actual conversion is left as an exercise for the interested reader.)

Nonetheless, the 745i continued to sell about as well as before. BMW production figures are by calendar year rather than model year, so the 1983 figures don’t distinguish the late M102 and early M106 cars, but total 1983 to 1986 production was 9,838, which includes the South African 24-valve cars. Mercedes-Benz W126 500SE and 500SEL sedan production for the same period totaled 60,167, plus a further 18,696 560SEL sedans built in 1985 and 1986. Grand total for E23 745i production, including pilot production cars built in 1979, was 16,031 units.