Porsche utilized a transaxle in the 928 to help achieve 50/50 front/rear weight distribution, aiding the car's balance. Although it weighed more than the difficult-to-handle 911, its more neutral weight balance and higher power output gave it similar performance on the track. The 928 was regarded as the more relaxing car to drive at the time. It came with either a five-speed dog leg manual transmission, or a Mercedes-Benz-derived automatic transmission, originally with three speeds, with four-speed from 1983 in North America and 1984 in other markets. More than 80% had the automatic transmission. Exact percentage of manual gearbox cars for entire production run is not known but its believed to be between 15 and 20%.
The body, styled by Wolfgang Möbius under guidance of Anatole Lapine, was mainly galvanized steel, but the doors, front fenders, and hood were aluminum in order to make the car more lightweight. It had a substantial luggage area accessed via a large hatchback. The new polyurethane elastic bumpers were integrated into the nose and tail and covered in body-colored plastic; an unusual feature for the time that aided the car visually and reduced its drag. Porsche opted not to offer a convertible variant but several aftermarket modifiers offered convertible conversions, most notably Carelli, based in Orange County, CA. The Carelli conversions were sold as complete cars, with the conversion doubling the price of the car. A reported 12 units were made.
The 928 qualified as a 2+2, having two small seats in the rear. Both rear seats could be folded down to enlarge the luggage area, and both the front and rear seats had sun visors for occupants. The rear seats are small (due to the prominent transmission hump) and have very little leg room; they are only suitable for adults on very short trips or children. The 928 was also the first vehicle in which the instrument cluster moved along with the adjustable steering wheel in order to maintain maximum instrument visibility.
The 928 included several other innovations such as the "Weissach Axle", a simple rear-wheel steering system that provides passive rear-wheel steering to increase stability while braking during a turn, and an un sleeved, silicon alloy engine block made of aluminum, which reduced weight and provided a highly durable cylinder bore.
Porsche's design and development efforts paid off during the 1978 European Car of the Year, where the 928 won ahead of the BMW 7 Series, and the Ford Granada. The 928 is the only sports car so far to have won this competition, where the usual winners are mainstream hatchbacks and sedans/saloons from major European manufacturers. This is regarded as proof of how advanced the 928 was, compared to its contemporaries.
Styling was the same in both 1978 and 1979, with the body lacking both front and rear spoilers. From 1980 (1983 in North America) through 1986, front and rear spoilers were present on "S" models, rear spoilers being integrated into the hatch. From 1987 through 1995, the front spoiler is integrated into the nose and the rear spoiler became a separated wing rather than an integrated piece, and side skirts were added. The rear tail-light configuration was also different from previous versions. GTS models had wider rear fenders added to give more room for 9" wide wheels. Another easily noticeable visual difference between versions is the style of the wheels. Early 928s had 15" or 16" "phone dial"-style wheels, while most 1980s 928s had 16" slotted "flat discs", CSs, SEs and 1989 GTs had 16" "Club Sport" wheels, later GTs had 16" "Design 90" style wheels which were also option on same period S4s, the GTS used two variations of the 17" "CUP" wheels.
Porsche introduced a refreshed 928 S into the European market in 1980 model year, although it was summer of 1982 and MY 1983 before the model reached North America. Externally, the S wore new front and rear spoilers and sported wider wheels and tires than the older variant, but the main change for the 928 S was under the hood, where a revised 4.7 L engine was used. European versions debuted with 300 PS (221 kW/297 hp), and were upgraded to 310 PS (228 kW/306 hp) for 1984 model year, though it is rumored [and proven on chassis dynamometers] that they typically made around 330 hp. From 1984 to 1986, the S model was called S2 in UK. These cars used Bosch LH-Jetronic fuel injection and purely electronic Bosch ignition, the same systems used on the later 32-valve cars, though without the pollution controls. North American-spec 1983 and 1984 S models used, among other differences, smaller valves, milder camshafts, smaller diameter intake manifolds, and additional pollution equipment in order to meet emissions regulations, and were limited to 234 hp (174 kW/230 PS) as a result. Due to low grade fuel 16V low compression S engine was made for Australian market in 1985 model year. It had 9.3:1 compression ratio pistons instead of normal 10.4:1 but used same large intake, high lift cams, large valves etc. of other S engines.
As the faster European model was not available in the United States and Canada during the first three years of its existence, a "Competition Group" option was created to allow North American customers to have an S model lookalike with spoilers, 16" flat disc wheels, sport seats, sport springs and Bilstein shocks. Customers could specify paint and interior colors the same way as on a normal 928. Two cars were made in late 1980 model year for U.S. with this option. The package was officially available in 1981 and 1982 model years and was canceled in 1983 when the S model became available for these markets. Many cars have had S model features added by subsequent owners, making original "Competition Group" cars difficult to distinguish without checking option codes.
In 1982 model year, two special models were available for different markets. 202 "Weissach Edition" cars were sold in North America. Unusual features were champagne gold metallic paint, matching brushed gold flat disc wheels, two-tone leather interior, a plaque containing the production number on the dash and the extremely collectible three-piece Porsche luggage set. It's believed these cars were not made with S spoilers even though these were available in U.S. during this time period as part of the "Competition Group" option. The "Weissach Edition" option was also available for the US market 911 in 1980 model year and 924 in 1981 model year.
141 special "50th Jubilee" 928 S models were available outside the U.S. and Canada to celebrate the company's 50 year existence as a car manufacturer. This model is also sometimes referred to as the "Ferry Porsche Edition" because his signature was embroidered into the front seats. It was painted meteor metallic and fitted with flat disc wheels, wine red leather and special striped fabric seat centers. Similar 911 and 924 specials were also made for world markets.
Porsche updated the North American 928 S for 1985, replacing the 4.7 L SOHC engine with a new 5.0 L DOHC unit sporting four valves per cylinder and producing 288 hp (215 kW/292 PS). Seats were also updated to a new style, these cars are sometimes unofficially called S3 to distinguish them from 16-valve "S" models. European models kept a 4.7 L engine, which was somewhat more powerful as standard, though lower 9.3:1 compression 32-valve engine together with catalytic converters became an option in some European countries and Australia for 1986. In 1986, revised suspension settings, larger brakes with 4-piston calipers and modified exhaust was installed on the 928S, marking the final changes to old body style cars. These were straight from the 928S4, which was slated to debut a few months later. These changes came starting from VIN 1001, which means that the first thousand '86's had the old brakes, but later cars had the later systems. This later 1986 model is sometimes referred to as a 19861⁄2 or 1986.5 because of these changes. The name is a little misleading as more than 3/4 of the 1986 production had these updates.
The 928 S4 variant debuted in the second half of 1986 as a 1987 model, an updated version of the 5.0 L V8 for all markets producing 320 PS (235 kW/316 hp), sporting a new single-disc clutch in manual gearbox cars, larger torque converter in automatics and fairly significant styling updates which gave the car a cleaner, sleeker look. S4 was much closer to being a truly world car than previous models as only major differences for North American models were instrumentation in either kilometers or miles, lighting, front and rear bumper shocks and the availability of catalytic converters in many other markets. The Australian market version was only one with different horsepower rating at 300 PS (221 kW/296 hp) due to preparation for possible low grade fuel. Even this was achieved without engine changes.
A Club Sport variant which was up to 100 kg (220 lb) lighter became available to continental Europe and U.S. in 1988. This model was watered down version of the 1987 factory prototype which had a lightened body. Also in 1987 the factory made four white lightened manual gearbox S4 models for racecar drivers who were on their payroll at the time. These were close to same as later actual Club Sport models and can also be considered prototypes for it. An SE (sometimes called the S4 Sport due to model designation on rear bumper), a sort of halfway point between a normally equipped S4 and the more race-oriented Club Sport, became available to the UK. It's generally believed these Porsche Motorsport-engined cars have more hp than the S4. They utilize parts which later became known as GT pistons, cams and engine ECU programs. Some of them had stronger, short geared manual gearbox. The automatic gearbox was not available.
For the 1989 model year, a visible change inside was digital trip computer in dashboard. At the same time Australian models received the same 320 PS (235 kW/316 hp) engine management setup as other markets. Porsche debuted the 928 GT in the late winter 1988/89 after dropping the slowly selling CS and SE. In terms of equipment, the GT was like the 928 SE, having more equipment than a Club Sport model but less than a 928 S4 to keep the weight down somewhat. It had the ZF 40% limited-slip differential as standard like the Club Sport and SE before it. Also like the CS and SE, the GT was only available with a manual gearbox. European 1989 CS and GT wheels had an RDK tire pressure monitoring system as standard, which was also optional for the same year S4. For 1990 model year Porsche made RDK and a 0-100% variable ratio limited-slip called PSD (Porsche SperrDifferential) standard in both GT and S4 models for all markets. This system is much like the one from the 959 and gives the vehicle even more grip. In 1990 the S4 was no longer available with a manual gearbox.
The S4 and GT variants were both cut at the end of 1991 model year, making way for the final version of the 928. The 928 GTS came for sale in late 1991 as a 1992 model in Europe and in spring of 1992 as an early 1993 model in North America. Changed bodywork, larger front brakes and a new, more powerful 5.4 L, 350 PS (257 kW/345 hp) engine were the big advertised changes; what Porsche wasn't advertising was the price. Loaded GTS models could eclipse US$100,000 in 1995, making them among the most expensive cars on the road at the time. This severely hampered sales despite the model's high competency and long standard equipment list. Porsche discontinued the GTS model that year after shipping only 77 of them to the United States. Total worldwide production for all years was a little over 61,000 cars.
Second-hand models' value decreased as a result of generally high maintenance costs due largely to spare parts that are expensive to manufacture. The earliest versions, however, especially those models with the Bosch K-Jetronic (CIS) injection system, have few electronic components and therefore can be repaired more easily provided spare parts can be found. Parts suppliers supported by various enthusiasts exist especially in the United States.
Source: Wikipedia, 2014