Porsche 928 History (1978-1995)
Article by Mark Trotta
For a short while in history, the fastest street-legal production car sold in America was the Porsche 928. It also had the distinction of being Porsche's first mass-produced V8 model, and it's only coupe powered by a front-mounted V8 engine.
Between 1972 and 1980, Dr. Ernst Fuhrmann was the chairman of Porsche AG (Aktiengesellschaft: German for a corporation limited by share ownership). Declining sales of the Porsche 911 seemed to confirm that the model was approaching the end of its economic life cycle.
In an effort to offer a new sports car that could be driven over long distances with comfort and power, Fuhrmann had planned to discontinue the 911 and replace it with the 928.
From the outset, the new liquid-cooled, front-engine car was designed to address the shortcomings of the air-cooled rear-engine 911. One of the reasons for the front-engine/rear-drive design was to allow room for required catalysts and mufflers. It was subsequently decided that the two cars would be sold side by side.
Exterior design of the two-door coupe was by Wolfgang Möbius, overseen by Head of Styling Tony Lapine. The body shape of the 928 was planned to offer high roof strength and crush resistance.
Most of the body was made from galvanized steel, with doors, front fenders, and hood made from aluminium to help keep weight down. Impact-resistant bumpers were integrated into both nose and tail and covered in body-colored plastic. The rear cargo area was relatively large for a sports car, and accessed via a large hatchback.
The 928's headlights lay flush when not in use, and when activated, popped up to reveal bullet-shaped "snail-eyes". The pop-up headlight design dates back to the 1950's. It's what Donald Healey had hoped for on his bug-eye Sprite sports car, but was out of Healey's budget.
Porsche 928 Engine
Displacing 4.5 litres (bore/stroke 95mm x 79mm) with a single overhead camshaft, the all-alloy V8 was designed to fit under a low hood while still giving maximum air flow efficiency. Thick, aluminium cylinder barrels were fitted into an aluminum block.
Cylinder heads were also aluminium, with spark plugs located at the top. Engine compression was 8.5:1.
First-year models produced 219 horsepower for the North American market and 237 horsepower in other markets.
In the mid-1970s, Porsche utilized a rear-mounted transaxle for the front-engine 924, and again with the 944, and then in the 928. The design allowed a more even weight distribution between the front and rear axles.
Other measures taken to achieve a 50/50 weight ratio included moving the engine back as far as possible, and locating the battery in the trunk area.
A large torque tube connected the engine and the gearbox to each other. Due to the prominent hump, there was very little leg room in the rear.
Rolling on a wheelbase of 98.3 inches, suspension was four-wheel independent, with double A-arms in front. Brakes on the 928 were power assist 11-inch discs at each corner.
At the rear, the Weissach axle was one of the many technical features first seen on the 928. It consisted of two lateral arms and one longitudinal arm per side, with an adjustable strut combining the spring and the shock absorber.
The function of the Weissach axle was to eliminate lift-throttle oversteer by allowing the rear suspension to adjust itself during cornering maneuvers. It helped keep the rear wheels on track, a significant change from the tail-happy 911 models.
Early 928 models were offered with either a three speed automatic or a four-speed manual transmission. Starting in 1983 in North America and 1984 in other markets, a 5-speed manual was available. Later models would be offered with a 4-speed automatic. More than 80% of 928's had an automatic transmission.
Base price of the 1978 928 was $26,000.
Interior options included power seats, power windows, power sunroof and air conditioning. The instrument cluster on the 928 moved with the adjustable steering wheel in order to maintain maximum instrument visibility.
In addition to the Pasha checkered interior, upholstery was available in either cloth, leather, or vinyl. The rear seats could be folded down to enlarge the luggage area.
Rear Sun Visors
Both front and rear seats had sun visors for occupants. The rear-passenger sun visors were mounted on the top front of the hatch, and folded rearward to keep sun and glare of the heads of rear passengers.
1978 Car of the Year
The Porsche 928 was voted European Car of the Year in 1978. To this day, it stands as the only sports car to have won this title.
1979-1980 Porsche 928
Styling remained the same for 1979, with neither years having a front or rear spoiler. Porsche upgraded the engine from mechanical to Bosch L-Jetronic electronic fuel injection in 1980 for U.S. models. Power rating remained the same.
85 MPH Speedometer
In September of 1979, the National Highway Traffic Safety Administration (NHTSA) passed a bill which stated that all car, truck, and motorcycle speedometers were to display a maximum speed of 85 miles-per-hour. The speedometer limits certainly didn't govern the speed of the car, and the 85 mph max looked pretty silly on cars like the Delorean, Pantera, and the 928.
The 85 mph speedometer law ended in 1981, after much debate and little proof it actually did anything to change driver behavior. Porsche was one of the first manufacturers to switch back, offering recalibration and retrofit dials for their cars produced during 1979 through 1982.
Porsche 928 S
Not offered in North America until 1983, the 928S had a larger, 4.7 16 valve engine and larger brakes. Front and rear spoilers were present on S models from 1980 (1983 in North America) through 1986. Rear spoilers were neatly integrated into the hatch.
For North American markets, the standard 928 model was dropped in favor of the 928S. The 4.7 litre engine produced 234 horsepower and had new hydraulic motor mounts. Car body and torque tube changed to accommodate the longer 4-speed automatic transmission.
Risky Business Porsche 928
Certainly the most well-known 928 was the one driven by Tom Cruise in the 1983 film "Risky Business". The 1979 model featured in the movie was the same car that young Tom Cruise actually learned to drive a stick-shift on. It's also the same car featured in the chase scene, but was spared the plunge into Lake Michigan. For that, a gutted model was used.
"So your folks are going out of town, you've got the place to yourself"
The 928S model was renamed "S2" for the U.K. market, and had Bosch LH-Jetronic injection and 4-speed automatic transmission (previously only available in North America) Torque tube shortened like on U.S. model in previous year. Bosch ABS brakes optional for the first time in Porsche.
The Bosch EZF ignition system was introduced, having dual distributors and allowing higher compression and increased torque. At 146 mph U.S. model top speed, Porsche advertised the 928S to be "the fastest street legal production car sold in the U.S."
Now with a 5.0 litre 32-valve engine and 288 horsepower, top speed on U.S. models was in excess of 155 mph. ABS brakes became standard for all markets during the 1986 model year.
A slight redesign saw revised front and rear bumper light assemblies giving a smoother looking body. The front spoiler was integrated into the nose and the rear spoiler became a separated wing rather than an integrated piece. The rear tail-light configuration was also revised.
1987 was the 928's best sales year, with 5,400 sold.
In February of 1989, the manual transmission-only 928 GT debuted.
Dual airbags became standard in 1990 on all U.S. bound Porsche models. Driver and front passenger airbags were optional elsewhere with only drivers side bag available in right-hand-drive markets. A tire pressure monitoring system became standard on all 928's.
Improvements in 1991 included a new steering rack, power steering pump, and additional soundproofing.
The 928 GTS became available in North America in January 1992 as an early 1993 model with later model year VIN. A longer stroke crankshaft and different compression height increased engine displacement to 5.4 litres. With 10.4:1 compression and four valves per cylinder, power output was at 345 horsepower. GTS models had wider rear fenders to fit the 9" wide wheels.
Porsche 928 Performance
Throughout it's eight-year production span, exterior design did not change much, but it did keep getting faster.
In 1978, the 928 engine displaced 4.5 litres and power output was 219 horsepower. With a weight of 3,411 pounds, top speed was 138 mph, with 0-60 mph times at seven seconds.
By 1992, the 928 GTS engine displaced 5.4 litres and produced 345 horsepower. It was capable of 170+ mph with 0-60 times in the low fives.
Built from 1977 to 1995, 61,067 examples were assembled at the Stuttgart, Germany factory.
Porsche did not offer a convertible 928, all left the factory as a 2-door coupe only. However, several aftermarket companies offered convertible conversions.
Porsche 928 Collectability
The 928 was never really successful enough to replace the 911. The collector market for the 928 has always been somewhat less enthusiastic than that of its rear-engine stable-mates.
Condescendingly referred to as the German Corvette by classic car snobs, the 928 has been slow to earn the respect and collectability of the 356 and 911 models. The 928S, S4, GT, and GTS models exchange hands for more money than the base 928 models.
Porsche 928 Reliability Issues
When properly maintained by someone who understands the car, second-hand 928s should have no significant issues. Many reliability complaints about the 928 were brought on by well-meaning but ignorant technicians. Maintenance records can give a lot of needed answers.
If you buy a second-hand 928 that had been poorly maintained, you can easily pay more than if you just spent the money and got a better maintained one to begin with.
Timing Belt Concerns
Proper maintenance requires timing belt replacement at regular intervals - before it breaks or wears out. Both the oil and water pumps are powered by the belt, and it is extremely long (about six feet). The timing belt on the 928 has a replacement interval of every 30K miles.
Mechanical engine damage will occur if the timing belt breaks - usually pistons hitting open valves, resulting in the need for expensive repairs. Be aware that the later, S4 version of the 928 had both a timing chain and timing belt.
If the warning light for the ABS or Traction Control is on, it could be a bad hydraulic pump. On later models like the S4 and GTS, there was a hydraulic pump in the left rear quarter panel that needed to be bled frequently along with the brakes. Many second-hand 928 owners don't know it's there so they don't get serviced.
With the exception of the engine, most parts from later 928 models will bolt on to earlier models. This includes suspension parts, ABS system, steering rack, alternator, p/s pump, and others. In comparison to other classic sports cars, Porsche replacement parts are expensive.