Market Segment:
Luxury Grand Tourer (GT), High-Performance Sports Car.
Competitors 1991:
Ferrari 412, Aston Martin Virage, Jaguar XJ-S, Chevrolet Corvette ZR-1.
Design Philosophy:
Front-engine, rear-wheel-drive layout for optimal weight distribution, advanced aerodynamics, luxury appointments.
Unique Selling Proposition:
V8 power, transaxle layout for balanced handling, distinctive coupe styling, Porsche engineering and prestige.
Powertrain:
Engine operation, cooling system, fuel system, ignition system, exhaust system.
Drivetrain:
Transmission operation (automatic), drive shafts, differential.
Chassis:
Braking system, steering system, suspension system (front and rear), wheel and tire information.
Electrical:
Lighting systems, dashboard indicators and warnings, fuses, basic electrical component operation (radio, wipers, etc.).
Body And Interior:
Doors, windows, seats, climate control, dashboard layout, interior features, locking mechanisms.
Safety Features:
Seat belts, airbags (if equipped, though less common in 1991), child safety features.
Operation:
Starting and stopping the engine, driving instructions, gear selection, use of controls.
Maintenance:
Checking fluid levels (oil, coolant, brake fluid, power steering fluid), tire pressure checks, basic cleaning procedures.
Troubleshooting:
Explanation of dashboard warning lights, basic troubleshooting for common minor issues.
Emergency:
Information on emergency procedures, spare tire and jack location and usage.
Depth Level:
Owner-level understanding and basic operational guidance. Focuses on safe and correct usage, not detailed repair procedures.
Digital Format:
PDF (if scanned/digitized)
Print Quality Description:
Original factory print quality, typically good with clear diagrams and text.
Binding Type Description:
Original perfect bound or stapled booklet.
Paper Type Description:
Standard quality paper for owner's manuals of the era.
Engine Code:
M64/01 (or similar variant for 1991 S4)
Engine Type:
V8, naturally aspirated
Displacement:
5.0 Liters (4957 cc)
Bore X Stroke:
97.0 mm x 84.0 mm
Compression Ratio:
10.0:1
Valve Train:
Dual Overhead Camshafts (DOHC), 4 valves per cylinder (32 valves total)
Horsepower Net:
320 bhp @ 6,000 rpm (approx.)
Torque Net:
317 lb-ft @ 3,000 rpm (approx.)
Fuel Injection:
Bosch Motronic M2.2
Fuel Type:
Unleaded Premium Gasoline (91 octane or higher)
Coolant Type:
Porsche specified coolant (typically propylene glycol based), 50/50 mix with distilled water.
Coolant Capacity:
Approximately 10.5 Liters (11.1 US Quarts)
Transmission Type:
4-speed Automatic Transaxle (Tiptronic optional in later years, but 1991 likely standard auto)
Transmission Type:
5-speed Manual Transaxle (available, but less common than automatic for S4)
Drive Layout:
Rear-Wheel Drive (RWD) with rear transaxle configuration.
Automatic Transmission Fluid Type:
Porsche approved ATF (e.g., Mobil ATF 220 or equivalent specified by Porsche).
Automatic Transmission Fluid Capacity:
Approximately 8.0 Liters (8.5 US Quarts) for complete fill.
Length:
4650 mm (183.1 in)
Height:
1280 mm (50.4 in)
Wheelbase:
2500 mm (98.4 in)
Front Track:
1520 mm (59.8 in)
Rear Track:
1510 mm (59.4 in)
Curb Weight:
Approximately 1540-1620 kg (3395-3571 lbs), depending on options.
Gross Vehicle Weight Rating Gvwr:
Approximately 2030 kg (4475 lbs)
Towing Capacity:
Not Recommended/Specified by Manufacturer.
Crash Test Ratings:
No standardized crash test ratings (e.g., NHTSA/IIHS) were universally applied or readily available for this era of European luxury cars in the same way as modern vehicles.
Braking System:
Four-wheel disc brakes with internal ventilation. ABS (Anti-lock Braking System) standard.
Suspension Features:
Transaxle design contributes to balanced weight distribution. Independent suspension front and rear.
Seat Belts:
Three-point inertia-reel seat belts with pretensioners (front), three-point belts (rear).
Airbags:
Driver's side airbag standard.
Structural Integrity:
Integrated safety cage, crumple zones.
Audio System:
Original Porsche (Blaupunkt or Becker) AM/FM Cassette stereo system, often with amplifier. CD changer might be an optional accessory.
Climate Control System:
Automatic climate control (Thermatronic) standard on S4, with manual AC and heating.
Cruise Control:
Standard.
ABS:
Standard (Anti-lock Braking System).
Connectivity Features:
No modern connectivity features like Bluetooth or USB. Analog systems only.
Oil Change Interval:
Every 10,000 km (6,000 miles) or annually.
Timing Belt Interval:
Every 72,000 km (45,000 miles) or 5 years (critical for this engine to prevent catastrophic failure).
Brake Fluid Flush:
Every 2 years.
Coolant Flush:
Every 2 years.
Engine Oil Type:
API SG or higher, viscosity grade SAE 0W-40, 5W-40, 10W-40, or 5W-50 depending on climate. Porsche A40 approval is ideal.
Engine Oil Capacity:
Approximately 8.5 Liters (9.0 US Quarts) with filter change.
Power Steering Fluid Type:
Pentosin CHF 11S or equivalent hydraulic fluid.
Brake Fluid Type:
DOT 4, low viscosity.
Differential Fluid Type:
API GL-5, SAE 75W-90.
Differential Fluid Capacity:
Approximately 1.5 Liters (1.6 US Quarts).
Common Issues:
Fuel line deterioration, intake manifold 'O' rings, coolant hoses and pipes, power steering leaks, electrical gremlins, ABS sensor failures, timing belt tensioner wear.
Maintenance Importance:
Regular maintenance, especially timing belt replacement, is crucial for longevity and preventing costly damage.
Brand Legacy:
Porsche is renowned for its performance-oriented sports cars, racing heritage, and engineering excellence.
928 Introduction:
The 928 was introduced in 1978 as a V8-powered replacement for the 911 in some markets, intended as a more comfortable and modern GT.
928 S4 Introduction:
The S4 variant, introduced in 1987, represented a significant upgrade over previous models with a more powerful engine, improved aerodynamics, and updated styling.
S4 Updates 1991:
Subtle refinements for the 1991 model year, maintaining the established S4 specifications.
Production Period:
1978-1995
S4 Production Years:
1987-1991
Manufacturing Location:
Stuttgart, Germany
Car And Driver 10 Best:
The 928, including S4 variants, was a consistent recipient of Car and Driver's '10Best' list in its early years, praised for its engineering and performance.
Performance Reviews:
Highly praised by automotive journalists for its high-speed stability, powerful V8, and unique GT character.
