The Ford Mustang Convertible IV 4.6 i V8 32V Cobra R, produced between 2003 and 2005, represented a high-performance iteration of the fourth-generation Mustang (SN-95) convertible. Positioned as a premium offering within the Mustang lineup, the Cobra R variant aimed to deliver a more focused driving experience compared to the standard V8 convertible models. It occupied the top performance tier for convertibles during its production run, sitting above the GT and base V6 models. The Mustang Convertible IV chassis, designated SN-95, was a significant redesign from previous generations, introducing a more modern aesthetic and improved structural rigidity.
Powertrain & Engine Architecture
The heart of the 2003-2005 Mustang Convertible IV Cobra R was the 4.6-liter Modular V8 engine, specifically the code designated as a variation of the Romeo engine family. This engine differed significantly from the standard 4.6L V8 found in the GT model, boasting a supercharger and intercooler to dramatically increase power output. The engine produced 390 horsepower at 6000 rpm and 390.17 lb-ft of torque at 3500 rpm. This power was achieved through a combination of factors, including a cast iron block, aluminum cylinder heads, and a Roots-type supercharger. The engine utilized a multi-port fuel injection system, delivering fuel directly to each cylinder for precise control.
The valvetrain featured dual overhead camshafts (DOHC) with four valves per cylinder, optimizing airflow for increased performance. The compression ratio was set at 8.5:1. The engine oil capacity was 5.7 liters (6.02 US quarts / 5.02 UK quarts), and Ford specified a particular oil grade for optimal lubrication and protection. Unlike the GT models which offered an automatic transmission option, the Cobra R was exclusively equipped with a 6-speed manual transmission, reinforcing its performance-oriented character. The transmission was a Borg-Warner T-56, known for its robust construction and precise shifting.
Transmission Details
The 6-speed manual transmission in the Cobra R featured gear ratios designed to maximize acceleration and track performance. First gear was relatively short, providing strong off-the-line acceleration, while sixth gear was geared for comfortable highway cruising. The transmission’s robust design was crucial for handling the increased torque output of the supercharged engine.
Driving Characteristics
The 2003-2005 Mustang Convertible IV Cobra R delivered a markedly different driving experience compared to the standard V8 convertible. The supercharger provided instant and substantial torque, resulting in exhilarating acceleration. The 6-speed manual transmission allowed drivers to maintain optimal engine speed for maximum performance. While the convertible body style inherently added some flex compared to the coupe, the Cobra R’s chassis enhancements and stiffer suspension minimized this effect. The car felt planted and responsive, particularly when cornering. Compared to the automatic transmission equipped GT models, the Cobra R offered a more engaging and direct connection between driver and machine. The manual transmission demanded more driver involvement, but rewarded with greater control and a more visceral driving experience. The supercharger also created a distinct exhaust note, further enhancing the driving experience.
Equipment & Trim Levels
The Cobra R trim level came standard with a number of performance-enhancing features. Interior appointments included sport seats, often upholstered in leather, and a unique instrument cluster with additional gauges monitoring engine performance. Standard features also included air conditioning, power windows and locks, and a premium sound system. Optional extras included a CD changer, upgraded audio systems, and various cosmetic enhancements. The interior design was focused on functionality and driver engagement, rather than outright luxury. The Cobra R also featured unique exterior styling cues, including a distinctive front fascia, side skirts, and a rear spoiler. The convertible top was power-operated and available in several colors.
Chassis & Braking
The Mustang Convertible IV Cobra R benefited from a revised suspension system designed to improve handling and stability. The front suspension utilized a wishbone configuration, while the rear suspension employed a trailing arm setup. Stiffer springs and dampers were used compared to the standard convertible models, reducing body roll and improving responsiveness. The braking system featured ventilated discs at all four wheels, providing ample stopping power. An Anti-lock Braking System (ABS) was standard, enhancing safety and control during hard braking. The steering system was a rack and pinion setup with hydraulic power assist, offering precise and responsive steering feel. The car rode on 17-inch wheels fitted with 245/40 R17 tires, providing a good balance of grip and ride comfort.
Market Reception & Comparison
The 2003-2005 Mustang Convertible IV Cobra R was generally well-received by automotive critics. Reviewers praised its powerful engine, engaging driving dynamics, and distinctive styling. However, some critics noted the convertible body style compromised structural rigidity compared to the coupe. Fuel economy was a concern, with reported figures of 14.7 l/100 km (16 US mpg / 19.2 UK mpg) in urban driving and 10.7 l/100 km (22 US mpg / 26.4 UK mpg) in extra-urban driving. Compared to the standard GT convertible, the Cobra R offered significantly more performance, but at a higher price point. The Cobra R also required more frequent maintenance due to its higher-output engine and supercharger. Compared to other performance convertibles of the era, such as the Chevrolet Corvette Convertible, the Mustang Cobra R offered a more affordable entry point into high-performance motoring.
Technical Specifications
| Brand | Ford |
| Model | Mustang |
| Generation | Mustang Convertible IV |
| Type (Engine) | 4.6 i V8 32V Cobra R (390 Hp) |
| Start of production | 2003 year |
| End of production | 2005 year |
| Fuel consumption (economy) – urban | 14.7 l/100 km (16 US mpg / 19.2 UK mpg) |
| Fuel consumption (economy) – extra urban | 10.7 l/100 km (22 US mpg / 26.4 UK mpg) |
| Fuel Type | Petrol (Gasoline) |
| Maximum speed | 280 km/h (173.98 mph) |
| Weight-to-power ratio | 4.5 kg/Hp, 223.5 Hp/tonne |
| Weight-to-torque ratio | 3.3 kg/Nm, 303.2 Nm/tonne |
| Power | 390 Hp @ 6000 rpm |
| Power per litre | 84.8 Hp/l |
| Torque | 529 Nm @ 3500 rpm (390.17 lb.-ft. @ 3500 rpm) |
| Engine layout | Front, Longitudinal |
| Engine displacement | 4601 cm3 (280.77 cu. in.) |
| Number of cylinders | 8 |
| Engine configuration | V-engine |
| Cylinder Bore | 90.2 mm (3.55 in.) |
| Piston Stroke | 90 mm (3.54 in.) |
| Compression ratio | 8.5:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Multi-port manifold injection |
| Engine aspiration | Supercharger, Intercooler |
| Valvetrain | DOHC |
| Engine oil capacity | 5.7 l (6.02 US qt | 5.02 UK qt) |
| Kerb Weight | 1745 kg (3847.07 lbs.) |
| Trunk (boot) space – minimum | 220 l (7.77 cu. ft.) |
| Fuel tank capacity | 59 l (15.59 US gal | 12.98 UK gal) |
| Length | 4661 mm (183.5 in.) |
| Width | 1857 mm (73.11 in.) |
| Height | 1344 mm (52.91 in.) |
| Wheelbase | 2573 mm (101.3 in.) |
| Front track | 1530 mm (60.24 in.) |
| Rear (Back) track | 1530 mm (60.24 in.) |
| Drivetrain Architecture | Rear wheel drive |
| Number of gears and type of gearbox | 6 gears, manual transmission |
| Front suspension | Wishbone |
| Rear suspension | Trailing arm |
| Front brakes | Ventilated discs |
| Rear brakes | Disc |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Steering rack and pinion |
| Power steering | Hydraulic Steering |
| Tires size | 245/40 R17 |
Legacy
The 2003-2005 Mustang Convertible IV Cobra R remains a desirable vehicle among Mustang enthusiasts. The supercharged engine and 6-speed manual transmission provide a thrilling driving experience that is still competitive today. While maintenance costs can be higher than standard Mustang models, the Cobra R’s performance and exclusivity justify the expense for many owners. On the used car market, well-maintained examples command a premium price. The powertrain, while robust, requires diligent maintenance to prevent issues related to the supercharger and fuel system. The Cobra R’s legacy is that of a potent and engaging performance convertible, representing a high point in the fourth-generation Mustang’s evolution.
