The BMW Z4 (E85) 2.5i Steptronic, produced from 2002 to 2006, represents a significant entry in BMW’s return to the affordable roadster market. Positioned as a mid-range offering within the E85 generation, it bridged the gap between the base 2.0i and the performance-oriented 3.0i models. This variant aimed to provide a balance of sporty handling, respectable power, and the convenience of an automatic transmission, appealing to a broader customer base than its more focused siblings. The E85 Z4 was BMW’s direct replacement for the Z3, offering a more refined and modern driving experience.
Technical Specifications
| Brand | BMW |
| Model | Z4 |
| Generation | Z4 (E85) |
| Type (Engine) | 2.5i (192 Hp) Steptronic |
| Start of production | 2002 |
| End of production | 2006 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Roadster |
| Seats | 2 |
| Doors | 2 |
| Fuel consumption (urban) | 11.25 l/100 km (20.9 US mpg) |
| Fuel consumption (extra urban) | 6 l/100 km (39.2 US mpg) |
| Fuel consumption (combined) | 7.7 l/100 km (30.5 US mpg) |
| Fuel Type | Petrol (Gasoline) |
| Acceleration 0 – 100 km/h | 7.5 sec |
| Acceleration 0 – 62 mph | 7.5 sec |
| Acceleration 0 – 60 mph | 7.1 sec |
| Maximum speed | 227 km/h (141.05 mph) |
| Emission standard | Euro 4 |
| Weight-to-power ratio | 7 kg/Hp |
| Weight-to-torque ratio | 5.4 kg/Nm |
| Power | 192 Hp @ 6000 rpm |
| Torque | 245 Nm @ 3500 rpm (180.7 lb.-ft. @ 3500 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | M54B25 |
| Engine displacement | 2494 cm3 (152.19 cu. in.) |
| Number of cylinders | 6 |
| Engine configuration | Inline |
| Cylinder Bore | 84 mm (3.31 in.) |
| Piston Stroke | 75 mm (2.95 in.) |
| Compression ratio | 10.5:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Multi-port manifold injection |
| Engine aspiration | Naturally aspirated engine |
| Valvetrain | DOHC |
| Engine oil capacity | 6.5 l (6.87 US qt | 5.72 UK qt) |
| Coolant capacity | 8.3 l (8.77 US qt | 7.3 UK qt) |
| Kerb Weight | 1335 kg (2943.17 lbs.) |
| Max. weight | 1560 kg (3439.21 lbs.) |
| Max load | 225 kg (496.04 lbs.) |
| Trunk (boot) space – minimum | 240 l (8.48 cu. ft.) |
| Trunk (boot) space – maximum | 260 l (9.18 cu. ft.) |
| Fuel tank capacity | 55 l (14.53 US gal | 12.1 UK gal) |
| Length | 4091 mm (161.06 in.) |
| Width | 1781 mm (70.12 in.) |
| Height | 1299 mm (51.14 in.) |
| Wheelbase | 2495 mm (98.23 in.) |
| Front track | 1473 mm (57.99 in.) |
| Rear track | 1523 mm (59.96 in.) |
| Minimum turning circle | 9.8 m (32.15 ft.) |
| Drivetrain | Rear wheel drive |
| Number of gears | 5 |
| Gearbox type | Automatic transmission |
| Front suspension | Spring Strut |
| Rear suspension | Coil spring |
| Front brakes | Ventilated discs |
| Rear brakes | Ventilated discs |
| Steering type | Steering rack and pinion |
| Power steering | Electric |
| Tires size | 225/50 R16 |
| Wheel rims size | 7J X 16 |
Powertrain & Engine Architecture
The heart of the 2.5i Steptronic is BMW’s M54B25 inline-six engine. This 2.5-liter powerplant is a naturally aspirated engine known for its smooth power delivery and reliability. The M54 engine family was a staple of BMW’s lineup in the early 2000s, representing a refinement of the earlier M52 design. It features double overhead camshafts (DOHC) and four valves per cylinder, contributing to its efficient breathing and respectable horsepower output. Fuel delivery is managed by a multi-port fuel injection system, providing precise fuel metering for optimal combustion. The engine produces 192 horsepower at 6000 rpm and 245 Nm (180.7 lb-ft) of torque at 3500 rpm.
Paired with the M54B25 is a 5-speed automatic transmission, marketed by BMW as “Steptronic.” This transmission offers both fully automatic operation and a manual shift mode, allowing drivers to have some control over gear selection. While not as sporty as a manual gearbox, the Steptronic provided a more accessible and convenient driving experience for many buyers. The transmission is designed to deliver smooth shifts and optimize fuel efficiency.
Driving Characteristics
The 2.5i Steptronic offers a comfortable and engaging driving experience. While not as overtly sporty as the 3.0i, it provides sufficient power for enjoyable cruising and spirited driving. The automatic transmission, while smooth, can sometimes feel hesitant during quick acceleration compared to the more responsive manual transmission available in other Z4 variants. The gear ratios are tuned for a balance of fuel economy and performance, prioritizing smooth operation over outright speed. Acceleration from 0 to 60 mph takes approximately 7.1 seconds, and the car has a top speed of 141 mph. The rear-wheel-drive configuration contributes to the Z4’s balanced handling and predictable cornering behavior.
Equipment & Trim Levels
The 2.5i Steptronic came standard with a respectable array of features, including leatherette upholstery, power windows and locks, air conditioning, and a basic audio system. Optional extras included premium leather upholstery, heated seats, a Harman Kardon sound system, and a navigation system. The interior design was focused on providing a driver-centric experience, with well-placed controls and a clear instrument cluster. The exterior styling was typical of the E85 Z4, featuring a long hood, short rear deck, and a sleek, modern profile.
Chassis & Braking
The Z4 E85 features a MacPherson strut front suspension and a multi-link rear suspension, providing a comfortable ride and responsive handling. The 2.5i model typically came equipped with ventilated disc brakes on all four wheels, offering ample stopping power. Anti-lock braking system (ABS) was standard, enhancing safety and control during emergency braking situations. The chassis was designed to be lightweight and rigid, contributing to the car’s agility and handling precision.
Market Reception & Comparison
The Z4 2.5i Steptronic was generally well-received by automotive critics. It was praised for its smooth engine, comfortable ride, and stylish design. However, some reviewers noted that the automatic transmission could detract from the overall driving experience compared to the manual gearbox. Compared to the 2.0i, the 2.5i offered a noticeable performance upgrade. Compared to the 3.0i, it provided a more affordable entry point into the Z4 range, albeit with less power. Fuel economy was respectable for a sports car, averaging around 30.5 US mpg in combined driving.
Legacy
The BMW Z4 E85 2.5i Steptronic has proven to be a relatively reliable vehicle, with the M54 engine being known for its durability. Common maintenance items include oil changes, coolant flushes, and spark plug replacements. The Steptronic automatic transmission, while generally reliable, may require servicing over time. Today, the E85 Z4 remains a popular choice among enthusiasts looking for an affordable and stylish roadster. The 2.5i variant offers a good balance of performance, comfort, and reliability, making it a compelling option in the used car market.
