The BMW Z4 (E85) facelift, introduced in 2006 and produced through 2008, represented a significant refresh of BMW’s popular roadster. The 2.5i variant, powered by the N52B25A engine producing 177 horsepower, occupied a middle ground in the Z4 lineup, offering a balance between performance and affordability. This model aimed to provide an engaging driving experience without the higher price tag of the more powerful 3.0si version. It was positioned as a more accessible entry point into the Z4 range, appealing to buyers seeking a stylish and sporty convertible.
Technical Specifications
| Brand | BMW |
| Model | Z4 |
| Generation | Z4 (E85 LCI, facelift 2006) |
| Type (Engine) | 2.5i (177 Hp) |
| Start of production | 2006 |
| End of production | 2008 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Roadster |
| Seats | 2 |
| Doors | 2 |
| Fuel consumption (urban) | 11.8 l/100 km (19.9 US mpg) |
| Fuel consumption (extra urban) | 6.1 l/100 km (38.6 US mpg) |
| Fuel Type | Petrol (Gasoline) |
| Acceleration 0 – 100 km/h | 7.1 sec |
| Acceleration 0 – 62 mph | 7.1 sec |
| Acceleration 0 – 60 mph | 6.7 sec |
| Maximum speed | 229 km/h (142.29 mph) |
| Weight-to-power ratio | 7.2 kg/Hp |
| Weight-to-torque ratio | 5.5 kg/Nm |
| Power | 177 Hp @ 5800 rpm |
| Power per litre | 70.9 Hp/l |
| Torque | 230 Nm @ 3500 rpm (169.64 lb.-ft. @ 3500 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | N52B25A |
| Engine displacement | 2497 cm3 (152.38 cu. in.) |
| Number of cylinders | 6 |
| Engine configuration | Inline |
| Cylinder Bore | 82 mm (3.23 in.) |
| Piston Stroke | 78.8 mm (3.1 in.) |
| Compression ratio | 11:1 |
| 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) |
| Kerb Weight | 1275 kg (2810.89 lbs.) |
| Max. weight | 1570 kg (3461.26 lbs.) |
| Max load | 295 kg (650.36 lbs.) |
| 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 (Back) track | 1523 mm (59.96 in.) |
| Drivetrain Architecture | Rear wheel drive |
| Drive wheel | Rear wheel drive |
| Number of gears | 6 gears, manual transmission |
| Front suspension | Independent, type McPherson with coil spring and anti-roll bar |
| Rear suspension | Coil spring |
| Front brakes | Disc |
| Rear brakes | Disc |
| Assisting systems | ABS (Anti-lock braking system) |
| Tires size | 225/50 R16 |
| Wheel rims size | 16 |
Introduction
The E85 Z4 facelift, launched in 2006, brought with it revised styling, improved interior materials, and refinements to the chassis and engine range. The 2.5i model, utilizing the naturally aspirated 2.5-liter inline-six engine (N52B25A), was a key component of this update. It was designed to appeal to drivers who wanted a sporty roadster experience without the higher running costs associated with the larger, more powerful engines. The E85 generation Z4, as a whole, aimed to recapture the spirit of the classic BMW roadsters, offering a driver-focused experience in a compact and stylish package.
Powertrain & Engine Architecture
The heart of the 2.5i Z4 is the N52B25A engine, a 2.5-liter inline-six cylinder powerplant. This engine is a naturally aspirated design, meaning it doesn’t rely on turbocharging or supercharging for power. It features double overhead camshafts (DOHC) and four valves per cylinder, contributing to its smooth power delivery and relatively high revving nature. Fuel is delivered via multi-port fuel injection, and the engine boasts a compression ratio of 11:1. The N52 engine family is known for its reliability and responsiveness. The 2.5i was typically paired with a six-speed manual transmission, but a six-speed automatic transmission was also available, offering convenience at the expense of some driver engagement. The automatic transmission featured adaptive shift programming, attempting to learn the driver’s style and adjust shift points accordingly.
Driving Characteristics
The 2.5i Z4 offered a balanced driving experience. While not as brutally quick as the 3.0si, the 177 horsepower and 169.64 lb-ft of torque provided ample power for spirited driving on winding roads. Acceleration from 0-60 mph took around 6.7 seconds, and the car could reach a top speed of 142.29 mph. The inline-six engine delivered a smooth and linear powerband, making it easy to modulate throttle and maintain control. The manual transmission offered precise shifts and a direct connection to the engine, while the automatic, though less engaging, provided smooth and comfortable gear changes. The Z4’s rear-wheel drive layout contributed to its balanced handling and predictable cornering behavior. The relatively lightweight construction of the E85 chassis further enhanced its agility.
Equipment & Trim Levels
The 2.5i Z4 came reasonably well-equipped as standard. Typical features included leatherette upholstery, power windows and locks, air conditioning, and a basic audio system. Optional extras were plentiful, allowing buyers to customize their Z4 to their preferences. Popular options included premium leather upholstery, heated seats, a premium sound system, navigation system, and sport suspension. The facelift models also benefited from improved interior materials compared to the earlier E85s, offering a more refined cabin experience. Trim levels were relatively simple, with most options being added individually rather than bundled into specific packages.
Chassis & Braking
The Z4 E85 utilized a McPherson strut front suspension and a multi-link rear suspension, providing a good balance of ride comfort and handling precision. Stabilizer bars were fitted front and rear to reduce body roll during cornering. The 2.5i model typically featured disc brakes on all four wheels, providing ample stopping power. Anti-lock braking system (ABS) was standard, enhancing safety and control in emergency braking situations. The car’s relatively low weight contributed to its nimble handling and efficient braking performance. The standard tire size was 225/50 R16, providing a good compromise between grip and ride comfort.
Market Reception & Comparison
The 2.5i Z4 was generally well-received by automotive critics. It was praised for its engaging driving dynamics, stylish design, and relatively affordable price point. Compared to the more powerful 3.0si, the 2.5i offered a more accessible entry into the Z4 range, appealing to a wider audience. Fuel economy was also a strong point, with the 2.5i achieving around 38.6 US mpg on the highway. However, some critics noted that the 2.5i’s performance was not as exhilarating as the 3.0si, and the automatic transmission lacked the engagement of the manual. Compared to competitors like the Porsche Boxster, the Z4 offered a more affordable and practical option, though it didn’t quite match the Boxster’s level of refinement or performance.
Legacy
The N52B25A engine, found in the 2.5i Z4, has proven to be a reliable and durable powerplant. With proper maintenance, these engines can easily exceed 150,000 miles. The E85 Z4, as a whole, has become a popular choice among enthusiasts seeking an affordable and engaging roadster experience. The 2.5i variant, in particular, offers a good balance of performance, reliability, and affordability, making it a desirable option in the used car market. While not as collectible as some of the more rare or high-performance Z4 variants, the 2.5i remains a well-regarded and enjoyable sports car.
