The unexpected diesel darling: bmw's n47d20 in the e87 1 series

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A diesel surprise

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When you think of sporty cars, a diesel engine isn’t usually the first thing that comes to mind. However, back in 2007, BMW’s N47D20 engine proved that diesel could deliver surprising performance without sacrificing fuel efficiency. It was a bold move, and one that gave the first-generation BMW 1 Series an unexpected edge.

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The diesel boom of the 2000s

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The early 2000s saw a surge in diesel engine popularity, and BMW remained a strong proponent. The N47D20 was introduced in 2007, a variant of the N47 family specifically designed for the BMW 123d. The goal was to strike a balance between exhilarating performance and impressive fuel economy – a combination that proved surprisingly successful.

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Engine specifications and technology

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The N47D20 was a four-cylinder, twin-turbocharged diesel engine, representing cutting-edge technology at the time. Its design was rooted in BMW’s EfficientDynamics philosophy. With a displacement of 1,995 cc (just under 2.0 liters), it produced a healthy 150 kW (204 hp) and a peak torque of 400 Nm. This resulted in approximately 100 hp per liter, a remarkable achievement for a diesel engine.

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Key features of the n47d20

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• Aluminum Cylinder Block: For reduced weight and improved efficiency.
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• Variable Twin Turbo VTT: A key innovation to minimize turbo lag.
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• Common Rail Injection: Precise fuel delivery for optimal combustion.
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• Energy Recovery System: Improved braking energy recovery.
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• Auto Start-Stop Function: Further enhanced fuel efficiency.
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Performance figures

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The BMW 123d with the N47D20 engine was surprisingly quick. The three-door model accelerated from 0 to 100 km/h (0-62 mph) in just 6.9 seconds, while the five-door took 7.0 seconds. Top speed was rated at 238 km/h (148 mph). These figures were impressive, especially considering the car’s focus on efficiency. It even outperformed contemporary rivals like the manual Volkswagen Golf GTI (which took 7.2 seconds to reach 100 km/h).

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The variable twin turbo advantage

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The secret to the N47D20’s responsiveness lay in its Variable Twin Turbo (VTT) system. This system, first introduced in the larger six-cylinder engine of the BMW 5 Series, used two turbochargers of different sizes. The smaller turbo provided immediate boost at lower RPMs, eliminating turbo lag, while the larger turbo kicked in at higher speeds for maximum power. This resulted in a remarkably linear power delivery, resembling that of a naturally aspirated engine.

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Power and torque delivery

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Peak torque was achieved from just 2,000 rpm, and maximum power arrived at 4,400 rpm. This wide powerband made the BMW 123d easily drivable in a variety of conditions. While not the outright fastest car in its class, it offered a progressive and elastic response thanks to the refined N47D20 engine.

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Driving experience and refinement

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Coupled with a six-speed manual transmission and the rear-wheel-drive configuration offered by the E87 1 Series, the BMW 123d provided a genuinely engaging driving experience. The optional M Sport package further enhanced handling with upgraded suspension components. While not a dedicated sports car like the later 1M, the 123d offered a unique blend of performance, efficiency, and refinement – a true