The new BMW 1 Series Coupé makes its world debut at the IAA Frankfurt prior to going on-sale in the UK in November and will be available in 120d, 123d and 135i guises. The launch of the 123d heralds the introduction of the world’s most powerful production four-cylinder diesel engine.

The 204hp four-cylinder engine in the BMW 123d Coupé sets a benchmark for small diesels. Its 1,995cc powerplant is the world’s first all aluminium diesel to have an output per litre figure in excess of 100hp – something only BMW M cars usually attain. It is also the first four-cylinder production diesel to come with twin-turbo technology.

Peak torque is 400Nm from 2,000rpm, while the engine revs to in excess of 4,400rpm where peak power is attained. This performance equates to a zero to 62mph time of 7.0 seconds and a top speed of 148mph – previously unheard of figures in such small capacity production diesels. By comparison the output of the four-cylinder BMW 123d betters that of established six-cylinder diesel engines from both Audi and Mercedes.

The BMW 123d Coupé also makes financial sense. Its 138g/km emissions figure sees it fall into the Band C Vehicle Excise Duty tier while the fuel consumption figure on the combined cycle is 54.3mpg. These impressive figures are inspired by elements from BMW’s renowned EfficientDynamics programme. The 123d comes with Auto Start-Stop technology, Brake Energy Regeneration, third-generation common-rail fuel injection, a diesel particulate filter, active aerodynamics, Electric Power Steering and low rolling resistance tyres.

For customers seeking an entry point into the new 1 Series Coupé range, the 120d offers another option of style, driving dynamics and parsimonious motoring. Its 1,995cc four-cylinder engine mixes a 177hp output and a zero to 62mph time of 7.6 seconds with 58.9mpg economy and emissions of just 128g/km. The same EfficientDynamics technologies used on the 123d are also deployed on the 120d.