BMW 123d Coupe M Sport
Until the 125i arrives next year, diesel is the dominant engine in the 1-Series Coupe range. How times change. The 120d boasts 177bhp but it’s the range-topper that’s the most interesting.
The 123d, benefiting from BMW’s sequential twin turbo technology already seen on the 535d, boosts this 2.0-liter four to 204bhp. That’s right – 100bhp per liter. That's a pretty exceptional achievement for petrol engines - but for a diesel to crack it is, well, quite something else.
It has 295lb ft of torque at just 2000rpm - which matches the twin-turbo 135i - but unlike the petrol flagship which likes a bit of a drink, the 123d returns 54.3mpg on the combined cycle. Yes, 54.3mpg. And it emits just 138g/km of CO2. And will still shoot to 62mph in 7.0 seconds and push on to 148mph.
That's a simply remarkable set of stats to sit in the same paragraph as each other. Apparently, BMW’s engineers celebrated by turning the water they were drinking into wine. Lafite Rothschild 1947, no less.
That's the beauty of the twin-turbo technology. As you know, a small turbine handles the low-rev stuff for instant low-speed pick-up, while a larger blower takes over as the revs rise for top end punch.
This is BMW’s latest-generation 2.0-liter diesel, which is significantly quieter and less clattery than its predecessor. Balancer shafts add smoothness, too. In practice, it’s surprisingly free-revving, makes a not completely unappealing noise and revs to its 5000rpm soft limiter with surprising keenness.
Plentiful torque at low revs and appreciable power over 3000rpm means gears are not essential and this powertrain proves that diesels can be genuinely athletic and engaging, with a throttle response devoid of that on-throttle pause many diesels suffer. The M Sport’s ride is on the firm side of firm, but the latest generation of runflat tires mean it’s not sickeningly harsh and crash anymore.
The 123d's diesel engine is lighter than the 135i's biturbo unit, and overall, the diesel car is lighter than the petrol (1495kg versus 1560kg) so the coupe's superb chassis balance is unaffected. From behind its thick-rimmed steering wheel it feels remarkably similar to the 135i.
The M Sport model has the same precise but anesthetist steering as the 135i, and the same propensity towards understeer when pushing hard. But turn off the traction control and all that torque can easily unsettle the chunky 245/35profile 18-inch rear tires, allowing you to drive the Beemer on the throttle - or easily boot out the tail end for smoke sideways action.
Inside, the two-seat rear is tight, of course, but the shallow boot is actually 20 litres bigger than the hatch. We also like the low-slung seats and driver-centric cabin, even if some of the plastics are far too cheap in a car costing this much.
Hyper-advanced engine technology aside, don't forget that the 1-series coupe comes with BMW's hyped Efficient Dynamics set-up. Start-Stop is the most obvious of these, and it’s although it's initially amusing to have a performance car that turns itself off at the traffic lights, it soon becomes second nature.
Even more pleasing is how this rival-less coupe costs £24,855 (or £26,290 in M Sport form), which is a good chunk less than the 135i. When you consider that even a base-spec 320d SE Coupe costs over £28k, the 123d looks like a relative performance bargain.
