What is it?
A good deal more torque, reduced consumption, lower emissions and less weight - but better? Before driving BMW’s new X1xDrive28i, the first model to feature the German car maker’s new turbocharged 2.0-litre four-cylinder petrol engine, I wasn’t so sure.
The new unit, known as the N20 and set to head into a whole range of models in the not-too-distant-future, has been conceived to (indirectly) replace one of the landmark engines of our time, BMW’s classic naturally aspirated 3.0-litre in-line six-cylinder, as part of an on-going downsizing program at the centre of the company’s much heralded EfficientDynamics initiative.
The new four-cylinder follows the blueprint laid down by BMW’s most recent turbocharged 3.0-litre in-line six-cylinder; it boasts the same 91mm bore centre spacing and runs a twin scroll turbocharger (albeit from Mitsubishi not Borg Warner), Valvetronic variable valve timing, Vanos camshaft control system and latest 200bar direct injection system from Bosch. At 144kg, it also weighs 18kg less than the old naturally aspirated six-cylinder.
What's it like?
First impressions reveal it to be well up to the job. With peak power and torque arriving 1600rpm and 1350rpm earlier than with the old six-cylinder, BMW’s latest four-cylinder doesn’t have to be worked anywhere near as hard before delivering its best.
In every day driving, it is noticeably more responsive, although its non-descript aural attributes are nowhere near as alluring as those of the engine it replaces (something BMW says will be rectified on certain models, including the upcoming Z4sdrive20i, by the addition of a electronic sound generator).
The new BMW engine might give away 12bhp to its perceived predecessor, but it is wonderfully refined and always feels more urgent; with 258lb ft of torque on tap at just 1250rpm its delivery is uncannily like a modern day diesel, with particularly strong low end attributes by four-cylinder standards and impressive flexibility across a wide range of revs. BMW puts the X1xDrive28i’s 50mph to 72mph fourth gear split at just 6.0secs.
Power builds in a smooth, free revving fashion without any hint of turbocharger lag right from the idle onwards. Work it hard and it also revs happily to 7000rpm, although like most modern direct injection engines there’s a distinct lack of engine braking on a trailing throttle; the engine’s powerful electronics package ensures maximum coasting potential is achieved by allowing the revs to fall away.