Now here’s a slightly complicated story. Bear with me. The BMW 320d comes as standard with features that BMW calls Efficient Dynamics: these are components and systems intended to improve the fuel efficiency of the car without harming its road performnce. These features are:
Brake energy regeneration: When you brake, some of the ‘spare’ kinetic energy is captured by the alternator and used to charge the battery.
Electric power steering: This is pretty old hat now, and more-or-less universal. The reason it’s better than the traditional form of power steering is that it’s ‘on demand’: the electric pump only starts working when the steering wheel is moved, and it provides only the assistance required.
Automatic stop-start: When the driver pulls up and the engine enters an idling phase, it is shut off; it’s automatically restarted when the driver takes action to pull away.
Gearchange prompter: A light suggests when you should change up. It is quite (so to speak) bright, in that if you are driving energetically it doesn’t suggest that you should change up at 2000rpm; nor does it discourage you from using engine braking.
On-demand management of ancillary units: Nothing works if it’s not actually needed. The most notable example is the alternator, which — apart from grabbing braking energy — cuts out under acceleration and when the battery is fully charged.
The air-conditioning compressor is detachable. Presubably this is to save weight, or to make it easier to service, because it’s perfectly possible to run the heating and ventilation system without the air-conditioning cutting in.
The slight complexity arises because, although the standard 320d has many Efficient Dynamics features, there is also a 320d Efficient Dynamics, which is emphatically not the same car.
BMW 320d Efficient Dynamics.
As you would expect, the 320d Efficient Dynamics has all of the Efficient Dynamics features from the standard model, plus a few extras. Principal among these are a remapped engine and a higher final drive ratio; all of the internal gearbox ratios remain unchanged. Additionally, the Efficient Dynamics car rides 15mm lower — though BMW quotes the same frontal area — and features aerodynamic alloy wheels and low rolling-resistance tyres as standard.
There’s no criticising a BMW driving position. The 320d’s wheel, seat and pedals are aligned as they should be, there’s plenty of room and ample adjustability. The driving seat is comfortable and locative, though someone of ample girth might find it a trifle narrow. Instrumentation and switchgear is mostly well laid-out, though a rotary dial instead of push-buttons for the ventilation fan would be helpful. The gear-lever falls conveniently to hand — always a feature of rear-driven cars, and something that the designers of front-wheel drive motors have only recently caught on to, using cable linkages to move the lever onto the dash. The BMW also has a cable linkage, for refinement rather than engineering reasons. The change quality itself is light and tolerably precise, but it felt rather cheap and flimsy for a premium car.
The Efficient Dynamics version of the 320d uses a final drive that’s fully 13 per cent. higher than the standard model’s. That’s really quite a lot. But the remapped engine delivers plenty of torque, and from low crankshaft speeds, so there is never a sense of driving an overgeared car, or one whose gear ratios are too far apart. It’s easy to maintain good progress without any real effort, and a glance at the rev-counter often reveals that engine speeds are a lot lower than you’d thought.
It’s not the just the low-end torque that makes the low engine speeds surprising. BMW’s diesels use aluminium blocks, and they exhibit the busy buzziness that’s characteristic of engines with aluminium crank-cases. That’s not to say that the 320d’s is a noisy engine: in fact, it is smooth and quiet by most standards; but there’s a constant background buzz from the block walls that never quite goes away.
Other aspects of refinement are competently controlled, with moderate levels of road noise on poor surfaces and wind noise at speed.
Ride and handling balance are beyond reproach, though I wasn’t greatly impressed by the outright grip offered by the low rolling-resistance tyres. What applies when a journo throws a car around a bend also applies when a normal person misjudges a corner or needs to make an emergency manoeuvre. Friction limitations also define braking limits: ABS cannot increase the coefficient of friction between the tyres and the road, it can only manage the situation when a wheel locks.
I had been looking forward to trying out BMW’s Efficient Dynamics measures in real life. It’s a sign of success in design and execution that the car feels completely free of unhelpful quirks. The 320d’s top end performance has been blunted a little by the adjustments to the engine and the gearing, but the payback is good flexibility and an easygoing character.
It’s still quite a quick car, though. BMW quotes a time of 8.0 seconds for standing-start acceleration to 100km/h — a trifling half-second behind the standard car, and a figure not to be sniffed at.
I’ve always liked the idea of low rolling-resistance tyres a lot more than the reality. BMW’s Dreier has an excellent chassis, and this version feels rather let down by its tyre equipment; more to the point, journalists and other misfits are not the only drivers to be affected by tyre grip.