BMW was a strict adherent to the unshakeable law of normally aspirated motoring: If you want quick and hearty throttle response, don’t turbocharge it – until it did a 180-degree handbrake turn and headed in the opposite direction at autobahn pace.

Now, a game of spot the non-turbo engine in the BMW range becomes harder than Where’s Wally as blowers spread quicker than coloured pills at an all-night rave party.

The latest BMW model to take the forced-induction route is the all-new 1 Series, which has wall-to-wall turbos on all three models on offer at launch – the 116i, 118i and 118d. And hooray, we say.

The tipping point for BMW came when new-generation turbos – including the twin-scroll units employed on its all-new TwinPower petrol engines – closed the gap on natural aspiration in terms of driving response.

Happily for both BMW customers and the planet they inhabit, that event coincided with massive pressure to cut fuel consumption, and so, like most other car companies, BMW realised it was time to make the leap into down-sized engines with an exhaust-powered fan to provide some steroids.

The new 1 Series – with a wider and longer body that gives the smallest BMW a more planted appearance – gets the latest blown engine from the BMW skunk works, the 1.6-litre petrol TwinPower four-cylinder that comes in two states of tune: 100kW/220Nm and 125kW/250Nm.

Those raw figures might not look so awesome that you would want to have your picture taken with them, but if you consider that they match the performance of the outgoing 2.0-litre petrol engines, then they are not so shabby.

When we take into account the fuel economy gains – about 22 per cent in the case of the new entry-level 116i – then BMW’s decision to take all its large-capacity, naturally aspirated engines down to the Munich tip becomes easier to understand.

But the best part of the story happens when the 1 Series hits the road. In a romp through the Victorian hills, the delightful driveability of the sweet little engine became abundantly apparent in a chassis built for the job.

We have to stop to insert a rider here – of the petrol engines, we drove only the more hairy-chested 125kW version of the TwinPower that goes into the 118i, so we unfortunately can’t shed too much light on the base 100kW version.

However, the more powerful version in the $42,800 118i belies its small engine capacity, using torque that was once the province of diesels to lope along, up hill and down dale.

In the cars we drove, the engine was hooked up to the optional eight-speed ZF automatic transmission – a first in the class – and it is a marriage made in heaven.

We haven’t always been a big fan of the willy-nilly use of eight-speeders as they haven’t always been used well, but in this case the powertrain works in uncommon harmony. Again, we did not get to sample the six-speed manual gearbox, but these days, who could be bothered?

The smallest BMW is not the fastest, but it aims to please, revving with quiet ease and obligingly responding to throttle inputs with a sparkling vigour – something the previous generation of 1 Series petrol fours struggled to do low in the rev range.

If you are that serious about saving fuel, then the diesel 118d is for you. Now with a price premium of just $700 over the 118i, the smooth and revvy 2.0-litre diesel engine is carried over from the previous generation, except for tweaks to give it a bit more torque.

Still one of the best small diesels around, this engine returned 5.2L/100km on our mainly highway run – worse than the 4.5L/100km claimed by the manufacturer but still handy.

This compares with 8.2L/100km we got for the petrol 118i, coming up short of the claimed 5.8L/100km, which we assume is achieved in the most fuel efficient but snoozy driving modes you can select at the push of a button – comfort, sport and EcoPro.

No, we don’t know how they came up with the name for the last one, but we are guessing you know it means “saving fuel mode”.

For the most part, we left the switch on comfort, which splits the difference between the sports setting – which holds gears longer and sharpens the throttle – and EcoPro, which does the opposite and feels like driving through molasses.

We suspect the EcoPro mode is going to gather a bit of dust in the real world, but it is the thought that counts. We tried it for a bit to see if we could achieve some top fuel figures – they were OK – but gave up on about the fifth hill when the car resisted yet another attempt to change down a cog, thus restoring our will to live.

Sport mode is great for a fling, but like that rather too flashy person you spent a weekend with in 1982, maybe you wouldn’t want to live with it. So we settled on comfort, and comfortable it was.

BMW has not always provided the most sumptuous ride around, with its sporting bent and all, but the new 1 Series is a true winner in this regard. Forgiving on big bumps, well insulated in high-frequency ones, the BMW chassis engineers have hit the target right on the scone.

If we have one teeny gripe, it would be that the rear end tended to chatter sideways on mid-corner tarmac corrugations a couple of times, but it quickly gathered its wits.

Ensconced behind the chunky sports steering wheel and comfortable in one of the most natural of driving positions, the driver just flows the 118i through the countryside, turning into corners with all the front-end grip you would expect of a car with a blue-and-white propeller badge, all the while providing loads of valuable feedback to the hands through the electric-assisted steering.

Like its predecessor that had a reputation as a driver’s car, the new 1 Series not only has plenty of lateral grip but is also highly predictable, engendering a comforting feeling of security that is helped by rear-drive composure.

Road noise likewise is among the best in the compact class – surprisingly when the 118i rides on hard run-flat, low-rolling-resistance tyres (and yes, there is no spare wheel, but more boot space).

One of the best new points of the new 1 Series hatch is the increase in cabin size, affording more elbow room and – importantly for rear seat passengers – knee room. Well, about 20mm’s worth.

The previous model was basically a 2+2, with back doors so tight the passengers had to be posted into place to avoid removing a kneecap. The new car is better, although we doubt anyone is going to hold a party back there. Two smallish adult passengers would just about fill the seat, but at least they can now.

Mercifully, 1 Series designers have reversed the trend to ever-higher and more claustrophobic side window sills, and lowered them to increase the glasshouse and let in the sunshine to give the 1 Series a more airy feel. Here’s one new car in which rear-seat passengers won’t feel like a six-year-old straining to peer out.

The cabin ambience in general has been elevated to a new level, and the latest ‘1’ takes on a true BMW tone.

A big multi-function screen driven by the BMW iDrive knob and console buttons – now one of the most intuitive of the lot – tops the dash, alongside a compact instrument binnacle with BMW’s typical plain, simple and functional dials and a smaller data screen that even tells you how much fuel you have saved in EcoPro mode.

The interior finishes can be had in a zillion combinations, depending on whether you opt for one of the two new ‘lines’ – $1600 option packs called Sports and Urban – or simply buy individual items from the long options list.

The Sports Line pack includes hip-hugging sports bucket seats with classy red contrast stitching and piping, along with a wide range of other extras. The Urban Line can be had with the most startling white trim on the grille, wheels, exterior mirrors and elsewhere – a visual assault that had most of the motoring journalists at the launch scratching their heads.

Back on planet earth, one of the two console cupholders now has an insert to securely hold the key fob for the keyless start, so it doesn’t get lost under the seat. Perhaps a keyhole would have been … never mind.

One brickbat: we were puzzled by the different textures of the soft-touch plastic atop the dash and on the doors, which were sufficiently close to look similar but sufficiently different to look like a factory mistake.

In general, the 1 Series is a delightful place to be, fulfilling BMW’s wish to deliver a prestige car in a small package for people wanting to step up to the brand, or urban downsizers wanting something smaller than a 3 Series or 5 Series.

The fact that the pricing starts at $36,900 (plus on-road costs) for the new entry-level 116i in manual form is just more impetus for buyers who always aspired to a BMW to finally realise their ambition.