A Ford Focus with a 1.0-litre engine! Isn’t that like getting Charles Hawtrey to compete for World’s Strongest Man, or sending Samson into battle after a crewcut? In one of the most extreme downsizing examples yet, Ford has plumbed an all-new, turbocharged three-cylinder petrol engine into its family hatch, all 1.2-odd tonnes of it. The 1.0-litre Ecoboost is available to order now, and it’ll be rolled out to the heavier C-Max and, less outlandishly, the Fiesta supermini by the end of 2012. That’s because Ford is very serious about – and proud of – its new three-pot.

Read our new Ford Focus review: we drive the latest hatchback

What’s so special about the 1.0-litre Ecoboost in the Ford Focus?

When Ford revealed the Focus in late 2009, executives guffed on rather emptily about how the Blue Oval would be the class-leader on economy. Here’s how: with a breakthrough engine worthy of the praise lavished upon Fiat’s TwinAir two-cylinder petrol – and one that’ll get much closer to its mid-50s mpg figure, Ford executives wisecrack, if you drive the Focus like you stole it.

The 999cc engine comes in two guises: with 99bhp and 123bhp. Both variants’ max torque is 125lb ft from a subterranean 1400rpm, though the 123bhp unit has an overboost function, which cranks peak torque up to 148lbft for a 30-second overtaking burst. The outputs equate to a 1.6-litre petrol engine’s, yet the 99bhp engine returns 58.8mpg and 109g/km of CO2 in the five-door Focus hatch. Economy dips to just 56.5mpg for the 123bhp engine, with carbon emissions still low at 114g/km.

That sounds like audacious corporate accounting: how do they do it?

The 1.0-litre 12-valver is a clean sheet of paper design – literally. The ultra compact block can sit on a sheet of A4, and above it towers a host of bespoke technology. Because it’s so small, the block can be made of cast iron without a weight penalty. Naturally having three slender cylinders, not four, reduces friction and pumping losses. There’s a split cooling system operating on the head and block, helping the engine and its catalyst get up to operating temperature quickly, reducing emissions.

The exhaust gases spin a tiny turbocharger, whose size reduces inertia and therefore lag at low revs. Other expensive, high-tech features include direct injection to precisely meter the amount and timing of fuel into the cylinders, and twin variable camshaft timing. The turbo, injection system and variable cam timing act as a holy trinity, optimising combustion to minimise consumption and boost torque.

Ford has devised an ingenuous system to counter a three-pot’s desire to rock sideways – and it isn’t a balancer shaft, which would add cost and weight. Instead the engineers unbalanced the flywheel, which also has the effect of minimising vibration. Naturally the triple has stop-start, which was an engineering challenge because the lack of friction makes the engine hard to stop swiftly, and it requires some advanced hardware and software to fire it up again instantly.

Enough tech: how does it drive?

The first thing you notice is a smoothness to make Gillette envious: this engine is barely perceptible at idle. And forget Charles Hawtrey, the 1.0-litre pulls like Charles Atlas, given its displacement. At 20mph in third or 30mph in fourth with barely 1500 revs on the clock, the Ecoboost briefly shudders like a shrug of the shoulders before the engine starts pumping and the acceleration starts building. Ford quotes 11.3secs for the sprint from standstill to 62mph in the 123bhp version we drove, which is coupled to a no-nonsense six-speed manual gearbox. Each gear pulls cleanly to the 6400rpm redline, and the engine really gets on song above 3000 revs, with the fluttery ringing of a three-cylinder engine. If anything the Focus’s exceptional mechanical refinement – you feel hermetically sealed inside – over-suppresses the engine’s wonderful note.

A little context is needed: the 1.0-litre Ecoboost may be responsive, linear in its power delivery and packing a broad torque spread, but it obviously doesn’t have the kick of a four-cylinder diesel. So it huffs and puffs a bit on hills where you might have to drop a cog or two, and you need a judicious gap for overtaking. But for enthusiasts, its free-revving nature and perky soundtrack make it hugely engaging, while the accountant in you will welcome zero road tax in year one, and trifling company car tax. And with the dressed engine weighing just 97kg – some 30 kilos less than the 1.6-litre it will replace – the Focus’s quick but anodyne steering feels lighter, the nose turns in more sharply than in heavier models, and the ride quality remains supremely comfortable.

Verdict

The 1.0 Ecoboost is already on Focus price lists, starting at £16,245 for the five-speed 99bhp unit, and £17,745 for the 123bhp six-speeder in the hatchback bodystyle. That’s just a £250 premium over the outgoing 1.6-litre engine, for a car that’ll be cheaper to run and more refined. No other mainstream family hatch can be coupled with a three-cylinder engine, giving Ford a powertrain edge you’d typically expect from the Volkswagen Group. If you like lashings of technology, a free-revving, charismatic engine and the pecuniary and ecological benefits of low consumption, the Focus Ecoboost is well worth a look. This lean upstart makes some bigger engines look puny.