Its tiny engine features the MultiAir electro-hydraulic valve propulsion system the company has been rolling out with other engines, which cuts pumping losses and improves efficiency by around 10 percent. Maintenance is low: TwinAir has both hydraulic tappets and long-life spark plugs, so ordinary servicing should be cheap.
The 500 TwinAir also features a standard stop-start system. What is more, its tiny internals cut friction to new lows, and its tiny turbo allows quick throttle response and practically eliminates turbo lag. It also promotes low-end torque, which amounts to an impressive 107lb ft at 1900rpm. Even more amazing is the fact that it produces fully 25 per cent more torque at that speed than the 1.4-litre.
This, surely, is the way of the future.
What’s it like
To put TwinAir’s achievements into perspective, Fiat engine guru Paolo Martinelli explains that a suite of engine improvements over the past 15 years have delivered about a 15 per cent average cut in European cars' CO2 outputs.
The new TwinAir offers the same improvement again – in just one step. Eventually, the TwinAir will be come in three power levels: 64bhp, today's 84bhp and a 104bhp variant. Together, they could replace the entire 500/Panda engine range, though Fiat doesn't suggest they will. But it does say production at the Polish manufacturing plant will hit 400,000 units, very soon.
As well as being 23 per cent shorter than a normal four, this tiny 900cc, eight-valve, turbocharged parallel twin (which features a balance shaft to damp the first order vibration) is 7kg lighter than Fiat's current 1.2-litre non-turbo FIRE four, and 13kg lighter than the 1.4-litre. It is, in effect, a briefcase-sized powerhouse, which drives through the owner’s choice of either a five-speed manual gearbox or Fiat's two-pedal semi-automatic gearbox, called Dualogic. Ours was a manual.
On the road, the 500 TwinAir is deeply impressive. Only at idle and under full acceleration are you truly aware of the engine's twin-cylinder format, and even then the noise is gruffly enjoyable and the balancer shaft keeps things four-cylinder smooth. We were able to cruise quietly at 90mph, more conscious of wind than engine noise, though other testers complained of a 'drone' which suggests some variability among early-build cars.
Despite its high specific output the car seemed relaxed, right up to its relaxed 6000 rpm redline, which you're encouraged to visit regularly. At an even 90mph (measured by sat-nav) the engine was pulling just 4000rpm in fifth. Fiat engineers claim there is 25 per cent more torque at 1900rpm than in the 1400, and it certainly felt that way. But the slightly odd sounds and vibes suggest that owners that will need slightly longer than we had with the car to get the best out of it.
Should I buy one?
Well, it looks pricey. And a twin-cylinder engine is unconventional. Early adopters will need to be open-minded to choose this model over a conventional 1.4-litre. But the economy is a spectacular 69mpg combined, with a CO2 output of just 95 g/km when the gearbox is the test car's manual, or 92 g/km with the Dualogic automated manual.
As well as saving the planet, such economy has the virtue of increasing the 500's marginal touring range by 60-80 miles. There’s a twin-clutch TwinAir about a year away, which should be even better.
In summary, the TwinAir shows that amazing advances are possible in the practical efficiency of small cars, and it makes an invaluable addition to Fiat's small-car range — already the lowest-polluting in Europe — that other manufacturers must surely envy. For potential customers it’s a great ownership proposition, and a lot of simple fun.
Fiat 500 TwinAir
Price: £12,000 (est); Top speed: 108mph; 0-60mph: 11.0sec; Economy: 69mpg; CO2: 95g/km; Kerb weight: 1030kg; Engine: two cylinders, 875cc, turbo, petrol; Power: 84bhp at 5500rpm; Torque: 107lb ft at 1900rpm; Gearbox: 5-speed manual