Cutaway of the 2-cylinder TwinAir 85 HP. Click to enlarge.

Fiat’s new two-cylinder TwinAir engine family made by Fiat Powertrain Technologies (FPT) made its debut with the TwinAir 85 HP in the Fiat 500 today. Fiat had previewed the two-cylinder at the Geneva show earlier this year. (Earlier post.)

The gasoline-fueled 85 hp (63 kW), 900 cc turbo two-cylinder features a small-sized turbine which, combined with dedicated valve management strategies, minimizes transient response times and keeps maximum power levels high. The TwinAir 85 HP also comes with “Start&Stop” as standard. Compared with a 1.2-liter 8v engine, the new 85 HP turbo has 23% more power and a 30% better performance index. The performance of the two-cylinder is not only equivalent to a 1.4-liter 16v engine, but fuel consumption is 30% lower.

Fiat 500 TwinAir 85 HP
Bore x stroke (mm) 80.5×86
Displacement (cm3) 875
Valves per cylinder 4
Compression ratio 10.0:1
Max. power (kW) 62.5 @ 5500
57 kW @ 5500 with ECO button
Max torque (N&iddot;m) 145 @ 1900
100 @ 2000 with ECO button

Equipped in this way, the Fiat 500 reaches a top speed of 173 km/h (108 mph) and accelerates from 0 to 100 km/h in 11 seconds. Fuel consumption and emissions are 4.1 L/100 km (57 mpg US) and 95 g/km respectively (with manual gearbox), and 4.0 L/100 km and 92 g/km with a Dualogic robotized gearbox.

The Fiat 500 with TwinAir 85 HP also features an ECO button. Two driving modes can be selected: Normal and ECO. In the first mode, the ECO function is off and the engine delivers the maximum available torque (145 N&iddot;m / 107 lb-ft). Steering assistance is also specifically calibrated for Normal mode. No indication appears on the dashboard in this mode (City is not selected).

In ECO mode, torque delivery is cut off to 100 N&iddot;m (74 lb-ft) at 1750 rpm to minimize consumption and promote a driving style more suitable for city traffic. The steering wheel is lighter (CITY mode is automatically selected). The driver only needs to press the specific button on the dashboard to activate the ECO function. The lettering ECO will appear on the panel (the letter “E” will appear on the panel if the car has a Dualogic robotized gearbox). The Dualogic shifting strategy also switches to ECO mode to further optimize fuel consumption.

Compared with a medium-sized four-cylinder of equal performance, the new engine is significantly shorter (-23%) and lighter (-10%), opening the way to further developments, such as methane fuel supply or hybrid technology combinations. The soon to be available methane version of the TwinAir will feature a pair of special injectors in addition to the gasoline injectors on the intake manifold ducts.

MultiAir. The two-cylinder implements the MultiAir technology developed and patented by FPT, which was introduced on FIRE engines last year for the first time. The heart of MultiAir is a new electro-hydraulic valve management system that reduces fuel consumption by controlling air directly via the inlet valves (without using the throttle). MultiAir reduces polluting emissions (thanks to combustion control) and also considerably improves performance by boosting driveability with respect to a traditional gasoline engine of equal displacement. (Earlier post.)

Advantages of MultiAir technology applied to gasoline engines include:

  • maximum power boosted by 10% compared with a traditional engine of equal size;
  • 15% more torque at low rpm and during transitions by applying early intake valve closing strategies to maximize the air introduced into the cylinders;
  • less fuel consumption and consequently lower CO2 emissions, equal to 10% by eliminating pumping losses and precise parameter calibration for optimizing combustion;
  • lower polluting emissions from the engine by optimizing valve control strategies during the intake stroke;
  • prompter response to accelerator commands due to the constant air pressure upstream of the cylinders combined with extremely fast control of the intake valves.