The Fiat Pratola Serra modular engines (also known as family B engines for the 4 cylinder units, and family C engines for the 5 cylinder units) are a family of engines produced by the Fiat Group since 1994 and used in Fiat, Alfa Romeo, Lancia and Jeep vehicles. They are named after the Pratola Serra municipality in which they're being produced.
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This new engine family debuted with the Lancia Kappa, and was born to allow the production of different units in various displacements and configurations while decreasing development and productions costs thanks to the modular architecture.
Launch versions:
The Pratola Serra modular engines are an evolution of the Fiat Twin Cam engine, incorporating TwinSpark technology in some applications to replace Alfa Romeo Twin Cam engines.
These engines are produced in the FGA's FMA (Fabbrica Motori Automobilistici) factory in Pratola Serra. It's an advanced factory, with a production capacity of 600,000 engines/year and producing both petrol and Diesel engines.
Started in 1993, it was developed to produce multiple engines with a single production line. The achieved result is that 8 different cylinder blocks are produced on the same line, that can in turn be coupled with 8 different crankshafts (5 different steel ones and 3 different cast iron ones), 15 different camshafts, 9 different cylinder heads, 6 different connecting rods, 5 different flywheels and 10 different intake manifolds, for a total of 90 possible engines.
In 2010 the Chinese GAC Group started the production of 1.8 and 2.0 Alfa Romeo Twin Spark 16V configurations of the Pratola Serra modular engine branded as VTML in China. These engines constitute however unique configurations, mating the single spark plug cylinder head from the 1.8 16V VFD to the 1747 and 1970 Twin Spark engine blocks, the latter with balance shafts, while retaining the power levels of the Twin Spark 16V. While these engines have been phased out in the European market in favor of Multijet turbodiesel configurations and the 1.4 MultiAir Turbo gasoline engine, they have later been updated with dual variable valve timing (branded DCVVT) and turbochargers, and are as of 2016 used in Trumpchi automobiles.
Engine specifications
Engine blocks: produced in four- and five-cylinder versions, they have similar specs. They are cast iron, with five main bearings for the four cylinder versions and six main bearings for the five cylinder versions, and can withstand turbocharging. Some versions have counter-rotating balance shafts to reduce vibrations. The aluminium pistons have graphite skirts to reduce internal engine friction, providing more reliability and efficiency.
Cylinder heads: built in aluminium alloy, they have an integrated coolant pump and lightly asymmetric combustion chambers with an angle of 47° between valves. The 1.9 8v e 2.4 10v turbodiesels have a different combustion chamber design, with two parallel valves per cylinder and a flat rather than angled design.
They have a DOHC valvetrain configuration with hydraulic tappets, driving four valves per cylinder. An exception is the 1.4 12V unit, also with hydraulic tappets but a SOHC valvetrain driving three valves per cylinder. The 1.9 8V e 2.4 10V turbodiesels have a SOHC valvetrain configuration with mechanical tappets. Some versions have variable valve timing (VVT). The camshafts are toothed belt-driven. The 1750 TBi gasoline and 16V Multijet diesel engines feature hydraulic tappets with roller rocker arms.
In addition to VVT, some versions have also variable-length intake manifold (VIS).
Behavior
Variable Valve Timing optimizes the engine's intake stroke, boosting thermal efficiency and achieving a broader and more regular torque curve.
The hydraulic tappets reduce noise levels and also maintenance needs.
Variable-length intake manifold improves the volumetric efficiency of the engine, providing better performance in the whole engine speed range.