The new Vespa GTS Supersport 300 HPE is equipped with the latest evolution of the 300 cc, 4-stroke, 4-valve single-cylinder engine, liquid-cooled and with electronic injection: the fruit of work by the Piaggio Group research and development centre and known as 300 HPE (High-Performance Engine), the unit has benefited from numerous interventions aimed at increasing performance and ride-ability, while simultaneously reducing fuel consumption and noise levels. It is the most powerful engine ever mounted on a Vespa with optimised thermodynamic performance and reduced friction; all without impacting on size or bulk, which remain the same as for the previous unit, at the top of its category.
The cylinder head is born out of a brand-new casting and is characterised by totally redesigned internal components: the ducts have a new geometry and diameter (now greater), as do the intake and exhaust valves, the diameter of which has been increased by 3 mm. The adoption of a new-look piston, particularly in terms of its head shape, has resulted in a highly efficient combustion chamber.
The single camshaft system with overhead valves is all-new, rockers equipped with roller tappets rather than sliders for increased fluidity and durability, and a reduction in mechanical loss. The profile of the camshaft has been redesigned to obtain different valve lift profiles, more extreme but also able to reduce the noise generated by the timing: essentially, greater valve lift duration ensures better filling of the combustion chamber, which translates into greater efficiency. As a result, the valve springs have also been altered in terms of load and size.
The introduction of a new high-pressure multi-jet injector has helped to improve combustion. A more generous intake line, equipped with a duct of optimised length, improves the torque delivered at low revs and ensures exceptionally smooth shifting at any speed. The new iridium spark plug ensures greater durability, conditions of use being equal.
The many modifications made to the engine have also boosted the already legendary Vespa GTS reliability, as demonstrated by the significant maintenance intervals, now extended to 10,000 km.
The transmission has also been overhauled, the CVT boasting a more robust belt and new materials designed to reduce friction and noise. All of this is enveloped by a new cover coated with sound-absorbing material, for a reduction in mechanical noise, also aided by a new and more rigid clutch drum.
The engine is controlled by a latest-generation Magneti Marelli MIUG4 ECU, which already conforms with the future Euro 5 standard: equipped with greater calculation capacity, it contributes to improving overall engine efficiency and allows for the engine to be started practically instantaneously, after just two rotations of the crankshaft.