ENGINE: WE WRITE TORQUE, YOU READ FUN
The new Euro 4 engine grows to 900 cc from the 750 cc on the first version. This increase was achieved thanks to the increased stroke that clearly increases torque in the mid-range, all to the advantage of a better response during acceleration and exiting corners. The 90 Nm of torque at 6,500 rpm that are consequently obtained guarantee pure fun in the saddle. This is was one of the main objectives for the Aprilia engineers in designing the new twin-cylinder. The power, which increased in any case to over 95 HP, stems from the decision to comply with the legal limits in order to be able to obtain approval for the version with power limited to 35 kW as well, that can be ridden with an A2 class driver’s license. Aprilia Shiver 900 is therefore an easy bike to ride even for new bikers, accompanying them in their personal evolution of experience in the saddle.
The new power-plant, that maintains the 90 degree angle between the two cylinders as well as the four-valve timing per cylinder, dual overhead cam and liquid cooling, was the subject of various changes, including an important operation aimed at reducing friction on the pistons, completely redesigned and now characterized by a special anti-friction feature on the mantle, whereas new pins new pins have led to a lightening of the alternated parts in motion. The crankshaft also changes, with revamped balancing.
On the other hand, a new and more efficient semi-dry carter internal lubrication circuit helps to reduce losses of power due to shaking and to keep consumption and temperature of the lubricant to a limit, thereby eliminating the need for an oil radiator. Improved efficiency was also achieved on the combustion front thanks to the introduction of new injectors: the increase of fuel pressure allows better fuel/air mixture spray with benefits for consumption and emissions. Contributing to bringing the engine to within the limits established by the Euro 4 pollution standard is also the exhaust system, fitted with a double oxygen sensor. The Aprilia Shiver 900 engine is also fitted with an automatic decompresser which makes it easier to start in low temperature conditions.
The unit fitted on the Aprilia Shiver 900 also gains the Marelli 7SM ECU: a substantial evolution that, on one hand, has allowed a refined traction control system to be introduced and that, on the other hand, has led to a significant simplification of the electrical system; in fact, the engine control and management systems, functions that were previously carried out by two separate electronic control units, are now integrated in a single hardware components, the same one fitted on the V4 models from Noale.
All of the clutch components have been redesigned: The load on the clutch lever has decreased by 15%, whereas the primary drive reduction ratio has been changed to optimize exploitation of the available power.