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The pneumatic valve system of the Aprilia RS3 explained

The pneumatic valve system of the Aprilia RS3 explained

The pneumatic valve system of the Aprilia RS3 explained

In a 4 stroke engine, the cycle is composed of 4 strokes; those being induction, compression, expansion and exhaust. In the induction stroke a mix of fuel and air enter the cylinder via the intake valve and exhaust gasses are expelled, in turn, from the cylinder via exhaust valve. Each cycle, intake and exhaust valves are operated via cams that drive them to open, while some helicoidal springs push them to close. The valve springs must provide sufficient force to return the valves to their closed position prior to the arrival of the engine piston, forcing the valve to stay in contact with the cam lobe.

In recent years the operating RPM of competition engines has increased dramatically due to the ever increasing requirement for higher horsepower, and of course, normally more RPM means more horsepower.$$$

This increase in maximum engine speed has placed great stress on the intake and exhaust springs, thus stronger valve springs are required. When space in the head is limited these large, and heavy, valve springs can be substituted with a pneumatic system.

The pneumatic "spring" utilizes the elastic effect obtained when a volume of air is compressed. In short, a small cylinder of air is created under the valve retainer that, when compressed by the opening valve, generates the closing force. The "spring" can be easily tuned to have different characteristics. To compensate for the small losses of air that can occur in operation, a small air bottle is used to "top up" the system. In brief, pneumatic valves, like those used on the Aprilia RS3, are an elegant solution that permit engines to achieve high RPM in a small efficient package.

MotoGP, 2002

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