Pneumatic Valve System

The workings of a pneumatic valve system

The pneumatic valve system is the improved version for closing the engine valves from the conventional coil spring system. This system was introduced by Renault in the F1 engine.

The conventional coil spring system will have problems with coil binding when used with higher lift camshafts. Metal fatigue will also set in, causing valve float and often leading to a catastrophic engine failure of valve impacting the piston.

The pneumatic valve system consists of a air pocket holding the inert gas nitrogen at constant pressure which will return the valve when the cam timing retards.

The pneumatic valve system will allow a faster rate at which the valve is closed, allowing the engine to rev to higher limits (along with other considerations such as piston speeds). This is a better alternative than the coil spring system as to have the spring close the valve at such high rpm, the springs need to be very stiff. A too stiff spring will sap power from the engine.

The system is slowly replacing the conventional system in MotoGP bikes. This is due to the successes that the different teams are slowly getting. However not this system is not all perfect as it adds additional weight to the engine, also there is a problem of gas leakage. This system is also more complicated than the coil spring system.

Think it'll still be a long way till this will be found in the production bikes. An interesting design concept though.