The Piston Deactivation Engine


For many decades it has been the desire of motor engineers to create a “flexible” engine with the ability to vary a number of parameters in order to achieve ultimate economy and/or ultimate performance. This flexibility is necessary to respond to the variable loads and conditions that are required by a vehicle to reduce fuel consumption. We have seen the introduction of many innovations, however, the “Holy Grail” of flexibility is Variable Capacity (VC) and to some degree, Variable Compression Ratio (VCR)

The Piston Deactivation Engine.

The Piston Deactivation Engine has been developed to allow complete flexibility in the quest to achieve maximum fuel economy in the way an engine is used in a vehicle. It is an innovative design that allows designated pistons to be stopped or “parked” when not required (unlike the cylinder deactivation engines where the pistons continue to be dragged within the cylinder). Not only do the active pistons operate at a higher efficiency, but the reduction in friction provided by the parked pistons, substantially increase fuel economy and reduce emissions. This is very much a fundamental requirement in the way an engine operates in a vehicle where partial loads are the norm.

 A prototype 1.7 litre three cylinder Piston Deactivation Engine (PDE) has run successfully on one, two and three pistons. The principal of operation is demonstrated in the cross sections below:


Figure 1 shows the engine in the active position and comprises of a conventional crankshaft connected to the piston via a rocking adjustable four bar mechanism that has all pin jointed connections positioned on the opposite side of the cylinder relative to the crankshaft. The angular movement of the piston conrod is very small throughout the cycle almost eliminating the piston side force and hence friction.

By rotating the adjustor relative to the oscillator, the lower pin of the piston conrod is positioned to be concentric with rotational axis of the oscillator and the piston motion is reduced to zero while the closed oscillating mechanism remains in sync with the crankshaft at all times. Activation and deactivation can be achieved very quickly in response to vehicle demand with a helical spline actuator (not shown).  See Fig 2.

By mounting the adjustor on small eccentrics,  Variable Compression Ratio can be added to the Piston Deactivation Engine to create a complete package for maximum fuel efficiency

The internals of the three cylinder engine with the front piston deactivated in shown in the following picture.



The application to a V6 engine produces a 2-4-6 as depicted above

The prototype three cylinder engine is a 1.7 litre capacity based on one half of a popular six cylinder engine and utilises part of the cylinder block with pistons, and the complete head and part of the manifold. Effectively creating a multi capacity engine of 567cc, 1130cc and 1700cc.



        • Substantial reduction in fuel consumption estimated in excess of 30% with similar reduction in emissions.  Ref. SAE Paper 2011-01-0368.
        • An estimated additional 5% to 10% fuel reduction with the inclusion of VCR. 
        • An estimated additional 10% to 15% fuel reduction with the inclusion of VCR and turbo charging. 
        • Applicable to Diesel engines and in particular to large diesel engines for road transport. 
        • Can be applied to V-type and horizontally opposed engines. 
        • Does not affect existing production of head, manifolds and fuelling systems. 
        • The small crankshaft to cylinder offset can be used to advantage for east-west installations. 
        • It uses conventional pin jointed and lubrication technology. 
        • Balancing requirements are within acceptable levels at all positions. 
        • Complementary to all other combustion technologies. 
        • Potential for reduced cooling system size. (Cost and weight reduction) 
        • Probable reduction in the size of starter motor and battery as the engine is started at minimum capacity. (Cost and weight reduction) 
        • Very low additional production cost relative to economy gains. 
        • Can be used in combination with a lower cost mini electric or flywheel hybrids. 

  • VCR can be added as described above.                

        Variations of the mechanism defined in the many granted patents, can produce Variable Compression Ratio Engines with

        and without the Atkinson effect; Variable Stroke Engines, and a true Atkinson Cycle Engine.