Scalzo Piston Deactivation Engine – Whole cylinder deactivation

Some engines can ‘deactivate’ cylinders by preventing the valves from actuating, and hence inhibiting any airflow through that cylinder. This is great for part load conditions, as it reduces some of the pumping losses of the engine. This system doesn’t quite achieve full cylinder deactivation though, as the piston still moves up and down in the cylinder, hence some energy is still lost to friction. The Scalzo ‘Piston Deactivation Engine’, however, can deactivate the whole cylinder and stop the piston from moving.


A full explanation is given on their website, and apparently can also be designed to provide a variable compression ratio.

The advantages stated are:

  • 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.

Apart from the advantages, some of the disadvantages might be

  • Increased complexity probably means higher initial cost (although this could be offset by savings)

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  1. Pingback: Honda Variable Cylinder Management Engine | An Engineer's Blog

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