Variable displacement is an automobile engine technology that allows the engine displacement to change for improved fuel economy. Many automobile manufacturers have adopted this technology as of 2005, but it is not a new concept.
Most variable displacement systems work by turning off a bank of cylinders in a V engine, but the initial systems worked differently. Pioneered on Cadillac's ill-fated V8 engine#L62 V8-6-4 engine, the original multi-displacement system turned off opposite pairs of cylinders, allowing the engine to have three different configurations and displacements. But the system was troublesome, and the technology was quickly retired.
No automaker attempted the same trick again until Mercedes-Benz experimented with their Multi-Displacement System V12 in the 1990s. It was not widely deployed until the 2004 DaimlerChrysler Chrysler Hemi engine#5.7. Other systems appeared in 2005 from General Motors (Displacement on Demand in the GM LS engine generation IV small-block) and Honda (Variable Cylinder Management on the Honda J engine). Honda's system works by deactivating a bank of cylinders, while the Chrysler Hemi shuts off opposing pairs.
Two issues to overcome with all of these systems is the unbalanced cooling and vibration of variable-displacement engines.
Variable displacement technologies
- General Motors Cadillac V8 engine#L62 V8-6-4|V8-6-4(
- General Motors Displacement on Demand (DoD)
- DaimlerChrysler Multi-Displacement System (MDS) (for Chrysler)
- DaimlerChrysler Active Cylinder Control (ACC) (for Mercedes-Benz)
- Honda Variable Cylinder Management (VCM)