Cylinder Deactivation
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Cylinder deactivation, also known by commercial names such as 'Cylinder on Demand' (COD) or 'Active Cylinder Technology' (ACT), is an advanced engine technology designed to improve the fuel efficiency of internal combustion engines, primarily gasoline engines. The principle involves temporarily interrupting the operation of a certain number of cylinders when the engine is under low load. In these driving conditions, such as at a steady highway speed or during smooth city driving, the full power of the engine is not required. The engine management system then deactivates fuel injection and valve lift for half of the cylinders (for example, 2 out of 4, or 4 out of 8). The engine thus operates like a smaller-displacement engine, reducing pumping losses and optimizing the efficiency of the remaining cylinders, which operate at a higher and therefore more efficient load. The transition between modes is managed electronically in a way that is imperceptible to the driver, ensuring optimal driving comfort without vibrations or surges. This technology represents an ingenious solution for balancing on-demand performance with controlled fuel consumption.
Benefits
- ✓Significant reduction in fuel consumption
- ✓Decrease in CO2 emissions and other pollutants
- ✓Optimization of engine efficiency at low load
- ✓Seamless and imperceptible transition for the driver
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What is cylinder deactivation technology?
Cylinder deactivation is an intelligent system integrated into modern internal combustion engines designed to reduce fuel consumption and pollutant emissions. Its principle is simple: when the vehicle does not need the engine's full power, the system temporarily puts a portion of the cylinders on standby. The engine then operates with a reduced displacement, which lowers its fuel consumption. Once reserved for large V8 or V12 engines, this technology has become widespread and can now be found on more common engines, such as 4-cylinders, under various names such as Cylinder on Demand (COD) or Active Cylinder Management (ACT).
How does cylinder deactivation work?
The operation of this system relies on highly refined electronic engine management. The Engine Control Unit (ECU) constantly analyzes dozens of parameters: vehicle speed, engine speed, accelerator pedal position, required load, etc. When conditions are met for low-load driving (steady speed, slight acceleration, downhill), the ECU sends a command to deactivate certain cylinders.
Deactivation occurs in two simultaneous ways:
- Fuel injection cutoff: The injector of the concerned cylinder stops sending fuel into the combustion chamber.
- Valve closure: A complex mechanism, often consisting of electromechanical actuators on the camshaft, prevents the intake and exhaust valves from opening. The piston continues to move up and down, but the trapped air in the cylinder acts as an air spring, minimizing energy losses (pumping losses).
As soon as the driver demands more power by pressing the accelerator, the system reactivates the cylinders in just a few milliseconds. The transition is so fast and smooth that it is generally completely imperceptible to the vehicle's occupants.
What are the benefits of this technology?
The main advantage of cylinder deactivation is both economic and ecological.
- Fuel savings: By running only the strictly necessary number of cylinders, the engine consumes less. Gains can reach up to 0.5 L/100 km in the combined cycle and exceed 1 L/100 km at steady highway speeds.
- Emission reduction: Less fuel burned means lower CO2 emissions, the primary greenhouse gas. This helps manufacturers comply with increasingly stringent environmental standards.
- Efficiency optimization: An engine is more efficient when operating at a higher load. By deactivating cylinders, the remaining cylinders work harder to maintain speed, placing them in an optimal efficiency range.
- Preserved comfort: Engineers have worked extensively to eliminate potential vibrations and surges associated with the transition. Thanks to dual-mass flywheels, active engine mounts, and precise electronic management, switching from one mode to the other is imperceptible.
A future-proof technology for the internal combustion engine
Faced with the growing electrification of the automotive fleet, the internal combustion engine continues to evolve to become more efficient and cleaner. Cylinder deactivation is one of many innovations, alongside the Stop & Start system and mild hybridisation, that help extend its relevance. It demonstrates that it is still possible to optimize the efficiency of combustion engines, offering a smart compromise between readily available performance and controlled everyday fuel consumption.
Compatible brands
Associated equipment
Variable Displacement
Variable displacement, also known as cylinder deactivation (Cylinder Deactivation or Cylinder on Demand - CoD), is an internal combustion engine technology designed to improve fuel efficiency. The principle involves temporarily deactivating a portion of the engine's cylinders when full power is not required, for example at a stabilized cruising speed or under light load. By cutting off the fuel injection and closing the intake and exhaust valves of the affected cylinders, the engine then operates with a reduced effective displacement. This decreases pumping and friction losses, forcing the remaining cylinders to work in a more optimal load range where their efficiency is maximal. The transition between full-capacity mode and economy mode is electronically managed and designed to be completely seamless for the driver. Initially reserved for large engines (V8, V12), this technology has become widespread and is now found on more modest 3- or 4-cylinder engines, actively contributing to the reduction of fuel consumption and CO2 emissions in modern vehicles.
Eco Mode
Eco Mode, also known by names such as 'Efficiency' or 'Eco Pro' depending on the manufacturer, is an increasingly common feature in modern vehicles, whether ICE, hybrid, or electric. Integrated into the drive mode selector, its main objective is to reduce fuel or energy consumption by optimizing the operation of several vehicle systems. To achieve this, it adjusts several key parameters. Accelerator pedal response is softened, requiring firmer pressure to achieve the same acceleration as in Normal or Sport mode. Automatic transmission management is also modified to shift up earlier and at lower engine speeds. Additionally, Eco Mode can reduce the power of certain energy consumers, such as air conditioning or seat heating. On electrified vehicles, it maximizes regenerative braking to recover more energy during deceleration. It is a valuable tool for calm, economical driving, particularly effective in urban areas and on highways at steady speeds.
Direct injection
Direct injection is an engine technology where fuel is injected at very high pressure directly into the combustion chamber of each cylinder, rather than into the intake manifold as with indirect injection. This method allows for extremely precise control of the air-fuel mixture, both in terms of metering and injection timing. By spraying fuel directly into the cylinder, more efficient vaporization is achieved along with a cooling effect that increases the density of the intake air. This phenomenon allows for a higher compression ratio to be used without the risk of engine knock, resulting in more complete and efficient combustion. Initially popularized on diesel engines (with Common Rail technology), direct injection has become widely adopted in modern gasoline engines (GDI, FSI, THP, etc.) as part of downsizing strategies. It has become a technological pillar for manufacturers seeking to balance increasingly strict requirements regarding performance, fuel consumption, and pollutant emission reduction.
Stop & Start
The Stop & Start system, also known as automatic engine stop and restart, is a technology designed to reduce fuel consumption and pollutant emissions in internal combustion vehicles. Its operating principle is simple: it automatically shuts off the engine when the vehicle is stationary for an extended period, such as at a red light or in a traffic jam, and restarts it instantly as soon as the driver wants to move off again. For a manual transmission, the engine cuts out when neutral is engaged and the clutch pedal is released. It restarts as soon as the driver presses the clutch again. On an automatic transmission, the system activates when the vehicle is immobilized with the brake pedal depressed and restarts as soon as the pedal is released. This technology relies on reinforced components, notably a more robust starter motor and battery (often AGM or EFB type) capable of withstanding a much higher number of starting cycles than a conventional system. An intelligent electronic control unit manages the whole setup, ensuring that optimal conditions (engine temperature, battery charge, etc.) are met before shutting down the engine, thereby guaranteeing safety and comfort.