Introduction
Volkswagen ACT (Active Cylinder Deactivation) technology, also referred to as cylinder deactivation, is an innovative engine management system integrated into their 1.5-litre TSI four-cylinder turbo petrol engines. This technology is designed to enhance fuel efficiency by deactivating two cylinders under low-load conditions, such as during steady cruising or in stop-and-go traffic, without compromising performance.
In India, ACT is featured in models such as the Skoda Kushaq, Volkswagen Taigun, Skoda Slavia, and Volkswagen Virtus, which are tailored to meet the demands of the Indian market under the Volkswagen Group’s India 2.0 strategy.
Technology Behind it
ACT functions by selectively shutting off two of the four cylinders in the 1.5-litre TSI engine when the engine operates under light load. This is achieved through a sophisticated system that closes the intake and exhaust valves of the deactivated cylinders, preventing the intake of fuel and air and halting combustion in those cylinders.
The engine control unit (ECU) continuously monitors parameters such as throttle position, vehicle speed, and engine load to determine when to engage or disengage ACT. The transition between two-cylinder and four-cylinder operation is seamless, occurring within milliseconds, and is imperceptible to the driver. When additional power is required, such as during acceleration, the deactivated cylinders are reactivated instantly to ensure optimal performance.
Benefits in the Real World Context
The primary advantage of ACT is its contribution to fuel efficiency, a critical factor in India due to high fuel prices and prevalent stop-and-go traffic conditions in urban areas. Real-world testing by Autocar India demonstrates that the Skoda Kushaq 1.5 TSI with a manual transmission achieves 11.5 kmpl in city driving and 16.5 kmpl on highways.
The automatic (DSG) variant records 8.9 kmpl in the city and 15.4 kmpl on highways. These figures are notable for a turbocharged petrol engine, positioning it as a competitive alternative to diesel engines in terms of fuel economy. The Skoda Slavia, another model equipped with ACT, has shown superior fuel efficiency compared to competitors like the Hyundai Verna in real-world tests, with an advantage of approximately 2 kmpl in both city and highway conditions.
In India’s urban environments, characterized by heavy traffic and frequent idling, ACT’s ability to reduce fuel consumption during low-load scenarios is particularly valuable. On highways, where steady cruising is common, the technology maximizes fuel savings, making it ideal for long-distance travel. Additionally, ACT contributes to reduced emissions, aligning with increasing environmental consciousness in India.
Potential Drawbacks and Concerns
Despite its benefits, some concerns have been raised about the long-term impact of cylinder deactivation on engine durability. Discussions on automotive forums, such as Team-BHP, highlight apprehensions about potential uneven wear due to repeated activation and deactivation of cylinders. Specific questions about the Skoda Slavia 1.5 TSI include whether the same cylinders are consistently deactivated and if the technology can be disabled without voiding warranties.
However, no definitive evidence of widespread issues has been reported. Historical examples, such as a 2007 Honda Accord with Variable Cylinder Management (VCM) performing reliably over 100,000 km, suggest that modern cylinder deactivation systems are robust when properly implemented.
The effectiveness of ACT can also vary based on driving conditions. In heavy traffic with frequent acceleration, the system may engage less frequently, potentially limiting fuel savings. Additionally, ambient conditions, such as high temperatures, can affect performance, as noted in tests where the auto stop-start feature, which complements ACT, was less effective due to air conditioning demands.
What Competitors Offer
In comparison to competitors like the Hyundai Verna, which also offers a 1.5-litre turbo petrol engine, the Skoda Slavia and Volkswagen Virtus with ACT demonstrate a fuel efficiency advantage of approximately 1.5–2 kmpl in real-world conditions. This edge is attributed to ACT and the seven-speed DSG transmission, which allows the engine to operate at lower RPMs during cruising.
Conclusion
Volkswagen’s Active Cylinder Technology is a significant advancement for the Indian automotive market, offering a compelling balance of performance and fuel efficiency. Its ability to reduce fuel consumption in urban and highway driving scenarios makes it particularly suitable for India’s diverse driving conditions and high fuel costs.
While theoretical concerns about long-term engine durability persist, practical evidence suggests that ACT is reliable, with no widespread issues reported. For Indian buyers seeking a premium compact SUV or sedan with strong performance and competitive fuel economy, the 1.5 TSI engine with ACT, as seen in models like the Skoda Kushaq and Volkswagen Virtus, represents a highly practical and efficient choice.
