Under low-load conditions such as highway cruising, the cylinder deactivation technology intelligently shuts down half of the cylinders (i.e., four) of a V8 engine through hydraulically controlled valve tongs, transforming it from an active working state to one that only follows the compressed air. This conversion process can be completed within 20 milliseconds and is almost imperceptible to the driver. According to a 2019 study by Argonne National Laboratory under the U.S. Department of Energy, for a 5.3-liter V8 engine, this move can reduce pumping losses by up to 8% and increase the load rate of the working cylinder from 15% to the more efficient 30% range, thereby directly improving fuel economy by 5% to 10%.
The core benefit of this technology lies in significantly reducing fuel consumption. Take the AFM (Active Fuel Management) system widely used by General Motors as an example. The Chevrolet Tahoe SUV equipped with this technology can improve fuel consumption from 17 miles per gallon to 19 miles per gallon in the EPA combined fuel consumption test, which is equivalent to saving about 0.6 gallons of fuel per 100 miles of travel. For a user who drives an average of 15,000 miles per year, this means saving nearly 55 gallons of fuel annually, which is approximately $200 in cost savings at current oil prices. This is like transforming a full-size SUV into a more economical four-cylinder sedan while cruising, and its economic benefits are comparable to a small-scale powertrain hybrid transformation.
To ensure a smooth transition from eight-cylinder mode to four-cylinder mode, the ECU (Engine Control Unit) works in coordination with the transmission TCU (Transmission Control Unit) to monitor over 20 parameters such as throttle opening, engine speed, and vehicle speed at a frequency of 100 times per second. For instance, when the system detects that the throttle opening suddenly increases by more than 25%, it will reactivate all cylinders within 100 milliseconds to ensure power response. As pointed out in the long-term test report of a pickup truck equipped with cylinder deactivation technology conducted by Auto & Driver magazine in 2021, the vast majority of drivers cannot perceive the mode switching in daily use, and its smoothness is comparable to the longitudinal control accuracy of the vehicle by advanced autonomous driving assistance systems.
From the perspective of cost and environmental return, the additional hardware cost for introducing the cylinder deactivation system is approximately $200 to $300 per vehicle. However, the fuel savings it brings can enable consumers to recover this initial investment within a 2 to 3-year usage period, with a considerable return rate. From a macro perspective, according to the estimation of the US Environmental Protection Agency (EPA), if 10% of V6 and above displacement vehicles in the United States were to apply this technology, millions of tons of carbon dioxide emissions could be reduced annually. This innovation is one of the core strategies of automakers in response to increasingly strict CAFE (Enterprise Average Fuel Economy) regulations. It demonstrates that in today’s highly mature internal combustion engine technology, through precise electronic control and mechanical optimization, it is still possible to continuously tap into huge energy efficiency potential.