Cylinder deactivation technology is likely to be a major design change in the next generation of heavy-duty diesel engines looking to meet stricter greenhouse gas/fuel efficiency regulations. As its work on this technology progresses, Jacobs Vehicle Systems has entered into a collaboration agreement with Tula Technology, an internal combustion controls company. The two businesses will work together to enable Jacobs to further develop cylinder deactivation technologies, which reduce engine fuel consumption and emissions.
Jacobs announced its Cylinder Deactivation (CDA) technology for medium- and heavy-duty commercial vehicle engines in 2018. Tula has licensed its Dynamic Skip Fire (DSF) technology for major automotive OEM gasoline applications.
According to Jacobs, the new partnership will use Tula’s DSF controls technology to support Jacobs’ expertise in diesel deactivation hardware development.
“Vehicle manufacturers are looking for new and improved technologies to comply with stricter legal limits on CO2 and NOx emissions," explained Robb Janak, director, new technology, Jacobs Vehicle Systems. "New test measures, such as Real Driving Emissions and CARB Low Load Cycle for heavy-duty trucks, are encouraging the adoption of smarter technologies that address these requirements. Cylinder deactivation is a great solution, technically proven, and cost effective.”
Jacobs’ CDA, cylinder deactivation mechanisms, originally designed for the company’s High Power Density (HPD) engine brake, are used in the valvetrain to disable the opening of the intake and exhaust valves. The hydraulically activated mechanism is integrated in a collapsing valve bridge system for overhead camshaft engines or with a collapsing pushrod system for cam-in-block engines. When this is combined with disabled injection in selected cylinders, multiple cylinders can be deactivated as needed. At low engine loads with three of six cylinders deactivated, fuel consumption can be improved by up to 20%.
Jacobs said its CDA technology reduces emissions by achieving higher exhaust temperatures, thus maintaining aftertreatment temperatures for optimal efficiency of SCR (selective catalytic reduction) systems, even when the engine is in idle or low load operation. CDA also enables faster warm-up after engine start-up of the aftertreatment system and minimizes cooling of aftertreatment during coasting. CDA additionally reduces camshaft friction, reduces pumping losses in part-load conditions, and can reduce or eliminate use of the intake throttle, all of which yields overall improvements in fuel consumption while increasing exhaust temperatures.
Tula has developed an infinitely variable cylinder deactivation system, integrating advanced digital signal processing and software with sophisticated engine control algorithms. This technology reduces fuel consumption of gasoline engines by 6-15% on real world drive cycles; the collaboration with Jacobs aims to enable Jacobs to develop and demonstrate deactivation hardware required for diesel engines.
The Tula DSF system makes dynamic firing decisions based on how much torque is requested and then selectively choosing which cylinders will be active or deactivated to meet performance demand. When more torque is required, the firing density increases, and when there is less demand for torque, firing density decreases. This means the control algorithm effectively creates an engine with optimal displacement for the torque required.
Tula’s control system also ensures production level noise, vibration and harshness in a vehicle, the company said. By having the ability to select which cylinders are fired every engine cycle, and by taking into account the frequencies and amplitudes of vibration produced by cylinder combinations, the control algorithm determines the cylinder firing sequences that deliver smooth operation and reduced cost at the fuel pump.