Tula Technology Inc. and Delphi Automotive PLC have revealed a radical step in engine control that takes dynamic cylinder deactivation, previously only found on large multi-cylinder engines, firmly into the realm of smaller 4-cylinder units. At the Aachen Colloquium, Tula and Delphi will demonstrate a 4-cylinder, 1.8 liter turbo GDi engineering vehicle fitted with Dynamic Skip Fire (DSF), the industry’s first fully variable engine cylinder deactivation technology.
DSF is said to improve fuel economy, and reduce CO2 by 10% compared with a state-of-the-art production 4-cylinder engine. The companies believe that in addition to these direct benefits, the system will also provide engine designers with new opportunities to optimise combustion strategies.
“Cylinder deactivation systems allow engines to operate more efficiently because the cylinders still firing run nearly unthrottled, increasing combustion efficiency and reducing pumping losses,” explained Tula’s CEO, Scott Bailey. “The challenge on smaller engines is that not firing some cylinders can create a refinement issue. Driving our new demonstration vehicle clearly shows that Tula and Delphi together have solved this challenge, making the substantial benefits of cylinder deactivation available across all popular powertrain configurations.”
DSF determines which cylinders fire in real-time, at each firing opportunity. Because it is an integral part of the engine control strategy, valve activation, throttle opening and ignition can all be optimised synergistically. The selection of which cylinders to deactivate is made based on avoiding known resonance patterns within the engine, providing exceptional refinement.
“By making a fire / no fire decision for every cylinder on every cycle, Dynamic Skip Fire takes cylinder deactivation technology to the theoretical limit,” added Tula’s vice president engineering, John Fuerst. “In future implementations we can integrate strategies to manage exhaust oxygen levels to protect aftertreatment on overrun, we can enhance Miller Cycle operation, we can complement hybridisation, even advanced combustion concepts like gasoline compression-ignition and much more.”
The joint development programme shows that DSF can reduce CO2 by at least 50% more than a conventional cylinder deactivation system when applied to a 4-cylinder engine, while enhancing refinement. Delphi’s vice-president engineering for Powertrain Systems, Martin Verschoor says that the benefits take a further step-up when combined with other Delphi technologies.
“For example, our research shows that the benefits to a 4-cylinder engine with DSF increase significantly when paired with “intelligent” electrification such as Delphi’s 48 V system,” he states. “Delphi’s 48v system on its own can reduce emissions and fuel consumption by more than 10% in direct injection engines. When combined with DSF, we anticipate a drop in both fuel consumption and CO2 emissions that could be 20%.”