Fuel Economy Gains through Dynamic-Skip-Fire in Spark Ignition Engines

Abstract

Pumping losses are one of the primary energy losses in throttled spark ignition engines. In order to reduce fuel consumption, engine manufacturers are incorporating devices that deactivate the valve-train in some cylinders. In the operating strategies currently implemented in the market, fixed sets of cylinders are deactivated, allowing 2 or 3 operating modes. In contrast, Tula Technology has developed Dynamic Skip Fire (DSF), in which the decision of whether or not to fire a cylinder is decided on a cycle-by-cycle basis. Testing the DSF technology in an independent certified lab on a 2010 GMC Denali, reduces the fuel consumption by 18% on a cycle-average basis, and simultaneously increases the ability to mitigate noise and vibration at objectionable frequencies. This paper outlines the results of the experiments that have been conducted on an eight cylinder engine over a wide range of conditions to investigate the fuel consumption gains and emissions impact when incorporating DSF technology. The experiments have been carried out over a wide range of engine speeds, loads, and DSF strategies and significant improvements have been observed.

Representing GHG Reduction Technologies in the Future Fleet with Full Vehicle Simulation

“…For example, Table 3 shows the effectiveness for two pairs of technology packages. The first pair contains a six speed transmission along with either a GDI engine with variable continuous cylinder deactivation [14,15] or an Atkinson engine. [9] The second pair contains a GDI engine, six speed transmission, and either 10% mass reduction or 15% reduction of both aerodynamic and rolling resistance.…”

“…A variable number of cylinders were deactivated in a continuous manner, similar to the strategy employed in the Tula Dynamic Skip Fire system. [14,15] The final result was 16 separate engine maps: eight without cylinder deactivation, and four each with the discrete and variable cylinder deactivation varieties.…”

A detailed study of a cylinder activation concept by efficiency loss analysis and 1D simulation

“…This concept has also been investigated by Ford in the EcoBoost 1.0 l three-cylinder engine [14], but was not transferred to series production. The Dynamic Skip Fire (DSF) system presented by Tula, on the other hand, allows individual cylinders to be deactivated when required [15,16]. For example, on a V8 engine, any possible combination of active and inactive cylinders can be realized.…”

Dynamic cylinder activation in diesel engines

“…While this is the first study that the authors are aware of for diesel engines, similar techniques have been studied, in various forms, on gasoline engines. Wilcutts et al 16 and Eisazadeh-Far and Younkins 17 investigated “dynamic skip fire (DSF)” as a fuel-efficient alternative to conventional eight-cylinder gasoline engine operation and demonstrated 14%–21% fuel savings on a General Motors V8 engine. Fuel efficiency benefits over fixed gasoline engine CDA were hypothesized as a result of a greater number of firing patterns allowing reduced usage of throttling to maintain a stoichiometric air-to-fuel ratio.…”