General Motors is improving the efficiency of its next-generation Chevrolet Volt by adding a new 1.5L, four-cylinder engine that should deliver 20 percent more electric acceleration, the automaker has announced.

GM is debuting the 2016-MY Volt at the North American International Auto Show in January, but has released some new details about the vehicle's powertrain, which has been re-engineered.

The drive unit that consists of a pair of Voltec electric motors operates between 5 and 12 percent more efficiently and weighs 100 pounds less than the current system. Additionally, the range-extending 1.5L four-cylinder gasoline engine uses direct injection, a high compression ratio (12.5:1), cooled exhaust gas recirculation, and a variable displacement oil pump.

General Motors is also increasing the percentage of U.S.- and Canadian-sourced parts in the 2016 Volt to about 70 percent. That represents a 20 percent increase from the first generation model that was introduced in late 2010.