GM will add several variants of the new Ecotec family, including a 1.0-liter 3-cylinder.

General Motors will invest $332 million to gear up four plants to launch an array of new powertrain components, including all-new 3-, 4- and 6-cylinders engines, as well as a new 8-speed transmission.

In a complex announcement, the maker also revealed plans to boost a previous investment at two Michigan plants by $46 million.  In all, the new and expanded programs will bring to $1.8 billion the money GM has committed to updating six Midwest powertrain facilities since just 2009.

“We are investing in technologies and manufacturing capabilities that produce high-quality, fuel-efficient vehicles and components for our customers,” said Diana Tremblay, vice president of GM North American Manufacturing.

The figures released today do not include the actually development costs of the new powertrain systems, which can add a billion or more to the various programs, according to industry analysts.

The largest portion of the new investment, $215 million, will go towards tooling up for an all-new global line of Ecotec gasoline engines that will be produced in both 3- and 4-cylinder configurations in displacements ranging from 1.0 to 1.5-liters.

With fuel prices hovering near record levels, American motorists have been rapidly downsizing, especially when it comes to engine size.  The biggest shift has been from six to four-cylinder designs. But there’s a small but burgeoning market for inline-three powertrains, industry planners forecast. Ford has a new I-3 for the Fiesta line, for example, and BMW will add one for its new i8 plug-in hybrid in 2014.

Eventually, GM expects the new Ecotec engine series could generate sales of 2 million or more annually.

Despite declining market share, V-6 engines are still one of the industry’s workhorses. And they’re actually gaining ground in some segments. More than half of the full-sized Ford F-Series pickups, for example, now use V-6s instead of more traditional V-8s. GM is expecting something of a similar shift.

But the maker has declined to provide specifics about the new six or where it will be used at the moment.

Another major shift in an industry facing tough new mileage standards is the use of advanced transmissions. The $332 million investment program will expand the capacity for 6-speed automatics but also help launch production of an even more fuel-efficient 8-speed transmission, according to GM.

The various new programs are expected to save 1,650 jobs at six different plants in Michigan, Indiana and Ohio.