General Motors Co. reports it will invest $483 million to expand production of its Ecotec engines at the powertrain plant in Spring Hill, Tenn. The engines will include current and forthcoming models of the Ecotec series — specific details of which are being held in reserve by the automaker.

The vehicle assembly plant at Spring Hill, the former Saturn operations, remains idle until more vehicle production capacity is needed, according to GM.

The Ecotec series engines are four-cylinder units that feature direct fuel injection, variable valve timing, and turbocharging. GM’s commitment to advanced four-cylinder engines is part of a broader strategy to replace larger-displacement engines with more compact models that optimize fuel savings and performance, and reduce emissions.

The Spring Hill plant already produces Ecotec 2.0-liter turbocharged direct injection 4-cylinder engines; Ecotec 2.4-liter MPFI 4-cylinder engines; and Ecotec 2.4-liter direct injection 4-cylinder engines, at a rate of about 270,000/year. These are installed in various GM models assembled worldwide.

Earlier this year GM outlined investments totaling $494 million for projects to support Ecotec engine production, including the assembly complex in Tonawanda, NY, the metalcasting plant at Defiance, Ohio; and the machining operation at Bay City, Mich.

Most of the new investment at Spring Hill, $460 million and 453 hourly and salaried jobs, is earmarked for production of the next-generation Ecotec engines, which GM indicates will have additional capabilities to improve fuel efficiency, reduce noise and vibration, and improve performance.”

“This new commitment to the Spring Hill team will help GM almost triple its North American production volume of four-cylinder engines with direct injection by 2012," stated GM North America president Mark Reuss.

The investment also includes $23 million for the current-generation Ecotec engine, which would add 30 hourly jobs to increase production beginning in Q1 2011.

“Both of these investments highlight the confidence the company has in the work force in Spring Hill to produce outstanding quality engines for our products of today and tomorrow,” according to Reuss.