SILAO, Mexico—Volkswagen is investing another $118-million in its engine plant in central Mexico, the automaker announced. The, located in the Guanajuato Puerto Interior industrial park in Silao, Mexico, produces Volkswagen’s turbocharged EA888 TSI engine used in a host of Volkswagen and Audi models. Volkswagen said the new investment will be used to equip the plant to manufacture new components to be used…