Ford Motor will unveil a new series of F-Series pickups powered by an optional new clean-burning diesel engine, company officials said. The new 6.4-liter diesel engine will be larger than the current 6-liter engine and will produce more horsepower, but it will have better fuel economy and be quieter than its predecessor. It also will comply with new federal regulations for diesel engines that call for a 90 percent reduction in particulate pollution for vehicles produced after Jan. 1. The company will achieve the reduction by using high-precision fuel injectors and a particulate filter similar to a small incinerator that further burns the particles to scrub the black smoke from exhaust fumes. The filter, which will be at the front of the exhaust system, will burn the particles safely, and the exhaust will be the same temperature as in current diesel vehicles by the time it reaches the tailpipe and will be as clean as the exhaust from gasoline engines. The trucks also will be cleaner because of low-sulfur diesel fuel standards that take effect across the country Oct. 15, according to the U.S. Environmental Protection Agency. The EPA said the fuel will cut sulfur emissions by 97 percent compared with fuel now being distributed. The F-250 and F-350 trucks will go on sale early next year. Ford would not release fuel economy statistics or pictures of the new trucks for competitive reasons, said spokesman Said Deep.