In 1987, the 6.9 liter engine was supplanted by the 7.3 liter upgrade, with over 300,000 6.9s shipped to Ford and countless numbers installed into medium-duty trucks, school buses, and the like. This engine features numerous improvements over the 6.9 liter, with most of the changes located in the heads; the block received an increase bore and select-fit pistons, while the heads received an enlarged prechamber, enlarged valve stem shields, harder valves, and other minor upgrades. The front cover was revised to reduce seepage.
Finally, in 1993 Ford made available a turbocharged edition of the 7.3L. An internally wastegated, AR.82 Garrett T3 series turbo was used as the OEM for the factory turbocharger system. The system was tuned to minimize performance loss at high elevation, rather than to improve peak performance. A primary limiting factor to the performance potential of the engine is an incredibly restrictive stock down-pipe. It is commonly believed, but not officially verified, that this is deliberate and due to Ford's impending release of the T444E (Powerstroke) engine. Factory turbo vehicles received numerous additional improvements. Pistons had an enlarged primary compression ring, added intermediate ring, an enlarged ring land and wrist pin, as well as an anodized piston face. Other improvements included tweaks to the injection pump, and an upgraded oil-coolant heat exchanger.[WIKI]
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