Usage:
793B (1HL) Trucks
- SUPPLEMENT: 08/07/95
Service Magazine; May 8, 1995; Page 9; "Selecting The Correct Turbocharger, Wastegate Orifice, And Personality Module For 3500 Engines Used In 793B Trucks"
Disregard this article. See the article with the same title in this issue.
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Reference: Service Magazine; August 22, 1994; Page 2; "Procedure To Modify 4P-4866 Coupling And 4P-4864 Housing To Work With New High Pressure Turbocharger"
Description of Change: Several changes have recently been made to improve the service life of the turbocharger and the performance of the engine. Each new change has resulted in new components in the turbocharger group. The changes and their benefits are listed below.
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- * Change One upgraded the 48 trim high pressure turbocharger to a 56 trim. The new turbocharger increased the quantity of air to the engine, resulting in lower exhaust temperatures. Also, the wastegate orifice was increased in size. The size of the orifice varies from 30 to 38 mm (1.2 to 1.5 in) depending on the machines' operating altitude.
- * Change Two decreased the wastegate orifice size to 24 mm (.9 in). This reduced orifice size increased the speed of the turbocharger under full load. With more air flow to the engine, the exhaust temperature was lowered even further than before. A new personality module was then added to maintain the cylinder pressure at the specified level.
- * Change Three added a new low pressure turbocharger with a larger compressor wheel and housing. The larger compressor wheel allowed the turbocharger to pump the same volume of air, but at a lower speed. This speed reduction resulted in longer service life of the turbine wheel. The wastegate orifice and the personality module were also changed to remain compatible with the new turbocharger.
- * Change Four added a new high pressure turbocharger. The turbocharger's turbine housing and center housing are made from the same material. This reduced the exhaust leakage between the center housing and the turbine housing because both parts expand and contract at the same rate.
- * Change Five added a new low pressure turbocharger. The turbocharger contains a new turbine wheel and shaft resulting in increased service life.
- * Change One upgraded the 48 trim high pressure turbocharger to a 56 trim. The new turbocharger increased the quantity of air to the engine, resulting in lower exhaust temperatures. Also, the wastegate orifice was increased in size. The size of the orifice varies from 30 to 38 mm (1.2 to 1.5 in) depending on the machines' operating altitude.
Whichever combination of components are on the truck, it is important not to change that combination. The charts in this article provide a list of compatible components and specifications. Using any other combination can cause excessive cylinder pressure or excessive exhaust temperature. Operating an engine outside the recommended ratings, in either area, can cause major engine problems.
Adaptable To: All the turbocharger variations can be upgraded to the latest change. The new 122-0351 Low Pressure Turbocharger Group and the 121-3850 High Pressure Turbocharger Group are direct replacements for the former turbocharger groups if the other components are also updated. The 4P-4693, 106-4557, and 4P-4646 High Pressure Turbocharger groups have been canceled.