Usage:
793 (3SJ) Trucks
- SUPPLEMENT: 08/07/95
Service Magazine; May 8, 1995; Page 8; "Selecting The Correct Turbocharger And Wastegate Orifice For 3500 Engines Used In 793 Trucks"
Disregard this article. See the article with the same title in this issue.
--------------- END SUPPLEMENT ---------------
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.
-
- * 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 33 to 38 mm (1.3 to 1.5 in) depending on the machines' operating altitude.
- * Change Two 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 was also changed to remain compatible with the new turbocharger.
- * Change Three added a new high pressure turbocharger. The turbocharger's turbine housing and center housing are now 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. Also the low pressure turbocharger changed to include a turbine wheel with lower stresses. This will result in a longer service life for the turbine wheel.
- * 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 33 to 38 mm (1.3 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 4P4646 High Pressure Turbocharger groups have been canceled.
