RACE-THRUST BEARING 1T0762 - Caterpillar

3406B/C (3ZJ, 2EK, 4CK) Truck EnginesSince the 1991 Model Year, all Caterpillar truck engines use recirculation ports (5) in the compressor housing (4) of the turbocharger to allow recirculation (C) of inlet air (B). This helps prevent compressor surge at deep lug operating conditions. This compressor surge (popping in the air inlet system) was sometimes present with high load factor operation at high altitudes, high ambient temperatures, and/or restricted inlet systems. The recirculation ports can cause a high pitched whistle on some trucks. This can be irritating to the operator. The whistle is generated by the blade pass frequency of the compressor wheel (6) over the recirculation ports (5). The whistle is broadcast into the large 6 inch air system of the 3406C truck engine.
The 1073186 and 1073187 Noise Baffles (1) are available to reduce the turbocharger whistle on the above truck engines. The noise baffle is placed into the inlet of the compressor housing (4) and retained with the standard air hose (2) and clamps (3) as shown in the illustration. The noise baffle (1) prevents the linear travel of the whistle while still allowing effective recirculation (C) of air flow to the compressor wheel. The chart identifies which noise baffle to use with which engine.
Location of the new 1073186 and 1073187 Noise Baffles in the inlet of the turbocharger compressor housing. (A) Compressor Housing Dimension. (B) Turbocharger inlet air flow. (C) Recirculation air flow. (1) Noise Baffle. (2) Typical Inlet Air Hose. (3) Hose Clamp. (4) Compressor Housing. (5) Recirculation Port. (6) Compressor Wheel. (7) Centerline Of Turbocharger.