Turbocharger Surge on G3500 Generator Sets and G3500 Generator Set Engines that are Equipped with Dual Turbochargers{1052, 1057, 1071} Caterpillar

Turbocharger Surge on G3500 Generator Sets and G3500 Generator Set Engines that are Equipped with Dual Turbochargers{1052, 1057, 1071}

Usage:

G3520C B9P

Generator Set:: G3516C (S/N: TJB1-UP; TJC1-UP); G3516E (S/N: GAS1-UP; SLY1-UP; GHP1-UP); G3520C (S/N: CWY1-200,204-206,208-218,222-UP; JBX1-UP; JBZ1-UP; GZJ1-UP; GZK1-UP; GZL1-UP; GZM1-142,149-UP; MAD1-UP; B9P1-UP; HAT1-UP; GDB1-38,42-44,46-UP); G3520E (S/N: GZG1-UP; GZH1-UP; SXY1-UP; GHR1-UP; HAL1-UP; GHM1-UP)
Engine:: G3516C (S/N: GZZ1-UP; RWA1-UP; DKR1-UP); G3520C (S/N: GHC1-UP)

Introduction

The problem that is identified below does not have a known permanent solution. Until a permanent solution is known, use the solution that is identified below.

Problem

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Illustration 1	g01259350
Typical example of the fluctuation of manifold air pressure

The turbochargers surge on some G3500C/E Generator Set engines. This condition occurs mainly in cold ambient conditions. A symptom of turbocharger surge is sudden fluctuations in the manifold air pressure. This generally occurs when the engine is above 50 percent load. Noise from the turbocharger may be present while the turbochargers surge.

The turbocharger surge is caused by an increase in the pressure across the turbochargers. Turbocharger boost increases allowing the engine to maintain higher manifold pressures at lower throttle positions. A reduction in the throttle position for a given manifold air pressure reduces the air flow through the compressor side of the turbocharger. When the air flow through the compressor decreases enough, the turbocharger compressor will surge. When the turbocharger surge occurs the air flow through the compressor can reverse. This will result in a sudden drop in manifold air pressure. Refer to Illustration 1. The turbocharger surge can be diagnosed by measuring the differential pressure across the throttle. The differential pressure across the throttle must be measured on an engine when the turbocharger surge is suspected.

Solution

Procedure to Adjust the Compressor Bypass Valve

The compressor bypass valve must be adjusted in order to achieve a pressure differential across the throttle of 40 ± 10 kPa (5.8 ± 1.5 psi). Perform the adjustment procedure if the turbocharger surge occurs. The procedure must be performed in the coldest ambient temperature in the engine's operating range. Use the following procedure to adjust the pressure differential across the throttle.

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Illustration 2	g01256245
Typical example (1) 162-0177 Plug As

Install the pressure differential gauge.
1. Stop the engine and remove one of the plugs (1) in the bottom of the 206-4168 Housing . Refer to Illustration 2.
1. Remove plug (2) from the 200-6543 Cover . Refer to Illustration 3.
1. Install a differential pressure gauge between the holes for plugs (1) and (2) .
1. Start the engine.
1. Apply a load to the engine until the full rated load is reached.
  If the engine cannot reach full load due to the turbocharger surge, apply the maximum load to the engine before the turbochargers begin to surge.
1. Allow the engine power to stabilize at full load for a period of five minutes.
1. Record the reading on the differential pressure gauge.

Stop the engine.
Adjust the bypass valve for the compressor if the differential pressure is greater than 40 ± 10 kPa (5.8 ± 1.5 psi).

Ensure that the engine control switch is in the STOP.
The Electronic Control Module (ECM) and the actuator for the compressor bypass must be active. This will keep the bypass actuator in the home position.

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The linkage can move and form a pinch point which can cause personal injury. Keep hands away from the linkage.

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Illustration 4	g01256573
Typical example (3) Roll pin (4) Set screw (5) Nut

Mark the location of roll pin (3) on nut (5) .
Note: The flats on nut (5) are 60 degrees from each other.

Use roll pin (3) and nut (5) as a reference. Rotate the shaft of the valve in the clockwise direction in relationship to the flywheel of the engine. The roll pin will move in the upward direction. Adjust the valve so that there is approximately 22.5 degrees between the reference mark on nut (5) and roll pin (3) .
This will slightly open the compressor bypass valve. Opening the bypass valve will lower the differential pressure across the throttle. A small adjustment of the bypass valve will have a large effect on the differential pressure of the throttle. If the bypass valve is adjusted too much the throttle will go to the 100 percent position before the engine reaches rated load. This is due to the loss of boost pressure.