3885523 Volvo.Penta Split pin

Air/Fuel Ratio
The correct air/fuel ratio is very important for the following considerations:
Margin of detonation
Control of emissions
Achieving optimum service life for the engineIf the air/fuel ratio is not appropriate for the fuel and the operating conditions, a failure of the engine may occur. The service life of the turbocharger, the valves, and other components may be reduced.Fuel Supply Pressure
Fluctuations of the fuel pressure can change the air/fuel ratio. For high pressure gas fuel systems, the maximum fluctuation that is allowed in the fuel pressure is 3.4 kPa (0.50 psi). For low pressure gas fuel systems, the maximum fluctuation that is allowed in the fuel pressure is 1.7 kPa (0.25 psi). Ensure a stable fuel pressure to the engine by installing a second gas pressure regulator prior to the gas pressure regulator on the engine.Gas Pressure Regulator
The gas pressure regulator maintains a pressure differential between the air and the fuel that is supplied to the carburetor. Set the pressure of the fuel supply to a maximum of 1.5 kPa (6 inch of H2O) more than the pressure of the air supply. The gas pressure regulator will maintain the pressure differential in response to changes in the air pressure. If high idle stability is important, lower the differential pressure to 1 kPa (4 inch of H2O). The higher differential pressures will give better engine response to load changes.A water manometer is used to measure the pressure differential. This measurement is taken when the engine is operating at high idle rpm. When a load is applied, the fuel pressure will usually decrease by approximately 0.25 to 0.5 kPa (1 to 2 inch of H2O). If the performance of the gas pressure regulator is erratic, the gas pressure regulator may require service.Temperature of the Fuel Supply
Changes in the temperature of the fuel supply affects the air/fuel ratio. Warmer fuel is less dense than cold fuel. This results in a leaner mixture that causes a noticeable reduction of power. The recommended temperature differential of the air and the fuel is 2.8 °C (5 °F).The maximum fuel temperature depends on the temperature regulator of the aftercooler:
For engines with a 32 °C (90 °F) aftercooler, the maximum temperature of the air/fuel mixture is 38 °C (100 °F).
For engines with a 54 °C (130 °F) aftercooler, the maximum temperature of the air/fuel mixture is 60 °C (140 °F). Consult your Caterpillar dealer for assistance.Temperature of the Air Supply
Changes in the temperature of the air supply affects the air/fuel ratio. In addition to seasonal changes, the air temperature changes overnight. Control of the temperature in the engine room will help to maintain the air/fuel ratio.To optimize the inlet air temperature, use ducting and a heat exchanger. This will help to avoid exposure to hot air from a generator. For more information, see Application and Installation Guide, LEBW4969, "Air Intake Systems Application and Installation Guide". Consult your Caterpillar dealer for assistance.Carburetor
This engine uses a carburetor for fuel delivery. The carburetor requires adjustment for proper engine operation. Optional carburetor jetting is available for fuels that are not standard.Optional Air/Fuel Ratio Control
The engine may be equipped with an air/fuel ratio control system. The system provides the following capabilities:
Control of exhaust emissions
Adjustment for changes in the fuel BTU
Adjustment for changes in ambient conditionsThe system consists of the following components:
Electronic Control Module (ECM)
Oxygen sensor or NOx sensor
Oxygen buffer or buffer for the NOx sensor
Speed sensor
Inlet manifold pressure sensor
Inlet manifold temperature sensor
Fuel valve
Throttle actuator
Input switchesFor more information regarding the Air/Fuel Ratio Control, see the Service Manual, "Systems Operation/Testing and Adjusting".Angle of the Throttle Plate
The angle of the throttle plate is adjusted for full load operation. The angle is adjusted by changing the setting of the exhaust bypass valve.
Adjust the angle of the throttle plate between 60 and 75 degrees.The following factors affect the angle of the throttle:
LHV of the fuel
Setting of the air/fuel ratio (inlet manifold air pressure)
Setting of the exhaust bypass (wastegate)
AltitudeEnsure that the angle of the throttle plate is properly set. This will maintain the margin for detonation. This will also enable the engine to accept load changes without lugging. The angle of the throttle will also affect the stability of the engine.Setting of the Exhaust Bypass (Wastegate)
The engines are equipped with exhaust bypass valves that are adjustable. This enables the throttle position to be correctly set for the application. Adjustments must be made for the following variables:
Altitude
Setting of the air/fuel ratio
Methane number of the fuelThe exhaust bypass is adjusted in order to achieve the proper angle of the throttle plate when the engine is operating under a rated load.Oil Consumption
High loads will cause the engine to consume more oil.The rate of oil consumption is called the Brake Specific Oil Consumption (BSOC). The unit of measure is grams per brake kilowatt hour (pounds per brake horsepower hour). The BSOC depends on the following factors: engine model, aspiration and operating load.Table 1 lists the normal mid-life BSOC for G3500 Engines under the following conditions:
Load factor of 100 percent
Maintenance is performed according to this Operation and Maintenance Manual, "Maintenance Interval Schedule" (Maintenance Section).
Table 1
BSOC for G3500 Engines    
Naturally Aspirated Engine    
0.913 g/bkw h (0.0015 lb/bhp h)    
Turbocharged Aftercooled Engine    
0.426 g/bkw h (0.0007 lb/bhp h)