889862 Volvo.Penta Protecting cover

Table 1
Performance Parameters of the Engine    
Parameter     Tolerance    
Jacket Water Coolant Temperature    
6 °C ( 10 °F)    
Inlet Manifold Air Temperature    
6 °C ( 10 °F)    
Temperature of the Gas    
6 °C ( 10 °F)    
Fuel Energy Content    
31.6 kJ ( 30 Btu)    
Load     5%    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.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, LEKQ7250, "Air Intake". Consult your Caterpillar dealer for assistance.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 (if equipped) of the aftercooler:
For engines with a 32 °C (90 °F) aftercooler, the maximum temperature of the air/fuel mixture is 43 °C (110 °F).
For engines with a 54 °C (130 °F) aftercooler, the maximum temperature of the air/fuel mixture is 65 °C (150 °F).For more information, see Application and Installation Guide, LEKQ7260, "Low BTU Engines". Consult your Caterpillar dealer for assistance.Fuel Supply Pressure
Fluctuations of the fuel pressure can change the air/fuel ratio. For low pressure gas fuel systems (10 kPa (1.5 psi) to 34.5 kPa (5 psi) fuel pressure into the regulator on the engine), the maximum fluctuation that is allowed in the fuel pressure is 1.7 kPa ( 0.25 psi). If more than one engine is using the fuel supply line, ensure a stable fuel pressure to the engine by installing a second gas pressure regulator prior to the gas pressure regulator on the engine.For high pressure fuel systems, the maximum fluctuation that is allowed in the fuel pressure is 6.9 kPa ( 1 psi).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 according to the instructions in Systems Operation/Testing and Adjusting. The gas pressure regulator will maintain the pressure differential in response to changes in the air pressure.A water manometer is used to measure the pressure differential. This measurement is taken when the engine is operating at high idle rpm with no load. When a load is applied, the fuel pressure will usually decrease by approximately 0.25 to 0.5 kPa (1 to 2 inches of H2O). If the performance of the gas pressure regulator is erratic, the gas pressure regulator may require service.Throttle Angle and Exhaust Bypass (Wastegate)
A throttle angle of approximately 70 degrees is recommended for full load operation.The following factors affect the angle of the throttle:
LHV of the fuel
Air/fuel ratio
Setting of the exhaust bypass (wastegate)
Altitude
Ignition timingAfter the desired exhaust emissions are achieved, the exhaust bypass is adjusted in order to achieve full load operation with the desired throttle angle. Excess boost generates back pressure in the exhaust manifold. This raises pumping losses which increase fuel consumption.Ensure 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 down and shutting off.