Idling
Idle speed is adjustable on Caterpillar electronic engines. Consult your Caterpillar dealer for information. The idle rpm is preset between 700 and 750 rpm.
Avoid excess idling. If the vehicle is parked for more than five minutes, stop the engine. An engine can burn from 2.8 L (0.7 US gal) to 5.7 L (1.5 US gal) of fuel per hour while the engine is idling. Excessive idling can cause carbon buildup and/or excessive idling can cause the engine to slobber. This is harmful to the engine.
If extended idle time is required, control the engine rpm to 1000 rpm or above 1000 rpm. Ensure that the coolant temperature exceeds 82° C (180° F). Consult your Caterpillar dealer for assistance.
Fast idle can be programmed within the range of 700 rpm to the top engine limit. Fast idle requires an "ON/OFF" switch on the dashboard. Consult your Caterpillar dealer for assistance.
Idle Shutdown Timer
The idle shutdown timer can be programmed in order to shut down the engine after a specific time period of idling. The idle time can be programmed from three minutes to 1440 minutes (24 hours). If the idle shutdown timer is set to 0 minutes, the idle shutdown feature is disabled. If the setting of the timer is unknown, allow the engine to idle. Observe the time that elapses before the engine shuts down. The following conditions must be met in order to activate the idle shutdown timer:
- The idle shutdown feature is selected.
- No vehicle speed is detected by the Electronic Control Module (ECM).
- The engine is not under load.
- The engine is at operating temperature. The engine is not in Cold Mode.
After the vehicle is stationary, the idle shutdown timer begins. The engine can be operating at low idle or at an idle rpm that is selected by the idle governor. The "CHECK ENGINE/DIAGNOSTIC" lamp will flash rapidly for 90 seconds prior to shutdown. Movement of the vehicle automatically resets the idle shutdown timer to the programmed setting.
The following conditions must be met in order to override the idle shutdown timer:
- Program the "ALLOW IDLE SHUTDOWN OVERRIDE" to "YES".
- The "CHECK ENGINE/DIAGNOSTIC"lamp will flash rapidly for 90 seconds prior to shutdown. Depress the service brake or the clutch pedal during the 90 seconds when the "CHECK ENGINE/DIAGNOSTIC" lamp flashes.
After an idle shutdown, the engine can be restarted without turning the ignition key switch to the OFF position.
The override function is disabled if the "ALLOW IDLE SHUTDOWN OVERRIDE" is programmed to "NO".
Cold Mode Operation
Cold mode is initiated if the sum of the coolant temperature and the inlet air temperature is below 35° C (127° F). In cold mode, the low idle is increased to 1000 rpm and the engine power is limited. The strategy for cold mode provides reduced smoke emission and faster warm-up time.
Cold mode is deactivated when the temperature condition is met, or when the engine has been operating for 12 minutes.
After the cold mode is completed, the engine should be operated at low rpm and low load until normal operating temperature is reached. The engine will reach normal operating temperature faster when the engine is operated at low rpm and low power demand. This method is faster than trying to reach operating temperature by idling with no load.
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It is not recommended that the vehicle be moved until the engine is out of cold mode. Power may be noticeably reduced if the vehicle is operated while the engine is in cold mode. At a speed above 8 km/h (5 mph), the low idle speed will be reduced to the customer programmed low idle speed. The power will still be reduced. |
Cold mode is disabled if the throttle, the service brake, or the clutch (if equipped) is depressed. The rpm for cold mode operation drops to the programmed low idle speed in order to allow the transmission to be put into gear.
Muffler and Converter (If Equipped)
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The muffler and converter will become extremly hot during engine operation. A hot muffler and converter can cause serious burns. Allow adaquate cooling time before working on or near the muffler and converter. |
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Proper operation, driving techniques and maintenance are key factors in obtaining the maximum service life of the muffler and converter. Some precautions should be taken if the engine is equipped with a muffler and converter.
Avoid excess idling. Excessive idling can cause the muffler and converter to plug. A plugged muffler and converter will lead to an increase in exhaust back pressure. Operating the engine in extremely cold conditions can cause the muffler and converter to plug sooner. Use the procedure below to clean out the muffler and converter if extended idle periods or extended low load periods are required.
If the engine is operated at low idle or at low load for 24 or more consecutive hours, the engine should be run at rated conditions for five to fifteen minutes. Running the engine at rated conditions should clean out the muffler and converter. If the engine has low power or the engine does not respond properly, refer to the Service Manual or an authorized Caterpillar Service Center.
Getting Started
Caterpillar electronic engines do not require long warm-up periods that needlessly waste fuel. Typically, the engine should be at normal operating temperature in a few minutes. Begin operating the engine at low load. After normal oil pressure is reached and the temperature gauges begin to rise, the engine may be operated at full load.
To get the vehicle in motion, use a gear that will result in a smooth start. Move the load without increasing the engine rpm above low idle or without slipping the clutch. Engage the clutch smoothly. Slipping the clutch and engaging the clutch can cause stress to occur on the drive train. This can also cause fuel to be wasted.
Use progressive shifting techniques. Progressive shifting is using only the rpm that is required in order to upshift into the next gear. Progressive shifting improves fuel economy.
- Keep the engine rpm to a minimum. Use an rpm that is from 1400 to 2000 rpm.
- Use only enough rpm to pick up the next gear.
Progressive shifting also reduces the acceleration rate. Top gear is reached sooner because less time is needed to synchronize the gears during shifting. In addition, the engine is operating at the highest range of torque.
The amount of rpm that is required to upshift increases as the vehicle speed increases, unless upshifts are made on upgrades. Experience with the vehicle will show the amount of rpm that is required to upshift under various conditions.
Note: These engines may be programmed to encourage progressive shifting. The acceleration rate may slow down at certain rpm in lower gears. If this occurs, progressive shift parameters may have been programmed into the ECM. Progressive shift parameters will limit the rpm when the vehicle is driven in higher gears. These parameters are protected by customer passwords. If the vehicle can be operated in a higher gear at a vehicle speed that is desired, select the highest gear that is available to pull the load. This recommendation will help to obtain fuel economy. The engine will be operating at the lowest rpm that is required to pull the load.
Vehicle Efficiency
An efficient vehicle performs the desired amount of work while the power demand on the engine is minimized. The following factors are major contributors to power demand:
- Aerodynamic drag (wind resistance)
- Rolling resistance of the tires
- Gross weight of the vehicle
- Losses in the drive train and the load from the engine driven accessories
For more information about vehicle efficiency, refer to Special Publication, LEDT2254, "CAT Answers Your Questions About Truck Performance".
Fuel Economy
Fuel is the largest single operating cost of today's on-highway vehicle engines. Improved fuel economy can have a substantial impact on operating profit. The following items are the most significant factors that influence vehicle fuel economy:
- Driver techniques
- Vehicle efficiency
- Operating conditions
- Engine efficiency
A No. 1 grade of fuel contains less energy per volume and increases fuel consumption. A greater volume of fuel must be injected in order to yield the same amount of work as a No. 2 fuel. The difference in the fuel economy between the two grades of fuel can be as great as 0.2 km/L (0.5 mpg) to 0.3 km/L (0.7 mpg).
For more information about fuel economy, refer to Special Publication, LEDT2254, "CAT Answers Your Questions About Truck Performance".
Rolling hills provide a great opportunity to reduce fuel consumption. Avoid downshifting on small hills. The vehicle should not be downshifted even if the engine must be lugged down to an rpm that is below the peak torque rpm. When the vehicle is going down a hill, use gravity instead of the engine's power to regain vehicle speed.
On grades that require more than one downshift, allow the engine to lug to peak torque rpm. If the rpm stabilizes with the engine running at peak torque rpm or above peak torque rpm remain in that gear.
Long steep down grades should be anticipated. Vehicle speed should be reduced before cresting the top of a hill and proceeding down a long steep grade. Minimize the amount of braking that is used in order to maintain a safe speed for maximizing fuel efficiency.
The engine's ability to hold the vehicle back increases with engine rpm. Select a gear that runs the engine near the high engine rpm limit for long steep hills when braking is required.
Speed reductions and future stops should be anticipated. Downshifts should be avoided. The amount of braking should be minimized in order to improve fuel consumption. By coasting to a stop, a vehicle can travel a considerable distance without consuming any fuel.
Cruising
Vehicles that are driven faster consume more fuel. Increasing the cruising speed from 88 km/h (55 mph) to 104 km/h (65 mph) will increase the fuel consumption of a typical Class 8 vehicle by approximately 0.4 km/L (1 mpg). When a vehicle is driven fast in order to allow more time for stops, the stops become very expensive. Cruising allows the engine to operate in the most efficient rpm range (1400 to 2000 rpm).
Cruise Control
The functionality of the cruise control can vary depending on the vehicle manufacturer. The Cruise Control switch may be programmed to operate in one of two modes:
- The SET position may operate as the SET/ACCEL SWITCH position or the RESUME/DECEL position.
- The RESUME position may operate as the SET/DECEL position or the RESUME/ACCEL position.
Refer to the markings on the Cruise Control switch or refer to your "Truck Service Manual".
Perform the following steps in order to set the Cruise Control:
- After accelerating to the desired speed, turn the "ON/OFF" switch to the ON position.
- Press the "SET/RESUME" switch to the SET position.
The ECM will control the vehicle speed until the clutch pedal or the service brake is depressed or the "ON/OFF" switch is turned to the OFF position.
Note: The vehicle can also be accelerated to the desired speed and the cruise control speed can be set by pressing the "SET/RESUME" switch to the ACCEL position.
Perform the following step in order to reset the Cruise Control:
- Press "RESUME" and the vehicle will return to the set speed.
Momentarily pressing or bumping the "SET/RESUME" switch to the ACCEL position will increase vehicle speed by one mph. Press the switch to the DECEL position in order to decrease the speed by one mph. The operating range of the cruise control has been programmed into the ECM.
Soft Cruise Control
The Cruise Control can be programmed to operate in one of two modes, "Soft Cruise = YES" or "Soft Cruise = NO".
Soft Cruise Control provides an operating range of 8 km/h (5 mph) around the setting for the cruise control. Engines that are shipped from Caterpillar are programmed to operate in the "Soft Cruise = YES" mode. Soft Cruise Control allows the vehicle to accelerate slightly while the engine is under power. The vehicle can proceed down a hill while momentum is gained for the next hill. Improved fuel economy can be gained in this mode.
When "Soft Cruise = NO" is programmed, the "SET" speed is maintained. Consult your Caterpillar dealer for more information.
Idle Mode
The cruise control function of the electronic engine works as an engine speed governor when the vehicle is stationary or when the vehicle is operated at a vehicle speed below the idle vehicle speed limit. The engine speed governor is activated and deactivated in the same way as the cruise control.
The engine speed governor will operate at any engine rpm from low idle to the maximum idle rpm limit. The maximum idle rpm limit is actually less than the rated engine rpm. The maximum idle governor speed is a Customer Specified Parameter.
Perform the following procedure in order to activate idle mode:
- Set the "ON/OFF" switch to the ON position. The throttle can then be used to determine the desired engine rpm.
- When the desired engine rpm is reached, place the "SET/RESUME" switch to the SET position and release the switch. The engine rpm will be maintained at this speed.
Note: If the "SET/RESUME" switch is held for more than one second in the ACCEL position, the ECM will increase the engine rpm until the "SET/RESUME" switch is released. If the parameter is programmed, the ECM will increase the engine rpm up to the idle engine rpm limit, or to the top engine limit (TEL).
Perform one of the following procedures in order to disengage the idle mode:
- Move the "Cruise/Idle ON/OFF" switch to the OFF position.
- Depress the clutch pedal.
- Depress the service brake pedal.
Perform the following procedure in order to resume the idle mode:
- Ensure that the "Cruise/Idle ON/OFF" switch is in the ON position.
- Move the "SET/RESUME" switch momentarily to the RESUME position.
Note: If the "SET/RESUME" switch is held for more than one second in the DECEL position, the ECM will decrease the engine rpm until the switch is released. A new set rpm is established when the switch is released.
Uphill Operation
For optimum performance, allow the engine to lug downward to peak torque rpm (1440 to 1550 rpm) before downshifting. Continue to downshift in this manner until a gear that maintains the desired speed is reached. Continue to operate at a low rpm (1440 to 1550 rpm) if the vehicle will proceed to the top without a downshift. Begin upshifting as the grade of the hill decreases and the engine begins to accelerate above 2000 rpm. Driving this way will provide optimum fuel economy and performance.
Note: Allowing the engine to lug below peak torque is permissible if the vehicle is cresting the top of a hill. However, extended operation at an engine rpm that is below peak torque (1400 rpm) will raise the exhaust temperature and the cylinder pressure. This can lead to reduced engine service life.
Downhill Operation
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DO NOT allow the engine rpm to exceed 2900 rpm, engine damage can result. |
On a downgrade, do not allow the vehicle to coast while the clutch pedal is depressed or while the transmission is in the NEUTRAL position. If a power loss is not desired, disengage the Cruise Control.
Select the correct gear that does not allow the engine rpm to exceed 2900 rpm. Use the service brakes to control the speed of the vehicle. As a basic rule, select the same gear that would be required to go up the grade. Refer to the rated rpm (full load) that is on the engine Information Plate.