Usage:
NOTE: Temporary corrections to the charts in this book will be printed in the publication ENGINE NEWS. Announcement for revised reprints of this book will be made in PREVIEW.
These instructions are intended to acquaint you with the content of the rack setting charts. A description is given of the information to be found under each column heading. Read these instructions carefully so you can better understand the information presented.
After reading and understanding these instructions, use the following suggestions to aid in the actual use of the rack setting charts.
1. Determine and write down the engine model and engine serial number.
2. Locate the correct rack setting chart.
3. Locate the correct segment of the chart being used. Particular attention must be focused on the model and serial number.
4. Read all notes pertaining to the engine being repaired. The notes are just as important as any other information that is presented on the rack setting chart.
Column Headings
Column headings and arrangement of material can vary from chart to chart according to data requirements for the engines. A brief description of each column heading, note and symbol follows. See Fig. 1.
Model
The MODEL column lists the description of the engine, and the serial number range to which the data applies. Be sure to use the data from the correct serial number range for the engine being repaired.
Engine Full Load RPM
The column lists the engine speed (under load) at which the rack is positioned to permit maximum allowable amount of fuel to the engine per unit of time. Turbocharger speed, inlet manifold pressure and horsepower output are at their maximum for the listed rack setting. A tolerance of ± 10 RPM is allowed.
Engine High Idle RPM
This column lists the high idle speed of the bare engine when driving a dynamometer. Use the figures in the chart when adjusting high idle in the truck. A tolerance of ± 30 RPM is allowed in most applications.
Brake Horsepower
This column lists the power available at the flywheel, without fan, and within the limitations indicated in the charts. A tolerance of ± 3% of this value is normal from a new or reconditioned engine.
Fig. 1
Rack Setting
The rack setting is the distance the rack must travel from the centered (sometimes referred to as zero) position, to supply sufficient fuel, to produce the expected power output of the engine. Rack setting is controlled by a stop bar or torque spring that is located within the governor. The stop bar and/or torque spring limits the maximum travel of the fuel rack. Rack setting procedure is explained and illustrated in the TESTING AND ADJUSTING Section of the applicable service manual.
All rack settings are plus (+) settings unless otherwise indicated with a minus (-) sign. See Fig. 2.
Torque Spring And Spacer
This column lists the part number and thickness of the torque spring, and only those spacers or shims installed between the torque spring and stop. Any shims located behind the stop are not listed. The dimensions are in inches and are for means of identification.
Fig. 2
SINGLE AND DOUBLE ASTERISKS (* and **): These two markings are used only in the column under the heading TORQUE SPRING AND SPACER. The single asterisk (*) denotes the part number of the TORQUE SPRING. The double asterisk (**) denotes the part number of the SPACER.
ARROWS: When two or more part numbers apply to more than two successive rack settings, the duplication is shown by an arrow. The arrow will extend from the first rack setting for which the part numbers apply to the rack setting where the part numbers change.
DITTO MARKS: Data that applies unchanged for several settings, but consists of only one item, is indicated by ditto marks. See Fig. 2.
Turbocharger Assembly
This column lists the part number of the turbocharger used.
Occasionally changes are made to a turbocharger that requires assigning a new turbocharger part number.
If the change does not affect engine performance, the column will state the either turbocharger can be used.
If a change to the turbocharger affects engine performance, or power settings, the change will be indicated by a break in the model serial numbers, and/or the new turbocharger part number.
A source for turbocharger interchangeability and models is the Technical Partsgram FEO00206.
Maximum Altitude
This column lists the maximum altitude in feet at which the engine can develop maximum engine output when set with the given chart values. See Fig. 3.
In order to be able to operate safely at higher altitude, the rack setting and high idle RPM must be changed. Engine damage and/or possible injury could result by overspeeding of the turbocharger if these changes are not made.
Rack setting charts for the 1100 Series engines include information for derating to limit smoke if an engine is to be operated at a higher altitude.
The maximum altitude stamped on the altitude warning plate and listed in the rack charts may be followed by either the letter "L" or "N". These letters designate two types of application: "Lug" and "Non-lug" in the derating procedures for some turbocharged engines. The proper application and maximum altitude must be considered when checking or adjusting power settings.
Governor Group And Spring
This column lists the governor group and governor spring part numbers. See Fig. 2.
The "GENERAL NOTES" at the bottom of the page list the part numbers and corresponding color codes of the governor springs used. The color code provides positive identification of each spring. In applications using two springs, the inner spring is not color coded. See Fig. 3.
Truck engine governor springs are selected for on-highway engine application. In certain power take-off applications, where engine speed control is critical, it may be desirable to install a special governor spring to obtain the desired engine speed. Contact your Caterpillar dealer for assistance concerning special requirements.
Inlet Manifold Pressure At Full Load And Speed
This column lists the inlet manifold pressure (boost) expected from a turbocharged engine, with the engine operating at full load and rated speed. The values are expressed as "gauge pressure in inches of mercury". See Fig. 3.
Gauge pressure is the difference between the recorded absolute pressure and the existing barometric pressure. The horsepower values and manifold pressure (boost) are corrected to 29.4 inches of mercury at 85° F. ambient temperature with 35 API fuel.
If the inlet manifold pressure is measured with a gauge that measures absolute pressure, gauge pressure can be calculated by subtracting the existing barometric pressure from the absolute pressure reading obtained.
The 4S6553 Instrument Group contains the necessary equipment for measuring manifold pressures. Included with the instrument group are the instructions form FEO36044.
General Notes
The information in these notes will apply to all models listed in the chart unless specifically stated otherwise in a "Specific Note".
Specific Notes
The information in these notes apply to a specific model. These notes are referenced by a letter (A), (B), (C), etc., in the column headed "See Notes".
Fig. 3
1674 Truck Engine Settings
1674 Truck Engine Settings
