Cummins N14 STC, Celect, Celect Plus – Service Manual 014-999   Engine Testing – Overview

General Information

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This section outlines engine testing and engine run-in recommendations for N14 engines. All engines must be run-in after a rebuild or a repair involving the replacement of one or more piston ring sets, cylinder liners, or cylinder kits.

Incorrect or insufficient break-in of the piston rings will lead to early oil consumption or high blowby complaints. Adherence to these run-in guidelines will allow the full durability of new pistons, liners, and rings to be realized.

Before running the engine, make sure the engine is filled with the correct coolant. Also, make sure the lubricating oil system is filled and primed.

 
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In Service Run-in

The majority of heavy duty diesel applications will provide sufficient run-in under normal loaded operations. However, light load/high rpm operation must be avoided during the run-in period. The following in-service run-in guidelines are recommended for N14 engines after a repair involving replacement of one or more of the piston ring sets, cylinder liners, or cylinder kits where engine or an engine dynamometer and/or chassis dynamometer run-in can not be performed.

Engine Dynamometer Run-in

This is the preferred method of run-in for engines that have been rebuilt out-of-chassis. It is not practical nor recommended that an engine be removed from the application to conduct the run-in after a rebuild or cylinder repair has been performed in-chassis. There is not a requirement and it is not recommended for an engine that has been run-in and tested on an engine dynamometer to be run-in again after it has been installed back into the vehicle or equipment.

Cummins Heavy Duty Engine Operating Curve Definitions

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  1. Peak torque (N•m [ft-lb]) – Maximum torque that the engine will produce. Also, sometimes referred to as command torque. This is listed on the engine dataplate.
  2. Peak torque rpm (rpm) – Engine speed at which peak torque is generated. This is listed on the engine dataplate.
  3. Maximum hp rpm (rpm) – Engine speed at which maximum power is developed. This is listed with advertised horsepower on the engine dataplate.
  4. Advertised horsepower (hp) – Maximum power that the engine will develop. This is provided on the engine dataplate with its corresponding engine speed.
  5. Command range (rpm) – The engine’s operating range from command torque or peak torque up to the engine’s governed speed.
  6. Command point – The point on the performance curve where maximum horsepower and optimum fuel economy come together. This is the point where advertised horsepower occurs.
  7. Full load governed speed (rpm) – Defined as the upper end of the engine’s full load operating range. This is listed on the engine dataplate.
  1. Line haul rating – An engine that has a line haul rating has a narrow operating range (rpm). A line haul rating is typically used for on-highway applications. These engines are used with larger (more gears, 13 speeds, etc.) transmissions with close ratio splits between gear shifts.

No-load governed speed (rpm) – (not shown) Maximum unloaded engine speed. This value is listed on the engine data sheet and in the FPEPS publications.

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  1. Peak torque (N•m [ft-lb]) – Maximum torque that the engine will produce. Also, sometimes referred to as command torque. This is listed on the engine dataplate.
  2. Peak torque rpm (rpm) – Engine speed at which peak torque is generated. This is listed on the engine dataplate.
  3. Maximum hp rpm (rpm) – Engine speed at which maximum power is developed. This is listed with advertised horsepower on the engine dataplate.
  4. Advertised horsepower (hp) – Maximum power that the engine will develop. This is provided on the engine dataplate with its corresponding engine speed.
  5. Command range (rpm) – The engine’s operating range from command torque or peak torque up to the engine’s governed speed.
  6. Command point – The point on the performance curve where maximum horsepower and optimum fuel economy come together. This is the point where advertised horsepower occurs.
  7. Full load governed speed (rpm) – Defined as the upper end of the engine’s full load operating range. This is listed on the engine dataplate.
  1. Vocational rating – A vocational rated engine has a wider operating range (rpm). This rating is typically used for on and off or off-highway applications. These engines are used with smaller (fewer gears, 9 speeds, etc.) transmissions with large ratio splits between gear shifts.

No-load governed speed (rpm) – (not shown) Maximum unloaded engine speed. This value is listed on the engine data sheet and in the FPEPS publications.

Run-In Instructions

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 CAUTION 

Check the General Engine Test Specifications in this section before operating the engine to avoid internal component damage.

The amount of time specified for the following engine run-in phases are minimums.

The engine can be operated for longer periods of time at each operating range or phase with the exception of engine idling which must be kept to five minutes or less.

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Start the engine and idle for an initial check.

Avoid long idle periods. Operate the engine at low idle only long enough (five minutes maximum) to check for correct oil pressure and any fuel, oil, water, or air leaks.

Do not operate the engine at idle speed longer than specified during engine run-in. Excessive carbon formation will occur and cause damage to the engine.

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 CAUTION 

To avoid internal component damage, do not allow the engine speed to exceed 1,000 rpm before run-in.
 
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While the engine is idling, listen for unusual noises; watch for coolant, fuel, and lubricating oil leaks; and check for correct engine operation in general.

Repair all leaks or component problems before continuing the engine run-in.

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 CAUTION 

Do not shut off the engine immediately after the run-in is completed. Allow the engine to cool by operating at low idle for a minimum of three minutes to avoid internal component damage.
 
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Fuel Flow Measurement on Engine or Chassis Dynamometer

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Accurate fuel flow measurement is important for evaluation of engine performance and troubleshooting on an engine or chassis dynamometer. The only way accurate fuel flow measurement can be obtained is through proper use of the available equipment. Below is a description of the fuel measuring device, available from Cummins Inc., along with installation and operation recommendations. The fuel measuring device, Part Number 3376375, can be used with either a chassis or engine dynamometer.

When installing the fuel measuring device, it is important to reduce the amount of air that can be introduced into the system when the device is not in use. The plumbing used must include non-restrictive shutoff valves, such as ballcock valves, to contain fuel in the device after each use. Additional installation considerations are:

  • The fuel measuring device, Part Number 3376375, must be mounted vertically for accuracy and proper operation.
  • A separate fuel supply for use on the dynamometer is recommended. All fuel used in the measuring device must be clean for consistent operation.
  • Care must be taken to reduce fuel line restriction to and from the engine. Minimum recommended hose sizes are Number 10 for the engine fuel inlet, and Number 8 for the engine fuel drain. The length of either hose must not exceed 4.572 m [15 ft].
  • For accurate fuel consumption or flow measurement while testing on a chassis dynamometer, it is recommended to use a fuel cooler to maintain inlet temperature to the fuel gear pump at 49°C [120°F] or below.
 
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Operation

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Fuel Measuring Device, Part Number 3376375

  1. Fuel filter
  2. Flow meter
  3. To float tank
  4. To fuel cooler
  5. Injector return

NOTE: Fuel cooler is not a part of fuel measuring device, Part Number 3376375; however, must be used when conducting test with the flow meter.

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Fuel Measuring Device Connection Points

  1. Fuel supply from tank
  2. Fuel flow to fuel meter
  3. Fuel flow from fuel meter
  4. Fuel flow to fuel cooler
  5. Injector return fuel
  6. Fuel rail pressure.

The fuel measuring device recirculates return fuel to the engine fuel inlet by routing the return fuel to the top side of the float tank. The fuel is deaerated as it passes through the baffling in the float tank. A ball float valve at the bottom of the float tank maintains an adequate volume in the tank for deaeration. The fuel is then returned to the engine fuel inlet. The illustration shows fuel line connection points on the fuel measuring device.

The fuel supply tank must be below the level of the fuel measuring device to prevent overflow of the float tank. If an overhead fuel supply tank is used, a float controlled reservoir must be installed between the fuel supply tank and the fuel measuring device, and below the level of the device.

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On CELECT™ and CELECT™ Plus engines, the engine fuel inlet line must flow through the ECM cooling plate to provide proper cooling of the ECM during engine operation.

The fuel measuring device is installed in series between the fuel supply tank and the engine fuel inlet. The quantity of fuel being drawn through the flowmeter is know as “make up” fuel or the amount of fuel being burned by the engine.

The flowmeter is graduated to read fuel flow in pounds per hour. The flowmeter contains two floats with respective scales on either side of the flowmeter. The small float is used to measure lower flows and must be read on the left scale, as shown. The larger float is for measuring higher flows and must be read on the right scale.

To obtain an accurate fuel rate measurement, the flowmeter reading must be corrected based on the fuel temperature. There is a fuel temperature gauge on the front panel of the fuel measuring device. The gauge is graduated in percent of error by which the reading requires correction. An example is: The fuel of an engine reads 125 lbs/hr on the flowmeter, and the temperature gauge reads +2 percent; the corrected fuel flow rate will be 125 plus 2 percent, or 127.5 lbs/hr.

Last Modified:  08-Feb-2005