ASTM D613-24

Standard Test Method for Cetane Number of Diesel Fuel Oil

SIGNIFICANCE AND USE
5.1 The cetane number provides a measure of the ignition characteristics of diesel fuel oil in compression ignition engines.  
5.2 This test method is used by engine manufacturers, petroleum refiners and marketers, and in commerce as a primary specification measurement related to matching of fuels and engines.  
5.3 Cetane number is determined at constant speed in a precombustion chamber type compression ignition test engine. The relationship of test engine performance to full scale, variable speed, variable load engines is not completely understood.  
5.4 This test method may be used for unconventional fuels such as synthetics, vegetable oils, and the like. However, the relationship to the performance of such materials in full scale engines is not completely understood.
SCOPE
1.1 This test method covers the determination of the rating of diesel fuel oil in terms of an arbitrary scale of cetane numbers using a standard single cylinder, four-stroke cycle, variable compression ratio, indirect injected diesel engine.  
1.2 The cetane number scale covers the range from zero (0) to 100, but typical testing is in the range of 30 to 65 cetane number.  
1.3 The values for operating conditions are stated in SI units and are to be regarded as the standard. The values given in parentheses are the historical inch-pound units for information only. In addition, the engine measurements continue to be in inch-pound units because of the extensive and expensive tooling that has been created for these units.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For more specific warning statements, see Annex A1.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Jan-2024
• ICS: 75.160.20 - Liquid fuels
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.01 - Combustion Characteristics

Relations

• Replaces: ASTM D613-23 - Standard Test Method for Cetane Number of Diesel Fuel Oil
• Effective Date: 01-Feb-2024
• Refers: ASTM D6708-24 - Standard Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purport to Measure the Same Property of a Material
• Effective Date: 01-Mar-2024
• Refers: ASTM D6300-24 - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Mar-2024
• Refers: ASTM D6300-23a - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Dec-2023
• Refers: ASTM E456-13a(2022) - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM E456-13a(2022)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM D6708-21 - Standard Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purport to Measure the Same Property of a Material
• Effective Date: 01-May-2021
• Referred By: ASTM D7484-23a - Standard Test Method for Evaluation of Automotive Engine Oils for Valve-Train Wear Performance in Cummins ISB Medium-Duty Diesel Engine
• Effective Date: 01-Feb-2024
• Referred By: ASTM D6890-22 - Standard Test Method for Determination of Ignition Delay and Derived Cetane Number (DCN) of Diesel Fuel Oils by Combustion in a Constant Volume Chamber
• Effective Date: 01-Feb-2024
• Referred By: ASTM F715-07(2023) - Standard Test Methods for Coated Fabrics Used for Oil Spill Control and Storage
• Effective Date: 01-Feb-2024
• Referred By: ASTM D975-23a - Standard Specification for Diesel Fuel
• Effective Date: 01-Feb-2024
• Referred By: ASTM D7468-22 - Standard Test Method for Cummins ISM Test
• Effective Date: 01-Feb-2024
• Referred By: ASTM D4737-21 - Standard Test Method for Calculated Cetane Index by Four Variable Equation
• Effective Date: 01-Feb-2024
• Referred By: ASTM D1655-24 - Standard Specification for Aviation Turbine Fuels
• Effective Date: 01-Feb-2024
• Referred By: ASTM D1160-18 - Standard Test Method for Distillation of Petroleum Products at Reduced Pressure
• Effective Date: 01-Feb-2024

Overview

ASTM D613-24 - Standard Test Method for Cetane Number of Diesel Fuel Oil outlines the procedures for determining the cetane number, a crucial parameter indicating the ignition quality of diesel fuel oil. Developed and maintained by ASTM International, this standard is widely used by petroleum refiners, engine manufacturers, fuel marketers, and regulatory agencies for both product specification and quality assurance.

The cetane number is measured using a standardized single-cylinder, four-stroke, variable compression ratio, indirect-injection diesel engine. This method is essential for evaluating how well a diesel fuel ignites and operates in compression ignition engines, directly impacting engine performance, efficiency, and emissions.

Key Topics

• Cetane Number Definition: The cetane number reflects the ignition quality of diesel fuel-the higher the number, the easier the fuel ignites under compression.
• Test Method Principle: The test compares the ignition characteristics of a diesel sample with reference blends of known cetane number under controlled engine conditions.
• Engine Setup: Utilizes a single-cylinder, four-stroke, variable-compression engine with indirect injection, operating at a constant speed.
• Reference Fuels: Blends of hexadecane, heptamethylnonane, pentamethylheptane, and their mixtures are the standard reference materials for establishing cetane values.
• Applicable Fuel Range: Valid for cetane numbers ranging from 0 to 100, though practical testing typically spans 30 to 65.
• Sample Handling: Fuel samples should be protected from light and stored in appropriate containers to prevent changes in chemical composition that could affect test results.
• Unit Standards: While measurements are in SI units for operating conditions, certain engine parameters remain in inch-pound units due to legacy equipment constraints.
• Safety Considerations: Users are responsible for following safety, health, and environmental practices specific to the test method.

Applications

ASTM D613-24 is critical for various applications in the petroleum and automotive industries:

• Fuel Specification and Quality Control: Used by refiners and marketers as a primary specification test for diesel fuel properties.
• Engine Design and Performance Matching: Enables engine manufacturers to match fuels with appropriate engine designs, aiding in the development of efficient, low-emissions engines.
• Regulatory Compliance: Required for commercial transactions and to meet governmental and industry fuel standards globally.
• Research and Development: Assists in evaluating alternative fuels such as synthetics and vegetable oils, though relationships to engine performance for these fuels may require further study.
• Dispute Resolution: In cases where ratings using secondary reference fuels and primary reference fuels differ, results from primary reference fuels are considered definitive.

Related Standards

Several ASTM and industry standards complement ASTM D613-24 in the area of diesel fuel and fuel testing:

• ASTM D975: Specification for Diesel Fuel Oils
• ASTM D3703: Test Method for Hydroperoxide Number of Aviation Turbine Fuels, Gasoline, and Diesel Fuels
• ASTM D4057 / D4177: Practices for Manual and Automatic Sampling of Petroleum and Petroleum Products
• ASTM D2500: Test Method for Cloud Point of Petroleum Products and Liquid Fuels
• ASTM D6299: Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• ASTM E542: Practice for Gravimetric Calibration of Laboratory Volumetric Instruments

Practical Value

Implementing ASTM D613-24 ensures reliable, repeatable, and globally recognized measurement of diesel fuel cetane number. This not only supports quality assurance, regulatory compliance, and product development but also contributes to the production and use of cleaner, higher-performing diesel fuels worldwide.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D613 − 24
Standard Test Method for
Cetane Number of Diesel Fuel Oil
This standard is issued under the fixed designation D613; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* D2500 Test Method for Cloud Point of Petroleum Products
and Liquid Fuels
1.1 This test method covers the determination of the rating
D3703 Test Method for Hydroperoxide Number of Aviation
of diesel fuel oil in terms of an arbitrary scale of cetane
Turbine Fuels, Gasoline and Diesel Fuels
numbers using a standard single cylinder, four-stroke cycle,
D4057 Practice for Manual Sampling of Petroleum and
variable compression ratio, indirect injected diesel engine.
Petroleum Products
1.2 The cetane number scale covers the range from zero (0)
D4175 Terminology Relating to Petroleum Products, Liquid
to 100, but typical testing is in the range of 30 to 65 cetane
Fuels, and Lubricants
number.
D4177 Practice for Automatic Sampling of Petroleum and
Petroleum Products
1.3 The values for operating conditions are stated in SI units
and are to be regarded as the standard. The values given in D6299 Practice for Applying Statistical Quality Assurance
and Control Charting Techniques to Evaluate Analytical
parentheses are the historical inch-pound units for information
only. In addition, the engine measurements continue to be in Measurement System Performance
D6300 Practice for Determination of Precision and Bias
inch-pound units because of the extensive and expensive
tooling that has been created for these units. Data for Use in Test Methods for Petroleum Products,
Liquid Fuels, and Lubricants
1.4 This standard does not purport to address all of the
D6708 Practice for Statistical Assessment and Improvement
safety concerns, if any, associated with its use. It is the
of Expected Agreement Between Two Test Methods that
responsibility of the user of this standard to establish appro-
Purport to Measure the Same Property of a Material
priate safety, health, and environmental practices and deter-
E456 Terminology Relating to Quality and Statistics
mine the applicability of regulatory limitations prior to use.
E542 Practice for Gravimetric Calibration of Laboratory
For more specific warning statements, see Annex A1.
Volumetric Instruments
1.5 This international standard was developed in accor-
E832 Specification for Laboratory Filter Papers
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
3. Terminology
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
3.1 Definitions:
Barriers to Trade (TBT) Committee.
3.1.1 accepted reference value (ARV), n—a value that serves
as an agreed-upon reference for comparison, and which is
2. Referenced Documents
derived as: (1) a theoretical or established value, based on
scientific principles, or (2) an assigned or certified value, based
2.1 ASTM Standards:
on experimental work of some national or international
D975 Specification for Diesel Fuel
organization, or (3) a consensus or certified value, based on
D1193 Specification for Reagent Water
collaborative experimental work under the auspices of a
scientific or engineering group. E456
3.1.1.1 Discussion—In the context of this test method,
This test method is under the jurisdiction of ASTM Committee D02 on
accepted reference value is understood to apply to the cetane
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.01 on Combustion Characteristics.
number of specific reference materials determined empirically
Current edition approved Feb. 1, 2024. Published February 2024. Originally
under reproducibility conditions by the National Exchange
approved in 1941. Last previous edition approved in 2023 as D613 – 23. DOI:
Group or another recognized exchange testing organization.
10.1520/D0613-24.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
3.1.2 cetane number (CN), n—a measure of the ignition
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
performance of a diesel fuel oil obtained by comparing it to
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. reference fuels in a standardized engine test. D4175
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D613 − 24
3.1.2.1 Discussion—In the context of this test method, 3.2.5 injector opening pressure, n—the fuel pressure that
ignition performance is understood to mean the ignition delay overcomes the resistance of the spring which normally holds
of the fuel as determined in a standard test engine under the nozzle pintle closed, and thus forces the pintle to lift and
controlled conditions of fuel flow rate, injection timing, and release an injection spray from the nozzle.
compression ratio.
3.2.6 injector pickup, n—transducer to detect motion of the
3.1.3 compression ratio (CR), n—the ratio of the volume of injector pintle, thereby indicating the beginning of injection.
the combustion chamber including the precombustion chamber
3.2.7 primary reference fuels (PRF), n—hexadecane
with the piston at bottom dead center to the comparable volume
(HXD), heptamethylnonane (HMN), pentamethylheptane
with the piston at top dead center.
(PMH), and volumetrically proportioned binary mixtures of
HXD with either HMN or PMH, which now define the cetane
3.1.4 ignition delay, n—that period of time, expressed in
number scale.
degrees of crank angle rotation, between the start of fuel
3.2.7.1 Discussion—In the context of this test method, the
injection and the start of combustion.
arbitrary cetane number scale was originally defined as the
3.1.5 injection timing (injection advance), n—that time in
volume percent of hexadecane in a blend with
the combustion cycle, measured in degrees of crank angle, at
1-methylnaphthalene (AMN) where HXD had an assigned
which fuel injection into the combustion chamber is initiated.
value of 100 and AMN an assigned value of zero (0). A change
3.1.6 quality control (QC) sample, n—for use in quality
from 1-methylnaphthalene to heptamethylnonane as the low
assurance programs to determine and monitor the precision and
cetane ingredient was made in 1962 to utilize a material of
stability of a measurement system, a stable and homogeneous
better storage stability and availability. Heptamethylnonane
material having physical or chemical properties, or both,
was determined to have a cetane number accepted reference
similar to those of typical samples tested by the analytical
value (CN ) of 15 based on engine testing by the ASTM
ARV
measurement system. The material is properly stored to ensure
Diesel National Exchange Group. A change to add a second
sample integrity, and is available in sufficient quantity for
low cetane ingredient, pentamethylheptane (PMH), as an
repeated, long term testing. D6299
alternative to HMN was made in 2018 to utilize a material of
higher purity and better availability. Pentamethylheptane was
3.1.7 repeatability conditions, n—conditions where inde-
determined to have a cetane number accepted reference value
pendent test results are obtained with the same method on
(CN ) of 16.3 based on engine testing by the ASTM Diesel
identical test items in the same laboratory by the same operator
ARV
National Exchange Group.
using the same equipment within short intervals of time. E456
3.2.7.2 Discussion—In the context of this test method, the
3.1.8 reproducibility conditions, n—conditions where test
Diesel National Exchange Group of Subcommittee D02.01 is
results are obtained with the same method on identical test
composed of petroleum industry, governmental, and indepen-
items in different laboratories with different operators using
dent laboratories. It conducts regular monthly exchange sample
different equipment. E456
analyses to generate precision data for this engine test standard
3.2 Definitions of Terms Specific to This Standard:
and determines the CN of reference materials used by all
ARV
3.2.1 cetane meter, n—the electronic apparatus which dis-
laboratories.
plays injection advance and ignition delay derived from input
3.2.8 reference pickups, n—transducers or optical sensors
pulses of multiple transducers (pickups).
mounted over the flywheel of the engine, triggered by a
3.2.1.1 Discussion—In the context of this test method, three
flywheel indicator, used to establish a top-dead-center (tdc)
generations of apparatus have been approved for use as cetane
reference and a time base for calibration of the cetane meter.
meters. These are (year of introduction is parenthesis) the Mark
3.2.9 repeatability conditions NEG, n—replicate testing
II Ignition Delay Meter (1974), the Dual Digital Cetane Meter
conditions employed by the National Exchange Group in
(1990), and the XCP Cetane Panel (2014).
which a single operator tests two specimens taken from a single
3.2.2 check fuels, n—for quality control testing, a diesel fuel
sample container with at least one other sample being tested
oil of selected characteristics having a cetane number accepted
between the two specimens.
reference value determined in accordance with Practice D6299
3.2.10 secondary reference fuels (SRF), n—volumetrically
requirements for check standards derived from interlaboratory
proportioned blends of two selected, numbered, and paired
exchange programs.
hydrocarbon mixtures designated T Fuel (high cetane) and U
Fuel (low cetane) that have been rated by the ASTM Diesel
3.2.2.1 Discussion—When evaluating the interlaboratory
National Exchange Group using primary reference fuels to
data to establish the ARV, outlier identification and rejection
criteria shall be applied at the 5 % significance level prior to
computing the average result.
Supporting data have been filed at ASTM International Headquarters and may
3.2.3 combustion pickup, n—pressure transducer exposed to
be obtained by requesting Research Report RR:D02-1092. Contact ASTM Customer
cylinder pressure to indicate the start of combustion.
Service at [e-mail].
Supporting data have been filed at ASTM International Headquarters and may
3.2.4 handwheel reading, n—an arbitrary numerical value,
be obtained by requesting Research Report RR:D02-1885. Contact ASTM Customer
related to compression ratio, obtained from a micrometer scale
Service at [e-mail].
that indicates the position of the variable compression plug in
Bylaws governing ASTM Subcommittee D02.01 on Combustion Characteris-
the precombustion chamber of the engine. tics are available from the subcommittee or from ASTM International.
D613 − 24
determine a cetane number accepted reference value for each 5.4 This test method may be used for unconventional fuels
individually and for various combinations of the two. such as synthetics, vegetable oils, and the like. However, the
relationship to the performance of such materials in full scale
3.3 Abbreviations:
engines is not completely understood.
3.3.1 ABDC—after bottom dead center
3.3.2 AMN—1-methylnaphthalene
6. Interferences
3.3.3 ARV—accepted reference value
6.1 (Warning—Avoid exposure of sample fuels and refer-
ence fuels to sunlight or fluorescent lamp UV emissions to
3.3.4 ATDC—after top dead center
minimize induced chemical reactions that can affect cetane
3.3.5 BBDC—before bottom dead center
number ratings.)
3.3.6 BTDC—before top dead center
6.1.1 Exposure of these fuels to UV wavelengths shorter
3.3.7 CN—cetane number
than 550 nm for a short period of time may significantly affect
cetane number ratings.
3.3.8 CR—compression ratio
6.2 Certain gases and fumes present in the area where the
3.3.9 DD—Dual Digital Cetane Meter
cetane test engine is located may have a measurable effect on
3.3.10 HMN—heptamethylnonane
the cetane number test result.
3.3.11 HRF—high reference fuel
6.3 This test method is not suitable for rating diesel fuel oils
3.3.12 HW—hand wheel
with fluid properties that interfere with unimpeded gravity flow
3.3.13 HXD—hexadecane
of fuel to the fuel pump or delivery through the injector nozzle.
3.3.14 IAT—intake air temperature
7. Apparatus
3.3.15 LRF—low reference fuel
7,8
7.1 Engine Equipment —This test method uses a single
3.3.16 NEG—National Exchange Group
cylinder engine which consists of a standard crankcase with
3.3.17 PMH—pentamethylheptane
fuel pump assembly, a cylinder with separate head assembly of
the precombustion type, thermal syphon recirculating jacket
3.3.18 PRF—primary reference fuels
coolant system, multiple fuel tank system with selector
3.3.19 r —repeatablility conditions NEG
NEG
valving, injector assembly with specific injector nozzle, elec-
3.3.20 SRF—secondary reference fuels
trical controls, and a suitable exhaust pipe. The engine is belt
3.3.21 TDC—top dead center
connected to a special electric power-absorption motor which
acts as a motor driver to start the engine and as a means to
3.3.22 UV—ultraviolet
absorb power at constant speed when combustion is occurring
3.3.23 XCP—XCP Cetane Panel
(engine firing). See Fig. 1 and Table 1.
7,8
7.2 Instrumentation —This test method uses electronic
4. Summary of Test Method
apparatus to measure injection and ignition delay timing as
4.1 The cetane number of a diesel fuel oil is determined by
well as conventional thermometry, gauges, and general purpose
comparing its combustion characteristics in a test engine with
meters.
those for blends of reference fuels of known cetane number
7.2.1 Cetane Meter—Use of an approved cetane meter is
under standard operating conditions. This is accomplished
mandatory; only the XCP Cetane Panel or the Dual Digital
using the bracketing handwheel procedure which varies the
Cetane Meter or the Mark II Ignition Delay Meter shall be used
compression ratio (handwheel reading) for the sample and each
for this test method.
of two bracketing reference fuels to obtain a specific ignition
7.3 Reference Fuel Dispensing Equipment—This test
delay permitting interpolation of cetane number in terms of
method requires repeated blending of two reference fuel
handwheel reading.
materials in volumetric proportions on an as-needed basis.
Measurement shall be performed accurately because rating
5. Significance and Use
error is proportional to blending error.
5.1 The cetane number provides a measure of the ignition
7.3.1 Volumetric Blending of Reference Fuels—Volumetric
characteristics of diesel fuel oil in compression ignition en-
blending has historically been employed to prepare the re-
gines.
quired blends of reference fuels. For volumetric blending, a set
5.2 This test method is used by engine manufacturers,
petroleum refiners and marketers, and in commerce as a
Supporting data have been filed at ASTM International Headquarters and may
primary specification measurement related to matching of fuels
be obtained by requesting Research Report RR:D02-1502. Contact ASTM Customer
Service at [e-mail].
and engines.
The sole source of supply of the engine equipment and instrumentation known
5.3 Cetane number is determined at constant speed in a
to the committee at this time is CFR Engines, Inc., N8 W22577 Johnson Dr.,
Pewaukee, WI 53186. CFR Engines, Inc. also has authorized sales and service
precombustion chamber type compression ignition test engine.
organizations in selected geographical areas.
The relationship of test engine performance to full scale,
If you are aware of alternative suppliers, please provide this information to
variable speed, variable load engines is not completely under-
ASTM International Headquarters. Your comments will receive careful consider-
stood. ation at a meeting of the responsible technical committee, which you may attend.
D613 − 24
A—Fuel Tanks
B—Air Heater Housing
C—Air Intake Silencer
D—Fuel Flow Rate Buret
E—Combustion Pickup
F—Safety Guard
G—Variable Compression Plug Handwheel
H—V.C.P. Locking Handwheel
I—Flywheel Pickups
J—Oil Filler Cap
K—Injection Pump Safety Shut-Off Solenoid
L—Injector Assembly
M—Fuel Injection Pump
N—Fuel Selector-Valve
O—Oil Filter
P—Crankcase Oil Heater Control
Q—Air Heater Switch
R—Engine Start-Stop Switch
S—Instrument Panel
T—Intake Air Temperature Controller
U—Dual Digital Cetane Meter
FIG. 1 Cetane Method Test Engine Assembly
of two burets or accurate volumetric ware shall be used and the 7.3.1.5 See Appendix X1, Volumetric Reference Fuel
desired batch quantity shall be collected in an appropriate Blending Apparatus and Procedures, for typical dispensing
container and thoroughly mixed before being introduced to the system information.
engine fuel system. 7.3.2 Gravimetric Blending of Reference Fuels—Use of
blending systems that allow preparation of the volumetrically
7.3.1.1 Calibrated burets or volumetric ware having a ca-
defined blends by gravimetric (mass) measurements based on
pacity of 400 mL or 500 mL and a maximum volumetric
the density of the individual components is also permitted,
tolerance of 60.2 % shall be used. Calibration shall be verified
provided the system meets the requirement for maximum
in accordance with Practice E542.
0.2 % blending tolerance limits.
7.3.1.2 Calibrated burets shall be outfitted with a dispensing
7.3.2.1 Calculate the mass equivalents of the
valve and delivery tip to accurately control dispensed volume.
volumetrically-defined blend components from the densities of
The delivery tip shall be of such size and design that shutoff tip
the individual components at 15.56 °C (60 °F).
discharge does not exceed 0.5 mL.
7.3.1.3 The rate of delivery from the dispensing system
7.4 Auxiliary Apparatus:
shall not exceed 500 mL per 60 s.
7.4.1 Injector Nozzle Tester—The injector nozzle assembly
7.3.1.4 The set of burets for the reference fuels shall be shall be checked whenever the injector nozzle is removed and
installed in such a manner and be supplied with fluids such that reassembled to ensure the initial pressure at which fuel is
all components of each batch or blend are dispensed at the discharged from the nozzle is properly set. It is also important
same temperature. to inspect the type of spray pattern. Commercial injector nozzle
D613 − 24
TABLE 1 General Engine Characteristics and Information
8.3 Primary Reference Fuels—(Warning—Primary Refer-
Item Description ence Fuel—Combustible. Vapor harmful. See Annex A1.)
Crankcase Model CFR-48 (Preferred), High or Low Speed 8.3.1 Hexadecane—Hexadecane meeting the specifications
Models (Optional)
in Table 2 shall be used as the designated 100 cetane number
Cylinder Type Single bore cast iron with integral coolant
component.
jacket
Cylinder Head Type Cast Iron with turbulence precombustion
8.3.2 Heptamethylnonane (2,2,4,4,6,8,8-heptamethyl-
chamber, variable compression plug
nonane)—Heptamethylnonane meeting the specifications in
passage, integral coolant passages, and
Table 2 may be used as the low cetane number component that
in-head valve assembly
Compression Ratio Adjustable 8:1 to 36:1 by external handwheel
is blended with hexadecane. In binary volumetric blends with
assembly
HXD, HMN has a cetane number ARV of 15.
Cylinder Bore (Diameter), in. 3.250 (Standard), Reboring to 0.010, 0.020,
8.3.2.1 The cetane number accepted reference value
0.030 over is acceptable
Stroke, in. 4.50
(CN ) for any mixture of HXD and HMN is given by the
ARV
Displacement, cu in. 37.33
relationship:
Valve Mechanism In-head with enclosure
Intake and Exhaust Valves Stellite faced, plain type without shroud
CN 5 volume-% HXD + 0.15 volume-% HMN (1)
~ !
ARV
Piston Cast iron, flat top
Piston Rings:
8.3.3 Pentamethylheptane (2,2,4,6,6-pentamethyl-
Compression Type 4, Ferrous, straight sided (Top may be chrome
heptane)—Pentamethylheptane meeting the specifications in
plated—Optional)
Table 2 may be used as the low cetane number component that
Oil Control 1, Cast iron, one piece, slotted (Type 85)
Camshaft Over lap, degree 5
is blended with hexadecane. In binary volumetric blends with
Fuel System Injection pump with variable timing device and
HXD, PMH has a cetane number ARV of 16.3.
injector
Injector Holder with bypass pressure release valve 8.3.3.1 The cetane number accepted reference value
Spray Nozzle Closed, differential-needle, hydraulically-
(CN ) for any mixture of HXD and PMH is given by the
ARV
operated, pintle type
relationship:
Weight of Engine Approximately 400 kg (880 lb)
Weight of Complete Test Unit Approximately 1250 kg (2750 lb)
CN 5 volume-% HXD+ 0.163~volume-% PMH! (2)
ARV
8.3.4 Store and use primary reference fuels at temperatures
of 20 °C or higher to avoid solidification of HXD, which has a
testers which include a lever-operated pressure cylinder, fuel
melting point of 18 °C.
reservoir and pressure gauge are available from several sources
8.4 Secondary Reference Fuels—(Warning—Secondary
as common diesel engine maintenance equipment.
reference fuel—combustible. Vapor harmful. See Annex A1.)
7.4.2 Special Maintenance Tools—A number of specialty
8.4.1 T Fuel—Diesel fuel meeting the specifications in
tools and measuring instruments should be utilized for easy,
Table 3.
convenient and effective maintenance of the engine and testing
8.4.2 U Fuel—Diesel fuel meeting the specifications in
equipment. Lists and descriptions of these tools and instru-
Table 3
ments are available from the manufacturers of the engine
8.4.3 Storage and use of T Fuel and U Fuel should be at
equipment and those organizations offering engineering and
temperatures above 0 °C (32 °F) to avoid potential
service support for this test method.
solidification, particularly of T Fuel. Before a container that
has been stored at low temperature is placed in service, it
8. Reagents and Reference Materials
should be warmed to a temperature of at least 14 °C (26 °F)
8.1 Cylinder Jacket Coolant—Water shall be used in the
above its Cloud Point. (See Test Method D2500.) It should be
cylinder jacket for laboratory locations where the resultant
held at this temperature for a period of at least 30 min and then
boiling temperature shall be 100 °C 6 2 °C (212 °F 6 3 °F).
the container should be thoroughly remixed.
Water with commercial glycol-based antifreeze added in suf-
8.4.4 As secondary reference fuel blends are rated in num-
ficient quantity to meet the boiling temperature requirement
bered pairs, they are not interchangeable with reference fuels
shall be used when laboratory altitude dictates. A commercial
from other numbered pairs and shall not be mixed.
multifunctional water treatment material should be used in the
8.5 Check Fuels —Diesel fuel oils having properties other
coolant to minimize corrosion and mineral scale that can alter
than CN that are typical of Specification D975 grade No. 2-D
heat transfer and rating results.
S15. (Warning—Check Fuel—Combustible. Vapor harmful.
8.1.1 Water shall be understood to mean reagent water
See Annex A1.)
conforming to Type IV of Specification D1193.
8.5.1 Low Cetane Check Fuel, meeting the specifications in
8.2 Engine Crankcase Lubricating Oil—An SAE 30 viscos-
Table 3.
ity grade oil meeting current API service classification or
8.5.2 High Cetane Check Fuel, meeting the specifications in
compatible previous API service classifications shall be used. It
Table 3.
shall contain a detergent additive and have a kinematic
8.6 In the event of a dispute between ratings obtained using
viscosity of 9.3 cSt to 12.5 cSt (mm per s) at 100 °C (212 °F)
secondary reference fuels and ratings obtained using primary
and a viscosity index of not less than 85. Oils containing
viscosity index improvers shall not be used. Multigraded oils
shall not be used. (Warning—Lubricating oil is combustible,
Blend Tables for batches of T Fuel and U Fuel can be obtained from the fuel
and its vapor is harmful. See Annex A1.) supplier.
D613 − 24
TABLE 2 Specifications for Primary Reference Fuels
Property Hexadecane Heptamethylnonane Pentamethylheptane Test Method
Purity, mass %, minimum 99.0 98.0 99.5 Gas chromatography
Hydroperoxide number, mg/kg as O, maximum 5.0 5.0 5.0 ASTM D3703
TABLE 3 Specifications for Secondary Reference Fuels and Check Fuels
Secondary Reference Check Fuels
Fuels
Property T-Fuel U-Fuel Low High Test Method
Cetane number ARV, minimum 73 19 38. 50. ASTM D613
Cetane number ARV, maximum 76 22 42. 55. ASTM D613
Hydroperoxide number, mg/kg as O, maximum 5.0 5.0 5.0 5.0 ASTM D3703
reference fuels, the ratings obtained using primary reference 10.2.1 Engine Speed—900 r ⁄min 6 9 r ⁄min, when the en-
fuels shall be considered the referee test result. gine is operating with combustion with a maximum variation
of 9 r ⁄min occurring during a rating. Engine speed when
9. Sampling combustion is occurring shall not be more than 3 r ⁄min greater
than that for motoring without combustion.
9.1 Collect samples in accordance with Practice D4057 or
10.2.2 Valve Timing—The engine uses a four-stroke cycle
D4177.
with two crankshaft revolutions for each complete combustion
9.1.1 Protection from Light—Collect and store sample fuels
cycle. The two critical valve events are those that occur near
in an opaque container such as a dark brown glass bottle, metal
TDC; intake valve opening and exhaust valve closing.
can, or a minimally reactive plastic container to minimize
10.2.2.1 Intake valve opening shall occur 10.0° 6 2.5°
exposure to UV emissions from sources such as sunlight or
ATDC with closing at 34° ABDC on one revolution of the
fluorescent lamps.
crankshaft and flywheel.
9.2 Fuel Temperature—Samples shall be brought to room
10.2.2.2 Exhaust valve opening shall occur 40° BBDC on
temperature typically 18 °C to 32 °C (65 °F to 90 °F) before
the second revolution of the crankshaft or flywheel with
engine testing.
closing at 15.0° 6 2.5° ATDC on the next revolution of the
9.2.1 The fuel temperature should be raised at least 14 °C
crankshaft or flywheel.
(26 °F) above the fuel’s cloud point. The fuel sample should be
10.2.3 Valve Lift—Intake and exhaust cam lobe contours,
homogeneous before engine testing or filtration (9.3).
while different in shape, shall have a contour rise of 6.223 mm
NOTE 1—Give consideration to the fuel’s composition related to sample to 6.350 mm (0.245 in. to 0.250 in.) from the base circle to the
temperature to avoid the loss of any lower boiling components that may
top of the lobe so that the resulting valve lift shall be 6.045 mm
affect the cetane rating.
6 0.05 mm (0.238 in. 6 0.002 in.).
9.3 Filtration—Samples may be filtered through a Type I,
10.2.4 Fuel Pump Timing—Closure of the pump plunger
Class A filter paper at room temperature and pressure before
inlet port shall occur at a flywheel crank angle between 300°
engine testing. See Specification E832.
and 306° on the engine compression stroke when the fuel
flow-rate-micrometer is set to a typical operating position and
10. Basic Engine and Instrument Settings and Standard
the variable timing device lever is at full advance (nearest to
Operating Conditions
operator).
10.2.5 Fuel Pump Inlet Pressure—A minimum fuel head
10.1 Installation of Engine Equipment and
established by assembly of the fuel tanks (storage reservoirs)
Instrumentation—Installation of the engine and instrumenta-
and flow rate measuring buret so that the discharge from them
tion requires placement of the engine on a suitable foundation
is 635 mm 6 25 mm (25 in. 6 1 in.) above the centerline of the
and hookup of all utilities. Engineering and technical support
fuel injection pump inlet.
for this function is required, and the user shall be responsible
to comply with all local and national codes and installation
10.3 Assembly Settings and Operating Conditions:
requirements.
10.3.1 Direction of Engine Rotation—Clockwise rotation of
10.1.1 Proper operation of the test engine requires assembly
the crankshaft when observed from the front of the engine.
of a number of engine components and adjustment of a series
10.3.2 Injection Timing—13.0° BTDC, for the sample and
of engine variables to prescribed specifications. Some of these
reference fuels.
settings are established by component specifications, others are
10.3.3 Injector Nozzle Opening Pressure—10.3 MPa 6
established at the time of engine assembly or after overhaul,
0.34 MPa (1500 psi 6 50 psi).
and still others are engine running conditions that must be
10.3.4 Injection Flow Rate—13.0 mL ⁄min 6 0.2 mL ⁄min
observed or determined by operator adjustment, or both, during
(60 s 6 1 s per 13.0 mL).
the testing process.
10.3.5 Injector Coolant Passage Temperature—38 °C 6
10.2 Conditions Based on Component Specifications: 3 °C (100 °F 6 5 °F).
D613 − 24
10.3.6 Valve Clearances:
10.3.6.1 Engine Running and Hot—The clearance for both
intake and exhaust valves shall be set to 0.20 mm 6 0.025 mm
(0.008 in. 6 0.001 in.), measured under standard operating
conditions with the engine running at equilibrium conditions
on a typical diesel fuel oil.
10.3.7 Oil Pressure—172 kPa to 207 kPa (25 psi to 30 psi).
10.3.8 Oil Temperature—57 °C 6 8 °C (135 °F 6 15 °F).
10.3.9 Cylinder Jacket Coolant Temperature—100 °C 6
FIG. 2 Typical Injector Spray Pattern
2 °C (212 °F 6 3 °F).
10.3.10 Intake Air Temperature—66 °C 6 0.5 °C (150 °F 6
suspended from one belt halfway between the flywheel and
1 °F).
motor pulley shall depress the belt approximately 12.5 mm
10.3.11 Basic Ignition Delay—13.0° for the sample and
(0.5 in.).
reference fuels.
10.3.19 Setting Injector Nozzle Assembly Pressure and
10.3.12 Cylinder Jacket Coolant Level:
Spray Pattern Check—(Warning—Personnel shall avoid con-
10.3.12.1 Engine Stopped and Cold—Treated water/coolant
tact with the spray pattern from injector nozzles because of the
added to the cooling condenser—cylinder jacket to a level just
high pressure which can penetrate the skin. Spray pattern
observable in the bottom of the condenser sight glass will
performance checks shall be made in a hood or where adequate
typically provide the controlling engine running and hot
ventilation insures that inhalation of the vapors is avoided.)
operating level.
10.3.19.1 Injector Opening or Release Pressure—The pres-
10.3.12.2 Engine Running and Hot—Coolant level in the
sure adjusting screw is adjustable and shall be set to release
condenser sight glass shall be within 61 cm (0.4 in.) of the
fuel at a pressure of 10.3 MPa 6 0.34 MPa (1500 psi 6
LEVEL HOT mark on the coolant condenser.
50 psi). Check this setting using an injector nozzle bench tester,
10.3.13 Engine Crankcase Lubricating Oil Level:
each time the nozzle is reassembled and after cleaning. Use of
10.3.13.1 Engine Stopped and Cold—Oil added to the
a commercial injector nozzle bench tester is recommended. See
crankcase so that the level is near the top of the sight glass will
Annex A2 for procedural detail.
typically provide the controlling engine running and hot
10.3.19.2 Injector Spray Pattern—Check the spray pattern
operating level.
for symmetry and characteristic by inspection of the impres-
10.3.13.2 Engine Running and Hot—Oil level shall be
sion of a single injection made on a piece of filter paper or
approximately mid-position in the crankcase oil sight glass.
other slightly absorbent material placed at a distance of
10.3.14 Crankcase Internal Pressure—As mentioned by a
approximately 7.6 cm (3 in.) from the nozzle. A typical spray
gauge or manometer connected to an opening to the inside of
pattern is illustrated in Fig. 2.
the crankcase through a snubber orifice to minimize pulsations,
10.3.20 Indexing Handwheel Reading—Handwheel read-
the pressure shall be less than zero (a vacuum) and typically
ings are a simple and convenient indication of engine com-
from 25 mm to 150 mm (1 in. to 6 in.) of water less than
pression ratio which is a critical variable in the cetane method
atmospheric pressure. Vacuum shall not exceed 255 mm
of test. The actual compression ratio is not important but an
(10 in.) of water.
indication of compression ratio which relates to cetane number
10.3.15 Exhaust Back Pressure—As measured by a gauge or
is a useful guide for selecting reference fuels to bracket the
manometer connected to an opening in the exhaust surge tank
sample of diesel fuel oil. The following procedure shall be used
or main exhaust stack through a snubber orifice to minimize
to index the handwheel reading when the engine is new or
pulsations, the static pressure should be as low as possible, but
anytime the matched handwheel assembly/cylinder head com-
shall not create a vacuum nor exceed 254 mm (10 in.) of water
bination is interchanged or mechanically reassembled.
differential in excess of atmospheric pressure.
10.3.20.1 Handwheel Micrometer Drum and Scale Setting—
10.3.16 Exhaust and Crankcase Breather System
Refer to Table 4 to select the appropriate handwheel reading to
Resonance—The exhaust and crankcase breather piping sys-
be used in aligning the drum and scale.
tems shall have internal volumes and be of such length that gas
10.3.20.2 Basic Setting of Variable Compression Plug—
resonance does not result.
Position the variable compression plug so that the flat surface
10.3.17 Piston Over-Travel—Assembly of the cylinder to is just visible and exactly in line with the edge of the threads
the crankcase shall result in the piston protruding above the top
of the combustion pickup hole, as verified with a straightedge.
of the cylinder surface 0.381 mm 6 0.025 mm (0.015 in. 6 10.3.20.3 Setting Handwheel Reading—Tighten the small
0.001 in.) when the piston is at top-dead-center. Proper posi-
locking handwheel snugly by hand to ensure that the variable
tioning is accomplished through the use of plastic or paper compression plug is held in place in the bore. Loosen the
gaskets, available in several thicknesses and selected by trial
locknut of the large handwheel and remove the locking
and error for assembly between the cylinder and crankcase L-shaped key. Turn the large handwheel so that the edge of the
deck.
drum is in alignment with the 1.000 graduation on the
10.3.18 Belt Tension—The belts connecting the flywheel to horizontal scale. Reinstall the L-shaped key in the nearest
the absorption motor shall be tightened, after an initial break- keyway slot of the large handwheel with the shorter leg in the
in, so that with the engine stopped, a 2.25 kg (5 lb) weight handwheel. A slight shifting of the handwheel to achieve slot
D613 − 24
TABLE 4 Handwheel Setting for Various Cylinder Bore Diameters
(Warning—The pump and timing gear box oil sumps are not
Cylinder Diameter, in. Handwheel Reading connected to each other and the lubrication for the two is
3.250 (Standard Bore) 1.000 independent.)
3.260 (Rebored 0.010 in. Oversize) 0.993
10.3.24 Instrumentation—Positioning of the reference pick-
3.270 (Rebored 0.020 in. Oversize) 0.986
ups and injector pickup is important to ensure that timing of the
3.280 (Rebored 0.030 in. Oversize) 0.978
injection and ignition delay functions is uniform and correct.
10.3.24.1 Setting Reference Pickups—These two pickups
are identical and interchangeable. They are installed in a
lineup will not affect the indexing. Tighten the locknut hand-
bracket positioned over the flywheel so that they clear the
tight to hold the key in place. Remove the locating screw from
flywheel indicator which triggers them.
the drum and rotate the drum so that the zero graduation mark
10.3.24.2 Position each pickup in the bracket so that it is
is in line with the selected reading from Table 4. Locate the
properly referenced to the flywheel indicator in accordance
screw hole in the drum which lines up with the handwheel hub
with the instructions supplied with the specific pickup.
hole and reinstall the locating screw. Wrench tighten the large
10.3.24.3 Measurement of pickup to flywheel indicator
handwheel locknut and recheck that the variable compression
clearance, if required, shall be made using a nonmagnetic
plug is properly positioned and the handwheel reading is in
feeler gauge.
accordance with the value in Table 4.
10.3.25 Setting Injector Pickup Gap—Set the air gap to
10.3.21 Basic Compression Pressure—At a handwheel
typically 1 mm (0.040 in.) with the engine stopped.
reading of 1.000, the compression pressure for an engine
10.3.25.1 Individual pickups may require more or less air
operated at standard barometric pressure of 760 mm Hg.
gap to obtain steady meter operation when the engine is
(29.92 in. Hg) shall be 3275 kPa 6 138 kPa (475 psi 6 20 psi)
ultimately running but too little gap can cause the ignition
when read as quickly as possible after shutdown of the engine
delay angle display to drive off scale. Follow instructions
which had been at standard operating conditions. If the
supplied with the specific pickup to optimize the gap setting.
condition is not within limits, recheck the basic handwheel
setting and, if necessary, perform mechanical maintenance. See
11. Engine Qualification
Annex A2 for the Checking Compression Pressure procedure.
11.1 Engine Compliance—It is assumed that the engine has
10.3.21.1 For engines operated at other than standard baro-
been commissioned and that all settings and operating vari-
metric pressure, the compression pressure will typically be in
ables are at equilibrium and in compliance with basic engine
proportion to the ratio of the local barometric pressure divided
and instrument settings and standard operating conditions.
by standard barometric pressure. As an example, an engine
11.1.1 Engine warm-up requires typically 1 h to ensure that
located where the barometric pressure is 710 mm Hg would be
all critical variables are stable.
expected to have a compression pressure of approximately
11.2 Fit-for-use Qualification:
3060 kPa 6 138 kPa (444 psi 6 20 psi). (Warning—In addi-
11.2.1 Every sample fuel CN determination shall be per-
tion to other precautions, compression pressure testing using a
formed using an engine that has been qualified as fit-for-use by
compression pressure gauge should be completed in as short a
rating a Check Fuel.
period of time as possible to avoid the possibility of combus-
11.2.2 Qualify the engine using the Low or High Cetane
tion occurrence due to the presence of any small amount of oil
Check Fuel in accordance with the following conditions:
in the gauge or combustion chamber.)
11.2.2.1 At least once during each 12 h period of rating.
Compression Pressure (3)
~LocalBaro.,mmHg!
11.2.2.2 After an engine has been shut down for more than
2 h.
5 3275 kPa × Local Baro./Standard Baro.
11.2.3 Test check fuels using the procedure described be-
Example: Compression Pressure low:
710mmHg
11.2.4 Engine performance is judged satisfactory if the
5 3275 × 710/760 5 3060 kPa
cetane rating obtained on the Check Fuel is within the Check
Fuel tolerance limits calculated as follows:
10.3.22 Fuel Pump Lubricating Oil Level—With the engine
stopped, sufficient engine crankcase lubricating oil shall be
Tolerance Limits 5 CN 61.5 × S (4)
ARV ARV
added to the pump sump so that the level is at the mark on the
where:
dip stick. (Warning—As a result of engine operation, espe-
CN = the cetane number accepted reference value of the
ARV
cially when the pump barrel/plunger assembly begins to wear,
Check Fuel,
the level in the sump will increase due to fuel dilution as
1.5 = a selected tolerance limit factor (K) for normal
observed through a clear plastic side plate on the pump
distributions,
housing. When the level rises appreciably, the sump should be
S = the standard deviation of the Check Fuel data used
ARV
drained and a fresh charge of oil added.)
to determine CN .
ARV
10.3.23 Fuel Pump Timing Gear Box Oil Level—With the
engine stopped, unplug the openings on the top and at the 11.2.4.1 In the context of this test method, the statistical
mid-height of either side of the gear box. Add sufficient engine tolerance limit factor (K), based on a sample size (n), permits
crankcase lubricating oil through the top hole to cause the level an estimation of the percentage of engines that would be able
to rise to the height of the side opening. Replug both openings. to rate the Check Fuel within the calculated tolerance limits.
D613 − 24
TABLE 5 Reference Fuel Blends for Samples with Cetane
Based on a data set of 17 to 20 ratings used to determine the
Number >T Fuel
Check Fuel CN , and a value of K = 1.5, it is estimated that
ARV
Blend T Fuel, vol- % HXD, vol- %
in the long run, in 19 cases out of 20, at least 70 % of the
1 100 0
engines would rate the Check Fuel within the calculated
2 75 25
tolerance limits.
3 50 50
4 25 75
11.2.5 If the results are outside this tolerance range, the
5 0 100
engine is not acceptable for rating samples and a check of all
operating conditions is warranted followed by mechanical
maintenance which may require critical parts replacement. The
12.1.5 Ignition Delay—Adjust the handwheel to change the
injector nozzle can be a very critical factor and this should be
compression ratio and obtain a 13.0° 6 0.2° ignition delay
the first item checked or replaced to achieve rating compliance.
reading. Make the final handwheel adjustment in the clockwise
11.3 Quality Control (QC Testing)—Users should conduct a
direction (viewed from front of engine) to eliminate backlash
regular statistical quality control program to monitor the engine
in the handwheel mechanism and a potential error.
is in statistical control over time.
12.1.6 Equilibration—It is important to achieve stable in-
11.3.1 This test method suggests validating the engine
jection advance and ignition delay readings.
system by the rating of a QC sample.
12.1.6.1 Stable readings should typically occur within 5 min
11.3.2 The QC sample is a diesel fuel oil having a cetane
to 10 min.
number within the normal operating range of the engine.
12.1.6.2 The time used for the sample and each of the
11.3.2.1 Users are encouraged to assess the normal operat-
reference fuels should be consistent and shall not be less than
ing range and determine if multiple QC samples are required
3 min.
based upon the cetane number range of the samples typically
12.1.7 Handwheel Reading—Observe and record the hand-
rated.
wheel reading as the representative indication of the combus-
11.3.3 Use appropriate control charts or other statistically
tion characteristic for this fuel sample.
equivalent techniques to assess the cetane number value.
NOTE 2—Experience has shown that if handwheel readings are taken
Control charts often used for this application are Individuals
when the fuel tank levels of samples and reference fuels are similar, more
and Moving Range (I/MR).
consistent results are obtained.
11.3.4 Specifics for control chart set up and interpretation
12.1.8 Reference Fuel No. 1—Select a reference fuel blend
can be found in Practice D6299.
close to the estimated cetane number of the sample.
11.3.5 If an out-of-statistical control situation is detected,
NOTE 3—The handwheel reading versus cetane number relationship
examine the engine system operation for assignable cause(s).
based on this procedure is engine and overhaul dependent but it can be
established for each engine as testing experience is gained after each
12. Procedure
overhaul. A plot or table of handwheel readings provides a simple guide
to selection of the reference fuel.
12.1 Bracketing by Handwheel Procedure—See Appendix
X2 for the details of engine operation and the adjustment of
12.1.8.1 If primary reference fuels are being used for the
each of the individual operating variables. rating, select a blend of HXD with either HMN or PMH having
12.1.1 Check that all engine operating conditions are in
a cetane number close to the estimated cetane number of the
compliance and equilibrated with the engine running on a sample.
typical diesel fuel oil. (Warning—In addition to other
12.1.8.2 If secondary reference fuels are being used for the
precautions, always position the Mark II Ignition Delay Meter rating and the cetane number of the sam
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D613 − 23 D613 − 24
Standard Test Method for
Cetane Number of Diesel Fuel Oil
This standard is issued under the fixed designation D613; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
1.1 This test method covers the determination of the rating of diesel fuel oil in terms of an arbitrary scale of cetane numbers using
a standard single cylinder, four-stroke cycle, variable compression ratio, indirect injected diesel engine.
1.2 The cetane number scale covers the range from zero (0) to 100, but typical testing is in the range of 30 to 65 cetane number.
1.3 The values for operating conditions are stated in SI units and are to be regarded as the standard. The values given in
parentheses are the historical inch-pound units for information only. In addition, the engine measurements continue to be in
inch-pound units because of the extensive and expensive tooling that has been created for these units.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use. For more specific warning statements, see Annex A1.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D975 Specification for Diesel Fuel
D1193 Specification for Reagent Water
D2500 Test Method for Cloud Point of Petroleum Products and Liquid Fuels
D3703 Test Method for Hydroperoxide Number of Aviation Turbine Fuels, Gasoline and Diesel Fuels
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
D6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measure-
ment System Performance
D6300 Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and
Lubricants
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.01 on Combustion Characteristics.
Current edition approved March 1, 2023Feb. 1, 2024. Published March 2023February 2024. Originally approved in 1941. Last previous edition approved in 20182023
ε1
as D613D613 – 23. – 18a . DOI: 10.1520/D0613-23.10.1520/D0613-24.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D613 − 24
D6708 Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purport
to Measure the Same Property of a Material
E456 Terminology Relating to Quality and Statistics
E542 Practice for Gravimetric Calibration of Laboratory Volumetric Instruments
E832 Specification for Laboratory Filter Papers
3. Terminology
3.1 Definitions:
3.1.1 accepted reference value (ARV), n—a value that serves as an agreed-upon reference for comparison, and which is derived
as: (1) a theoretical or established value, based on scientific principles, or (2) an assigned or certified value, based on experimental
work of some national or international organization, or (3) a consensus or certified value, based on collaborative experimental work
under the auspices of a scientific or engineering group. E456
3.1.1.1 Discussion—
In the context of this test method, accepted reference value is understood to apply to the cetane number of specific reference
materials determined empirically under reproducibility conditions by the National Exchange Group or another recognized
exchange testing organization.
3.1.2 cetane number (CN), n—a measure of the ignition performance of a diesel fuel oil obtained by comparing it to reference fuels
in a standardized engine test. D4175
3.1.2.1 Discussion—
In the context of this test method, ignition performance is understood to mean the ignition delay of the fuel as determined in a
standard test engine under controlled conditions of fuel flow rate, injection timing, and compression ratio.
3.1.3 compression ratio (CR), n—the ratio of the volume of the combustion chamber including the precombustion chamber with
the piston at bottom dead center to the comparable volume with the piston at top dead center.
3.1.4 ignition delay, n—that period of time, expressed in degrees of crank angle rotation, between the start of fuel injection and
the start of combustion.
3.1.5 injection timing (injection advance), n—that time in the combustion cycle, measured in degrees of crank angle, at which fuel
injection into the combustion chamber is initiated.
3.1.6 quality control (QC) sample, n—for use in quality assurance programs to determine and monitor the precision and stability
of a measurement system, a stable and homogeneous material having physical or chemical properties, or both, similar to those of
typical samples tested by the analytical measurement system. The material is properly stored to ensure sample integrity, and is
available in sufficient quantity for repeated, long term testing. D6299
3.1.7 repeatability conditions, n—conditions where independent test results are obtained with the same method on identical test
items in the same laboratory by the same operator using the same equipment within short intervals of time. E456
3.1.8 reproducibility conditions, n—conditions where test results are obtained with the same method on identical test items in
different laboratories with different operators using different equipment. E456
3.2 Definitions of Terms Specific to This Standard:
3.2.1 cetane meter, n—the electronic apparatus which displays injection advance and ignition delay derived from input pulses of
multiple transducers (pickups).
3.2.1.1 Discussion—
In the context of this test method, three generations of apparatus have been approved for use as cetane meters. These are (year of
introduction is parenthesis) the Mark II Ignition Delay Meter (1974), the Dual Digital Cetane Meter (1990), and the XCP Cetane
Panel (2014).
3.2.2 check fuels, n—for quality control testing, a diesel fuel oil of selected characteristics having a cetane number accepted
reference value determined in accordance with Practice D6299 requirements for check standards derived from interlaboratory
exchange programs.
3.2.2.1 Discussion—
D613 − 24
When evaluating the interlaboratory data to establish the ARV, outlier identification and rejection criteria shall be applied at the
5 % significance level prior to computing the average result.
3.2.3 combustion pickup, n—pressure transducer exposed to cylinder pressure to indicate the start of combustion.
3.2.4 handwheel reading, n—an arbitrary numerical value, related to compression ratio, obtained from a micrometer scale that
indicates the position of the variable compression plug in the precombustion chamber of the engine.
3.2.5 injector opening pressure, n—the fuel pressure that overcomes the resistance of the spring which normally holds the nozzle
pintle closed, and thus forces the pintle to lift and release an injection spray from the nozzle.
3.2.6 injector pickup, n—transducer to detect motion of the injector pintle, thereby indicating the beginning of injection.
3.2.7 primary reference fuels (PRF), n—hexadecane (HXD), heptamethylnonane (HMN), pentamethylheptane (PMH), and
volumetrically proportioned binary mixtures of HXD with either HMN or PMH, which now define the cetane number scale.
3.2.7.1 Discussion—
In the context of this test method, the arbitrary cetane number scale was originally defined as the volume percent of hexadecane
in a blend with 1-methylnaphthalene (AMN) where HXD had an assigned value of 100 and AMN an assigned value of zero (0).
A change from 1-methylnaphthalene to heptamethylnonane as the low cetane ingredient was made in 1962 to utilize a material of
better storage stability and availability. Heptamethylnonane was determined to have a cetane number accepted reference value
(CN ) of 15 based on engine testing by the ASTM Diesel National Exchange Group. A change to add a second low cetane
ARV
ingredient, pentamethylheptane (PMH), as an alternative to HMN was made in 2018 to utilize a material of higher purity and better
availability. Pentamethylheptane was determined to have a cetane number accepted reference value (CN ) of 16.3 based on
ARV
engine testing by the ASTM Diesel National Exchange Group.
3.2.7.2 Discussion—
In the context of this test method, the Diesel National Exchange Group of Subcommittee D02.01 is composed of petroleum
industry, governmental, and independent laboratories. It conducts regular monthly exchange sample analyses to generate precision
data for this engine test standard and determines the CN of reference materials used by all laboratories.
ARV
3.2.8 reference pickups, n—transducers or optical sensors mounted over the flywheel of the engine, triggered by a flywheel
indicator, used to establish a top-dead-center (tdc) reference and a time base for calibration of the cetane meter.
3.2.9 repeatability conditions NEG, n—replicate testing conditions employed by the National Exchange Group in which a single
operator tests two specimens taken from a single sample container with at least one other sample being tested between the two
specimens.
3.2.10 secondary reference fuels (SRF), n—volumetrically proportioned blends of two selected, numbered, and paired
hydrocarbon mixtures designated T Fuel (high cetane) and U Fuel (low cetane) that have been rated by the ASTM Diesel National
Exchange Group using primary reference fuels to determine a cetane number accepted reference value for each individually and
for various combinations of the two.
3.3 Abbreviations:
3.3.1 ABDC—after bottom dead center
3.3.2 AMN—1-methylnaphthalene
3.3.3 ARV—accepted reference value
3.3.4 ATDC—after top dead center
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D02-1092. Contact ASTM Customer
Service at [e-mail].
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D02-1885. Contact ASTM Customer
Service at [e-mail].
Bylaws governing ASTM Subcommittee D02.01 on Combustion Characteristics are available from the subcommittee or from ASTM International.
D613 − 24
3.3.5 BBDC—before bottom dead center
3.3.6 BTDC—before top dead center
3.3.7 CN—cetane number
3.3.8 CR—compression ratio
3.3.9 DD—Dual Digital Cetane Meter
3.3.10 HMN—heptamethylnonane
3.3.11 HRF—high reference fuel
3.3.12 HW—hand wheel
3.3.13 HXD—hexadecane
3.3.14 IAT—intake air temperature
3.3.15 LRF—low reference fuel
3.3.16 NEG—National Exchange Group
3.3.17 PMH—pentamethylheptane
3.3.18 PRF—primary reference fuels
3.3.19 r —repeatablility conditions NEG
NEG
3.3.20 SRF—secondary reference fuels
3.3.21 TDC—top dead center
3.3.22 UV—ultraviolet
3.3.23 XCP—XCP Cetane Panel
4. Summary of Test Method
4.1 The cetane number of a diesel fuel oil is determined by comparing its combustion characteristics in a test engine with those
for blends of reference fuels of known cetane number under standard operating conditions. This is accomplished using the
bracketing handwheel procedure which varies the compression ratio (handwheel reading) for the sample and each of two
bracketing reference fuels to obtain a specific ignition delay permitting interpolation of cetane number in terms of handwheel
reading.
5. Significance and Use
5.1 The cetane number provides a measure of the ignition characteristics of diesel fuel oil in compression ignition engines.
5.2 This test method is used by engine manufacturers, petroleum refiners and marketers, and in commerce as a primary
specification measurement related to matching of fuels and engines.
D613 − 24
5.3 Cetane number is determined at constant speed in a precombustion chamber type compression ignition test engine. The
relationship of test engine performance to full scale, variable speed, variable load engines is not completely understood.
5.4 This test method may be used for unconventional fuels such as synthetics, vegetable oils, and the like. However, the
relationship to the performance of such materials in full scale engines is not completely understood.
6. Interferences
6.1 (Warning—Avoid exposure of sample fuels and reference fuels to sunlight or fluorescent lamp UV emissions to minimize
induced chemical reactions that can affect cetane number ratings.)
6.1.1 Exposure of these fuels to UV wavelengths shorter than 550 nm for a short period of time may significantly affect cetane
number ratings.
6.2 Certain gases and fumes present in the area where the cetane test engine is located may have a measurable effect on the cetane
number test result.
6.3 This test method is not suitable for rating diesel fuel oils with fluid properties that interfere with unimpeded gravity flow of
fuel to the fuel pump or delivery through the injector nozzle.
7. Apparatus
7,8
7.1 Engine Equipment —This test method uses a single cylinder engine which consists of a standard crankcase with fuel pump
assembly, a cylinder with separate head assembly of the precombustion type, thermal syphon recirculating jacket coolant system,
multiple fuel tank system with selector valving, injector assembly with specific injector nozzle, electrical controls, and a suitable
exhaust pipe. The engine is belt connected to a special electric power-absorption motor which acts as a motor driver to start the
engine and as a means to absorb power at constant speed when combustion is occurring (engine firing). See Fig. 1 and Table 1.
7,8
7.2 Instrumentation —This test method uses electronic apparatus to measure injection and ignition delay timing as well as
conventional thermometry, gauges, and general purpose meters.
7.2.1 Cetane Meter—Use of an approved cetane meter is mandatory; only the XCP Cetane Panel or the Dual Digital Cetane Meter
or the Mark II Ignition Delay Meter shall be used for this test method.
7.3 Reference Fuel Dispensing Equipment—This test method requires repeated blending of two reference fuel materials in
volumetric proportions on an as-needed basis. Measurement shall be performed accurately because rating error is proportional to
blending error.
7.3.1 Volumetric Blending of Reference Fuels—Volumetric blending has historically been employed to prepare the required blends
of reference fuels. For volumetric blending, a set of two burets or accurate volumetric ware shall be used and the desired batch
quantity shall be collected in an appropriate container and thoroughly mixed before being introduced to the engine fuel system.
7.3.1.1 Calibrated burets or volumetric ware having a capacity of 400 mL or 500 mL and a maximum volumetric tolerance of
60.2 % shall be used. Calibration shall be verified in accordance with Practice E542.
7.3.1.2 Calibrated burets shall be outfitted with a dispensing valve and delivery tip to accurately control dispensed volume. The
delivery tip shall be of such size and design that shutoff tip discharge does not exceed 0.5 mL.
7.3.1.3 The rate of delivery from the dispensing system shall not exceed 500 mL per 60 s.
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D02-1502. Contact ASTM Customer
Service at [e-mail].
The sole source of supply of the engine equipment and instrumentation known to the committee at this time is CFR Engines, Inc., N8 W22577 Johnson Dr., Pewaukee,
WI 53186. CFR Engines, Inc. also has authorized sales and service organizations in selected geographical areas.
If you are aware of alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at a
meeting of the responsible technical committee, which you may attend.
D613 − 24
A—Fuel Tanks
B—Air Heater Housing
C—Air Intake Silencer
D—Fuel Flow Rate Buret
E—Combustion Pickup
F—Safety Guard
G—Variable Compression Plug Handwheel
H—V.C.P. Locking Handwheel
I—Flywheel Pickups
J—Oil Filler Cap
K—Injection Pump Safety Shut-Off Solenoid
L—Injector Assembly
M—Fuel Injection Pump
N—Fuel Selector-Valve
O—Oil Filter
P—Crankcase Oil Heater Control
Q—Air Heater Switch
R—Engine Start-Stop Switch
S—Instrument Panel
T—Intake Air Temperature Controller
U—Dual Digital Cetane Meter
FIG. 1 Cetane Method Test Engine Assembly
7.3.1.4 The set of burets for the reference fuels shall be installed in such a manner and be supplied with fluids such that all
components of each batch or blend are dispensed at the same temperature.
7.3.1.5 See Appendix X1, Volumetric Reference Fuel Blending Apparatus and Procedures, for typical dispensing system
information.
7.3.2 Gravimetric Blending of Reference Fuels—Use of blending systems that allow preparation of the volumetrically defined
blends by gravimetric (mass) measurements based on the density of the individual components is also permitted, provided the
system meets the requirement for maximum 0.2 % blending tolerance limits.
7.3.2.1 Calculate the mass equivalents of the volumetrically-defined blend components from the densities of the individual
components at 15.56 °C (60 °F).
7.4 Auxiliary Apparatus:
7.4.1 Injector Nozzle Tester—The injector nozzle assembly shall be checked whenever the injector nozzle is removed and
reassembled to ensure the initial pressure at which fuel is discharged from the nozzle is properly set. It is also important to inspect
the type of spray pattern. Commercial injector nozzle testers which include a lever-operated pressure cylinder, fuel reservoir and
pressure gauge are available from several sources as common diesel engine maintenance equipment.
D613 − 24
TABLE 1 General Engine Characteristics and Information
Item Description
Crankcase Model CFR-48 (Preferred), High or Low Speed
Models (Optional)
Cylinder Type Single bore cast iron with integral coolant
jacket
Cylinder Head Type Cast Iron with turbulence precombustion
chamber, variable compression plug
passage, integral coolant passages, and
in-head valve assembly
Compression Ratio Adjustable 8:1 to 36:1 by external handwheel
assembly
Cylinder Bore (Diameter), in. 3.250 (Standard), Reboring to 0.010, 0.020,
0.030 over is acceptable
Stroke, in. 4.50
Displacement, cu in. 37.33
Valve Mechanism In-head with enclosure
Intake and Exhaust Valves Stellite faced, plain type without shroud
Piston Cast iron, flat top
Piston Rings:
Compression Type 4, Ferrous, straight sided (Top may be chrome
plated—Optional)
Oil Control 1, Cast iron, one piece, slotted (Type 85)
Camshaft Over lap, degree 5
Fuel System Injection pump with variable timing device and
injector
Injector Holder with bypass pressure release valve
Spray Nozzle Closed, differential-needle, hydraulically-
operated, pintle type
Weight of Engine Approximately 400 kg (880 lb)
Weight of Complete Test Unit Approximately 1250 kg (2750 lb)
7.4.2 Special Maintenance Tools—A number of specialty tools and measuring instruments should be utilized for easy, convenient
and effective maintenance of the engine and testing equipment. Lists and descriptions of these tools and instruments are available
from the manufacturers of the engine equipment and those organizations offering engineering and service support for this test
method.
8. Reagents and Reference Materials
8.1 Cylinder Jacket Coolant—Water shall be used in the cylinder jacket for laboratory locations where the resultant boiling
temperature shall be 100 °C 6 2 °C (212 °F 6 3 °F). Water with commercial glycol-based antifreeze added in sufficient quantity
to meet the boiling temperature requirement shall be used when laboratory altitude dictates. A commercial multifunctional water
treatment material should be used in the coolant to minimize corrosion and mineral scale that can alter heat transfer and rating
results.
8.1.1 Water shall be understood to mean reagent water conforming to Type IV of Specification D1193.
8.2 Engine Crankcase Lubricating Oil—An SAE 30 viscosity grade oil meeting current API service classification or compatible
previous API service classifications shall be used. It shall contain a detergent additive and have a kinematic viscosity of 9.3 cSt
to 12.5 cSt (mm per s) at 100 °C (212 °F) and a viscosity index of not less than 85. Oils containing viscosity index improvers shall
not be used. Multigraded oils shall not be used. (Warning—Lubricating oil is combustible, and its vapor is harmful. See Annex
A1.)
8.3 Primary Reference Fuels—(Warning—Primary Reference Fuel—Combustible. Vapor harmful. See Annex A1.)
8.3.1 Hexadecane—Hexadecane meeting the specifications in Table 2 shall be used as the designated 100 cetane number
component.
8.3.2 Heptamethylnonane (2,2,4,4,6,8,8-heptamethyl-
nonane)—Heptamethylnonane meeting the specifications in Table 2 may be used as the low cetane number component that is
blended with hexadecane. In binary volumetric blends with HXD, HMN has a cetane number ARV of 15.
8.3.2.1 The cetane number accepted reference value (CN ) for any mixture of HXD and HMN is given by the relationship:
ARV
D613 − 24
TABLE 2 Specifications for Primary Reference Fuels
Property Hexadecane Heptamethylnonane Pentamethylheptane Test Method
Purity, mass %, minimum 99.0 98.0 99.5 Gas chromatography
Hydroperoxide number, mg/kg as O, maximum 5.0 5.0 5.0 ASTM D3703
CN 5 volume-% HXD + 0.15~volume-% HMN! (1)
ARV
8.3.3 Pentamethylheptane (2,2,4,6,6-pentamethyl-
heptane)—Pentamethylheptane meeting the specifications in Table 2 may be used as the low cetane number component that is
blended with hexadecane. In binary volumetric blends with HXD, PMH has a cetane number ARV of 16.3.
8.3.3.1 The cetane number accepted reference value (CN ) for any mixture of HXD and PMH is given by the relationship:
ARV
CN 5 volume-%HXD+ 0.163 volume-% PMH (2)
~ !
ARV
8.3.4 Store and use primary reference fuels at temperatures of 20 °C or higher to avoid solidification of HXD, which has a melting
point of 18 °C.
8.4 Secondary Reference Fuels—(Warning—Secondary reference fuel—combustible. Vapor harmful. See Annex A1.)
8.4.1 T Fuel—Diesel fuel meeting the specifications in Table 3.
8.4.2 U Fuel—Diesel fuel meeting the specifications in Table 3
8.4.3 Storage and use of T Fuel and U Fuel should be at temperatures above 0 °C (32 °F) to avoid potential solidification,
particularly of T Fuel. Before a container that has been stored at low temperature is placed in service, it should be warmed to a
temperature of at least 14 °C (26 °F) above its Cloud Point. (See Test Method D2500.) It should be held at this temperature for
a period of at least 30 min and then the container should be thoroughly remixed.
8.4.4 As secondary reference fuel blends are rated in numbered pairs, they are not interchangeable with reference fuels from other
numbered pairs and shall not be mixed.
8.5 Check Fuels —Diesel fuel oils having properties other than CN that are typical of Specification D975 grade No. 2-D S15.
(Warning—Check Fuel—Combustible. Vapor harmful. See Annex A1.)
8.5.1 Low Cetane Check Fuel, meeting the specifications in Table 3.
8.5.2 High Cetane Check Fuel, meeting the specifications in Table 3.
8.6 In the event of a dispute between ratings obtained using secondary reference fuels and ratings obtained using primary reference
fuels, the ratings obtained using primary reference fuels shall be considered the referee test result.
9. Sampling
9.1 Collect samples in accordance with Practice D4057 or D4177.
9.1.1 Protection from Light—Collect and store sample fuels in an opaque container such as a dark brown glass bottle, metal can,
or a minimally reactive plastic container to minimize exposure to UV emissions from sources such as sunlight or fluorescent lamps.
9.2 Fuel Temperature—Samples shall be brought to room temperature typically 18 °C to 32 °C (65 °F to 90 °F) before engine
testing.
9.2.1 The fuel temperature should be raised at least 14 °C (26 °F) above the fuel’s cloud point. The fuel sample should be
homogeneous before engine testing or filtration (9.3).
Blend Tables for batches of T Fuel and U Fuel can be obtained from the fuel supplier.
D613 − 24
TABLE 3 Specifications for Secondary Reference Fuels and Check Fuels
Secondary Reference Check Fuels
Fuels
Property T-Fuel U-Fuel Low High Test Method
Cetane number ARV, minimum 73 19 38. 50. ASTM D613
Cetane number ARV, maximum 76 22 42. 55. ASTM D613
Hydroperoxide number, mg/kg as O, maximum 5.0 5.0 5.0 5.0 ASTM D3703
NOTE 1—Give consideration to the fuel’s composition related to sample temperature to avoid the loss of any lower boiling components that may affect
the cetane rating.
9.3 Filtration—Samples may be filtered through a Type I, Class A filter paper at room temperature and pressure before engine
testing. See Specification E832.
10. Basic Engine and Instrument Settings and Standard Operating Conditions
10.1 Installation of Engine Equipment and Instrumentation—Installation of the engine and instrumentation requires placement of
the engine on a suitable foundation and hookup of all utilities. Engineering and technical support for this function is required, and
the user shall be responsible to comply with all local and national codes and installation requirements.
10.1.1 Proper operation of the test engine requires assembly of a number of engine components and adjustment of a series of
engine variables to prescribed specifications. Some of these settings are established by component specifications, others are
established at the time of engine assembly or after overhaul, and still others are engine running conditions that must be observed
or determined by operator adjustment, or both, during the testing process.
10.2 Conditions Based on Component Specifications:
10.2.1 Engine Speed—900 r ⁄min 6 9 r ⁄min, when the engine is operating with combustion with a maximum variation of 9 r ⁄min
occurring during a rating. Engine speed when combustion is occurring shall not be more than 3 r ⁄min greater than that for motoring
without combustion.
10.2.2 Valve Timing—The engine uses a four-stroke cycle with two crankshaft revolutions for each complete combustion cycle.
The two critical valve events are those that occur near TDC; intake valve opening and exhaust valve closing.
10.2.2.1 Intake valve opening shall occur 10.0° 6 2.5° ATDC with closing at 34° ABDC on one revolution of the crankshaft and
flywheel.
10.2.2.2 Exhaust valve opening shall occur 40° BBDC on the second revolution of the crankshaft or flywheel with closing at 15.0°
6 2.5° ATDC on the next revolution of the crankshaft or flywheel.
10.2.3 Valve Lift—Intake and exhaust cam lobe contours, while different in shape, shall have a contour rise of 6.223 mm to
6.350 mm (0.245 in. to 0.250 in.) from the base circle to the top of the lobe so that the resulting valve lift shall be 6.045 mm 6
0.05 mm (0.238 in. 6 0.002 in.).
10.2.4 Fuel Pump Timing—Closure of the pump plunger inlet port shall occur at a flywheel crank angle between 300° and 306°
on the engine compression stroke when the fuel flow-rate-micrometer is set to a typical operating position and the variable timing
device lever is at full advance (nearest to operator).
10.2.5 Fuel Pump Inlet Pressure—A minimum fuel head established by assembly of the fuel tanks (storage reservoirs) and flow
rate measuring buret so that the discharge from them is 635 mm 6 25 mm (25 in. 6 1 in.) above the centerline of the fuel injection
pump inlet.
10.3 Assembly Settings and Operating Conditions:
10.3.1 Direction of Engine Rotation—Clockwise rotation of the crankshaft when observed from the front of the engine.
10.3.2 Injection Timing—13.0° BTDC, for the sample and reference fuels.
D613 − 24
10.3.3 Injector Nozzle Opening Pressure—10.3 MPa 6 0.34 MPa (1500 psi 6 50 psi).
10.3.4 Injection Flow Rate—13.0 mL ⁄min 6 0.2 mL ⁄min (60 s 6 1 s per 13.0 mL).
10.3.5 Injector Coolant Passage Temperature—38 °C 6 3 °C (100 °F 6 5 °F).
10.3.6 Valve Clearances:
10.3.6.1 Engine Running and Hot—The clearance for both intake and exhaust valves shall be set to 0.20 mm 6 0.025 mm
(0.008 in. 6 0.001 in.), measured under standard operating conditions with the engine running at equilibrium conditions on a
typical diesel fuel oil.
10.3.7 Oil Pressure—172 kPa to 207 kPa (25 psi to 30 psi).
10.3.8 Oil Temperature—57 °C 6 8 °C (135 °F 6 15 °F).
10.3.9 Cylinder Jacket Coolant Temperature—100 °C 6 2 °C (212 °F 6 3 °F).
10.3.10 Intake Air Temperature—66 °C 6 0.5 °C (150 °F 6 1 °F).
10.3.11 Basic Ignition Delay—13.0° for the sample and reference fuels.
10.3.12 Cylinder Jacket Coolant Level:
10.3.12.1 Engine Stopped and Cold—Treated water/coolant added to the cooling condenser—cylinder jacket to a level just
observable in the bottom of the condenser sight glass will typically provide the controlling engine running and hot operating level.
10.3.12.2 Engine Running and Hot—Coolant level in the condenser sight glass shall be within 61 cm (0.4 in.) of the LEVEL HOT
mark on the coolant condenser.
10.3.13 Engine Crankcase Lubricating Oil Level:
10.3.13.1 Engine Stopped and Cold—Oil added to the crankcase so that the level is near the top of the sight glass will typically
provide the controlling engine running and hot operating level.
10.3.13.2 Engine Running and Hot—Oil level shall be approximately mid-position in the crankcase oil sight glass.
10.3.14 Crankcase Internal Pressure—As mentioned by a gauge or manometer connected to an opening to the inside of the
crankcase through a snubber orifice to minimize pulsations, the pressure shall be less than zero (a vacuum) and typically from
25 mm to 150 mm (1 in. to 6 in.) of water less than atmospheric pressure. Vacuum shall not exceed 255 mm (10 in.) of water.
10.3.15 Exhaust Back Pressure—As measured by a gauge or manometer connected to an opening in the exhaust surge tank or main
exhaust stack through a snubber orifice to minimize pulsations, the static pressure should be as low as possible, but shall not create
a vacuum nor exceed 254 mm (10 in.) of water differential in excess of atmospheric pressure.
10.3.16 Exhaust and Crankcase Breather System Resonance—The exhaust and crankcase breather piping systems shall have
internal volumes and be of such length that gas resonance does not result.
10.3.17 Piston Over-Travel—Assembly of the cylinder to the crankcase shall result in the piston protruding above the top of the
cylinder surface 0.381 mm 6 0.025 mm (0.015 in. 6 0.001 in.) when the piston is at top-dead-center. Proper positioning is
accomplished through the use of plastic or paper gaskets, available in several thicknesses and selected by trial and error for
assembly between the cylinder and crankcase deck.
10.3.18 Belt Tension—The belts connecting the flywheel to the absorption motor shall be tightened, after an initial break-in, so
that with the engine stopped, a 2.25 kg (5 lb) weight suspended from one belt halfway between the flywheel and motor pulley shall
depress the belt approximately 12.5 mm (0.5 in.).
D613 − 24
FIG. 2 Typical Injector Spray Pattern
10.3.19 Setting Injector Nozzle Assembly Pressure and Spray Pattern Check—(Warning—Personnel shall avoid contact with the
spray pattern from injector nozzles because of the high pressure which can penetrate the skin. Spray pattern performance checks
shall be made in a hood or where adequate ventilation insures that inhalation of the vapors is avoided.)
10.3.19.1 Injector Opening or Release Pressure—The pressure adjusting screw is adjustable and shall be set to release fuel at a
pressure of 10.3 MPa 6 0.34 MPa (1500 psi 6 50 psi). Check this setting using an injector nozzle bench tester, each time the
nozzle is reassembled and after cleaning. Use of a commercial injector nozzle bench tester is recommended. See Annex A2 for
procedural detail.
10.3.19.2 Injector Spray Pattern—Check the spray pattern for symmetry and characteristic by inspection of the impression of a
single injection made on a piece of filter paper or other slightly absorbent material placed at a distance of approximately 7.6 cm
(3 in.) from the nozzle. A typical spray pattern is illustrated in Fig. 2.
10.3.20 Indexing Handwheel Reading—Handwheel readings are a simple and convenient indication of engine compression ratio
which is a critical variable in the cetane method of test. The actual compression ratio is not important but an indication of
compression ratio which relates to cetane number is a useful guide for selecting reference fuels to bracket the sample of diesel fuel
oil. The following procedure shall be used to index the handwheel reading when the engine is new or anytime the matched
handwheel assembly/cylinder head combination is interchanged or mechanically reassembled.
10.3.20.1 Handwheel Micrometer Drum and Scale Setting—Refer to Table 4 to select the appropriate handwheel reading to be
used in aligning the drum and scale.
10.3.20.2 Basic Setting of Variable Compression Plug—Position the variable compression plug so that the flat surface is just
visible and exactly in line with the edge of the threads of the combustion pickup hole, as verified with a straightedge.
10.3.20.3 Setting Handwheel Reading—Tighten the small locking handwheel snugly by hand to ensure that the variable
compression plug is held in place in the bore. Loosen the locknut of the large handwheel and remove the locking L-shaped key.
Turn the large handwheel so that the edge of the drum is in alignment with the 1.000 graduation on the horizontal scale. Reinstall
the L-shaped key in the nearest keyway slot of the large handwheel with the shorter leg in the handwheel. A slight shifting of the
handwheel to achieve slot lineup will not affect the indexing. Tighten the locknut hand-tight to hold the key in place. Remove the
locating screw from the drum and rotate the drum so that the zero graduation mark is in line with the selected reading from Table
4. Locate the screw hole in the drum which lines up with the handwheel hub hole and reinstall the locating screw. Wrench tighten
the large handwheel locknut and recheck that the variable compression plug is properly positioned and the handwheel reading is
in accordance with the value in Table 4.
10.3.21 Basic Compression Pressure—At a handwheel reading of 1.000, the compression pressure for an engine operated at
standard barometric pressure of 760 mm Hg. (29.92 in. Hg) shall be 3275 kPa 6 138 kPa (475 psi 6 20 psi) when read as quickly
as possible after shutdown of the engine which had been at standard operating conditions. If the condition is not within limits,
recheck the basic handwheel setting and, if necessary, perform mechanical maintenance. See Annex A2 for the Checking
Compression Pressure procedure.
10.3.21.1 For engines operated at other than standard barometric pressure, the compression pressure will typically be in proportion
to the ratio of the local barometric pressure divided by standard barometric pressure. As an example, an engine located where the
barometric pressure is 710 mm Hg would be expected to have a compression pressure of approximately 3060 kPa 6 138 kPa
(444 psi 6 20 psi). (Warning—In addition to other precautions, compression pressure testing using a compression pressure gauge
should be completed in as short a period of time as possible to avoid the possibility of combustion occurrence due to the presence
of any small amount of oil in the gauge or combustion chamber.)
D613 − 24
TABLE 4 Handwheel Setting for Various Cylinder Bore Diameters
Cylinder Diameter, in. Handwheel Reading
3.250 (Standard Bore) 1.000
3.260 (Rebored 0.010 in. Oversize) 0.993
3.270 (Rebored 0.020 in. Oversize) 0.986
3.280 (Rebored 0.030 in. Oversize) 0.978
Compression Pressure (3)
LocalBaro.,mmHg
~ !
5 3275 kPa ×Local Baro./Standard Baro.
Example:Compression Pressure
710mmHg
5 3275 ×710/760 5 3060 kPa
10.3.22 Fuel Pump Lubricating Oil Level—With the engine stopped, sufficient engine crankcase lubricating oil shall be added to
the pump sump so that the level is at the mark on the dip stick. (Warning—As a result of engine operation, especially when the
pump barrel/plunger assembly begins to wear, the level in the sump will increase due to fuel dilution as observed through a clear
plastic side plate on the pump housing. When the level rises appreciably, the sump should be drained and a fresh charge of oil
added.)
10.3.23 Fuel Pump Timing Gear Box Oil Level—With the engine stopped, unplug the openings on the top and at the mid-height
of either side of the gear box. Add sufficient engine crankcase lubricating oil through the top hole to cause the level to rise to the
height of the side opening. Replug both openings. (Warning—The pump and timing gear box oil sumps are not connected to each
other and the lubrication for the two is independent.)
10.3.24 Instrumentation—Positioning of the reference pickups and injector pickup is important to ensure that timing of the
injection and ignition delay functions is uniform and correct.
10.3.24.1 Setting Reference Pickups—These two pickups are identical and interchangeable. They are installed in a bracket
positioned over the flywheel so that they clear the flywheel indicator which triggers them.
10.3.24.2 Position each pickup in the bracket so that it is properly referenced to the flywheel indicator in accordance with the
instructions supplied with the specific pickup.
10.3.24.3 Measurement of pickup to flywheel indicator clearance, if required, shall be made using a nonmagnetic feeler gauge.
10.3.25 Setting Injector Pickup Gap—Set the air gap to typically 1 mm (0.040 in.) with the engine stopped.
10.3.25.1 Individual pickups may require more or less air gap to obtain steady meter operation when the engine is ultimately
running but too little gap can cause the ignition delay angle display to drive off scale. Follow instructions supplied with the specific
pickup to optimize the gap setting.
11. Engine Qualification
11.1 Engine Compliance—It is assumed that the engine has been commissioned and that all settings and operating variables are
at equilibrium and in compliance with basic engine and instrument settings and standard operating conditions.
11.1.1 Engine warm-up requires typically 1 h to ensure that all critical variables are stable.
11.2 Fit-for-use Qualification:
11.2.1 Every sample fuel CN determination shall be performed using an engine that has been qualified as fit-for-use by rating a
Check Fuel.
11.2.2 Qualify the engine using the Low or High Cetane Check Fuel in accordance with the following conditions:
11.2.2.1 At least once during each 12 h period of rating.
D613 − 24
11.2.2.2 After an engine has been shut down for more than 2 h.
11.2.3 Test check fuels using the procedure described below:
11.2.4 Engine performance is judged satisfactory if the cetane rating obtained on the Check Fuel is within the Check Fuel tolerance
limits calculated as follows:
Tolerance Limits 5 CN 61.5 ×S (4)
ARV ARV
where:
CN = the cetane number accepted reference value of the Check Fuel,
ARV
1.5 = a selected tolerance limit factor (K) for normal distributions,
S = the standard deviation of the Check Fuel data used to determine CN .
ARV ARV
11.2.4.1 In the context of this test method, the statistical tolerance limit factor (K), based on a sample size (n), permits an
estimation of the percentage of engines that would be able to rate the Check Fuel within the calculated tolerance limits. Based on
a data set of 17 to 20 ratings used to determine the Check Fuel CN , and a value of K = 1.5, it is estimated that in the long
ARV
run, in 19 cases out of 20, at least 70 % of the engines would rate the Check Fuel within the calculated tolerance limits.
11.2.5 If the results are outside this tolerance range, the engine is not acceptable for rating samples and a check of all operating
conditions is warranted followed by mechanical maintenance which may require critical parts replacement. The injector nozzle can
be a very critical factor and this should be the first item checked or replaced to achieve rating compliance.
11.3 Quality Control (QC Testing)—Users should conduct a regular statistical quality control program to monitor the engine is in
statistical control over time.
11.3.1 This test method suggests validating the engine system by the rating of a QC sample.
11.3.2 The QC sample is a diesel fuel oil having a cetane number within the normal operating range of the engine.
11.3.2.1 Users are encouraged to assess the normal operating range and determine if multiple QC samples are required based upon
the cetane number range of the samples typically rated.
11.3.3 Use appropriate control charts or other statistically equivalent techniques to assess the cetane number value. Control charts
often used for this application are Individuals and Moving Range (I/MR).
11.3.4 Specifics for control chart set up and interpretation can be found in Practice D6299.
11.3.5 If an out-of-statistical control situation is detected, examine the engine system operation for assignable cause(s).
12. Procedure
12.1 Bracketing by Handwheel Procedure—See Appendix X2 for the details of engine operation and the adjustment of each of
the individual operating variables.
12.1.1 Check that all engine operating conditions are in compliance and equilibrated with the engine running on a typical diesel
fuel oil. (Warning—In addition to other precautions, always position the Mark II Ignition Delay Meter to CALIBRATE before
proceeding with fuel switching so that violent meter needle full-scale pegging does not occur. Calibration adjustment should be
checked before each rating but never changed during a rating.)
12.1.2 Introduce the sample to an empty fuel tank, rinse the fuel buret, purge any air from the fuel line to the pump and position
the fuel-selector valve to operate the engine on this fuel. (Warning—Sample and Fuel—Combustible. Vapor harmful. See Annex
A1.)
12.1.3 Fuel Flow Rate—Check the fuel flow rate and adjust the flow-rate-micrometer of the fuel pump to obtain 13 mL per min
consumption. The final flow rate measurement shall be made over a full 60 s 6 1 s period. Note the flow-rate-micrometer reading
for reference.
D613 − 24
TABLE 5 Reference Fuel Blends for Samples with Cetane
Number >T Fuel
Blend T Fuel, vol- % HXD, vol- %
1 100 0
2 75 25
3 50 50
4 25 75
5 0 100
12.1.4 Fuel Injection Timing—After establishing the fuel flow rate, adjust the injection-timing-micrometer of the fuel pump
assembly to obtain a 13.0° 6 0.2° injection advance reading. Note the injection-timing-micrometer reading for reference.
12.1.5 Ignition Delay—Adjust the handwheel to change the compression ratio and obtain a 13.0° 6 0.2° ignition delay reading.
Make the final handwheel adjustment in the clockwise directi
...