ISO 1585:2020
(Main)Road vehicles — Engine test code — Net power
Road vehicles — Engine test code — Net power
This document specifies a method for testing engines designed for automotive vehicles. It applies to the evaluation of their performance with a view, in particular to presenting curves of power and specific fuel consumption at full load as a function of engine speed. It applies only to net power assessment. This document concerns internal combustion engines used for propulsion of passenger cars, trucks and other motor vehicles, excluding motorcycles, mopeds and agricultural tractors normally travelling on roads, and included in one of the following categories: — reciprocating internal combustion engines (spark-ignition or compression-ignition) but excluding free piston engines; — rotary piston engines. These engines can be naturally aspirated or pressure-charged, either using a mechanical supercharger or turbocharger.
Véhicules routiers — Code d'essai des moteurs — Puissance nette
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 1585
Fourth edition
2020-07
Road vehicles — Engine test code —
Net power
Véhicules routiers — Code d'essai des moteurs — Puissance nette
Reference number
©
ISO 2020
© ISO 2020
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ii © ISO 2020 – All rights reserved
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Accuracy of measuring equipment and instruments . 2
4.1 Torque . 2
4.2 Engine speed (rotational frequency) . 2
4.3 Fuel flow . 2
4.4 Fuel temperature. 2
4.5 Air temperature . 2
4.6 Barometric pressure . 2
4.7 Back pressure in exhaust system . 2
4.8 Depression in inlet system . 3
4.9 Absolute pressure in inlet duct . 3
5 Tests . 6
5.1 Auxiliaries . 6
5.1.1 Auxiliaries to be fitted . 6
5.1.2 Auxiliaries to be removed . 6
5.1.3 Compression-ignition engine starting auxiliaries . 6
5.2 Setting conditions . 6
5.3 Test conditions . 7
5.4 Test procedure . 8
5.5 Data to be recorded . 8
6 Power correction factors . 9
6.1 Definition of factor α for power correction . 9
6.2 Atmospheric conditions . 9
6.2.1 Reference atmospheric conditions . 9
6.2.2 Test atmospheric conditions . 9
6.3 Determination of power correction factors . 9
6.3.1 Naturally aspirated and pressure-charged spark-ignition engines — Factor α .10
a
6.3.2 Compression-ignition engines — Factor α . .10
c
6.3.3 Turbocharged engine with a system compensating the ambient conditions .12
6.3.4 Other types of engine .12
7 Measurement of and correction for smoke value for compression-ignition engines .12
7.1 Correction factor for light absorption coefficient of smoke .12
7.2 Determination of correction factor for light absorption coefficient of smoke .13
7.3 Limits of application.13
8 Test report .13
8.1 Compression-ignition engines — Essential characteristics .13
8.1.1 Description of engine .13
8.1.2 Cooling system .14
8.1.3 Temperatures specified by the manufacturer .14
8.1.4 Pressure charger (with/without) (delete where inapplicable) .15
8.1.5 Inlet system .15
8.1.6 Additional smoke control devices (if any, and if not covered by another
heading) . .15
8.1.7 Fuel feed system .16
8.1.8 Valve timing .17
8.1.9 Exhaust system .17
8.1.10 Lubrication system .17
8.1.11 Electrical equipment .17
8.1.12 Other engine-driven equipment .17
8.2 Spark-ignition engines — Essential characteristics .17
8.2.1 Description of engine .17
8.2.2 Cooling system .18
8.2.3 Temperature specified by the manufacturer .19
8.2.4 Pressure charger (with/without) (delete where inapplicable) .19
8.2.5 Inlet system .19
8.2.6 Additional anti-pollution devices (if any, and if not covered by another
heading) .20
8.2.7 Fuel feed system .20
8.2.8 Valve timing .20
8.2.9 Ignition system .20
8.2.10 Exhaust system .21
8.2.11 Lubrication system .21
8.2.12 Electrical equipment .22
8.2.13 Other auxiliaries fitted to engine .22
8.3 Test conditions for measuring engine net power .22
8.4 Statement of results as function of engine speed.24
9 Verification of engine performance .25
9.1 Designation .25
9.2 Notation .25
9.2.1 Declared net power and corresponding engine speed (range) .25
9.2.2 Declared net torque and corresponding engine speed (range) .26
9.2.3 Declared specific net fuel consumption and corresponding engine speed
(range) .26
9.3 Tolerances — Declared values .26
9.3.1 Power .26
9.3.2 Torque .27
9.3.3 Specific fuel consumption .27
9.3.4 Numerical tolerances .27
Bibliography .32
iv © ISO 2020 – All rights reserved
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 34,
Propulsion, powertrain and powertrain fluids.
This fourth edition cancels and replaces the third edition (ISO 1585:1992), which has been technically
revised. The main changes compared to the previous edition are as follows:
— the air induction system definition has been updated to clarify included components;
— a requirement for exhaust particulate filter restriction has been added;
— a requirement for engine cooling active thermal management system settings has been added;
— a power correction factor for turbocharged engines with a system compensating the ambient
conditions has been added.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
INTERNATIONAL STANDARD ISO 1585:2020(E)
Road vehicles — Engine test code — Net power
1 Scope
This document specifies a method for testing engines designed for automotive vehicles. It applies to the
evaluation of their performance with a view, in particular to presenting curves of power and specific
fuel consumption at full load as a function of engine speed.
It applies only to net power assessment.
This document concerns internal combustion engines used for propulsion of passenger cars, trucks and
other motor vehicles, excluding motorcycles, mopeds and agricultural tractors normally travelling on
roads, and included in one of the following categories:
— reciprocating internal combustion engines (spark-ignition or compression-ignition) but excluding
free piston engines;
— rotary piston engines.
These engines can be naturally aspirated or pressure-charged, either using a mechanical supercharger
or turbocharger.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 2710-1, Reciprocating internal combustion engines — Vocabulary — Part 1: Terms for engine design
and operation
ISO 7876-1, Fuel injection equipment — Vocabulary — Part 1: Fuel injection pumps
ISO 7967-1, Reciprocating internal combustion engines — Vocabulary of components and systems — Part 1:
Structure and external covers
ISO 7967-2, Reciprocating internal combustion engines — Vocabulary of components and systems —
Part 2: Main running gear
ISO 7967-3, Reciprocating internal combustion engines — Vocabulary of components and systems —
Part 3: Valves, camshaft drives and actuating mechanisms
ISO 7967-4, Reciprocating internal combustion engines — Vocabulary of components and systems —
Part 4: Pressure charging and air/exhaust gas ducting systems
ISO 7967-5, Reciprocating internal combustion engines — Vocabulary of components and systems —
Part 5: Cooling systems
ISO 7967-8, Reciprocating internal combustion engines — Vocabulary of components and systems —
Part 8: Starting systems
ISO 11614, Reciprocating internal combustion compression-ignition engines — Apparatus for measurement
of the opacity and for determination of the light absorption coefficient of exhaust gas
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 2710-1, ISO 7876-1, ISO 7967-1,
ISO 7967-2, ISO 7967-3, ISO 7967-4, ISO 7967-5 and ISO 7967-8 and the following definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
net power
power obtained on a test bed at the end of the crankshaft or its equivalent at the corresponding engine
speed with the equipment and auxiliaries listed in Table 1
Note 1 to entry: If the power measurement can only be carried out with a mounted gearbox, the losses in the
gearbox should be added to the measured power to give the engine power.
3.2
standard production equipment
any equipment provided by the manufacturer for a particular engine application
4 Accuracy of measuring equipment and instruments
4.1 Torque
The dynamometer torque-measuring system shall have an accuracy within ±1 % in the range of scale
values required for the test.
4.2 Engine speed (rotational frequency)
The engine speed (rotational frequency) measuring system shall have an accuracy of ±0,5 %.
4.3 Fuel flow
The fuel flow measuring system shall have an accuracy of ±1 %.
4.4 Fuel temperature
The fuel temperature measuring system shall have an accuracy of ±2 K.
4.5 Air temperature
The air temperature measuring system shall have an accuracy of ±1 K.
4.6 Barometric pressure
The barometric pressure measuring system shall have an accuracy of ±100 Pa.
NOTE 1 Pa = 1 N/m .
4.7 Back pressure in exhaust system
The system used to measure the back pressure in the exhaust system shall have an accuracy of ±200 Pa.
The measurement shall be made subject to footnote b of Table 1.
2 © ISO 2020 – All rights reserved
4.8 Depression in inlet system
The system used to measure the depression in the inlet system shall have an accuracy of ±50 Pa. The
measurement shall be made subject to footnote a of Table 1.
4.9 Absolute pressure in inlet duct
The system used to measure the absolute pressure in the inlet duct shall have an accuracy of ±2 % of
the measured pressure.
Table 1 — Installation of equipment and auxiliaries during test
No. Equipment and auxiliaries Fitted for net power test
1 Inlet system
Inlet manifold
Crankcase emission control system
Control devices for dual induction inlet manifold system
Air flow meter Yes, standard production equipment
a
Air inlet ductwork
a
Air filter
a
Inlet silencer
a
Speed-limiting device
2 Induction heating device of inlet manifold Yes, standard production equipment
If possible, to be set in the most
favourable position.
3 Exhaust system
b
Exhaust purifier(s)
Exhaust manifold
Pressure-charging devices
Yes, standard production equipment
c
Connecting pipes
c
Silencer
c
Tail pipe
d
Exhaust brake
e
4 Fuel supply pump Yes, standard production equipment
5 Carburation equipment
Carburettor
Electronic control system, air-flow meter, etc. (if fitted)
Equipment for gaseous fuel engines Yes, standard production equipment
Pressure reducer
Evaporator
Mixer
Table 1 (continued)
No. Equipment and auxiliaries Fitted for net power test
6 Fuel injection equipment [spark-ignition and compression
ignition (diesel)]
Prefilter
Filter
Pump
High-pressure pipe Yes, standard production equipment
Injector
f
Air inlet valve (if fitted)
Electronic control system, etc. (if fitted)
Governor/control system: automatic full-load stop for
the control depending on atmospheric conditions
7 Liquid cooling equipment
Radiator
g,h
Fan
Yes, standard production equipment
Fan cowl
Water pump
i
Thermostat or thermal management system
8 Air cooling
Cowl
Yes, standard production equipment
g,h
Fan or blower
Temperature regulating device
9 Electrical or electronic equipment
j
Generator/alternator
Spark distribution system
Coil(s)
Yes, standard production equipment
Wiring
Spark-plugs
Electronic control system including knock sensor/spark
m
retard system
10 Pressure-charging equipment (if fitted)
Compressor driven either directly by the engine,
and/or by the exhaust gases
n
Boost control Yes, standard production equipment
g,h,k
Charge-air-cooler
Coolant pump or fan(engine-driven)
Coolant flow control devices (if fitted)
11 Auxiliary test bed fan Yes, if necessary
l
12 Anti-pollution devices Yes, standard production equipment
4 © ISO 2020 – All rights reserved
Table 1 (continued)
No. Equipment and auxiliaries Fitted for net power test
a
The air induction system begins where the air enters the system from atmosphere. Except when there is a risk
of the system having a noticeable influence upon engine power, an equivalent system may be used. In this case, a
check should be made to ascertain that inlet depression does not differ by more than 100 Pa from the limit
specified by the manufacturer for a clean air filter.
b
For the case of an exhaust particulate filter, the filter or equivalent restriction shall represent the clean state.
c
Except when there is a risk of the system having a noticeable influence upon engine power, an equivalent
system may be used. In this case, a check should be made to ascertain that the backpressure in the engine ex-
haust system does not differ by more than 1 000 Pa from that specified by the manufacturer.
d
If an exhaust brake is incorporated in the engine, the throttle valve shall be fixed fully open.
e
The fuel feed pressure may be adjusted, if necessary, to reproduce the inlet pump pressure conditions consist-
ent with the particular engine application (particularly where a "fuel return" system, e.g. to tank or filter, is used).
f
The air inlet valve is the control valve for the pneumatic governor of the injection pump. The governor of the
fuel injection equipment may contain other devices which may affect the amount of fuel injected.
g
The radiator, fan, fan cowl, water pump and thermostat shall be located on the test bed in the same relative
positions that they will occupy on the vehicle. The cooling liquid circulation shall be operated by the engine
water pump only.
Cooling of the liquid may be produced either by the engine radiator or by an external circuit, provided that the
pressure loss of this circuit and the pressure at the pump inlet remain substantially the same as those of the
engine cooling system. The radiator shutter, if incorporated, shall be in the open position.
Where the fan, radiator and cowl system cannot conveniently be fitted to the engine, the power absorbed by
the fan when separately mounted in its correct position in relation to the radiator and cowl (if used), shall
be determined at the speeds corresponding to the engine speeds used for measurement of the engine power
either by calculation from standard characteristics or by practical tests. This power corrected to the standard
atmospheric conditions defined in 6.2 shall be deducted from the corrected power.
h
Where a separate disconnectable or progressive fan or blower is incorporated, the test shall be made with
the disconnectable fan or blower disconnected or with the progressive fan running at the maximum slip.
i
The thermostat may be fixed in the fully open position. For the case of an active thermal management sys-
tem, control settings shall be representative of full load operation.
j
Minimum power of the generator/alternator: the power of the generator/alternator shall be limited to that
necessary for the operation of accessories which are indispensable for engine operation. If the connection of a
battery is necessary, a fully charged battery in good order shall be used.
k
Charge-air-cooled engines shall be tested complete with charge-air-cooling whether liquid or air-cooled
but if the engine manufacturer prefers, a test bed system may replace the air-cooled cooler. In either case, the
measurement of power at each speed shall be made with the pressure drop and temperature drop of the engine
air across the charge air cooler in the test bed the same as those specified by the manufacturer for the system
on the complete vehicle.
If a test bed system is used on a compression-ignition engine without a wastegate, or with the wastegate not
operating, the correction factor given in 6.3.2.1 b) is to be used. If a wastegate is both fitted and operating,
then the correction factor in 6.3.2.1 a) is to be used.
l
They may include for example EGR system, catalytic converter, particulate filter, thermal reactor, secondary
air supply system and fuel evaporating protecting system.
m
The spark advance shall be representative of in-use conditions established with the minimum octane fuel
recommended by the manufacturer.
n
For engines equipped with variable boost as a function of charge or inlet air temperature, octane rating and/
or engine speed, the boost pressure shall be representative of in-vehicle conditions established with the mini-
mum octane fuel as recommended by the manufacturer.
5 Tests
5.1 Auxiliaries
5.1.1 Auxiliaries to be fitted
During the test, auxiliaries necessary to make an engine acceptable for service in the intended
application (as listed in Table 1) shall be installed on the test bed as far as possible in the same position
as in the intended application.
5.1.2 Auxiliaries to be removed
Certain vehicle accessories necessary only for the operation of the vehicle, and which may be mounted
on the engine, shall be removed for the test. The following non-exhaustive list is given as an example:
— air compressor for brakes;
— power steering pump;
— suspension compressor;
— air-conditioning system compressor.
Where accessories cannot be removed, the power absorbed by them in the unloaded condition may be
determined and added to the measured engine power.
5.1.3 Compression-ignition engine starting auxiliaries
For auxiliaries used to start compression-ignition engines, the two following cases shall be considered:
a) electrical starting: the generator/alternator is fitted and supplies, where necessary, electricity to
the accessories indispensable to the operation of the engine;
b) starting other than electrical: if there are any electrically operated accessories indispensable to the
operation of the engine, the generator/alternator is fitted to supply these accessories; otherwise, it
is removed.
In either case, the system for producing and accumulating the energy necessary for starting is fitted
and operates in the unloaded condition.
5.2 Setting conditions
The setting conditions for the test for determination of net power are indicated in Table 2.
Table 2 — Setting conditions
1 Setting of fuel delivery system
2 Setting of injection pump delivery system
In accordance with the manufacturer's production
3 Ignition or injection timing (timing curve)
specifications and used without further alteration for
4 Governor setting
the particular application.
5 Anti-pollution devices
6 Boost control
6 © ISO 2020 – All rights reserved
5.3 Test conditions
5.3.1 The net power test shall consist of a run at full throttle for spark-ignition engines and at the
fixed full-load fuel injection pump setting for compression-ignition engines, the engine being equipped
as specified in Table 1.
5.3.2 Performance data shall be obtained under stabilized operating conditions, with an adequate
fresh air supply to the engine.
Engines shall have been run-in, started and warmed up in accordance with the manufacturer's
recommendations. Combustion chambers may contain deposits, but in limited quantity. Test conditions
such as inlet air temperature shall be selected as near to reference conditions (see 6.2) as possible in
order to minimise the correction factor.
5.3.3 The temperature of the inlet air to the engine (ambient air), shall be measured within 0,15 m
upstream of the air inlet duct work.
The thermometer or thermocouple shall be shielded from radiant heat and located directly in the
airstream. It shall also be shielded from fuel spray back. A sufficient number of locations shall be used
to give a representative average inlet temperature.
5.3.4 The inlet depression shall be measured downstream of the entry ducts, air filter, inlet silencer,
speed-limiting device (if they are fitted) or their equivalents.
5.3.5 The absolute pressure at the entry to the engine, downstream of the compressor and heat
exchanger, if they are fitted, shall be measured in the inlet manifold and at any other point where pressure
has to be measured to calculate correction factors.
5.3.6 The exhaust back pressure shall be measured at a point at least three pipe diameters from the
outlet flange(s) of the exhaust manifold(s) and downstream of the turbocharger(s), if fitted. The location
shall be specified.
5.3.7 No data shall be taken until torque, speed and temperature have been maintained substantially
constant for at least 1 min.
5.3.8 The engine speed during a run or reading shall not deviate from the selected speed by more than
–1
±1 % or ±10 min , whichever is greater.
5.3.9 Observed brake load, fuel flow and inlet air temperature data shall be taken virtually
simultaneously and shall, in each case, be the average of two stabilized consecutive readings which do
not vary more than 2 % for the brake load and fuel consumption. The second reading shall be determined
without any adjustment of the engine, approximately 1 min after the first.
5.3.10 The coolant temperature at the engine outlet shall be kept within ±5 K of the upper
thermostatically controlled temperature specified by the manufacturer. If no temperature is specified,
the temperature shall be 353 K ± 5 K.
For air-cooled engines, the temperature at a point indicated by the manufacturer shall be kept within
K of the maximum value specified by the manufacturer in the reference conditions.
−20
5.3.11 Fuel temperature shall be as follows:
a) For spark-ignition engines, the fuel temperature shall be measured as near as possible to the inlet
of the carburettor or assembly of fuel injectors. Fuel temperature shall be maintained within ±5 K
of the temperature specified by the manufacturer. However, the minimum test fuel temperature
allowed shall be the ambient air temperature. If the test fuel temperature is not specified by the
manufacturer, it shall be 298 K ± 5 K;
b) For compression-ignition engines, the fuel temperature shall be measured at the inlet to the fuel-
injection pump. At the manufacturer's request the fuel temperature measurement can be made
at another point in the pump representative of the engine operating condition. Fuel temperature
shall be maintained within ±3 K of the temperature specified by the manufacturer. In all cases, the
minimum allowable fuel temperature at the pump entrance is 303 K. If the test fuel temperature is
not specified by the manufacturer, it shall be 313 K ± 3 K.
5.3.12 The lubricant temperature shall be measured at the oil gallery inlet or the cooler outlet if fitted,
unless some other measuring location is specified by the manufacturer. The temperature shall be
maintained within the limits specified by the manufacturer.
5.3.13 An auxiliary regulation system may be used if necessary to maintain temperature within limits
specified in 5.3.10, 5.3.11 and 5.3.12.
5.3.14 It is recommended that a reference fuel is used; for example a non-exhaustive list of such fuel
includes the following:
— CEC RF-01-A-80;
— CEC RF-08-A-85;
— CEC RF-03-A-84;
NOTE Coordinating European Council for the Development of Performance Tests for Lubricants and
Engines Fuels.
— JIS K 2202;
— JIS K 2204;
NOTE Japan Industrial Standards.
— 40 CFR, Part 86.113-04 or the latest edition for spark-ignition engines;
— 40 CFR, Part 86.1313-04 or the latest edition for compression-ignition engines.
NOTE Title 40, Code of Federal Regulations, USA.
A commercially available fuel may be used, providing its characteristics are specified in 8.3 and that is
does not contain any supplementary smoke-suppressant or additive.
5.4 Test procedure
Measurements shall be taken at a sufficient number of engine speeds to define the power curve
completely between the lowest and the highest engine speeds recommended by the manufacturer. This
range of speeds shall include the revolution speed at which the engine produces its maximum power.
5.5 Data to be recorded
Data to be recorded shall be those indicated in Clause 8.
8 © ISO 2020 – All rights reserved
6 Power correction factors
6.1 Definition of factor α for power correction
This is the factor by which the observed power shall be multiplied to determine the engine power at
the reference atmospheric conditions specified in 6.2. The corrected power (i.e. power at reference
conditions), P , is given in Formula (1):
ref
P = α·P (1)
ref y
where
α is the correction factor (α being the correction factor for spark-ignition engines and α the
a c
correction factor for compression-ignition engines);
P is the measured (observed) power.
y
6.2 Atmospheric conditions
6.2.1 Reference atmospheric conditions
For the purposes of determining the power and fuel consumption of engines, the reference atmospheric
conditions given in 6.2.1.1 and 6.2.1.2 shall be used.
6.2.1.1 Temperature
The reference temperature, T , is 298 K (25 °C).
ref
6.2.1.2 Dry pressure
The reference dry barometric pressure, p , is 99 kPa.
d, ref
NOTE The dry barometric pressure is based on a total pressure of 100 kPa and a vapour pressure of 1 kPa.
6.2.2 Test atmospheric conditions
The test atmospheric conditions shall be within the values given in 6.2.2.1 and 6.2.2.2 during the test.
6.2.2.1 Temperature, T
For spark-ignition engines:
288 K ≤ T ≤ 308 K
For compression-ignition engines:
283 K ≤ T ≤ 313 K
6.2.2.2 Dry pressure, p
d
For all engines:
80 kPa ≤ p ≤ 110 kPa
d
6.3 Determination of power correction factors
The test may be carried out in air-conditioned test rooms where the atmospheric conditions are
controlled in order to maintain the correction factor as close to 1 as possible.
Where an influencing parameter is controlled by an automatic device, no power correction for that
parameter shall be applied, provided that the relevant parameter is within the relevant range of the
device. This applies in particular to:
a) automatic air temperature controls where the device is still operating at 298 K;
b) automatic boost control, independent of atmospheric pressure, when the atmospheric pressure is
such that the boost control is working;
c) automatic fuel control where the governor adjusts the fuel flow for constant power output (by
compensating for the influence of ambient pressure and temperature).
However, in the case of a), if the automatic air temperature device is fully closed at full load at 298 K
(no heated air added to the intake air), the test shall be carried out with the device fully closed, and the
normal correction factor applied. In the case of c), the fuel flow for compression-ignition engines shall
be corrected by the reciprocal of the power correction factor.
6.3.1 Naturally aspirated and pressure-charged spark-ignition engines — Factor α
a
The correction factor, α , for spark-ignition engines shall be calculated following Formula (2):
a
12,
06,
99 T
α = (2)
a
p 298
d
where
T is the absolute temperature, in kelvins, at the engine air inlet;
p is the dry atmospheric pressure, in kilopascals, i.e. the total barometric pressure minus the
d
water vapor pressure.
Formula (2) applies to carburettor-equipped engines and to other engines where the management
system is designed to maintain a relatively constant fuel/air ratio as ambient conditions change. For
other engine types see 6.3.3.
Formula (2) only applies if
0,93 ≤ α ≤ 1,07
a
If these limits are exceeded, the corrected value obtained shall be given, and the test conditions
(temperature and pressure) precisely stated in the test report.
6.3.2 Compression-ignition engines — Factor α
c
The power correction factor, α , for compression-ignition engines at constant fuel delivery setting is
c
obtained by applying Formula (3):
f
m
α = f (3)
()
ca
where
f is the atmospheric factor (see 6.3.2.1);
a
f is the characteristic parameter for each type of engine and adjustment (see 6.3.2.2).
m
10 © ISO 2020 – All rights reserved
6.3.2.1 Atmospheric factor, f
a
The atmospheric factor, f , which indicates the effect of environmental conditions (pressure, temperature
a
and humidity) on the air drawn in by the engine shall be calculated with Formulae (4), (5) or (6):
a) naturally aspirated engines, mechanically pressure-charged engines and turbocharged engines
with wastegates operating:
NOTE For engine speeds when the wastegate of a turbocharged engine is not operating, Formulae (5) or
(6) is used, depending on the type of charge air cooling, if any.
07,
99 T
f = (4)
a
p 298
d
b) turbocharged engines without charge air cooling or with charge cooling by air/air cooler:
07,
12,
99 T
f = (5)
a
p 298
d
c) turbocharged engines with charge air cooling by engine coolant:
07,
07,
99 T
f = (6)
a
p 298
d
where T and p are as defined in 6.3.1.
d
6.3.2.2 Engine factor, f
m
Within the limits established for α in 6.3.2, the engine factor, f , is a function of the corrected fuel
c m
delivery parameter, q , and is calculated following Formulae (7) to (9):
c
fq=−0,,036 114 (7)
mc
where
q
q = (8)
c
r
in which q is the fuel delivery parameter, in milligrams per cycle per litre of engine swept volume [mg/
(l cycle)]:
()Z ×[]fuel flow ()gs/
q= (9)
−1
displacement ()le× nginespeed min
[] ()
where
Z equals 120 000 for 4-stroke cycle engines and Z= 60 000 for 2-stroke cycle engines;
r is the ratio between the absolute static pressure at the outlet of the pressure charger, or
charge air cooler if fitted, and the ambient pressure (r = 1 for naturally aspirated engines).
The formula for the engine factor, f [Formula (7)], is only valid for a 37,2 mg/(l·cycle) ≤ q ≤ 65 mg/
m c
(l cycle). For values less than 37,2 mg/(l·cycle), a constant value of f equal to 0,2 shall be taken; for
m
values greater than 65 mg/(l·cycle), a constant value of f equal to 1,2 shall be taken (see Figure 1).
m
Figure 1 — Engine factor, f , as a function of corrected fuel delivery parameter, q
m c
6.3.2.3 Limitation in use of correction formula
This correction formula only applies if:
0,9 ≤ α ≤ 1,1
c
If these limits are exceeded, the corrected value obtained shall be given, and the test conditions
(temperature and pressure) precisely stated in the test report.
6.3.3 Turbocharged engine with a system compensating the ambient conditions
When a turbocharged engine is fitted with a system which allows compensating the ambient conditions
temperature and altitude the correction factor α or α shall be set to the value of “1".
a c
6.3.4 Other types of engine
For e
...
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