ISO 10521-1:2006

Road vehicles — Road load — Part 1: Determination under reference atmospheric conditions

ISO 10521-1:2006 specifies methods of determining the road load of road vehicles for subsequent test purposes, for example, fuel consumption tests or exhaust emission measurements. This determines the road load of a vehicle running on a level road under reference atmospheric conditions. It is achieved by either the coastdown method, the torquemeter method or the wind-tunnel/chassis-dynamometer method. ISO 10521-1:2006 is applicable to motor vehicles, as defined in ISO 3833:1977, up to a gross vehicle mass of 3 500 kg.

Véhicules routiers — Résistance sur route — Partie 1: Détermination dans les conditions atmosphériques de référence

General Information

• Status: Published
• Publication Date: 02-Oct-2006
• ICS: 43.020 - Road vehicles in general
• Technical Committee: ISO/TC 22/SC 34 - Propulsion, powertrain and powertrain fluids
• Drafting Committee: ISO/TC 22/SC 34 - Propulsion, powertrain and powertrain fluids
• Current Stage: 9093 - International Standard confirmed
• Completion Date: 13-Dec-2020

Relations

• Revises: ISO 10521:1992 - Motor vehicle road load — Determination under reference atmospheric conditions and reproduction on chassis dynamometer
• Effective Date: 15-Apr-2008

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 10521-1
First edition
2006-10-01

Road vehicles — Road load —
Part 1:
Determination under reference
atmospheric conditions
Véhicules routiers — Résistance sur route —
Partie 1: Détermination dans les conditions atmosphériques de
référence




Reference number
ISO 10521-1:2006(E)
©
ISO 2006

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ISO 10521-1:2006(E)
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©  ISO 2006
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ISO 10521-1:2006(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope .1
2 Normative references .1
3 Terms and definitions .1
4 Required overall measurement accuracy .2
5 Road-load measurement on road.3
5.1 Requirements for road test.3
5.1.1 Atmospheric conditions for road test.3
5.1.2 Test road.3
5.2 Preparation for road test.4
5.2.1 Vehicle preparation.4
5.2.2 Installation of instruments.4
5.2.3 Vehicle preconditioning .5
5.3 Measurement of total resistance by coastdown method .5
5.3.1 Multi-segment method .5
5.3.2 Average deceleration method .8
5.3.3 Direct regression method .10
5.4 Onboard-anemometer based coastdown method.11
5.4.1 Selection of speed range for road-load curve determination .12
5.4.2 Data collection .12
5.4.3 Vehicle coastdown.12
5.4.4 Determination of coefficients .12
5.4.5 Determination of total resistance.13
5.5 Measurement of running resistance by torquemeter method .13
5.5.1 Installation of torquemeter .13
5.5.2 Vehicle running and data sampling .13
5.5.3 Calculation of mean speed and mean torque .14
5.5.4 Running resistance curve determination.16
5.6 Correction to standard atmospheric conditions .16
5.6.1 Correction factors.16
5.6.2 Road-load curve correction.17
6 Road-load measurement by wind tunnel/chassis dynamometer .19
6.1 Aerodynamic drag measurement in wind tunnel .19
6.1.1 Requirements for wind tunnel.19
6.1.2 Testing procedure.19
6.1.3 Test result.19
6.2 Rolling resistance determination with chassis dynamometer.19
6.2.1 Testing device.19
6.2.2 Testing procedure.20
6.2.3 Test results.21
6.3 Total-resistance calculation .21
6.4 Total-resistance curve determination.22
Annex A (informative) Examples of onboard-anemometer calibration procedure.23
Annex B (informative) Examples of dynamometer-measured rolling-resistance correction method.26

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ISO 10521-1:2006(E)
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 10521-1 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 5, Engine
tests.
This first edition, together with ISO 10521-2, cancels and replaces ISO 10521:1992, which has been
technically revised.
ISO 10521 consists of the following parts, under the general title Road vehicles — Road load:
⎯ Part 1: Determination under reference atmospheric conditions
⎯ Part 2: Reproduction on chassis dynamometer
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ISO 10521-1:2006(E)
Introduction
It is known that wind gives much influence to vehicle road-load measurement on test roads. Therefore, no
international standards or national standards/regulations allowed conducting on-road tests under windy (e.g. 3
m/s or more) conditions in terms of measurement accuracy. In this standard, wind effect correction
methodology is newly introduced into the conventional coastdown method and torquemeter method, and it
offers wider (up to wind speed of 10 m/s) opportunity of on-road tests. In addition, more realistic road load can
be simulated even under lower wind conditions.
This part of ISO 10521 also adopts the off-road road-load measurement method as the comparable alternative.
The method is based on the separation of the total road load into two components, aerodynamic drag and
rolling resistance, where the former is measured in a wind tunnel and the latter with a chassis dynamometer.
This alternative enables the standard users to carry out road-load measurement regardless of atmospheric
conditions or other requirements necessary for the on-road test. It is not the scope of this standard to define
all requirements of wind-tunnel design or test practice. Nevertheless, the standard users are encouraged to
conduct the measurement with state-of-the-art wind-tunnel technologies and to respect the highest quality
management standards such as ISO 17025, so as to secure the measurement reliability and repeatability.
In view of accessibility of the standard, International Standard ISO 10521 is divided into two parts in this
second edition in order to provide two separate standards for the two different technical aspects,
determination of road load and reproduction of road load on chassis dynamometer.
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INTERNATIONAL STANDARD ISO 10521-1:2006(E)

Road vehicles — Road load —
Part 1:
Determination under reference atmospheric conditions
1 Scope
This part of ISO 10521 specifies methods of determining the road load of road vehicles for subsequent test
purposes, for example, fuel consumption tests or exhaust emission measurements. This determines the road
load of a vehicle running on a level road under reference atmospheric conditions. It is achieved by either the
coastdown method, the torquemeter method or the wind-tunnel/chassis-dynamometer method.
This part of ISO 10521 is applicable to motor vehicles, as defined in ISO 3833, up to a gross vehicle mass of
3 500 kg.
2 Normative references
The following referenced documents are indispensable for the application 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 3833, Road vehicles — Types — Terms and definitions
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 3833 and the following apply.
3.1
total resistance
total force-resisting movement of a vehicle, measured either by the coastdown method or by the wind-
tunnel/chassis-dynamometer method, including the friction forces in the drive-train
3.2
running resistance
torque-resisting movement of a vehicle, measured by the torquemeter installed in the drive-train of a vehicle,
including the friction torque in the drive-train downstream of the torquemeter
3.3
road load
general meaning of the force or torque which opposes the movement of a vehicle, including total resistance
and/or running resistance
3.4
aerodynamic drag
resistance of the air to the motion of a vehicle
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ISO 10521-1:2006(E)
3.5
rolling resistance
opposing force in the drive-train, axles and tyres to the motion of a vehicle
3.6
reference speed
a vehicle speed at which a chassis-dynamometer load is verified
3.7
reference atmospheric conditions
atmospheric conditions of the following values, to which the road-load measurement results are corrected:
a) atmospheric pressure: p = 100 kPa, unless otherwise specified by regulations;
0
b) atmospheric temperature: t = 293 K, unless otherwise specified by regulations;
0
3
c) dry air density: ρ = 1,189 kg/m , unless otherwise specified by regulations;
0
d) wind speed: 0 m/s.
3.8
stationary anemometry
measurement of wind speed and direction with an anemometer at a location and height above road level
alongside the test road where the most representative wind conditions will be experienced
3.9
onboard anemometry
measurement of wind speed and direction with an anemometer appropriately installed to the test vehicle
3.10
wind correction
correction of the effect of wind on road load, which is achieved either by stationary or by onboard anemometry
3.11
aerodynamic stagnation point
point on the surface of a vehicle where the wind velocity is equal to zero
4 Required overall measurement accuracy
The required overall measurement accuracy shall be as follows:
a) vehicle speed: ± 0,5 km/h or ± 1 %, whichever is greater;
b) time: ± 50 ms or ± 0,1 %, whichever is greater;
c) wheel torque: ± 3 N·m or ± 0,5 %, whichever is greater;
d) wind speed: ± 0,3 m/s;
e) wind direction: ± 3°;
f) atmospheric temperature: ± 1 K;
g) atmospheric pressure: ± 0,3 kPa;
h) vehicle mass: ± 10 kg;
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ISO 10521-1:2006(E)
i) tyre pressure: ± 5 kPa;
j) product of aerodynamic coefficient and frontal projected area (SCd): ± 2 %;
k) chassis-dynamometer roller speed: ± 0,5 km/h or ± 1 %, whichever is greater;
l) chassis-dynamometer force:
Category 1 chassis dynamometer: ± 6 N, or
Category 2 chassis dynamometer: ± 10 N or ± 0,1 % of full scale, whichever is greater.
NOTE The Category 2 chassis dynamometer usually has a greater load capacity, e.g. 130 kW or more.
5 Road-load measurement on road
5.1 Requirements for road test
5.1.1 Atmospheric conditions for road test
5.1.1.1 Wind
The average wind speed over the test road shall not exceed 10 m/s, nor wind gusts exceed 14 m/s. Relevant
wind correction shall be conducted according to the applicable type of anemometry specified in Table 1. In
order to decide the applicability of each anemometry type, the average wind speed shall be determined by
continuous wind speed measurement, using a recognized meteorological instrument, at a location and height
above the road level alongside the test road where the most representative wind conditions will be
experienced.
NOTE Wind correction may be waived when the average wind speed is 3 m/s or less.
Table 1 — Applicable anemometry depending on average wind speed and cross-wind component
Wind speed in metres per second (m/s)
Average wind speed
Absolute wind speed
Absolute wind speed v ≤ 5
Type of anemometry
5 < v ≤ 10
Cross-wind component (v ) Cross-wind component (v )
c c
v ≤ 3 3 < v ≤ 5
c c
Stationary anemometry Applicable Not applicable Not applicable
Onboard anemometry Applicable Applicable Applicable
NOTE The stationary anemometry is recommended when the absolute wind speed is less than 1 m/s.

5.1.1.2 Atmospheric temperature
The atmospheric temperature shall be within the range of 274 to 308 K, inclusive.
5.1.2 Test road
The road surface shall be flat, dry and hard, and its texture and composition shall be representative of current
urban and highway road surfaces. The test-road longitudinal slope shall not exceed ± 1 %. The local
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ISO 10521-1:2006(E)
inclination between any points 3 m apart shall not deviate more than ± 0,5 % from this longitudinal slope. The
maximum cross-sectional camber of the test road shall be 1,5 %.
5.2 Preparation for road test
5.2.1 Vehicle preparation
5.2.1.1 Vehicle condition
The test vehicle shall be suitably run-in for the purpose of the subsequent test. The tyres shall be suitably
broken-in for the purpose of the subsequent test, while still having a tread depth of not less than 50 % of the
initial tread depth.
Unless any particular purpose is intended, the vehicle shall be in normal vehicle conditions, as specified by
the manufacturer. That is, tyre pressure (see 5.2.1.2), wheel alignment, vehicle height, lubricants in the drive-
train and wheel-bearings, and brake adjustment to avoid unrepresentative parasitic drag.
During the road test, the engine bonnet/hood and all windows shall be closed so that they will not influence
the road-load measurement. Any covers of the air ventilation system, headlamps, etc., shall be closed, and
the air-conditioning switched off.
The vehicle mass shall be adjusted to meet the requirement of the intended subsequent test, including the
mass of the driver and instruments.
5.2.1.2 Tyre-pressure adjustment
If the difference between the ambient and soak temperature is more than 5 K, the tyre pressure shall be
adjusted as follows.
Soak the tyres for more than 4 h at 10 % above the target pressure. Just before testing, reduce the pressure
down to the manufacturer’s recommended inflation pressure, adjusted for difference between the soaking-
environment temperature and the ambient test temperature at a rate of 0,8 kPa per 1 K using the following
formula:
∆=PT0,8× −T
()
t soak amb
where
∆ P is the tyre pressure adjustment, in kilopascals (kPa);
t
0,8 is the pressure adjustment factor, in kilopascals per kelvin (kPa/K);
T is the tyre-soaking temperature, in kelvins (K);
soak
T is the test ambient temperature, in kelvins (K).
amb
5.2.2 Installation of instruments
Any instruments, especially for those installed outside the vehicle, shall be installed on the vehicle in such a
manner as to minimize effects on the operating characteristics of the vehicle.
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ISO 10521-1:2006(E)
5.2.3 Vehicle preconditioning
Prior to the test, the vehicle shall be preconditioned appropriately, until stabilized and normal vehicle operating
temperatures have been reached. It is recommended that the vehicle should be driven at the most appropriate
reference speed for a period of 30 min. During this preconditioning period, the vehicle speed shall not exceed
the highest reference speed.
5.3 Measurement of total resistance by coastdown method
The total resistance shall be determined by either the multi-segment method (5.3.1), the average deceleration
method (5.3.2) or the direct regression method (5.3.3).
5.3.1 Multi-segment method
5.3.1.1 Selection of speed points for road-load curve determination
In order to obtain a road-load curve as a function of vehicle speed, a minimum of four speed points, V (j = 1, 2,
j
etc.) shall be selected. The highest speed point shall not be lower than the highest reference speed, and the
lowest speed point shall not be higher than the lowest reference speed. The interval between each speed
point shall not be greater than 20 km/h.
5.3.1.2 Data collection
During the test, a) and b) shall be measured and recorded at a maximum of 0,2 s intervals, and c) and d) at a
maximum of 1,0 s intervals.
a) elapsed time;
b) vehicle speed;
c) wind speed;
d) wind direction.
NOTE The wind speed and the wind direction are measured by the stationary anemometry.
5.3.1.3 Vehicle coastdown
5.3.1.3.1 Following preconditioning, and immediately prior to each test measurement, drive the vehicle at
the highest reference speed for, at most, 1 min, if necessary. Then accelerate the vehicle to 5 km/h more than
the speed at which the coastdown time measurement begins (V + ∆V) and begin the coastdown immediately.
j
5.3.1.3.2 During coastdown, the transmission shall be in neutral, and the engine shall run at idle. In the
case of vehicles with manual transmission, the clutch shall be engaged. Movement of steering-wheel shall be
avoided as much as possible, and the vehicle brakes shall not be operated until the end of the coastdown.
5.3.1.3.3 Repeat the test, taking care to begin the coastdown at the same speed and preconditions.
5.3.1.3.4 Although it is recommended that each coastdown run be performed without interruption, split runs
are permitted if data cannot be collected in a continuous fashion for the entire speed range. For split runs,
care shall be taken so that the vehicle condition be constant as much as possible at each split point.
5.3.1.4 Determination of total resistance by coastdown time measurement
5.3.1.4.1 Measure the coastdown time corresponding to the speed V as the elapsed time from the vehicle
j
speed (V + ∆V) to (V − ∆V). It is recommended that ∆V be 10 km/h when the vehicle speed is more than
j j
60 km/h, and 5 km/h when the vehicle speed is 60 km/h or less.
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ISO 10521-1:2006(E)
5.3.1.4.2 Carry out these measurements in both directions until a minimum of three consecutive pairs of
figures have been obtained which satisfy the statistical accuracy p, in percent, defined below.
ts 100
p=× ≤ 3%
∆T
n
j
where
n is the number of pairs of measurements;
∆T is the mean coastdown time at speed V , in seconds (s), given by the formula:
j j
n
1
∆=TT∆
jji
∑
n
i=1
in which
∆T is the harmonized average coastdown time of the ith pair of measurements at speed V , in
ji j
seconds (s) given by the formula:
2
∆=T
ji
11∆+TT∆
()jiab()j i
and in which
th
∆T and ∆T are the coastdown times of the i measurement at speed V in each direction,
jai jbi j
respectively, in seconds (s);
s is the standard deviation, in seconds (s), defined by the formula:
n
2
1
sT=∆−∆T
()
∑ ji j
n −1
i=1
t is the coefficient given in Table 2.
Table 2
t

n t
n
3 4,3 2,48
4 3,2 1,60
5 2,8 1,25
6 2,6 1,06
7 2,5 0,94
8 2,4 0,85
9 2,3 0,77
10 2,3 0,73
11 2,2 0,66
12 2,2 0,64
13 2,2 0,61
14 2,2 0,59
15 2,2 0,57
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ISO 10521-1:2006(E)
5.3.1.4.3 If, during a measurement in one direction, the driver is forced to change the vehicle direction
sharply, this measurement and the paired measurement in the opposite direction shall be rejected.
5.3.1.4.4 The total resistances, F and F at speed V in each direction, in newtons, are determined by the
ja jb j
formulae:
12×∆V
Fm=− × +m ×
()
jar
3,6 ∆T
ja
12×∆V
Fm=− × +m ×
()
jbr
3,6 ∆T
jb
where
m is the test vehicle mass including the driver and instruments, in kilograms (kg);
m is the equivalent effective mass of all the wheels and vehicle components rotating with the
r
wheels during coastdown on the road, in kilograms (kg); m should be measured or
r
calculated by an appropriate technique. As an alternative, m may be estimated as 3 % of
r
the unladen vehicle mass;
∆T and ∆T are the mean coastdown times in each direction, respectively, corresponding to speed V ,
ja jb j
in seconds (s), given by the formulae:
n
1
∆=TT∆
jjaa∑i
n
i=1
n
1
∆=TT∆
jjbb∑i
n
i=1
5.3.1.4.5 The total-resistance curve shall be determined as follows. Fit the following regression curve to the
data sets (V , F ) and (V , F ) corresponding to all the speed points V (j = 1, 2, etc.) and direction (a, b) to
j ja j jb j
determine f , f and f :
0 1 2
2
F=+ffV+fV
a0a 1a 2a
2
F=+ffV+fV
b0b 1b 2b
where
F and F are the total resistances in each direction, in newtons (N);
a b
f and f are the constant terms in each direction, in newtons (N);
0a 0b
f and f are the coefficients of the first-order term of the vehicle speed in each direction, in newtons
1a 1b
hour per kilometre (N·h/km); f may be assumed to be zero, if the value of f V is no greater
1 1
than 3 % of F at the reference speed(s); in this case, the coefficients f and f shall be
0 2
recalculated;
f and f are the coefficients of the second-order term of the vehicle speed in each direction, in
2a 2b
2
newtons hour squared per kilometre squared [(N⋅(h/km) ];
V is the vehicle speed, in kilometres per hour (km/h).
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ISO 10521-1:2006(E)
Then calculate the coefficients f , f and f in the total-resistance equation using the following formulae:
0 1 2
f + f
0a 0b
f =
0
2
f + f
1a 1b
f =
1
2
f + f
2a 2b
f =
2
2
where f , f and f are the average coefficients in the following average total-resistance equation:
0 1 2
2
F =+ffV+fV
avg 0 1 2
and in which F is the average total resistance, in newtons (N).
avg
NOTE As a simple alternative to the above calculation, the following formula may be applied to compute the average
total resistance, where the harmonized average of the alternate coastdown time is used instead of the average of alternate
total resistance.
12×∆V
Fm=− ×()+m ×
j r
3,6 ∆T
j
where ∆T is the harmonized average of alternate coastdown time measurements at speed V , in seconds (s), given by the
j j
formula:
2
∆=T
j
11∆+TT∆
()()
jabj
and in which ∆T and ∆T are the coastdown time at speed V in each direction, respectively, in seconds (s).
ja jb j
Then, calculate the coefficients f , f and f in the total-resistance equation with the regression analysis.
0 1 2
5.3.2 Average deceleration method
As an alternative to the determination in 5.3.1, the total resistance may also be determined by the procedures
described in 5.3.2.1 to 5.3.2.4.
5.3.2.1 Selection of speed points for road-load curve determination
Speed points shall be selected as specified in 5.3.1.1.
5.3.2.2 Data collection
Data shall be measured and recorded as specified in 5.3.1.2.
5.3.2.3 Vehicle coastdown
Vehicle coastdown shall be conducted as specified in 5.3.1.3.
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ISO 10521-1:2006(E)
5.3.2.4 Determination of total resistance by coastdown measurement
5.3.2.4.1 Record the speed-versus-time data during coastdown from vehicle speed (V + ∆V) to (V − ∆V),
j j
where ∆V is more than 10 km/h.
5.3.2.4.2 Fit the following function to the group of data by polynomial regression to determine the
coefficients A , A , A and A :
0 1 2 3
23
Vt()=+A A t+A t+A t
a0a 1a 2a 3a

23
Vt=+A A t+A t+A t
()
b0b 1b 2b 3b
where
V (t), V (t) is the vehicle speed, in kilometres per hour (km/h);
a b
t is the time, in seconds (s);
A , A , A , A , A , A , A and A are the coefficients.
0a 1a 2a 3a 0b 1b 2b 3b
5.3.2.4.3 Determine the deceleration, γ , in metres per second squared, at the speed V as follows:
j j
1
2
γ = ×AA+×23t +×At
jj()12 3j
3,6
where t is the time at which the vehicle speed given by the function in 5.3.2.4.2 is equal to V .
j j
5.3.2.4.4 Repeat the measurements in both directions, until a minimum of four consecutive pairs of the
data have been obtained which satisfy the statistical accuracy p, in percent, below. The validity of the data
shall be decided in accordance with 5.3.1.4.3.
ts 100
p=× ≤ 3%
Γ
n
j
where
n is the number of pairs of measurements;
2
Γ is the mean average deceleration at the speed V , in metres per second squared (m/s ), given by the
j j
formula:
n
1
ΓΓ=
jj∑i
n
i=1
in which
1
Γγ=× +γ
()
jjabiji
2
and in which
γ and γ are the decelerations of the ith measurement at the speed V defined in 5.3.2.4.3
jai jbi j
2
for each direction, respectively, in metres per second squared (m/s );
2
s is the standard deviation, in metres per second squared (m/s ), defined by the
formula:
© ISO
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