ISO 6855-1:2012

INTERNATIONAL ISO
STANDARD 6855-1
First edition
2012-09-15
Mopeds — Measurement method for
gaseous exhaust emissions and fuel
consumption —
Part 1:
General test requirements
Cyclomoteurs — Méthode de mesure des émissions de gaz polluants et
de consommation de combustible —
Partie 1: Exigences générales d’essai
Reference number
©
ISO 2012
© ISO 2012
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any
means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the
address below or ISO’s member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2012 – All rights reserved

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 2
5 Standard reference conditions . 4
6 Tests . 4
6.1 Measurement of gaseous exhaust emissions . 4
6.2 Measurement of fuel consumption . 5
7 Measurement equipment . 5
7.1 Chassis dynamometer . 5
7.2 Gas-collection equipment . 5
7.3 Analytical equipment . 6
7.4 Cooling equipment. 6
7.5 Fuel consumption measurement . 7
7.6 Accuracy of instruments and measurements . 7
8 Preparing the test . 8
8.1 Engine fuel and lubricants . 8
8.2 Description of the test moped. 8
8.3 Conditioning/preparation of the test moped . 8
8.4 Adjustment of the analytical apparatus . . 8
9 System check procedure . 9
9.1 Accuracy of the CVS system . 9
9.2 Metering a constant flow of pure gas (CO or C H ) using a critical flow orifice . 9
3 8
9.3 Metering a limited quantity of pure gas (CO or C H ) by means of a
3 8
gravimetric technique . 9
10 Procedure for sampling, analysing and measuring the volume of gaseous
exhaust emissions . 9
10.1 Operations to be carried out before the moped start up . 9
10.2 Beginning of sampling and volume measurement .12
10.3 End of sampling and volume measurement .12
10.4 Analysis.12
10.5 Measuring the driving distance .13
10.6 Open type CVS system .13
11 Determination of the quantity of gaseous exhaust emissions .13
11.1 Total diluted exhaust mixture volume corrected to the standard reference conditions .13
11.2 Exhaust gas sampling and the dilution factor .14
11.3 Mass of the gaseous exhaust emissions .14
12 Determination of the fuel consumption .16
12.1 Carbon balance method .16
12.2 Fuel flow measurement method .17
12.3 Calculation of results in litres per 100 km .18
12.4 Criteria of the statistical accuracy for the fuel consumption measurements .18
Annex A (normative) Method and equipment for measuring fuel consumption by the fuel flow
measurement method .19
Annex B (informative) Example for record form of test fuel specifications .30
Annex C (informative) Exhaust gas leakage check procedure for the open type CVS system.31
Annex D (informative) Determination of the dilution factor .36
Annex E (informative) Principle of the carbon balance method .44
Annex F (informative) Simplified determination method of the atom number ratio of hydrogen
and carbon, and that of oxygen and carbon in gasoline .47
Annex G (normative) Fuel consumption for two-stroke engines .49
Annex H (informative) Criteria of the statistical accuracy for the fuel
consumption measurements .50
Bibliography .52
iv © ISO 2012 – 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.
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 6855-1 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 23, Mopeds.
ISO 6855-1 cancels and replaces ISO 6855:1983 and ISO 7859:2000, both of which have been
technically revised.
ISO 6855 consists of the following parts, under the general title Mopeds — Measurement method for
gaseous exhaust emissions and fuel consumption:
— Part 1: General test requirements
— Part 2: Test cycles and specific test conditions
— Part 3: Fuel consumption measurement at a constant speed
Introduction
For measurement of moped fuel consumption, the carbon balance method, where the fuel consumption
is calculated from analysis of the carbon quantity in the exhaust gas, is now widely used in addition to
the conventional fuel flow measurement. Therefore, the measurement of exhaust gas and that of fuel
consumption are inseparably related to each other.
ISO 6855 now covers in one single series of standards the two subjects that were previously covered
separately by ISO 6855:1983 and by ISO 7859:2000. This part of ISO 6855 defines fundamental elements
such as the measurement accuracy, test vehicle conditions and the details of the carbon balance method.
Measurement of gaseous exhaust gas emissions and fuel consumption of test cycles can be conducted
with this part of ISO 6855 and ISO 6855-2. Together with ISO 6855-3, they also give details of those
measurements at a constant speed.
While the most up-to-date technologies are reflected in the ISO 6855 series, further technical
development in the following aspects will be necessary in the future, when measurement of exhaust gas
at a lower level is required:
— cleaning of the background air (i.e the air in the test room which is used for the dilution air);
— heating of the sampling line;
— control of the test room humidity;
— the exhaust gas analysis system for low-level emissions;
— consideration for the evaporated fuel from the test moped.
In addition to the above future issues, the chassis dynamometer with electrically simulated inertia is
at the stage of practical application. Standardization of the verification method and the allowance of
simulated inertia would be necessary for this recent development.
vi © ISO 2012 – All rights reserved

INTERNATIONAL STANDARD ISO 6855-1:2012(E)
Mopeds — Measurement method for gaseous exhaust
emissions and fuel consumption —
Part 1:
General test requirements
1 Scope
This part of ISO 6855 specifies the general test requirements for measurement for the gaseous exhaust
emissions from mopeds, and for determining the fuel consumption of mopeds as defined in ISO 3833. It
is applicable to mope
...