# Commission Regulation (EU) 2017/2400 of 12 December 2017 implementing Regulation (EC) No 595/2009 of the European Parliament and of the Council as regards the determination of the CO2 emissions and fuel consumption of heavy-duty vehicles and amending Directive 2007/46/EC of the European Parliament and of the Council and Commission Regulation (EU) No 582/2011 (Text with EEA relevance), Division 5.1: Methods for establishing retarder drag losses

Extent: E+W+S+N.I.

The retarder drag torque loss is a function of the retarder rotor speed. Since the retarder can be integrated in different parts of the vehicle driveline, the retarder rotor speed depends on the drive part (= speed reference) and step-up ratio between drive part and retarder rotor as shown in Table 2.
Table 2
Retarder rotor speeds
Configuration
Speed reference
Retarder rotor speed calculation
A.
Engine Retarder
Engine Speed
nretarder = nengine * istep-up
B.
Transmission Input Retarder
Transmission Input Shaft Speed
nretarder = ntransm.input * istep-up
= ntransm.output * itransm * istep-up
C.
Transmission Output Retarder or Propshaft Retarder
Transmission Output Shaft Speed
nretarder = ntransm.output * istep-up
where:
istep-up step-up ratio = retarder rotor speed/drive part speed
itransm transmission ratio = transmission input speed/transmission output speed
Retarder configurations that are integrated in the engine and cannot be separated from the engine shall be tested in combination with the engine. This section does not cover these non-separable engine integrated retarders.
Retarders that can be disconnected from the driveline or the engine by any kind of clutch are considered to have zero rotor speed in disconnected condition and therefore have no power losses.
The retarder drag losses shall be measured with one of the following two methods:
(1)Measurement on the retarder as a stand-alone unit
(2)Measurement in combination with the transmission

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Source: https://www.legislation.gov.uk/eur/2017/2400/annex/VI/division/5/division/5.1 (the official version)
Page: https://openlegislation.uk/eu-regulation-2017-2400/annex-VI/division-5/division-5.1
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.