JT/T 889-2014 in English

Requirements and test methods of engine retarder for bus

1 Scope

This standard specifies the technical requirements and test methods of engine retarder for bus.

This standard is applicable to Categories M2 and M3 buses, and also serves as reference for other buses.

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 documents (including any amendments) applies.

GB/T 3730.1 Motor vehicles and trailers — Types — Terms and definitions
GB/T 3730.2 Road vehicle — Masses — Vocabulary and codes
GB/T 12534 Motor vehicles — General rules of road test method
GB/T 12536 Coastdown test method of motor vehicles

3 Terms and definitions

For the purposes of this document, the terms and definitions given in GB/T 3730.1 and GB/T 3730.2 and the following apply.

3.1
engine retarder
device that retards the vehicle through providing braking efficiency by using the resistance generated by engine exhaust throttling

4 Technical requirements

4.1 The engine retarder shall be provided with manual switch and corresponding working gear (at least two gears). The brake torque controlled in the first gear shall not be less than 50% of the maximum brake torque of the engine retarder.

4.2 When the test vehicle runs at a constant speed of 50 km/h ± 5 km/h and the engine retarder brakes alone until the speed of the test vehicle drops by 20 km/h, the average deceleration a shall not be less than 0.71 m/s2, or the deceleration time t shall not be greater than 7.8 s.
5 Test method

5.1 Test conditions

5.1.1 The test vehicle shall meet the requirements of GB/T 12534.

5.1.2 The engine retarder shall not be adjusted during the test.

5.2 Test apparatus and equipment

Foreword i
1 Scope １
2 Normative references １
3 Terms and definitions １
4 Technical requirements １
5 Test method ２