ISO 8178-4

Steady-State Cycles (Discrete Mode)

The ISO 8178-4 is an international standard for exhaust emission measurement from a number of non-road engine applications. It is used for emission certification and/or type approval testing in many countries, including the United States, China, India, Japan, and the European Union. Depending on the legislation, the cycle can be defined by reference to the ISO 8178 standard, or else by specifying a test cycle equivalent to ISO 8178 in the national legislation (as it is the case with the US EPA regulations).

The ISO 8178-4 includes a collection of steady-state engine dynamometer test cycles (designated as type C1, C2, D1, etc.) designed for different classes of engines and equipment. Each of these cycles represents a sequence of several steady-state modes with different weighting factors.

The ISO 8178 test cycle—or its 8-mode schedule C1 in particular—is also referred to as the Non-Road Steady Cycle or Non-Road Steady-state Cycle (NRSC).

The engine operating modes and their weighting factors for B-type (11 mode) test cycles are listed in Table 1. The standard also includes an A-type 13-mode cycle, not listed in the table.

Ramped Mode Cycles

In addition to discrete mode cycles, the ISO 8178-4:2017 standard introduced ramped mode cycles (RMC), Table 2 and Table 3.

The percent torque in the tables is relative to the maximum torque at the commanded engine speed. The advance from one mode to the next should occur within a 20 second transition phase, with a linear progression from both the torque and speed settings of the current mode to the torque and speed setting of the next mode.

Locomotive Test Cycle (Type F)

ISO 8178 defines Type F cycle for locomotive testing, Table 4. This cycle has been modified on several occasions.

In the first edition of the standard (ISO 8178-4:1996), the Type F weighting factors were 0.25 at rated speed & 100% torque, 0.15 at intermediate speed & 50% torque, and 0.60 for idle. In the second edition (ISO 8178-4:2007), the rated speed point was reduced from 0.25 to 0.15 and the intermediate speed point was increased from 0.15 to 0.25, based on measurements on in-service locomotives in Europe. Additionally, the idling point was changed from “no load” to 5% of torque to account for the engine driving the air brakes compressor and other electrical loads.

In ISO 8178-4:2017, the load points have been defined based on percent power, rather than percent torque, in alignment with EU emission standards for nonroad mobile machinery (the test cycle F for Stage III A/B locomotives was based on %torque, while the cycle for Stage V locomotives is based on %power).

Marine Propeller Law Test Cycles

The engine operating modes and their weighting factors for ISO 8178 test cycles for marine propeller law applications are listed in Table 5.