The ISO 8178 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, European Union and Japan. 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 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, NRSC.

The particular 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, which is not listed in the table (ISO standards can be ordered through the ISO web site).

Table 1
Weighting Factors of B-Type ISO 8178 Test Cycles
Mode number 1 2 3 4 5 6 7 8 9 10 11
Torque, % 100 75 50 25 10 100 75 50 25 10 0
Speed Rated speed Intermediate speed Low
idle
Off-road vehicles
Type C1 0.15 0.15 0.15 - 0.10 0.10 0.10 0.10 - - 0.15
Type C2 - - - 0.06 - 0.02 0.05 0.32 0.30 0.10 0.15
Constant speed
Type D1 0.30 0.50 0.20 - - - - - - - -
Type D2 0.05 0.25 0.30 0.30 0.10 - - - - - -
Locomotives
Type F 0.25 - - - - - - 0.15 - - 0.60
Utility, lawn and garden
Type G1 - - - - - 0.09 0.20 0.29 0.30 0.07 0.05
Type G2 0.09 0.20 0.29 0.30 0.07 - - - - - 0.05
Type G3 0.90 - - - - - - - - - 0.10
Marine application
Type E1 0.08 0.11 - - - - 0.19 0.32 - - 0.30
Type E2 0.20 0.50 0.15 0.15 - - - - - - -
Marine application propeller law
Type E3, Mode # 1 2 3 4    
Power, % 100 75 50 25    
Speed, % 100 91 80 63    
Weighting factor 0.2 0.5 0.15 0.15    
Type E4, Mode # 1 2 3 4 5  
Power, % 100 80 60 40 0  
Speed, % 100 71.6 46.5 25.3 Idle  
Weighting factor 0.06 0.14 0.15 0.25 0.4  
Type E5, Mode # 1 2 3 4 5  
Power, % 100 75 50 25 0  
Speed, % 100 91 80 63 Idle  
Weighting factor 0.08 0.13 0.17 0.32 0.3  
Notes:
  • Engine torque is expressed in percent of the maximum available torque at a given engine speed
  • Rated speed is the speed at which the manufacturer specifies the rated engine power
  • Intermediate speed is the speed corresponding to the peak engine torque.