Regulations last checked for updates: Jan 31, 2025

Title 40 - Protection of Environment last revised: Nov 08, 2025
All TitlesTitle 40Chapter IPart 1039Subpart IAppendix Appendix II - Appendix II to Part 1039—Steady-State Duty Cycles
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Appendix Appendix II - Appendix II to Part 1039—Steady-State Duty Cycles

(a) The following duty cycles apply for constant-speed engines:

(1) The following duty cycle applies for discrete-mode testing:

D2 mode number Engine speed Torque
(percent) 1 		Weighting
factors
1Engine governed1000.05
2Engine governed750.25
3Engine governed500.30
4Engine governed250.30
5Engine governed100.10

1 The percent torque is relative to maximum test torque.

(2) The following duty cycle applies for ramped-modal testing:

RMC mode Time in mode
(seconds) 		Engine speed Torque
(percent) 1 2
1a Steady-state53Engine governed100.
1b Transition20Engine governedLinear transition.
2a Steady-state101Engine governed10.
2b Transition20Engine governedLinear transition.
3a Steady-state277Engine governed75.
3b Transition20Engine governedLinear transition.
4a Steady-state339Engine governed25.
4b Transition20Engine governedLinear transition.
5 Steady-state350Engine governed50.

1 The percent torque is relative to maximum test torque.

2 Advance from one mode to the next within a 20-second transition phase. During the transition phase, command a linear progression from the torque setting of the current mode to the torque setting of the next mode.

(b) The following duty cycles apply for variable-speed engines with maximum engine power below 19 kW:

(1) The following duty cycle applies for discrete-mode testing:

G2 mode number Engine speed 1 Torque
(percent) 2 		Weighting
factors
1Maximum test speed1000.09
2Maximum test speed750.20
3Maximum test speed500.29
4Maximum test speed250.30
5Maximum test speed100.07
6Warm idle00.05

1 Speed terms are defined in 40 CFR part 1065.

2 The percent torque is relative to the maximum torque at the commanded test speed.

(2) The following duty cycle applies for ramped-modal testing:

RMC mode Time in mode
(seconds) 		Engine speed 1 3 Torque
(percent) 2 3
1a Steady-state41Warm idle0.
1b Transition20Linear transitionLinear transition.
2a Steady-state135Maximum test speed100.
2b Transition20Maximum test speedLinear transition.
3a Steady-state112Maximum test speed10.
3b Transition20Maximum test speedLinear transition.
4a Steady-state337Maximum test speed75.
4b Transition20Maximum test speedLinear transition.
5a Steady-state518Maximum test speed25.
5b Transition20Maximum test speedLinear transition.
6a Steady-state494Maximum test speed50.
6b Transition20Linear transitionLinear transition.
7 Steady-state43Warm idle0.

1 Speed terms are defined in 40 CFR part 1065.

2 The percent torque is relative to the maximum torque at the commanded engine speed.

3 Advance from one mode to the next within a 20-second transition phase. During the transition phase, command a linear progression from the torque setting of the current mode to the torque setting of the next mode, and simultaneously command a similar linear progression for engine speed if there is a change in speed setting.

(c) The following duty cycles apply for variable-speed engines with maximum engine power at or above 19 kW:

(1) The following duty cycle applies for discrete-mode testing:

C1 mode number Engine speed 1 Torque
(percent) 2 		Weighting
factors
1Maximum test speed1000.15
2Maximum test speed750.15
3Maximum test speed500.15
4Maximum test speed100.10
5Intermediate test speed1000.10
6Intermediate test speed750.10
7Intermediate test speed500.10
8Warm idle00.15

1 Speed terms are defined in 40 CFR part 1065.

2 The percent torque is relative to the maximum torque at the commanded test speed.

(2) The following duty cycle applies for ramped-modal testing:

RMC mode Time in mode
(seconds) 		Engine speed 1 3 Torque
(percent) 2 3
1a Steady-state126Warm Idle0.
1b Transition20Linear TransitionLinear Transition.
2a Steady-state159Intermediate Speed100.
2b Transition20Intermediate SpeedLinear Transition.
3a Steady-state160Intermediate Speed50.
3b Transition20Intermediate SpeedLinear Transition.
4a Steady-state162Intermediate Speed75.
4b Transition20Linear TransitionLinear Transition.
5a Steady-state246Maximum Test Speed100.
5b Transition20Maximum Test SpeedLinear Transition.
6a Steady-state164Maximum Test Speed10.
6b Transition20Maximum Test SpeedLinear Transition.
7a Steady-state248Maximum Test Speed75.
7b Transition20Maximum Test SpeedLinear Transition.
8a Steady-state247Maximum Test Speed50.
8b Transition20Linear TransitionLinear Transition.
9 Steady-state128Warm Idle0.

1 Speed terms are defined in 40 CFR part 1065.

2 The percent torque is relative to the maximum torque at the commanded engine speed.

3 Advance from one mode to the next within a 20-second transition phase. During the transition phase, command a linear progression from the torque setting of the current mode to the torque setting of the next mode, and simultaneously command a similar linear progression for engine speed if there is a change in speed setting.

[69 FR 39213, June 29, 2004, as amended at 73 FR 37241, June 30, 2008]
authority: 42 U.S.C. 7401-7671q.
source: 69 FR 39213, June 29, 2004, unless otherwise noted.
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