40 CFR § 1039.510 - Which duty cycles do I use for transient testing?
---
identifier: "/us/cfr/t40/s1039.510"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 1039.510 - Which duty cycles do I use for transient testing?"
title_number: 40
title_name: "Protection of Environment"
section_number: "1039.510"
section_name: "Which duty cycles do I use for transient testing?"
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "U"
subchapter_name: "AIR POLLUTION CONTROLS"
part_number: "1039"
part_name: "CONTROL OF EMISSIONS FROM NEW AND IN-USE NONROAD COMPRESSION-IGNITION ENGINES"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "42 U.S.C. 7401-7671q."
regulatory_source: "69 FR 39213, June 29, 2004, unless otherwise noted."
cfr_part: "1039"
---
# 1039.510 Which duty cycles do I use for transient testing?
(a) Measure emissions by testing the engine on a dynamometer with one of the following transient duty cycles to determine whether it meets the transient emission standards in § 1039.101(a):
(1) For variable-speed engines, use the transient duty cycle described in appendix VI of this part.
(2) [Reserved]
(b) The transient test sequence consists of an initial run through the transient duty cycle from a cold start, 20 minutes with no engine operation, then a final run through the same transient duty cycle. Calculate the official transient emission result from the following equation:
[69 FR 39213, June 29, 2004, as amended at 70 FR 40463, July 13, 2005; 75 FR 22991, Apr. 30, 2010; 76 FR 57437, Sept. 15, 2011; 79 FR 23751, Apr. 28, 2014]