This section describes how to calculate and apply emission adjustment factors for engines using aftertreatment technology with infrequent regeneration events that may occur during testing. These adjustment factors are typically calculated based on measurements conducted for the purposes of engine certification, and then used to adjust the results of testing related to demonstrating compliance with emission standards. For this section, "regeneration" means an intended event during which emission levels change while the system restores aftertreatment performance. For example, exhaust gas temperatures may increase temporarily to remove sulfur from an adsorber or SCR catalyst or to oxidize accumulated particulate matter in a trap. The duration of this event extends until the aftertreatment performance and emission levels have returned to normal baseline levels. Also, "infrequent" refers to regeneration events that are expected to occur on average less than once over a transient or ramped-modal duty cycle, or on average less than once per mode in a discrete-mode test.
Where:
EFA[cycle] = the average emission factor over the test segment as determined in paragraph (a)(4) of this section.
EFL[cycle] = measured emissions over a complete test segment in which active regeneration does not occur.
Example:
EFARMC = 0.15 g/kW·hr
EFLRMC = 0.11 g/kW·hr
UAFRMC = 0.15 - 0.11 = 0.04 g/kW·hr
Where:
EFH[cycle] = measured emissions over the test segment from a complete regeneration event, or the average emission rate over multiple complete test segments with regeneration if the complete regeneration event lasts longer than one test segment.
Example:
EFARMC = 0.15 g/kW·hr
EFHRMC = 0.50 g/kW·hr
DAFRMC = 0.50 - 0.15 = 0.35 g/kW·hr
Where:
F[cycle] = the frequency of the regeneration event during the test segment, expressed in terms of the fraction of equivalent test segments during which active regeneration occurs, as described in paragraph (a)(5) of this section.
Example:
FRMC = 0.10
EFARMC = 0.10 · 0.50 + (1.00 - 0.10) · 0.11 = 0.15 g/kW·hr
Where:
ir[cycle] = the number of successive test segments required to complete an active regeneration, rounded up to the next whole number.
if[cycle] = the number of test segments from the end of one complete regeneration event to the start of the next active regeneration, without rounding.
Example:
irRMC = 2
ifRMC = 17.86
40 C.F.R. §1065.680