This section describes how to adjust emission results from engines using aftertreatment technology with infrequent regeneration events. See paragraph (e) of this section for how to adjust ramped-modal testing. See paragraph (f) of this section for how to adjust discrete-mode testing. 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 adsorbers or to oxidize accumulated particulate matter in a trap. For this section, ``infrequent'' refers to regeneration events that are expected to occur on average less than once over the applicable transient duty cycle or ramped-modal cycle, or on average less than once per typical mode in a discrete-mode test.
(a) Developing adjustment factors. Develop an upward adjustment factor and a downward adjustment factor for each pollutant based on measured emission data and observed regeneration frequency. Adjustment factors should generally apply to an entire engine family, but you may develop separate adjustment factors for different engine configurations within an engine family. If you use adjustment factors for certification, you must identify the frequency factor, F, from paragraph (b) of this section in your application for certification and use the adjustment factors in all testing for that engine family. You may use carryover or carry-across data to establish adjustment factors for an engine family, as described in Sec. 1042.235(d), consistent with good engineering judgment. All adjustment factors for regeneration are additive. Determine adjustment factors separately for different test segments. For example, determine separate adjustment factors for different modes of a discrete-mode steady-state test. You may use either of the following different approaches for engines that use aftertreatment with infrequent regeneration events:
(1) You may disregard this section if regeneration does not significantly affect emission levels for an engine family (or configuration) or if it is not practical to identify when regeneration occurs. If you do not use adjustment factors under this section, your engines must meet emission standards for all testing, without regard to regeneration.
(2) If your engines use aftertreatment technology with extremely infrequent regeneration and you are unable to apply the provisions of this section, you may ask us to approve an alternate methodology to account for regeneration events.
(b) Calculating average adjustment factors. Calculate the average adjustment factor (EFA) based on the following equation: EFA = (F)(EFH) + (1-F)(EFL) Where: F = The frequency of the regeneration event during normal in-use
operation, expressed in terms of the fraction of equivalent
tests during which the regeneration occurs. You may determine
F from in-use operating data or running replicate tests. For
example, if you observe
that the regeneration occurs 125 times during 1,000 MW-hrs of
operation, and your engine typically accumulates 1 MW-hr per
test, F would be (125) / (1,000) / (1) = 0.125. No further
adjustments, including weighting factors, may be applied to F.EFH = Measured emissions from a test segment in which the
regeneration occurs.EFL = Measured emissions from a test segment in which the
regeneration does not occur.
(c) Applying adjustment factors. Apply adjustment factors based on whether regeneration occurs during the test run. You must be able to identify regeneration in a way that is readily apparent during all testing.
(1) If regeneration does not occur during a test segment, add an upward adjustment factor to the measured emission rate. Determine the upward adjustment factor (UAF) using the following equation: UAF = EFA-EFL
(2) If regeneration occurs or starts to occur during a test segment, subtract a downward adjustment factor from the measured emission rate. Determine the downward adjustment factor (DAF) using the following equation: DAF = EFH-EFA
(d) Sample calculation. If EFL is 0.10 g/kW-hr, EFH is 0.50 g/kW-hr, and F is 0.1 (the regeneration occurs once for each ten tests), then: EFA = (0.1)(0.5 g/kW-hr) + (1.0-0.1)(0.1 g/kW-hr) = 0.14 g/kW-hr.UAF = 0.14 g/kW-hr-0.10 g/kW-hr = 0.04 g/kW-hr.DAF = 0.50 g/kW-hr-0.14 g/kW-hr = 0.36 g/kW-hr.
(e) Ramped-modal testing. Develop a single sets of adjustment factors for the entire test. If a regeneration has started but has not been completed when you reach the end of a test, use good engineering judgment to reduce your downward adjustments to be proportional to the emission impact that occurred in the test.
(f) Discrete-mode testing. Develop separate adjustment factors for each test mode. If a regeneration has started but has not been completed when you reach the end of the sampling time for a test mode extend the sampling period for that mode until the regeneration is completed.
(g) Category 3 engines. We may specify an alternate methodology to account for regeneration events from Category 3 engines. If we do not, the provisions of this section apply as specified. [73 FR 37243, June 30, 2008, as amended at 75 FR 23005, Apr. 30, 2010]