Proposed Interpretation of 40CFR86.1370-2007(d)(2) 

on Minimum NTE Time with Discrete Regeneration 

By W. T. Martin, Cummins Inc., 2009-07-29 

Page 1 of 11 

BACKGROUND

The NTE minimum time for discrete regeneration in 86.1370-2007(d)(2) is difficult to interpret. 

This has led to misunderstanding between regulators and engine manufacturers. The purpose 

of this document is three fold: 

1. to provide an interpretation of this language that is fair and consistent with its intent and 

to communicate it in sufficient detail so that all parties can reach agreement on the 

interpretation of this language; 

2. to provide sufficient detail to enable EPA to issue a guidance letter consistent with the 

agreed interpretation of this language; and 

3. to enable programmers of in-use data analysis software to properly calculate and apply 

this minimum NTE time. 

INTERPRETATION OF THE CFR LANGUAGE (For a Single Regeneration Process)

The CFR language for this minimum NTE time is: 

“For engines equipped with emission controls that include discrete regeneration events, if 

a regeneration event occurs during the NTE test, then the averaging period must be at 

least as long as the time between the events multiplied by the number of full regeneration 

events within the sampling period. The requirement in this paragraph (d)(2) only applies 

for engines that send an electronic signal indicating the start of the regeneration event.“ 

This language is cited in the previous paragraph, (d)(1), which specifies the minimum NTE 

sample time of 30 s, “except where a longer averaging period is required by paragraph (d)(2) of 

this section.” Thus, paragraph (d)(2) must result in another minimum sample time that is an 

alternative to the 30 s value. 

There is consensus that the intent of this language is to exclude candidate NTE events where 

potentially higher emissions during a discrete regeneration event could cause the NTE event to 

capture unrepresentatively high emissions compared to the average emissions over a complete 

regeneration cycle (time period with the regeneration active plus the time period with the 

regeneration inactive). The interpretation proposed in this document is based on this concept 

and on the assumption that the brake specific emissions are constant at two levels with and 

without discrete regeneration. This assumption simplifies the interpretation and analysis, but it 

is not fully reflective of real-world operations. Therefore, EMA proposes that the minimum 

NTE time be computed based on this assumption and if a resulting valid NTE event with 

overlapping operation with discrete regeneration fails because the NTE event captured 

unrepresentatively high emissions due to variable emissions, engine manufacturers may 

petition EPA and CARB to either void the NTE event or declare it a pass. This petition 

would be based on an engineering analysis that shows that the NTE event captured an 

unrepresentative sample of emissions or would have passed if the NTE event had included a 

more representative sample. 

Effectively this concept and simplifying assumption means that, in order to include a candidate 

NTE event that contains a discrete regeneration event or any part thereof, the duty cycle ( DC ) 

(fraction of time or percent on time) of discrete regeneration during the candidate NTE event 
Proposed Interpretation of 40CFR86.1370-2007(d)(2) 

on Minimum NTE Time with Discrete Regeneration 

By W. T. Martin, Cummins Inc., 2009-07-29 

Page 2 of 11 

needs to be less than or equal to the duty cycle of representative complete regeneration cycles 

associated with the th i candidate NTE event. The following equations begin with this 

DC requirement and translate it into a minimum NTE event time as used in the CFR language. 

This provides the basis for the interpretation of the existing language that is necessary to 

accomplish this intent. 

This duty cycle requirement can be expressed mathematically as 

DCNTE,i ≤ DCREGEN ,rep,i[1] 

where 

DCNTE,iis the duty cycle of the regeneration signal during the th i candidate NTE event; and 

DCREGEN ,rep,i is the duty cycle of the regeneration signal over a complete regeneration cycle that 

is representative of the operation in the th i candidate NTE event. This is the time period with the 

regeneration signal active or on plus the time period with the regeneration signal inactive or off. 

Recall that the CFR language requires an alternative minimum NTE sample time. Equation [1] 

can be rearranged to yield an expression for the NTE sample time for the th i candidate NTE 

event, NTE it

,

. 

REGEN rep i

ON REGEN rep i

NTE i

ON NTE i

t

t

t

t

, ,

, , ,

,

, ,

≤ [2] 

Rearranging again yields an expression for the minimum NTE sample time for the th i NTE event, 

NTE i

t

,

, as used in the CFR language. 

NTE i

ON REGEN rep i

ON NTE i

REGEN rep i

t

t

t

t

,

, , ,

, ,

, ,

⋅ ≤ [3] 

or 

ON REGEN rep i

ON NTE i

NTE i REGEN rep i

t

t

t t

, , ,

, ,

, , , ≥ ⋅ [4a] 

This can also be expressed in terms of the duty cycle for a compete regeneration cycle that is 

representative for the th i candidate NTE event as follows: 

REGEN rep i

ON NTE i

ON REGEN rep i REGEN rep i

ON NTE i

ON REGEN rep i

ON NTE i

NTE i REGEN rep i DC

t

t t

t

t

t

t t

, ,

, ,

, , , , ,

, ,

, , ,

, ,

, ≥ , ,

⋅ = = [4b] 

Equation [4a] will be used to show how the existing CFR language must be interpreted to be 

consistent with the consensus understanding of its intent and the assumption of two levels of 

constant brake specific emissions. Equation [4b] is a more convenient form for purposes of data 

analysis software. 

To see how to interpret the CFR language, let’s now recall the key CFR language and express it 

in mathematical terms. The key language is 

“the averaging period must be at least as long as the time between the events multiplied 

by the number of full regeneration events within the sampling period” 

This language can be expressed mathematically as follows: 
Proposed Interpretation of 40CFR86.1370-2007(d)(2) 

on Minimum NTE Time with Discrete Regeneration 

By W. T. Martin, Cummins Inc., 2009-07-29 

Page 3 of 11 

NTE i REGEN i

t ≥ t ⋅ x ,

[5] 

where 

NTE i

t

,

is “the averaging period”; 

REGEN t is “the time between the events”; and 

i

x is “the number of full regeneration events within the sampling period” 

By comparing eq. [5] to eq. [4a], an interpretation of these terms can be derived that meets the 

consensus understanding of its intent as follows: 

(discrete) regeneration event means a period of time where the discrete regeneration signal is 

active or on, i.e. the period of time that the ECM is broadcasting an electronic signal that 

regeneration is active as described in the AECD disclosure. Note that the electronic signal must 

also be capable of indicating the end of a discrete regeneration event. This point is not clear in 

the CFR language, which only mentions the start of the regeneration event. 

NTE test means an otherwise valid candidate NTE event. 

within the sampling period and averaging period are synonyms and they both mean the length 

of time of an otherwise valid candidate NTE event. This is given the symbol NTE i

t

,

 in the 

equations above. 

time between events means a representative period of time for a full regeneration cycle, which 

is the period of time with discrete regeneration signal active or on plus the period of time with 

regeneration signal inactive or off. Since this period of time can vary, a representative value 

must be established. If the representative value is taken to be a variable, then a representative 

value appropriate for the candidate th i NTE event must be established. A significant amount of 

additional interpretation is required to determine this value and will be discussed later. This 

term is given the symbol REGEN rep i

t

, ,

 in equation [4a] and REGEN t in equation [5]. 

number of full regeneration events within the sampling period means the effective number of 

regeneration events that were within the candidate th i NTE event. It is a real number, not an 

integer number of regeneration events within the candidate NTE event. It can be a value less 

than one. It is equal to total time within the candidate NTE event that the discrete regeneration 

signal is active or on, divided by the representative period of time the regeneration signal is 

active or on for a full regeneration cycle. This term is given the symbol i

x in equation [5]. 

To make the DC based equation [4a] equal to the CFR based equation [5], the second term on 

the right hand side of each expression must be equal as follows: 

ON REGEN rep i

ON NTE i

i

t

t

x

, , ,

, ,

= [6] 

where 

ON NTE i

t

, ,

is the total time within the candidate NTE event that the discrete regeneration signal is 

active or on; and 
Proposed Interpretation of 40CFR86.1370-2007(d)(2) 

on Minimum NTE Time with Discrete Regeneration 

By W. T. Martin, Cummins Inc., 2009-07-29 

Page 4 of 11 

ON REGEN rep i

t

, , ,

is the representative period of time the regeneration signal is active or on for a full 

regeneration cycle. 

Since ON REGEN rep it

, , ,

 can vary, a representative value for this term must be established. If the 

representative value is taken to be a variable, then a representative value appropriate for the 

candidate th i NTE event must be established. Again a significant amount of additional 

interpretation is required to determine this value and will be discussed later. It must be 

determined consistent with the way that the representative period of time for a full regeneration 

cycle, REGEN rep it

, ,

, is determined above. By examining equation [4b] you will see that all that is 

really required for applying this language is the ratio of these representative values, which is a 

representative value of the duty cycle for full regeneration cycles. 

The derivation above shows how the current CFR language must be interpreted to be consistent 

with the consensus understanding of its intent. Note that this interpretation applies regardless of 

the relative frequency of regeneration and NTE events. Also note that this interpretation does 

not include any provisions for subdividing or windowing the NTE event so that the duty cycle 

requirement is met. It simply calculates an alternative minimum NTE time for the candidate NTE 

event. 

To help illustrate this interpretation, consider a candidate NTE event that is 100 s long with a 

regeneration signal active for the last 10 s. Further, the representative duty cycle for a complete 

regeneration cycle has been determined to be 5% or 0.05. For this example, paragraph (d)(2) 

applies because there is some period of time within the NTE event with a regeneration signal 

active or on. The minimum NTE time per equation [4b] is 

200s

0.05

10s

, ,

, ,

, ≥ = =

REGEN rep i

ON NTE i

NTE i DC

t

t

Since 200 s is longer than the default 30 s, 200 s is the correct minimum NTE time. Since the 

candidate NTE event of 100 s is less than this minimum, it is not a valid NTE event. 

MULTIPLE REGENERATION PROCESSES

The CFR language does not explicitly address the situation where an engine utilizes multiple 

discrete regeneration processes (e.g. de-soot, de-NOx, de-SOx, etc.). For this situation the 

minimum NTE time for a candidate NTE event is interpreted to be the larger of the following: 30 

s from paragraph (d)(1) and the minimum times determined for each regeneration process per 

paragraph (d)(2). Paragraph (d)(2) can only be applied if the engine outputs corresponding 

electronic discrete regeneration signals characterizing these multiple discrete regeneration 

processes. 

ESTABLISHING A REPRESENTATIVE REGENERATION DUTY CYCLE

Regeneration processes can be complex. For example de-soot processes burn off soot 

deposited on the trap when exhaust temperatures and oxidants reach adequate levels. These 

conditions can occur under normal engine operation. Passive regeneration occurs when the 
Proposed Interpretation of 40CFR86.1370-2007(d)(2) 

on Minimum NTE Time with Discrete Regeneration 

By W. T. Martin, Cummins Inc., 2009-07-29 

Page 5 of 11 

engine is operating at a normal condition and where the soot burns off at a rate that exceeds the 

soot deposition rate. When there is insufficient passive regeneration or even a risk of 

insufficient passive regeneration, the engine and aftertreatment controls take some action off 

the normal controls to enhance the oxidation of soot. This is active de-soot regeneration. The 

controls may take a variety off-normal actions to enhance de-soot regeneration. For example 

the engine timing may be retarded or fuel may be injected in the exhaust upstream of an 

oxidation catalyst to increase the exhaust temperature; or air handling system components like 

variable geometry turbines or EGR valves may be adjusted to reduce the air to fuel ratio to 

increase the exhaust temperature. These actions may require certain operating conditions and 

may switch on and off during the period of time that the controls are trying to actively regenerate 

the trap. So, there can be a variety of signals available from the ECM that indicate the status of 

each of these complex regeneration processes. 

To apply equation [4b] we need to be able to determine ON NTE it

, ,

 and DCREGEN ,rep,i. For purposes 

of determining ON NTE i

t

, ,

, one bi-state discrete signal is required to indicate when any action 

related to the applicable regeneration process is being taken which operates the system off the 

normal controls. For example it would have a value of 0 when no off-normal control actions are 

being taken and would have a value of 1 when any off-normal control action is being taken. The 

value of ON NTE it

, ,

 is simply the total time this signal is on during the candidate NTE event. 

To determine DCREGEN ,rep,i

, or its components, ON REGEN rep it

, , ,

 and REGEN rep it

, ,

, additional information is 

required. Consider regeneration processes that switch the above bi-state discrete regeneration 

signal between 0 (off) and 1 (on) multiple times while the controls are trying to regenerate or 

empty the device. De-soot regeneration processes for DPF’s work this way. For this case, a 

representative time period for determining any value of DCREGEN ,rep,i

 must cover whole or 

complete filling and emptying events not just the DC over whole or complete off-on cycles 

during the emptying part of the complete regeneration cycle. Therefore, for these types of 

regeneration processes, a second bi-state discrete regeneration signal is needed to identify 

these filling and emptying events. For example it would have a value of 0 when the device is in 

the filling part of the cycle and it would have a value of 1 when the device is in the emptying part 

of the cycle. During the filling part, no off-normal control actions are being taken. During the 

emptying part, the controls have determined that the device needs emptying and any off-normal 

control action to enhance regeneration may be active. It would return to 0 after the controls 

have determined that the device has been emptied and no off-normal control action is needed to 

regenerate the device. This second bi-state discrete signal would be used to identify complete 

filling and emptying events over which DCREGEN ,rep,i would be determined. 

Note that these two bi-state discrete signals can be reduced to a single tri-state discrete signal 

as follows: 
Proposed Interpretation of 40CFR86.1370-2007(d)(2) 

on Minimum NTE Time with Discrete Regeneration 

By W. T. Martin, Cummins Inc., 2009-07-29 

Page 6 of 11 

Bi-state signal for indicating 

actual active regeneration 

0 = no active regen. 

1 = active regen. 

Bi-state signal for indicating a 

need for active regeneration 

0 = regen. not needed 

1 = regen. needed 

Tri-state signal combining 

these two bi-state signals 

0 0 0 = no active regen. and 

no regen. is pending 

0 1 1 = no active regen. but 

active regen. pending 

1 0 invalid combination that 

should not occur 

1 1 2 = active regen. 

During filling events this tri-state signal has a value of 0. During emptying events this tri-state 

signal has a value of 1 or 2. During active regeneration this tri-state signal has a value of 2. 

The level 2 state may include time for the aftertreatment device to stabilize and restore 

emissions to normal levels after the controls are returned to normal operation. 

For regeneration processes where state 1 is not appropriate or for regeneration processes that 

do not distinguish between states 0 and 1, this tri-state signal would just revert to a bi-state 

signal with values of 0 and 2. For example, state 1 would never be set for regeneration 

processes that use off-normal control action over the entire emptying event. Another example is 

a regeneration process that does not utilized the concept of identifying that a discrete 

regeneration is needed and is pending proper operating conditions. 

Different engine makes, model years and even models may have different regeneration 

processes and regeneration signals. To support common in-use data analysis software, it is 

proposed that manufacturers provide the necessary ECM parameters to be logged and the logic 

necessary to generate the tri-state discrete signal above. And this tri-state discrete signal would 

be a common input for the in-use data analysis software. This tri-state signal is recommended 

because there is already a consensus standard that identified this signal and some 

manufacturers may already have this signal available from their ECM’s. 

With this one tri-state regeneration signal DCREGEN ,rep,i

 can be calculated from any set of engine 

operating data that has at least one complete fill event and one complete empty event. The 

calculation method will be illustrated later. In general, DCREGEN ,rep,i

 varies and, therefore, it 

should be determined based on the source of data that is deemed to be most representative. 

Because the value of DCREGEN ,rep,i

is expected to vary with the in-use engine duty cycle, the most 

representative values would be determined from the data recorded/logged during the in-use 

emissions test. Currently it is believed that there may be significant variation in this value 

throughout the in-use emissions test due to noise factors and that it would be most 

representative to determine a single value for DCREGEN ,rep based on as much of the data log as 

possible, and apply it to all candidate NTE events during that in-use emissions test. 
Proposed Interpretation of 40CFR86.1370-2007(d)(2) 

on Minimum NTE Time with Discrete Regeneration 

By W. T. Martin, Cummins Inc., 2009-07-29 

Page 7 of 11 

LOGIC FOR CALCULATION OF THE REPRESENTATIVE REGENERATION DUTY CYCLE

AND MINIMUM NTE TIME

The following logic illustrates how the post processor would determine the alternative minimum 

NTE time and which candidate NTE events satisfy the base and alternate minimum times. It 

assumes the mission log file has recorded the necessary ECM signals. Statements that are 

executed when a logical is true are placed on the next line and indented. Indent levels are 

indicated with a gray vertical bar, |. When multiple statements are to be executed when a 

logical is true, brackets are used to delineate those statements. Brackets are also used to 

delineate multiple statements for a given loop operation. Comments are preceded by a pound 

sign, #. There are two main “For” loops. The first determines the representative regeneration 

duty cycle for each regeneration process. The second determines whether each candidate NTE 

event meets the minimum time requirement. 

Input the number of discrete regeneration processes. 

Calculate the total mission time. 

For each discrete regeneration process, j: 

[ 

 |Input the function to convert the ECM regen. signals to the tri-state regen. signal; 

 |Input the ECM regen. signals from the mission log; 

 |Calculate the tri-state regen. signal for the entire mission log; 

 |# Initialize the duty cycle for this regeneration in case there is insufficient data in the log. 

 |Set the regeneration duty cycle for this regeneration process to zero; 

 |# Note this is a global variable array that must be available for use in the logic to 

 |# determine the minimum time for each candidate NTE event. 

 |# 0 DCREGEN, j,rep =

 |Scan the tri-state signal over the entire mission log, identify and count complete filling events 

 |(periods from a transition from 1 or 2 to 0 and from 0 to 1 or 2); 

 |If the number of complete filling events found is > 0, then 

 | |Calculate the total time for all the complete filling events. 

 |Scan the tri-state signal over the entire mission log, identify and count complete emptying events 

 |(periods from a transition from 0 to 1 or 2 and from 1 or 2 to 0); 

 |If the number of complete emptying events found is > 0, then 

 |[ 

 | |Calculate the total time for all the complete emptying events; 

 | |Calculate the total time at state 2 during all the complete emptying events; 

 |] #End of “If the number of complete emptying events found is > 0” 

 |If the number of complete filling and emptying events found are both > 0, then; 

 |[ 

 | |# Verify that the number of complete filling and emptying events are within 1. 

 | |If ABS(number of complete filling events – number of complete emptying events) > 1, then 

 | | |Output error message that this regeneration signal is not valid. 

 | |Else # numbers of complete filling and emptying cycles are valid. 

 | | |Calculate the duty cycle for this regeneration process 

 | | |# 

number of complete emptying events

total time for all complete emptying events

number of complete filling events

total time for all complete filling events

number of complete emptying events

total time at state 2 during all complete emptying events

, ,

+

DCREGEN j rep =

 |] # of “If the number of complete filling and emptying events found are both > 0” 

] #End of “For each discrete regeneration process”.

For each candidate NTE event, i, when checking for the minimum time: 

[ 

 |Calculate the actual time of this NTE event. 

 |Set the minimum time for this candidate NTE event to 30 s; 

 |# Note this can be a local variable and be reused for each NTE event. 

 |# 30. t NTE,min =

 |For each regeneration process, j; 

 |[ 
Proposed Interpretation of 40CFR86.1370-2007(d)(2) 

on Minimum NTE Time with Discrete Regeneration 

By W. T. Martin, Cummins Inc., 2009-07-29 

Page 8 of 11 

 | |Scan the tri-state signal over the candidate NTE, indentify and add up any level 2 time 

 | |for this regeneration process. 

 | |If there is any level 2 time for this regeneration process in the candidate NTE, then 

 | |[ 

 | | |If the regen duty cycle for this regeneration process is > 0, then 

 | | | |Calculate the alt. min. time for this candidate NTE event for this regeneration process 

 | | | |# 

REGEN j rep

NTE alt DC

t

, ,

, ,min

total time at state 2 during the candidate NTE event

=

 | | | |

 | | |Else # this regeneration process has a duty cycle of 0, i.e. it could not be calculated, so 

 | | | |Set the alternative minimum time equal to the total mission time plus 1 s 

 | | | |# Setting the alt. min time to this large value will prevent any candidate NTE event with 

 | | | |# overlapping state 2 time with this regeneration process to be void. 

 | | | |# tNTE,alt,min = tmission +1

 | | |If the alt. min. time is > minimum time for this candidate NTE event, then 

 | | | |Set the minimum time for this candidate NTE event to the alternate minimum time. 

 | | | |# Note that this step will find the largest of the following: 

 | | | |# the default minimum time of 30 s; and 

 | | | |# the alt. minimum NTE times for all applicable regeneration processes. 

 | | | |# NTE,min NTE,alt,min t = t

 | |] # End of “If there is any level 2 time for this regen. process in this candidate NTE event” 

 | |# Note that if there is no level 2 time for this regen. process, then the min. time for this NTE 

 | |# event is left unchanged, either 30 s or an alt. value from another regen. process. 

 |] # End of for loop “For each regeneration process, j” 

 |If the actual time of this candidate NTE event is >/= to the minimum for this cand. NTE event, then 

 | |Flag this candidate NTE event as valid for minimum time requirements. 

 |Else 

 | |Flag this candidate NTE event as void for minimum time requirements. 

 

] # End of for loop “For each candidate NTE event, i..”. 

EXAMPLE CALCULATION OF THE REPRESENTATIVE REGENERATION DUTY CYCLE

The following example illustrates a hypothetical in-use mission log with one regeneration 

process. The ECM regeneration signals have already been combined and the resulting tri-state 

signal is shown. This example will be used to illustrate how the tri-state regeneration signal is 

used to determine the proposed mission based representative regeneration duty cycle. The 

mission lasted almost 9 h (31,876 s). The tri-state signal is illustrated as a red trace. The 

mission started at state 1; ended at state 2; and had multiple transitions during the mission as 

illustrated. Emptying events (states 1 or 2) are shaded blue. Filling events (state 0) are shaded 

green. There were four emptying events - their durations were E 1,t , E 2,t , E 3,t , and E 4,t . There 

were three filling events – their durations were F 1,t , F 2,t , and F 3,t . The total time that the tri-state 

signal was at state 2 during each of the four emptying events were ,2 E 1,

t , ,2 E 2,t , ,2 E 3,t , and ,2 E 4,t . 

There are different methods one could use to calculate a regeneration duty cycle, but the most 

representative method uses all data during complete emptying and filling events and excludes 

data during any partial events. The most representative value of DCREGEN ,rep is given by equation 

[7]. It accounts for the possibility of an unpaired event. It effectively ratios the average of the 

total time at state 2 during all the complete emptying events to the average length of all the 

complete emptying events plus the average length of all the complete filling events. 

EXAMPLE CALCULATION OF THE MINIMUM NTE TIME

Once the representative regeneration duty cycle is determined from the mission log, it would 

then be used to determine the minimum time for each candidate NTE in the mission log. The 
Proposed Interpretation of 40CFR86.1370-2007(d)(2) 

on Minimum NTE Time with Discrete Regeneration 

By W. T. Martin, Cummins Inc., 2009-07-29 

Page 9 of 11 

alternative minimum NTE event time in 86.1370-2007(d)(2) only applies if the candidate NTE 

event contains operation with discrete regeneration, i.e. it overlaps state 2 of the tri-state 

regeneration signal. If the candidate NTE event contains only tri-state signal values of 0 or 1, 

then this provision does not apply and only the standard minimum NTE event time in 86.1370-

2007(d)(1) applies. The provision in paragraph (d)(2) applies if there is any state 2 operation 

anywhere in the candidate NTE event. It could be at the beginning, end, middle, or even have 

multiple state 2 events. 

Consider an example illustrated below. This example shows a candidate NTE event in the 

mission log of the previous example that occurred during the 3rd emptying event when the signal 

dropped to 1. This NTE event overlaps state 2 operation at the beginning and the end of the 

NTE event. Since there is state 2 operation within the NTE event, then the alternate minimum 

time applies. Equation [9] calculates the alternative minimum time. Since it is longer than the 

standard minimum time of 30 s, it becomes the minimum time for this candidate NTE event. In 

this example, the candidate NTE event is not long enough and is, therefore, void. 
Proposed Interpretation of 40CFR86.1370-2007(d)(2) 

on Minimum NTE Time with Discrete Regeneration 

By W. T. Martin, Cummins Inc., 2009-07-29 

Page 10 of 11 

number of complete emptying events

total time for all complete emptying events

number of complete filling events

total time for all complete filling events

number of complete emptying events

total time at state 2 during all complete emptying events

, ,

+

DCREGEN j rep = 

.0 2406 24 06. %

5059 7. 6180

2704

2

8440 3920

3

5424 6676 3079

2

2769 2639

3 2

2

1, 2, 3, 2, 3,

,2 2, ,2 3,

, ,

= =

+

=

+

+

+ +

+

=

+

+

+ +

+

=

F F F E E

E E

REGEN j rep t t t t t

t t

DC 

012

0:00:00 1:00:00 2:00:00 3:00:00 4:00:00 5:00:00 6:00:00 7:00:00 

Mission Elapse Time

Tri-state Regeneration Signal Filling Events Emptying Events

F 1, t E 1, t E 2, t F 2, t E 3, t 

t = ∑of ,2 E 1,

,2 E 2, t

t = ∑

,2 E 3,

Partial Complete Complete Complete Comp

Example Mission Log:

Total Mission Time: 31,876 s, 531.3 min, 8.854 h, 8:51:16Emptying Events: 2 Partial, 2 CompleteFilling Events: 3 Complete
Proposed Interpretation of 40CFR86.1370-2007(d)(2) 

on Minimum NTE Time with Discrete Regeneration 

By W. T. Martin, Cummins Inc., 2009-07-29 

Page 11 of 11 

320 s 0.

.0 2406

77 s 

.0 2406

total time at state 2 during the candidate NTE event 37 s 40 s 

, ,

,2 ,

, ,

, ,min = =

+

= = =

REGEN j rep

NTE i

REGEN j rep

NTE alt DC

t

DC

t 

270 s tNTE,i = . Since NTE,i NTE,atl,min t < t this candidate NTE event is void. 

M is sion Log with a c and id ate NTE e ve nt, i, in b la ck.

012

0 :0 0:00 1 :00 :0 0 2 :0 0:00 3 :00 :0 0 4 :0 0:00 5 :00:0 0 6:00 :0 0 7 :0 0:0 0 

M iss io n E lap s e T im e

Tri-state Regeneration 

Signal

012

7 :0 7:00 7 :08 :00 7 :0 9 :0 0 7 :1 0:0 0 7 :1 1 :0 0 7:1 2:00 7:13 :0 0 

M is s io n E la p se T im e

Tri-state Regeneration 

Signal

NT E i t ,

t = t = ∑ o f ON ,N TE ,i ,2 N TE ,i

an d

Ca ndida te NTE e ven t, i