## 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 8 6.1370-2007(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 th at 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 is sue a guidance letter consistent with the agreed interpretation of this language; and 3. to enable programmers of in-use data analysis so ftware 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 in clude discrete regeneration events, if a regeneration event occurs during the NTE test, th en the averaging period must be at least as long as the time between the events multip lied 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 indicati ng 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 mi nimum 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 rege neration 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 regenerati on active plus the time period with the regeneration inactive). The interpretation propose d in this document is based on this concept and on the assumption that the brake specific emiss ions are constant at two levels with and without discrete regeneration. This assumption sim plifies 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 i f a resulting valid NTE event with overlapping operation with discrete regeneration fa ils because the NTE event captured unrepresentatively high emissions due to variable e missions, 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 show s 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 eve nt or any part thereof, the duty cycle ( DC 

## ) (fraction of time or percent on time) of discrete r egeneration 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 begi n with this

DC requirement and translate it into a minimum NTE eve nt time as used in the CFR language. This provides the basis for the interpretation of t he existing language that is necessary to accomplish this intent.

This duty cycle requirement can be expressed mathem atically as

i rep REGEN i NTE 

## DC DC

, , , 

## ≤ 

## [1]

where

i NTE 

## DC

, 

## is the duty cycle of the regeneration signal during the
th 

## i 

## candidate NTE event; and

i rep REGEN 

## DC

,

, 

## 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 peri od with the regeneration signal inactive or off.

Recall that the CFR language requires an alternativ e minimum NTE sample time. Equation [1] can be rearranged to yield an expression for the NT E sample time for the
th 

## i 

## candidate NTE

event,
i

NTE 

## t

, 

## .

i

rep REGEN i

rep REGEN ON

i NTE i NTE ON



## t t

t t

, , , , ,

, , , 

## ≤ 

## [2]

Rearranging again yields an expression for the mini mum NTE sample time for the
th 

## i 

## NTE event,

i NTE 

## t

, 

## , as used in the CFR language.

i NTE

i rep REGEN ON i NTE ON

i rep REGEN 

## t
t t t

,

, , , , ,

, , 

## ≤

⋅ [3]

or

i rep REGEN ON i NTE ON

i rep REGEN i NTE 

## t t t t

, , , , ,

, , , 

## ⋅ ≥ [4a]

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



## i 

## candidate NTE event as follows:

i rep REGEN i NTE ON

i rep REGEN i rep REGEN ON i

NTE ON

i rep REGEN ON i NTE ON

i rep REGEN i NTE 

## 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] i s 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 th e time between the events multiplied by the number of full regeneration events within th e sampling period ” This language can be expressed mathematically as fo llows:

## 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 i REGEN i NTE 

## x t t



## ⋅ ≥

, 

## [5]

where

i NTE 

## t

, 

## is “the averaging period”;

REGEN 

## t 

## is “the time between the events”; and

i 

## x 

## is “the number of full regeneration events within t he 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 regenera tion 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 dis closure. 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

i NTE 

## t

, 

## in the

equations above.

time between events

means a representative period of time for a full r egeneration cycle, which is the period of time with discrete regeneration si gnal active or on plus the period of time with regeneration signal inactive or off. Since this pe riod of time can vary, a representative value must be established. If the representative value i s taken to be a variable, then a representative value appropriate for the candidate
th 

## i 

## NTE event must be established. A significant amoun t of

additional interpretation is required to determine this value and will be discussed later. This term is given the symbol

i rep REGEN 

## t

, , 

## in equation [4a] and

REGEN 

## t 

## in equation [5].

number of full regeneration events within the sampl ing 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 ca ndidate NTE event. It can be a value less than one. It is equal to total time within the can didate NTE event that the discrete regeneration signal is active or on, divided by the representati ve period of time the regeneration signal is active or on for a full regeneration cycle. This t erm 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 equa l as follows:

i rep REGEN ON i NTE ON

i 

## t t

x

,

, , , , 

## = [6]

where

i NTE ON 

## t

, , 

## is the total time within the candidate NTE event th at 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 i rep REGEN ON 

## t

,

, , 

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

regeneration cycle.

Since

i rep REGEN ON 

## t

,

, , 

## can vary, a representative value for this term mus t be established. If the

representative value is taken to be a variable, the n 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 represe ntative period of time for a full regeneration cycle,

i

rep REGEN 

## t

, , 

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

really required for applying this language is the r atio of these representative values, which is a representative value of the duty cycle for full reg eneration cycles.

The derivation above shows how the current CFR lang uage must be interpreted to be consistent with the consensus understanding of its intent. No te that this interpretation applies regardless of the relative frequency of regeneration and NTE even ts. Also note that this interpretation does not include any provisions for subdividing or windo wing the NTE event so that the duty cycle requirement is met. It simply calculates an altern ative 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. Furt her, 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 [4 b] is

s 200 0.05 s 10

, , , ,

, 

## =

= ≥

i

rep REGEN i NTE ON

i NTE 

## 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 mini mum, it is not a valid NTE event.

MULTIPLE REGENERATION PROCESSES

The CFR language does not explicitly address the si tuation where an engine utilizes multiple discrete regeneration processes (e.g. de-soot, de-N Ox, de-SOx, etc.). For this situation the

minimum NTE time for a candidate NTE event is inter preted to be the larger of the following: 30 s from paragraph (d)(1) and the minimum times deter mined for each regeneration process per paragraph (d)(2). Paragraph (d)(2) can only be app lied if the engine outputs corresponding electronic discrete regeneration signals characteri zing these multiple discrete regeneration

processes.

ESTABLISHING A REPRESENTATIVE REGENERATION DUTY CYC LE

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 p assive regeneration or even a risk of insufficient passive regeneration, the engine and a ftertreatment controls take some action off

the normal controls to enhance the oxidation of soo t. This is active de-soot regeneration. The controls may take a variety off-normal actions to e nhance de-soot regeneration. For example the engine timing may be retarded or fuel may be in jected in the exhaust upstream of an oxidation catalyst to increase the exhaust temperat ure; or air handling system components like variable geometry turbines or EGR valves may be adj usted to reduce the air to fuel ratio to increase the exhaust temperature. These actions ma y require certain operating conditions and may switch on and off during the period of time tha t the controls are trying to actively regenerate the trap. So, there can be a variety of signals av ailable from the ECM that indicate the status of each of these complex regeneration processes.

To apply equation [4b] we need to be able to determ ine

i NTE ON 

## t

, , 

## and

i rep REGEN 

## DC

,

, 

## . For purposes

of determining

i NTE ON 

## t

, , 

## , one bi-state discrete signal is required to indic ate when any action

related to the applicable regeneration process is b eing 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 of f-normal control action is being taken. The

value of

i

NTE ON 

## t

, , 

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

To determine

i rep REGEN 

## DC

,

, 

## , or its components,

i rep REGEN ON 

## t

,

, , 

## and

i rep REGEN 

## t

, , 

## , additional information is

required. Consider regeneration processes that swi tch the above bi-state discrete regeneration signal between 0 (off) and 1 (on) multiple times wh ile the controls are trying to regenerate or empty the device. De-soot regeneration processes f or DPF’s work this way. For this case, a representative time period for determining any valu e of

i rep REGEN 

## DC

,

, 

## 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 regenerati on 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 v alue of 1 when the device is in the emptying part of the cycle. During the filling part, no off-norm al control actions are being taken. During the emptying part, the controls have determined that th e device needs emptying and any off-normal control action to enhance regeneration may be activ e. It would return to 0 after the controls have determined that the device has been emptied an d no off-normal control action is needed to regenerate the device. This second bi-state discret e signal would be used to identify complete filling and emptying events over which

i rep REGEN 

## DC

,

, 

## would be determined.

Note that these two bi-state discrete signals can b e 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 v alue of 0. During emptying events this tri-state signal has a value of 1 or 2. During active regene ration this tri-state signal has a value of 2. The level 2 state may include time for the aftertre atment device to stabilize and restore

emissions to normal levels after the controls are r eturned to normal operation.

For regeneration processes where state 1 is not app ropriate 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 t he entire emptying event. Another example is a regeneration process that does not utilized the c oncept of identifying that a discrete regeneration is needed and is pending proper operat ing conditions.

Different engine makes, model years and even models may have different regeneration processes and regeneration signals. To support com mon in-use data analysis software, it is proposed that manufacturers provide the necessary E CM 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 soft ware. 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 availabl e from their ECM’s.

With this one tri-state regeneration signal

i rep REGEN 

## DC

,

, 

## 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 g eneral,

i rep REGEN 

## DC

,

, 

## varies and, therefore, it

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

Because the value of

i rep REGEN 

## DC

,

, 

## is expected to vary with the in-use engine duty cyc le, the most

representative values would be determined from the data recorded/logged during the in-use emissions test. Currently it is believed that ther e may be significant variation in this value throughout the in-use emissions test due to noise f actors and that it would be most representative to determine a single value for

rep REGEN 

## DC

, 

## 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 REGENER ATION DUTY CYCLE

AND MINIMUM NTE TIME

The following logic illustrates how the post proces sor 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 neces sary ECM signals. Statements that are executed when a logical is true are placed on the n ext 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 tho se statements. Brackets are also used to delineate multiple statements for a given loop oper ation. Comments are preceded by a pound sign, #. There are two main “For” loops. The firs t determines the representative regeneration duty cycle for each regeneration process. The seco nd 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. signal s to the tri-state regen. signal;

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

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

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

| Set the regeneration duty cycle for this regenerati on 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

, , 

## = rep j REGEN 

## DC

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

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

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

| | Calculate the total time for all the complete filli ng events.

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

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

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

| [

| | Calculate the total time for all the complete empty ing events;

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

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

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

| [

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

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

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

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

| | | Calculate the duty cycle for this regeneration proc ess

| | | #



## events emptying complete of number events

emptying complete all for time total

events filling complete of number events

filling complete all for time total events emptying complete of number events emptying complete all during 2 state at time total

, , 

## + = rep j REGEN 

## DC

| ] # of “If the number of complete filling and empty ing 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 t o 30 s;

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

| #



## .

30 min

, 

## = NTE 

## t

| 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, i ndentify 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 proce ss is > 0, then

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

| | | | #

rep j REGEN alt NTE 

## DC t

, , min

, , 

## event NTE candidate the during 2 state at time total

=

| | | |

| | | Else # this regeneration process has a duty cycle o f 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 wil l prevent any candidate NTE event with

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

| | | | # 

## 1 min

, , 

## + = mission alt NTE 

## t t

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

| | | | Set the minimum time for this candidate NTE event t o 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 reg eneration processes.

| | | | # min

, , min

, alt

NTE NTE 

## t t =

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

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

| | # event is left unchanged, either 30 s or an alt. v alue 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 t ime requirements.

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



## EXAMPLE CALCULATION OF THE REPRESENTATIVE REGENERAT ION 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 illu strate how the tri-state regeneration signal is used to determine the proposed mission based repres entative regeneration duty cycle. The mission lasted almost 9 h (31,876 s). The tri-stat e signal is illustrated as a red trace. The mission started at state 1; ended at state 2; and h ad multiple transitions during the mission as illustrated. Emptying events (states 1 or 2) are s haded blue. Filling events (state 0) are shaded green. There were four emptying events - their dur ations were 1, E 

## t



## , 2, E 

## t



## , 3,

E 

## t 

## , and 4,

E 

## t 

## . There

were three filling events – their durations were 1, F 

## t



## , 2, F 

## t 

## , and 3,

F 

## t 

## . The total time that the tri-state

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

## t



## , 2,

,2 E 

## t



## , 3,

,2 E 

## t 

## , and 4,

,2 E 

## t



## . There are different methods one could use to calcul ate 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 represent ative value of

rep REGEN 

## DC

, 

## is given by equation

[7]. It accounts for the possibility of an unpaire d event. It effectively ratios the average of the total time at state 2 during all the complete empty ing 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 co ntains only tri-state signal values of 0 or 1, then this provision does not apply and only the sta ndard 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 a t the beginning, end, middle, or even have multiple state 2 events.

Consider an example illustrated below. This exampl e shows a candidate NTE event in the mission log of the previous example that occurred d uring the 3 rd 

## emptying event when the signal dropped to 1. This NTE event overlaps state 2 oper ation 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 alternat ive minimum time. Since it is longer than the standard minimum time of 30 s, it becomes the minim um time for this candidate NTE event. In this example, the candidate NTE event is not long e nough and is, therefore, void.Proposed Interpretation of 40CFR86.1370-2007(d)(2)on Minimum NTE Time with Discrete RegenerationBy W. T. Martin, Cummins Inc., 2009-07-29Page 10 of 11eventsemptyingcompleteofnumbereventsemptyingcompleteallfortimetotaleventsfillingcompleteofnumbereventsfillingcompleteallfortimetotaleventsemptyingcompleteofnumbereventsemptyingcompleteallduring2stateattimetotal,,+=repjREGENDC[7]%06.242406.061807.5059704223920844033079667654242263927692323,2,3,2,1,3,,22,,2,,==+=+++++=+++++=EEFFFEErepjREGENtttttttDC[8]0120:00:00 1:00:00 2:00:00 3:00:00 4:00:00 5:00:00 6:00:00 7:00:00 8:00:00 9:00:00Mission Elapse Time

Tri-state Regeneration SignalEmptying EventsFilling Events1,Ft1,Et2,Et2,Ft3,Et3,Ft4,Et∑=oftE1,,22,,2Et∑=oftE3,,24,,2EtCompleteCompleteCompleteCompleteCompletePartialPartialExample Mission Log:Total Mission Time: 31,876 s, 531.3 min, 8.854 h, 8:51:16Emptying Events: 2 Partial, 2 CompleteFilling Events: 3 CompleteProposed Interpretation of 40CFR86.1370-2007(d)(2)on Minimum NTE Time with Discrete RegenerationBy W. T. Martin, Cummins Inc., 2009-07-29Page 11 of 11s 0.3202406.0s772406.0s40s37eventNTEcandidatetheduring2stateattimetotal,,,,2,,min,,==+===repjREGENiNTErepjREGENaltNTEDCtDCt[9]s270,=iNTEt. Sincemin,,,atlNTEiNTEtt<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.0120 :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 8:00 :0 0 9 :0 0:0 0M iss io n E lap s e T im e

Tri-state Regeneration Signal0127 :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 7 :14 :0 0 7:1 5:00M is s io n E la p se T im e

Tri-state Regeneration SignaliNT Et,∑==o fttiN TEiN TEON,,2,,an dCa ndida te NTE e ven t, i