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Title:
CYLINDER DEACTIVATION AND ENGINE BRAKING FOR START OR STOP HARMONICS MANAGEMENT
Document Type and Number:
WIPO Patent Application WO/2017/117289
Kind Code:
A1
Abstract:
A method for engine-braking a multiple-cylinder diesel engine can comprise selectively firing cylinders of the multiple-cylinder diesel engine in a combustion mode and selectively engine-braking a cylinder of the multiple-cylinder diesel engine. Engine-braking can comprise terminating fuel injection to the cylinder and opening one or more valves affiliated with the cylinder after a respective piston of the cylinder has completed a compression stroke. Modulating the timing of the engine braking balances engine vibrations.

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WO/2002/035074CONTROLLER OF HYBRID VEHICLE
WO/2016/088336CONTROL DEVICE
Inventors:
NIELSEN DOUGLAS (US)
MCCARTHY JR JAMES E (US)
Application Number:
PCT/US2016/069013
Publication Date:
July 06, 2017
Filing Date:
December 28, 2016
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
EATON CORP (US)
International Classes:
F02D17/02; F02D13/02; F02D41/00; F02D41/10; F02D41/12
Foreign References:
US7523734B22009-04-28
EP0447697B11994-05-25
US7930087B22011-04-19
US20030172900A12003-09-18
US6553962B12003-04-29
Attorney, Agent or Firm:
COLANTONI, Krystyna et al. (US)
Download PDF:
Claims:
WHAT IS CLAIMED IS:

1 . A system for vibration management in a multiple-cylinder diesel engine, the engine comprising respective reciprocating pistons in the multiple cylinders, the respective reciprocating pistons connected to a crankshaft for rotation of the crankshaft, a computer-controllable fuel injection system configured to inject fuel in to the multiple cylinders, respective computer-controllable intake valves and exhaust valves for opening and closing the multiple cylinders, and a computer control network connected to the fuel injection system and the respective intake valves and respective exhaust valves, the network comprising a processor, a tangible memory device, and processor-executable control algorithms for implementing a method for vibration management, the method comprising:

sensing one of a start-up signal or a shut-down signal to the engine;

selecting one of a start-up operation mode of the engine or a shut-down

operation mode of the engine based on the sensed start-up signal or the sensed shut-down signal, wherein the start-up operation mode comprises a start-up slope from a shut-down condition to an idled condition, and wherein the shut-down operation mode comprises a shut-down slope from the idled condition to the shut-down condition;

adjusting fuel injection to the multiple-cylinders based on a vibration profile of the crankshaft, the vibration profile comprising a peak vibration disturbance;

wherein adjusting fuel injection comprises terminating fuel injection to at least one of the cylinders of the multiple-cylinders to adjust the vibration profile of the crankshaft to avoid the peak vibration disturbance.

2. The system of claim 1 , wherein adjusting fuel injection to the multiple- cylinders comprises increasing fuel injection to combustion cylinders of the multiple- cylinders to increase a torque output of the combustion cylinders.

3. The system of claim 1 , wherein adjusting fuel injection comprises terminating fuel injection to at least half of the cylinders of the multiple-cylinders.

4. The system of claim 1 , wherein adjusting fuel injection comprises terminating fuel injection to all of the cylinders of the multiple-cylinders.

5. The system of claim 1 , further comprising a motor configured to spin the crankshaft, wherein the method comprises activating the motor in response to sensing the start-up signal.

6. The system of claim 1 , wherein adjusting fuel injection to the multiple cylinders comprises adjusting the number of cylinders of the multiple-cylinders terminating fuel injection as the engine progresses through the selected start-up operation mode or the selected shut-down operation mode.

7. The system of claim 1 , wherein the multiple-cylinders are distributed in the engine, and wherein adjusting fuel injection further comprises changing which at least one cylinder in the distribution terminates fuel injection as the engine progresses through the selected start-up operation mode or the selected shut-down operation mode.

8. The system of any one of claims 3-7, wherein adjusting fuel injection to the multiple-cylinders comprises increasing fuel injection to combustion cylinders of the multiple-cylinders to increase a torque output of the combustion cylinders.

9. The system of one of claims 1 -7, wherein the method further comprises deactivating respective computer-controllable intake valves and exhaust valves for the at least one the cylinder having terminated fuel injection.

10. The system of claim 9, wherein deactivating respective computer-controllable intake valves and exhaust valves accelerates a rate of change for the start-up slope or for the shut-down slope.

1 1 . The system of claim 9, wherein adjusting fuel injection to the multiple- cylinders comprises increasing fuel injection to combustion cylinders of the multiple- cylinders to increase a torque output of the combustion cylinders to be greater than a desired engine torque output, and wherein deactivating respective computer- controllable intake valves and exhaust valves is selected to reduce the torque output of the at least one cylinder having terminated fuel injection to result in the desired engine torque output.

12. The system of one of claims 1 -7, wherein the method further comprises activating engine braking on respective computer-controllable intake valves and exhaust valves for the at least one the cylinders having terminated fuel injection, wherein activating engine braking comprises opening at least one of the respective computer-controllable intake valves and exhaust valves after the respective reciprocating piston for the at least one of the cylinders has completed a

compression stroke.

13. The system of claim 12, wherein activating engine braking on respective computer-controllable intake valves and exhaust valves accelerates a rate of change for the start-up slope or for the shut-down slope.

14. The system of claim 12, wherein activating engine braking comprises implementing a 2-stroke braking technique.

15. The system of claim 12, wherein the respective reciprocating piston cycles between top-dead-center and bottom -dead-center, and wherein opening the at least one of the respective computer-controllable intake valves and exhaust valves occurs as the piston nears top-dead-center.

16. The system of claim 12, wherein the respective reciprocating piston cycles between top-dead-center and bottom -dead-center, and wherein opening the at least one of the respective computer-controllable intake valves and exhaust valves occurs when the piston reaches top-dead-center.

17. The system of claim 12, wherein the respective reciprocating piston cycles between top-dead-center and bottom -dead-center, and wherein opening the at least one of the respective computer-controllable intake valves and exhaust valves occurs when the piston departs top-dead-center.

18. The system of claim 12, wherein adjusting fuel injection to the multiple- cylinders comprises increasing fuel injection to combustion cylinders of the multiple- cylinders to increase a torque output of the combustion cylinders to be greater than a desired engine torque output, and wherein activating engine-braking is selected to reduce the torque output of the at least one cylinder having terminated fuel injection to result in the desired engine torque output.

19. A method for engine braking a multiple-cylinder diesel engine, comprising: selectively firing cylinders of the multiple-cylinder diesel engine in a combustion mode;

selectively engine-braking a cylinder of the multiple-cylinder diesel engine, wherein engine-braking comprises terminating fuel injection to the cylinder and opening one or more valves affiliated with the cylinder after a respective piston of the cylinder has completed a compression stroke; and

modulating the timing of the engine braking to balance engine vibrations.

20. The method of claim 19, further comprising increasing the number of cylinders of the multiple-cylinders selectively engine-braking as the engine progresses through a start-up operation mode or a shut-down operation mode.

21 . The method of claim 19, wherein the multiple-cylinders are distributed in the engine, and wherein the method further comprises changing which cylinder in the distribution constitutes the engine-braking cylinder.

22. The method of claim 19, wherein selectively firing cylinders comprises increasing fuel injected in to the firing cylinders to increase torque output from the firing cylinders.

23. The method of claim 19, wherein engine-braking accelerates a rate of change for a crankshaft of the engine.

24. The method of claim 19, wherein engine-braking comprises implementing a 2-stroke braking technique.

25. The method of claim 19, further comprising switching between selectively engine-braking the cylinder of the multiple-cylinder diesel engine and selectively firing the cylinder of the multiple-cylinder diesel engine to shift engine harmonics.

26. The method of claim 19, further comprising switching one or more of the firing cylinders of the multiple-cylinder diesel engine to engine-braking cylinders of the multiple-cylinder diesel engine to shift engine harmonics.

27. The method of claim 26, wherein switching one or more of the firing cylinders of the multiple-cylinder diesel engine to engine-braking cylinders of the multiple- cylinder diesel engine to shift engine harmonics comprises switching all of the firing cylinders to engine-braking cylinders.

28. The method of any one of claim 19-26, wherein the engine-braking of a cylinder is limited to start-up operation modes and shut-down operation modes.

29. The method of any one of claim 19-26, wherein selectively firing cylinders comprises increasing the torque output of the firing cylinders to be greater than a desired engine torque output, and wherein the engine-braking of the cylinder is selected to reduce the torque output of the engine-braking cylinder to result in the desired engine torque output.

Description:
CYLINDER DEACTIVATION AND ENGINE BRAKING FOR START OR STOP

HARMONICS MANAGEMENT

Field

[001 ] This application provides an engine where cylinders are selectively deactivated and reactivated while other cylinders selectively engine brake.

Background

[002] Engine systems experience undesired vibrations during start and stop modes. The user experience suffers, and the vibrations cause wear on the engine.

SUMMARY

[003] The methods disclosed herein overcome the above disadvantages and improves the art by way of a method for engine braking a multi-cylinder diesel engine can comprise selectively firing cylinders of the diesel engine, selectively engine-braking other cylinders of the diesel engine, and selectively cycling the timing of the engine braking. The method can further comprise selectively entering a cylinder deactivation mode on cylinders of the diesel engine.

[004] A system for vibration management in a multiple-cylinder diesel engine can comprise an engine and an appropriate control network. The engine can comprise respective reciprocating pistons in the multiple cylinders, the respective reciprocating pistons connected to a crankshaft for rotation of the crankshaft. A computer-controllable fuel injection system can be configured to inject fuel in to the multiple cylinders. Respective computer-controllable intake valves and exhaust valves for the multiple cylinders can be connected to open and close the respective valves. A computer control network can be connected to the fuel injection system and the respective intake valves and respective exhaust valves. The network can comprise a processor, a tangible memory device, and processor-executable control algorithms for implementing a method for vibration management.

[005] The method for vibration management can comprise sensing one of a start-up signal or a shut-down signal to the engine. Based on the sensed start-up signal or the sensed shut-down signal, selecting one of a start-up operation mode of the engine or a shut-down operation mode of the engine, wherein the start-up operation mode comprises a start-up slope from a shut-down condition to an idled condition, and wherein the shut-down operation mode comprises a shut-down slope from the idled condition to the shut-down condition. Based on a vibration profile of the crankshaft, adjusting fuel injection to the multiple-cylinders, the vibration profile comprising a peak vibration disturbance. Adjusting fuel injection can comprise terminating fuel injection to at least one of the cylinders of the multiple-cylinders to adjust the vibration profile of the crankshaft to avoid the peak vibration disturbance.

[006] A method for engine-braking a multiple-cylinder diesel engine can comprise selectively firing cylinders of the multiple-cylinder diesel engine in a combustion mode and selectively engine-braking a cylinder of the multiple-cylinder diesel engine. Engine-braking can comprise terminating fuel injection to the cylinder and opening one or more valves affiliated with the cylinder after a respective piston of the cylinder has completed a compression stroke. Modulating the timing of the engine braking balances engine vibrations.

[007] Additional objects and advantages will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the disclosure. The objects and advantages will also be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[008] Figure 1 is an end torque pattern for 6 combustion mode cylinders.

[009] Figure 2 is an end torque pattern for 3 combustion mode cylinders and three cylinder deactivation mode cylinders.

[010] Figures 3A & 3B show aspects of engine braking mode operation.

[01 1 ] Figures 4A-4D show power setting aspects.

[012] Figure 5 shows crankshaft vibration profiles.

[013] Figure 6 shows and explanatory schematic for an engine system.

[014] Figure 7 shows a computer control system block diagram.

[015] Figures 8A-8C show aspects of cylinder operation.

[016] Figure 9 shows a flow diagram for a method of vibration management.

[017] Figure 10 shows a decision tree for a method of vibration

management. DETAILED DESCRIPTION

[018] Reference will now be made in detail to the examples which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. Directional references such as "left" and "right" are for ease of reference to the figures. Phrases such as "upstream" and "downstream" are used to assist with directionality of flow from a fluid input point to a fluid output point. Fluids in this disclosure can comprise a variety of compositions, including fresh or ambient air, exhaust gas, other combustion gasses, vaporized fuel, among others. This disclosure primarily focusses on diesel engine operation, but aspects of the disclosure can be applied to other fueled engines and engine systems, including those fueled by biofuels and other petroleum products such as gasoline, and including hybrid-electric vehicles. Heavy-duty, light-duty, and medium-duty vehicles can benefit from the techniques disclosed herein. Hybrid vehicles and vehicles such as buses that have start/stop/load duty cycles can also benefit from the disclosure.

[019] Turning to Figure 6, a schematic for an engine system 10 is shown. An engine 100 comprises 6 cylinders 1 -6. Other numbers of cylinders can be used, but for discussion, 6 cylinders are illustrated. The cylinders 1 -6 receive intake fluid, which is combustion gas, such as air, or air mixed with exhaust (exhaust gas recirculation "EGR"), from the intake manifold 103. An intake manifold sensor 173 can monitor the pressure, flow rate, oxygen content, exhaust content or other qualities of the intake fluid. The intake manifold 103 connects to intake ports 133 in the engine block to provide intake fluid to the cylinders 1 -6. In a diesel engine, the intake manifold has a vacuum except when the intake manifold is boosted. CDA is beneficial, because the cylinder can be closed. Fuel efficiency is gained by not drawing the piston down against the manifold vacuum. When the cylinder is deactivated, the crankshaft 101 has less resistance from the piston, and the crankshaft can output more torque from the firing cylinders.

[020] Fuel is injected to individual cylinders via a fuel injection controller 300. The fuel injection controller 300 can adjust the amount and timing of fuel injected in to each cylinder and can shut off and resume fuel injection to each cylinder. The fuel injection for each cylinder 1 -6 can be the same or unique for each cylinder 106, such that one cylinder can have more fuel than another, and one cylinder can have no fuel injection, while others have fuel.

[021 ] A variable valve actuator (WA) 200 also couples to the cylinders 1 -6 to actuate intake valves 130 and exhaust valves 150. The WA 200 can change the actuation of the intake valves 130 and exhaust valves 150 so as to open or close the valves normally, early, or late, or combinations thereof, or cease operation of the valves. VVA 200 can cooperate with a valve actuator 185, such as a hydraulic, electric, or electric solenoid system to control the intake and exhaust valves 130, 150. The engine 100 can be cam or camless, or a hybrid "cam-camless WA." So, the intake and exhaust valves 130, 150 can either couple to a cam system for actuation, as the camshafts 181 , 182 example of Figure 8A, a hydraulic rail, a latched rocker arm, other rocker arm, an electro hydraulic actuator, etc. Or a camless direct acting mechanism can selectively operate the individual valves to open and close the cylinders. The crankshaft 101 can be coupled to transfer energy between the crankshaft 101 and the camshafts 181 , 182 as by a torque transfer mechanism 1 15, which can comprise gear sets, belts, or other transfer

mechanisms. Starter device 900 can be connected to the transfer mechanism 1 15 to assist with initial starting of the engine 100. Starter device 900 can comprise a battery connected to a motor or the like. While Figures 8B &8C show one intake valve 130 and one exhaust valve 150, it is possible to have two intake valves 130 and two exhaust valves 150 per each cylinder, as in Figure 8A. The engine block 102 is removed for the example of Figure 8A for clarity, and the cylinders are shown in broken lines.

[022] A diesel engine works by compressing intake fluid in a cylinder 1 -6 using a piston 160. Fuel is injected via fuel injector 310. The high heat and compression ignites the fuel, and combustion forces the piston from top dead center (TDC) shown in Figure 8B to bottom dead center (BDC) shown in Figure 8C and torque is thereby directed to the crankshaft 101 . Diesel operation can be referred to as "4 stroke," though other operation modes such as 2-stroke, 6-stroke, and 8- stroke are possible and known in the art. In 4-stroke combustion mode, the piston moves from TDC to BDC to fill the cylinder with intake fluid (stroke 1 ). The start of the cycle is shown in Figure 8B, and Figure 8C shows the end of stroke 1 , when the cylinder is full of intake fluid. The piston rises back to TDC (stroke 2). Fuel is injected and ignites to push the piston 160 to BDC (stroke 3). The piston rises again to TDC to expel the exhaust out the exhaust valve (stroke 4). The intake valve 130 is open during stroke 1 and closed during strokes 2-4, though the WA 200 can adjust the timing of opening and closing. The exhaust valve 150 is open during stroke 4 and closed during strokes 2-4, though the WA 200 can adjust the timing of opening and closing. Compression occurs on the second stroke, and combustion occurs on the third stroke. 6-stroke and 8-stroke techniques include additional aspects of compression and injection after the intake valve has closed and prior to the exhaust valve opening. The application will discuss 4-stroke combustion techniques in detail, but where compatible, the 4-stroke combustion techniques can be applied to augment art-recognized 6-stroke or 8-stroke combustion techniques. 2-stroke engine-braking techniques can be used with 2-, 4-, 6- or 8- stroke combustion techniques.

[023] Exhaust gases leave cylinders through exhaust ports 155 in engine block 102. Exhaust ports 155 communicate with an exhaust manifold 105. An exhaust manifold sensor 175 can monitor the pressure, flow rate, oxygen content, nitrous or nitric oxide (NOx) content, sulphur content, other pollution content or other qualities of the exhaust gas. Exhaust gas can power a turbine 510 of a variable geometry turbocharger (VGT) 501 or other turbocharger. The turbocharger 501 can be controlled via a turbocharger controller 500 to adjust a coupling 514 between the turbine 510 and the compressor 512. The VGT can be adjusted so as to control intake or exhaust flow rate or back pressure in the exhaust.

[024] Exhaust gas is filtered in an aftertreatment system comprising catalyst 800. At least one exhaust sensor 807 is placed in the aftertreatment system to measure exhaust conditions such as tailpipe emissions, NOx content, exhaust temperature, flow rate, etc. The exhaust sensor 807 can comprise more than one type of sensor, such as chemical, thermal, optical, resistive, velocity, pressure, etc. A sensor linked with the turbocharger 501 can also be included to detect turbine and compressor activity.

[025] Exhaust can exit the system after being filtered by the at least one catalyst 800. Or, exhaust can be redirected to the intake manifold 103. An optional EGR cooler 455 is included. An EGR controller 400 actuates an EGR valve 410 to selectively control the amount of EGR supplied to the intake manifold 103. The exhaust recirculated to the intake manifold 103 impacts the air fuel ration (AFR) in the cylinder. Exhaust dilutes the oxygen content in the intake manifold 103.

Unburned fuel from the fuel doser, or unburned fuel remaining after combustion increases the fuel amount in the AFR. Soot and other particulates and pollution gases also reduce the air portion of the air fuel ratio. While fresh air brought in through the intake system 700 can raise the AFR, EGR can lower AFR, and fuel injection to the cylinders can lower the AFR further. Thus, the EGR controller 400, fuel injection controller 300 and intake assist controller 600 can tailor the air fuel ratio to the engine operating conditions by respectively operating EGR valve 410, fuel injector 310, and intake assist device 610. So, adjusting the air fuel ratio to a firing cylinder can comprise one of boosting fresh air from intake system 700 to the at least one firing cylinder by controlling an intake air assist device 601 , such as a supercharger, or decreasing air fuel ratio to a firing cylinder by boosting with exhaust gas recirculation to the firing cylinder. A charge air cooler 650 can optionally be included to regulate intake flow temperature. This can be done with or without augmenting with a turbocharger 501 . Numerous alternative arrangements are possible for controlling air fuel ratio and other subcombinations and

combinations of exhaust gas recirculation, turbocharging and supercharging are possible.

[026] Additionally, terminating fuel injection to one or more cylinders 1 -6 adjusts the air fuel ratio of exhaust gas, and deactivating a cylinder decreases the quantity of exhaust. Cylinder deactivation impacts the ability to power the turbine 510 to run the compressor 512. Implementing engine braking also impacts the quantity and composition of exhaust gasses. Altering the pressure and temperature of fluid exiting the cylinder also impacts the harmonics of the engine system.

[027] The engine 100 vibrates as it moves through operation modes and creates harmonics at certain operation points or operation ranges. Some harmonics are easily addressed using driveline components such as clutches and dampers. Other harmonics are more troublesome. In systems having fuel saving engine start- stop modes, the user experience is impacted regularly by the starting and stopping. In heavy-duty and medium-duty vehicles, the harmonics can have even higher magnitudes. [028] Cylinder deactivation (CDA), where the intake valve, exhaust valve, and fuel injection are shut off for a selected cylinder cycle can be used to idle all or some of the valves in a valvetrain. When implemented at certain operation modes of the engine 100, CDA alleviates issues of harmonics.

[029] The crankshaft 101 , as the output of the engine and the input to the drivetrain (O/l), can have a certain stiffness that stabilizes the frequency of the engine's shaking. A flywheel 1 10 can be an inertial component and interface for coupling the crankshaft 101 to a clutch or other downstream component. A output/input sensor 107 can sense the rotations per minute (RPM) and vibration, sensing also peak vibration disturbances. From a shut-down, or off, condition to an idled condition, the frequency (Hz) of the engine shaking changes according to the curves of Figure 5. The start-up operation mode comprises a start-up slope from a shut-down condition to an idled condition, and the shut-down operation mode comprises a shut-down slope from the idled condition to the shut-down condition. For example, from zero RPMs, or shut-down condition to profile point 41 , 51 , 61 , the example output/input O/l has a fairly stable frequency profile and with a modest upward slope. The stiffer the output/input O/l shaft, the longer the frequency can be stable. Vibration profile 1 has a softer output/input shaft O/l that vibration profiles 2 & 3, for example, so the shaft is not without vibrations for very long. A peak vibration disturbance occurs at points 43, 53, 63 in the vibration profiles 1 , 2, 3. The vibrations reach a harmonic that causes the engine to rock about the engine bay. This impacts the user experience and vehicle durability. Because of the high compression combustion events, diesel systems tend to have higher levels of rocking than gasoline systems. The peak vibration disturbances have a positive slope from points 41 , 51 , 61 to peaks at points 43, 53, 63. The slope is negative from points 43, 53, 63 to operation points 45, 55, 65. From the operation points, the examples do not include another harmonic that rivals the peak vibration

disturbances in magnitude. Typically, a vehicle clutch or other damping component is designed for and engages at the operation point 45, 55, 65 and the frequency of the output/input O/l shaft is fairly stable during vehicle operation.

[030] In one aspect of the disclosure, a six-cylinder diesel engine can include a cylinder deactivation system that works to deactivate all, or less than all, of the cylinders. The CDA system can switch between all cylinders active, three cylinders deactivated, two cylinders deactivated, one cylinder deactivated and all cylinders deactivated. Other modes can be implemented also, such as four cylinder and 5 cylinder deactivation, and engines having a number of cylinders greater or less than six can be accommodated by the present teachings.

[031 ] The natural harmonics of the various operational modes can be determined. For purposes of explanation, assume an engine has a natural harmonic at 100 Hz when operating in a six-cylinder mode. Assume also that the harmonic doubles when operating in a three cylinder CDA mode. Should the engine switch between a six cylinder active mode and a three cylinder active mode, the harmonic switches from 100 Hz to 200 Hz. The higher harmonics are deleterious. So, when higher harmonics are present, it is possible to skip the harmonic by selecting another valve actuation profile. For example, it is possible to select vibration profile 1 for a start-up from zero RPMs to profile point 61 , and then convert to profile 1 or 2 to avoid the peak vibration disturbance at point 63. For this discussion, vibration profile 1 is an example of engine braking, vibration profile 2 is an example of cylinder deactivation mode, and vibration profile 3 is an example of 6-cylinder engine operation. The peak vibration disturbances occur at different RPMs in this example. The output/Input shaft O/l spins up over time, so in a sense, the rotations per minute RPM axis is also a time axis, and the output/input O/l shaft changes over time. The peak vibration disturbances 43, 53, 63 are related to the RPM of the crankshaft 101 , as the internal engine vibrations caused by deflections of internal parts such as valves, actuators, rails, rods, weights, etc. impact the external vibration of the engine and the critical speed at which the engine shudders. The vibration profiles 1 -3 are examples only, and other profiles are possible. By switching between engine-braking, cylinder deactivation and regular engine firing, it is possible to avoid the higher harmonics ranges on the output/input O/l shaft. This is most beneficial when the vehicle is transitioning during a start mode or a stop mode, where engine shaking is most severe.

[032] The deactivation mode selected skips or avoids the deleterious harmonic by switching to a different number of active or deactivated cylinders. For example, the CDA system switches from three-cylinders deactivated to 6-cylinders deactivated. Switching the cylinder mode in this way moves the natural harmonic and the deleterious harmonic is avoided. Open Cycle Efficiency Increase Via Engine Braking and Cylinder

Deactivation

[033] This strategy applies engine braking or CDA to one half of an engine block, and increases fuel use to the remaining cylinders. Several aspects are shown in Figures 4A-4D.

[034] Figure 4A shows an ordinary engine operation mode, where all 6 cylinders 1 -6 are fired at the same power setting, +5, to achieve a net torque output of 30 horse power (HP). The fuel efficiency of this low power setting is poor, and the quality of the exhaust is low. It is more fuel efficient to increase the power setting of the cylinder. So, in Figure 4B, cylinders 1 -3 are configured to output +15 HP.

Cylinders 4-6 are set to engine-brake, and these cylinders subtract -5 HP from the power setting. The net is still 30 HP. In Figure 4C, cylinders 1 -3 receive +40 HP power setting while cylinders 4-6 have a -30 HP power setting. The Figure 4C arrangement could have a peak vibration disturbance that differs in magnitude and timing from the Figure 4B arrangement. In Figure 4D, cylinders 1 -3 receive a +10 HP power setting, while cylinders 4-6 are deactivated to result in a zero power setting. The positive power settings can be adjusted by using any one of the air-fuel ratio adjusting techniques discussed above, such as EGR, fresh air boosting, turbocharging, and fuel injection modifications to quantity and timing of fuel injection.

[035] Implementing one of engine braking and cylinder deactivation leads to an overall increase to open cycle efficiency, fuel efficiency and output temperature.

Engine Harmonics Management via Cylinder Deactivation

[036] A 6-cylinder engine outputs torque (power pulses) in a firing order, and the torque is transferred to the output/input O/l (crankshaft 101 ). While a non-firing cylinder may "see" zero torque output, the crankshaft does not "see" zero torque input. A minimum torque is experienced on the crankshaft as the cylinders follow their firing sequence, resulting in an "end torque pattern." The "end torque pattern" can shake the engine in the engine bay.

[037] Aspects of these concepts are shown in Figures 1 -3B. In Figure 1 , power pulses for each of the 6 cylinders 1 -6 are shown. For convenience of discussion, the cylinders fire in numerical order and have been shown linearly in Figures 4A-4D and 6 in a block diagram. In practice, many engines fire in a different sequence, such as 1 , 3, 5 together then 2, 4, 6 together. The engine is considered to have a "front half" and a "back half," and the engine can be divided via layout of the valve actuators 185 in to a front half that fires or engine brakes and a back half that fires or deactivates. Or, all cylinders can be designed, via their valve actuators 185, to switch between all three of firing, engine-braking, or deactivating. Then, individual cylinders can be chosen to have one of the firing, engine-braking or deactivation operation modes during a particular firing sequence.

[038] Because a firing sequence can result in some cylinders 1 -6 firing at a point in time that is offset from another cylinder, because the pistons 160 are offset and do not all reach top-dead-center or bottom-dead-center together, and because the cylinders do not have identical corresponding intake and exhaust valve opening and closing patterns, it is convenient to link the firing sequence to the stroke of the piston. A firing sequence has all cylinders 1 -6 follow a given set of reciprocations of their respective piston 160. For example, to implement a two-stroke braking technique, all cylinders would at least reciprocate from BDC to TDC and back to BDC before that firing sequence would be considered complete. To implement a four-stroke firing sequence and two stroke braking, the firing cylinders would reciprocate from BDC to TDC and back to BDC two times, and the engine-braking cylinders would two-stroke brake twice. So, the firing sequence comprises the most comprehensive stroke pattern, and all cylinders would have their piston 160 reciprocate the most comprehensive number of times, even if their respective intake and exhaust valves 130, 150 follow different opening and closing patterns. The firing order can differ among firing sequences so long as the end result is all cylinders having had the requisite reciprocations of their respective piston 160 during the firing sequence. In instances where no cylinders are fired during a firing sequence, such as when the engine is coasting, the respective pistons 160 are still

reciprocating, and all cylinders experience the requisite number of reciprocations before that "unfired" firing sequence is considered complete.

[039] In another alternative, a firing sequence for an engine in normal operation mode can be 1 , 5, 3, 6, 2, 4. In CDA mode, cylinders 4, 5, 6 are

deactivated. The remaining cylinders fire in sequence 1 , 3, 2. When engine braking, cylinders 1 , 3, 2 could fire, with cylinders 5, 6, 4 braking. Other engine layouts are possible, such as in-line, "V," or "boxer." A type I, II, III, IV or V engine can be used with the aspects disclosed herein. Numerous alternatives can be accommodated without departing from the principles disclosed herein, and numerous

subcombinations of the disclosed aspects are possible.

[040] Figure 1 shows 6 power pulses in Newton-meters (Nm). The end torque pattern is overlaid on the power pulses. The end torque pattern has highs and lows, and certain power pulses will vibrate at a critical speed and excite the harmonic peak vibration disturbance, shaking the engine.

[041 ] In Figure 2, cylinder deactivation (CDA) turns off one or more cylinders. Cylinders 1 , 3, 5 fire and convey power to the crankshaft 101 . Cylinders 2, 4, 6 are deactivated. Some benefits of CDA are not conveyed in Figure 2, including the power pulses that the crankshaft receives when the piston springs-back after the compression stroke, and the negative energy of the piston compressing the trapped charge is not shown. An additional benefit inures because of the friction reduction resulting from the deactivated cylinder. Start-up can be faster by deactivating one or more cylinders because the deactivated cylinder resists spin-up of the crankshaft less. Increasing the power setting of the combustion mode firing cylinders makes up for power losses on the deactivated cylinder. Figure 2 illustrates the crankshaft as "seeing" zero input for the instance where the cylinder would have had a power pulse. The end torque pattern is ideally smoothed, as by adjusting the power setting of the firing cylinder

[042] That is, it is possible to adjust the amplitude of the torque from the firing cylinders to be higher. Fuel injection controller 300 can increase fuel to the firing cylinders to yield the same torque output using less of the cylinders. For a 6 cylinder engine using 3 cylinder CDA, the result is twice the amplitude power pulses from the active cylinders, with negative power during the CDA cylinder

deactivations. Twice the power emits from the cylinders 1 -6 at half the frequency of the 6 cylinder mode. While a net torque is experienced on the crankshaft, the NVH (noise, vibration, harshness) strain is high. Designing driveline components, such as a clutch, for the larger amplitude cylinders and for the lack of output becomes difficult. However, during start-up, the clutch, transmission, and most of a vehicle's driveline are not connected to the engine, so acceleration of the crankshaft does not have to be as smooth as post-idle engine operation. Jumps in the rate of change for the crankshaft are acceptable, so long as the engine does not experience a peak vibration disturbance at a critical speed.

[043] CDA can be applied during engine start-up to reduce the resistance to motion of the crankshaft. Deactivating one or more cylinders reduces motoring torque, or torque necessary to move the engine components. There is less resistance to crankshaft motion using CDA mode on some cylinders, which yields more efficient torque output to the crankshaft via the reduced resistance to crankshaft motion. This can reduce strain on an electric starter, such as a battery and motor combination. When the power setting of the firing cylinders is also increased, CDA use results in an acceleration in the rate of change of the

crankshaft 101 so that the engine 100 is idle-ready sooner than customary 6- cylinder operation.

[044] During shut-down, CDA is beneficial to avoiding excessive fuel consumption and for skipping over the peak vibration disturbance 43, 53, 63. The WA controller 200 can be controlled to toggle among firing cylinders and

deactivated cylinders. The number and distribution of the firing and deactivated cylinders can changed based on engine needs. For example, during shut-down, the cylinders can fire just often enough to keep oil supply lines at the proper pressure or to avoid a harsh stalling of the engine. But, CDA use can be maximized to avoid excess fuel consumption and peak vibration disturbances. At times, the engine 100 can have all cylinders 1 -6 deactivated in cylinder deactivation mode.

[045] Figures 3A & 3B extend to engine-braking modes of operation. Using engine braking, the crankshaft "sees" torque input from the firing cylinders, but sees torque removed from the braked cylinders. If a net torque is desired, to coast to a stop, for example, the amplitude of the torque from the firing cylinders is higher than the absolute value of the engine braking loss. While a net torque is experienced on the crankshaft, the NVH strain is high. However, during start-up and shut-down, the clutch, transmission, and most of a vehicle's driveline are not connected to the engine, so acceleration and deceleration of the crankshaft does not have to be as smooth as post-idle engine operation. Jumps in the rate of change for the

crankshaft 101 are acceptable, so long as the engine 100 does not experience a peak vibration disturbance at a critical speed. [046] The firing cylinders are chosen in Figure 3B to have a power setting that is greater than the negative power of the engine-braked cylinders. The end torque pattern can be selected to continue spinning up the crankshaft 101 during a start-up mode. Increasing the power setting of the firing cylinders can increase the rate of change between start-up and idle so that the engine is ready to idle sooner than customary 6-cylinder operation. Ideally, the end torque pattern is somewhat smoothed. In Figure 3B, the end torque pattern avoids completely stalling the engine, but there are gaps in the end torque pattern. Such a strategy can be used during shut down to brake the engine during shut-down, thus accelerating the rate of change on the crankshaft 101 between idle and shut-down. The number and distribution of firing cylinders can be adjusted as the RPMS of the crankshaft change to avoid harsh stalling of the engine, to provide requisite power to shutdown components such as lubrication circuits or other vehicle components, yet avoid the peak vibration disturbances.

[047] Corollary, the range of harmonics is large. From engine start to regular engine operation, a large frequency range is traversed on the output/input (O/l) shaft.

[048] Engine operation (load, idle) above points 45, 55 & 65 is designed to obtain as smooth harmonic operation as possible, so the clutch is designed to smooth and damp vibrations for the majority of the operation zone. As torque output increases, the need for the clutch increases. Ordinarily, the clutch is designed to damp NVH in the end torque pattern. This leaves much of the harmonics range on the output/input O/l shaft undamped. So the output/input (O/l) shaft has harmonics that shake the vehicle outside of the clutch operation zone. Little damping is needed when the frequency of the harmonics is static, as when the O/l shaft is stiff. But the shaft cannot be stiff always.

[049] A harsh transition zone happens during start and stop of the engine, as illustrated by the peak vibration disturbances 43, 53, 63. The stiff O/l shaft moves from stopped at zero RPMs to idled at points 45, 55, 65, to loaded and operational. Because a majority of damping mechanisms are applied to the loaded and operational zones of Figure 5, and because the clutch is typically disengaged from the engine prior to points 45, 55, 65, the engine shakes during start-up and shutdown. It is beneficial to get through this shaking period as quickly as possible. This can be done in one aspect by increasing fuel injection to firing cylinders via fuel injection controller 300. It can be done in another aspect by reducing resistance to crankshaft motion by deactivating one or more cylinders. And, in another aspect, engine braking can contribute to getting across the shut-down to idle transition period as quickly as possible. Combinations of these engine modulation techniques can also be used. Should the designer choose, the engine can experience the peak vibration disturbance 43, 53, 63, but traverse it more quickly using a disclosed technique for changing the rate of change of the crankshaft acceleration or deceleration. Or, the engine can experience only part of a peak vibration

disturbance 43, 53, 63, as by traversing some portion of the curve from point 41 , 51 , 61 to point 43, 53, 63, or as by traversing some portion of the curve from point 45, 55, 65 to point 41 , 51 , 61 prior to switching to another engine modulation technique.

[050] Toggling the cylinder deactivation and engine-braking affectively skips the harmonic that causes the peak vibration disturbance at shut down or start up by switching to a different number of active cylinders and moving (or missing) the harmonic. In systems that are switched hydraulically, the deactivation system can rely on one or more of residual pressure, electric oil pump pressure, one or more hydraulic accumulators, etc. to power the valve actuator 185. The valve actuator 185 for the deactivation system can also be switched electrically in a camless arrangement or in a fully electrical system. A combination of hydraulic and electrical systems can also be used. All of this would enable a very quiet and relatively vibrationless diesel start stop system.

[051 ] A system for vibration management in a multiple-cylinder diesel engine can be understood comparing Figures 6-9. The engine comprises

respective reciprocating pistons 160 in the multiple cylinders 1 -4 or 1 -6. The respective reciprocating pistons 160 are connected to a crankshaft 101 for rotation of the crankshaft. The pistons 160 reciprocate from TDC to BDC as explained above, while fuel injection controller 300 modulates timing and amounts of fuel and while VVA controller 200 modulates valve opening and closing. Fuel injection controller 300 is part of a computer-controllable fuel injection system configured to inject fuel in to the multiple cylinders 1 -4 or 1 -6. VVA controller 200 is part of a system for respective computer-controllable intake valves 130 and exhaust valves 150. [052] A computer control network is outlined in Figure 7, and is connected to fuel injector 310 of fuel injection system and valve actuators 185 for respective intake valves and respective exhaust valves. The network can comprise a BUS for collecting data from various sensors, such as output/input (crankshaft) sensor 107, intake manifold sensor 173, exhaust manifold sensor 175, exhaust sensor 807, etc. The sensors can be used for making real-time adjustments to the fuel injection and valve opening and closing timing. Additional functionality can be pre-programmed and stored on the memory device 1401 . The additional functionality can comprise pre-programmed thresholds, tables, and other comparison and calculation structures for determining power settings for the cylinders, durations for the power settings and number and distribution cylinders at particular power settings.

[053] Memory device 1401 is a tangible readable memory structure, such as RAM, EPROM, mass storage device, removable media drive, DRAM, hard disk drive, etc. Signals per se are excluded. The algorithms necessary for carrying out the methods disclosed herein are stored in the memory device 1401 for execution by the processor 1403. When optional variable geometry turbocharger control is implemented, the VGT control 1415 is transferred from the memory 1401 to the processor for execution, and the computer control system functions as a

turbocharger controller. Likewise, the computer control system 1400 implements stored algorithms for EGR control 1414 to implement an EGR controller 400;

implements stored algorithms for intake assist device control 1416 to implement intake assist controller 600; and implements stored algorithms for fuel injection control 1413 to implement fuel injection controller 300. When implementing stored algorithms for WA control 1412, various intake valve controller and exhaust valve controller strategies are possible relating to valve timing and valve lift strategies, as detailed elsewhere in this application, and these strategies can be implemented by WA controller 200. A controller area network (CAN) can be connected to

appropriate actuation mechanisms to implement the commands of the processor 1403 and various controllers.

[054] While the computer control system 1400 is illustrated as a centralized component with a single processor, the computer control system 1400 can be distributed to have multiple processors, or allocation programming to

compartmentalize the processor 1403. Or, a distributed computer network can place a computer structure near one or more of the controlled structures. The distributed computer network can communicate with a centralized computer control system or can network between distributed computer structures. For example, a computer structure can be near the turbocharger 501 for VGT controller 500, another computer structure can be near the EGR valve 410 for EGR controller 400, another computer structure can be near the intake and exhaust valves for variable valve actuator 200, yet another computer controller can be placed for fuel injection controller 300, and yet another computer controller can be implemented for intake assist controller 600. Subroutines can be stored at the distributed computer structures, with centralized or core processing conducted at computer control system 1400.

[055] The computer network comprises the processor 1403, at least one tangible memory device 1401 , and processor-executable control algorithms for implementing the methods disclosed herein stored in the memory device 1401 and executable by the processor 1403. In one alternative, the stored processor- executable control algorithms implement the below method. A start-up or shut-down operation mode is selected, as by a user pressing a button, turning a key, engaging a brake, pressing an acceleration pedal, etc. Automation of the shut-down mode can be initiated by being in an idle condition for a predetermined amount of time, or being at idle with a manual brake engaged, among other initiation methods.

[056] A method for implementing vibration management can comprise a series of decisions, as outlined in Figure 10. The method can progress as decisions are made based on sensor feedback and execution of control algorithms. In step 1010, a first decision can comprise determining whether one of a start-up signal or a shut-down signal to the engine has been sensed. Based on the sensed start-up signal or the sensed shut-down signal, the method can comprise selecting one of a start-up operation mode of the engine or a shut-down operation mode of the engine. The start-up operation mode can comprise a start-up slope from a shut-down condition to an idled condition. The shut-down operation mode comprises a shutdown slope from the idled condition to the shut-down condition. The start-up slope and shut-down slope can comprise the peak vibration disturbances 43, 53, 63 and other points outlined in Figure 5. Based on the start-up slopes and shut-down slopes, decisions to deactivate a cylinder in block 1020, fire one or more cylinders in block 1022, or engine-brake a cylinder in block 1024 can be made. The decisions can comprise situation-specific subroutines. For example, if an accelerator was pressed to initiate an engine start-up after a fuel-saving shut-down, the decision tree can result in more cylinder deactivations and higher power settings on firing cylinders that when an engine start-up is initiated via use of a manual user ignition mechanism. User comfort and fuel economy can influence manual user ignition start-up decisions, while speed of engine readiness can influence accelerator-based start-ups. Likewise, shut-down due to idling in traffic can result in engine-braking and other decisions that differ from other user-initiated shut down of the engine, such as purposeful "off" selection.

[057] Vibration profiles such as those shown in Figure 5 can influence the decisions for adjusting fuel injection to the multiple-cylinders. The vibration profiles of the crankshaft 101 can comprise peak vibration disturbances. When the engine is operating near a peak vibration disturbance, the control algorithm can comprise decisions, as in block 1030, to adjust the engine harmonics away from the peak vibration disturbance. Real-time sensing of the crankshaft vibrations or crankshaft RPMs via crankshaft sensor 107 can be used with real-time analysis and

calculations. Or, preprogrammed data, such as crankshaft RPMs and look-up tables (LUTS) can be combined with sensor data to know when to switch cylinder operation modes. Additional and different sensors than those illustrated can augment system functionality.

[058] If engine operation is sufficient, and peak vibration disturbances are avoidable, than current operating parameters can be maintained. If the engine is operating near a peak vibration disturbance 43, 53, 63, or is following a rate of change and slope to reach a peak vibration disturbance, the control algorithms can comprise functionality to decide to adjust the cylinder operation modes. In block 1040, the control algorithms can decide whether to convert one or more deactivated cylinders to one or more firing cylinders. In block 1042, a decision can be made for whether to convert one or more firing cylinders to an engine-braking or deactivated cylinder. Further decisions with respect to the firing cylinder can be whether to adjust the power setting for any firing cylinders, as by adjusting the fueling to the firing cylinder in block 1046. And, a decision can be made whether to convert a braking cylinder to a firing cylinder in block 1048. Appropriate commands are issued by the processor 1403 and implemented across the CAN. The decisions and adjustments can iterate until the desired terminus is achieved. During start-up operation mode, the terminus is reaching idle at one of points 45, 55, 65 by increasing engine RPMs. During engine shut-down operation mode, the terminus is achieved by reaching zero RPMs and a turned-off engine.

[059] Adjusting fuel injection can comprise terminating fuel injection to at least one of the cylinders 1 -6 of the multiple-cylinders to adjust the vibration profile of the crankshaft 101 to avoid the peak vibration disturbance 43, 53, 63. Fuel injection controller 300 can issue commands to fuel injectors 310 to implement this. Adjusting fuel injection to the multiple-cylinders can comprise increasing fuel injection to combustion cylinders of the multiple-cylinders to increase a torque output of the combustion cylinders. Variants can comprise terminating fuel injection to at least half of the cylinders of the multiple-cylinders, terminating fuel injection to all of the cylinders of the multiple-cylinders, or terminating some other number of cylinders' fuel injection.

[060] In power-assisted engine systems, it is possible to have a battery- powered motor or other starter device 900 affiliated with the engine to initiate crankshaft motion, cam rail motion, or to power fuel injectors 310, or other valve actuators 185. For example, a motor can be configured to spin the crankshaft, and the control algorithm can comprise a method for activating the motor. The starter device 900 can be activated in response to sensing the start-up signal. The decisions for distributing cylinder deactivation or engine braking or fuel injection can be based on alleviating strain on the starter device 900. Implementing cylinder deactivation can be chosen to accelerate a rate of change for the start-up slope or for the shut-down slope to arrive at the desired terminus faster than ordinary 6- cylinder operation mode.

[061 ] Adjusting fuel injection to the multiple cylinders can comprise adjusting the number of cylinders of the multiple-cylinders terminating fuel injection as the engine progresses through the selected start-up operation mode or the selected shut-down operation mode. The multiple-cylinders 1 -6 can be distributed in the engine 100, and adjusting fuel injection can comprise changing which at least one cylinder in the distribution terminates fuel injection as the engine 100 progresses through the selected start-up operation mode or the selected shut-down operation mode.

[062] Adjusting fuel injection to the multiple-cylinders can comprise increasing fuel injection to combustion cylinders of the multiple-cylinders to increase a torque output, or power setting, of the combustion cylinders.

[063] Deactivating respective computer-controllable intake valves 130 and exhaust valves 150 for at least one the cylinder having terminated fuel injection can implement CDA operation mode. Deactivating respective computer-controllable intake valves and exhaust valves can be used to accelerate a rate of change for the start-up slope or for the shut-down slope. Adjusting fuel injection to the multiple- cylinders can comprise increasing fuel injection to combustion cylinders of the multiple-cylinders to increase a torque output of the combustion cylinders to be greater than a desired engine torque output. Deactivating respective computer- controllable intake valves and exhaust valves can be selected to reduce the torque output of the at least one cylinder having terminated fuel injection to result in the desired engine torque output.

[064] Likewise, the control algorithms for the method for implementing vibration management can comprise activating engine braking on respective computer-controllable intake valves 130 and exhaust valves 150 for the at least one the cylinders having terminated fuel injection. Activating engine braking can comprise opening at least one of the respective computer-controllable intake valves and exhaust valves after the respective reciprocating piston 160 for the at least one of the cylinders has completed a compression stroke. Activating engine braking on respective computer-controllable intake valves and exhaust valves can accelerate a rate of change for the start-up slope or for the shut-down slope to arrive at the desired terminus faster than ordinary 6-cylinder operation mode.

[065] Many stroke-strategies can be implemented to choose when to open the computer-controllable intake valves and exhaust valves. If a stroke comprises the piston 160 traveling between TDC and BDC in either direction, engine-braking can comprise implementing a 2-stroke braking technique, where a compression stroke is followed by opening a valve for releasing pressure. Instead of transferring the energy of the compressed charge to the crankshaft 101 , the compressed charge is released to either the intake manifold or the exhaust manifold, depending on which of the intake valve or exhaust valves were opened. The compressed charge dissipates. The energy loss results in braking of the crankshaft 101 . Using 2-stroke braking, the engine brakes every revolution of the crankshaft 101.

[066] In this aspect, both cylinder deactivation (CDA) and 2-stroke engine braking function can be enabled on a diesel engine with a single set of hardware. A Variable Valve Actuation (VVA) system can comprise of a deactivating component capable of eliminating the main lift events with lost motion and independent added motion arms capable of adding brake event valve motion with an independent control circuit for each. This can be used to perform both cylinder deactivation and 2-stroke engine braking functions. Using a new capsule design adds CDA to the braking outlay.

[067] It is further possible to provide engine braking at the same time as hydraulic lash adjustment (HLA). Few concepts can do both. It is possible to use a rocker arm lost motion capsule with reset to modularly perform HLA and braking. Other designs can include HLA and engine brake in a cam or camless engine.

[068] As illustrated in Figures 4B & 4C, the negative power setting of the engine-braking is as tailorable as the positive power setting controllable by fuel injection. The braking power can be based on the fuel injection, in that the

crankshaft is moving the pistons 160 based on the fuel to the firing cylinders, so a braking operation releases compressed fluid in relation to the compression happening on the firing cylinders. Also, the extent of valve opening via WA controller 200 can influence the quantity of compressed fluid released, and the amount of time at which compression of the charge can occur prior to brakine. So, the stroke pattern for the engine braking can be controlled, and the power setting for the braked cylinder can be controlled.

[069] For example, opening the at least one of the respective computer- controllable intake valves and exhaust valves can occur as the piston nears top- dead-center. Full charge compression has not occurred, and an early release of what has been compressed tailors the power robbed from the crankshaft 101 .

Another power setting can be selected by opening the at least one of the respective computer-controllable intake valves and exhaust valves when the piston reaches top-dead-center. Other timing can comprise opening the at least one of the respective computer-controllable intake valves and exhaust valves occurs when the piston departs top-dead-center.

[070] Adjusting fuel injection to the multiple-cylinders 1 -6 can comprise increasing fuel injection to combustion cylinders of the multiple-cylinders to increase a torque output of the combustion cylinders to be greater than a desired engine torque output. And, activating engine-braking can be selected to reduce the torque output of the at least one cylinder having terminated fuel injection to result in the desired engine torque output.

[071 ] Engine-braking to balance harmonics can have greater applicability outside start and stop operation modes. So, Figure 9 shows a more simplified method. In step S101 , the control algorithm determines that a peak vibration disturbance is imminent. Being in a particular operation mode, at a particular RPM, at a particular load, or other engine status can indicate imminence of a peak vibration disturbance. As above, pre-programming, real-time calculations, and combinations of the two can be used to determine the imminence. Selectively braking all cylinders is possible. To do so, fuel to the cylinders must be shut off in step S103. This terminates fuel injection to the selected cylinder. Fewer than all cylinders can be shut off. To build up releasable energy in the engine-braking cylinder, the intake and exhaust valves are closed in step S105. A charge is trapped in step S107 to build energy in the cylinder. Then, in step S109, at least one of the respective computer-controllable intake valves and exhaust valves is opened to release the compressed energy after a respective piston of the cylinder has completed a compression stroke. The technique of Figure 9 can also be used for vibration management of the engine by modulating the timing of the engine braking to balance engine vibrations.

[072] The method can further comprise increasing the number of cylinders of the multiple-cylinders selectively engine-braking as the engine progresses through a start-up operation mode or a shut-down operation mode. The multiple- cylinders are distributed in the engine, and the method can further comprise changing which cylinder in the distribution constitutes the engine-braking cylinder. The method can further comprise increasing fuel injected in to the firing cylinders to increase torque output from the filing cylinders. And, the engine-braking can accelerate a rate of change for a crankshaft of the engine. [073] To increase harmonics management, the valve actuators 185 can be configured to switch between selectively engine-braking the cylinder of the multiple- cylinder diesel engine and selectively firing the cylinder of the multiple-cylinder diesel engine to shift engine harmonics. So, the method for managing engine vibrations can comprise switching one or more of the firing cylinders of the multiple- cylinder diesel engine to engine-braking cylinders of the multiple-cylinder diesel engine, and vice versa, to shift engine harmonics.

[074] The methods and systems disclosed here can be limited to start-up operation modes and shut-down operation modes.

[075] Electrically or hydraulically actuated valves can be in CDA mode when a user selects shut-down. This can cause critical shifts, which are undesired. When an engine shuts down, a timing strategy should shift the cylinders back out of cylinder deactivation (CDA) to avoid issues. For a hydraulically actuated valve system, shutting the engine off will depressurize the oil feed. The valves will gradually return to "normal" mode, whether or not control intervention is made. However, the slow depressurization can cause critical shifts. Likewise, in an electrically actuated system, a charge of fluid is trapped in the cylinder, and fluids leak out.

[076] So, a timing strategy returns the cylinders to "normal" mode conditions (returns the valves to lift condition) to avoid pressure issues and to avoid critical shifts. CDA is exited to open the valves back up. This lift condition can be implemented for hydraulically actuated valves, while for electronically controlled CDA, the system can remain in CDA mode for portions of the stop/start cycle.

[077] Also, it is beneficial to turn an engine on in normal mode to have all 6 cylinders firing at initial start up. The engine harmonics are more harsh for 3 cylinders than for 6. So starting the engine in CDA would cause the engine to shake violently. Sequencing the order of firing, engine-braking, and cylinder deactivation lessens the harsh shaking.

[078] And, by monitoring the engine RPMS, it can be determined when the engine is about to hit the harmonic range for violent shaking. CDA can be implemented to convert to 3 cylinder mode to jump the harmonic at that RPM. This cuts the frequency in half, thus reducing the harmonic for shaking. [079] The inverse is true for shut-down. It is possible to begin in 6 cylinder mode at idle. It is possible to go to 3 cylinders for engine-braking or CDA to skip the harmonic, then return to 6 cylinders at shut down.

[080] For an electric-control engine, this is not a problem. For oil controlled systems, there must be sufficient oil pressure to activate the cylinders. In most circumstances, there should be enough oil pressure to activate CDA during shutdown because not much pressure has yet bled off. But, it can be beneficial to include an accumulator to supply the start-up oil pressure for switching modes, or the accumulator can assist shut-down switching between CDA & normal mode. It can also be beneficial to include an electric oil pump to ensure oil pressure during this CDA activation point. The electric oil pump can replace a gear oil pump. Other strategies such as check valves and pressure regulators can be included to limit oil bleed during start/stop.

[081 ] Other implementations will be apparent to those skilled in the art from consideration of the specification and practice of the examples disclosed herein.