Patent Publication Number: US-11391229-B2

Title: System and method for starting an engine

Description:
BACKGROUND/SUMMARY 
     Legislated vehicle emissions levels continue to reduce allowable levels of vehicle emissions. Through considerable efforts, vehicle emissions have been significantly reduced for driving portions of vehicle operation. For example, during vehicle cruise and after engine warmup, engine emissions may be reduced substantially. As a result, opportunities to decrease vehicle emissions levels after engine warmup may be small. Therefore, efforts to reduce vehicle emissions have concentrated on reducing vehicle emissions within the first few minutes of vehicle operation. However, an engine may generate higher emissions levels just after the engine has been cold started and the vehicle&#39;s after treatment system may be less efficient during this time. Therefore, it may be desirable to provide a way of reducing vehicle emissions during such conditions. 
     The inventors herein have recognized the above-mentioned disadvantages and have developed an engine operating method, comprising: activating an electrically heated catalyst and opening an exhaust gas recirculation (EGR) valve in response to an indication that an engine start request is imminent. 
     By activating an electrically heated catalyst and opening an EGR valve, it may be possible to compound heat air circulated in an engine and engine exhaust after treatment devices so that temperatures of the after treatment devices increase at a higher rate. Further, heating of the after treatment devices via heated air may commence before an engine is started so that when the engine is started, emissions of the engine may be converted with higher efficiency. 
     The present description may provide several advantages. In particular, the approach may reduce vehicle emission during cold start conditions. In addition, the approach may be applied to petrol and diesel engines. Further, the approach may be provided without degrading vehicle drivability. 
     The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings. 
     It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows a detailed schematic depiction of an example engine; 
         FIG. 2  shows an example vehicle that includes an engine; 
         FIG. 3  shows an example vehicle operating sequence according to the present method; and 
         FIG. 4  shows an example method for operating a vehicle to reduce vehicle emissions. 
     
    
    
     DETAILED DESCRIPTION 
     The present description is related to operating an engine that may be cold started from time to time.  FIG. 1  shows one example of an electrically boosted engine. By electrically boosting the engine, it may be possible to provide significant amounts of compressed air to the engine while the engine is not rotating so that emissions after treatment devices may be heated before an engine is started. Air flow generated by the electrically booster may be recirculated so that the air may be compound heated. In other words, the air may be heated a first time and then the air may be recirculated back to the heater to be heated again so that the temperature of the heated air increases as compared to a condition where the air is exhausted from the engine without being reheated. The air may be heated in an engine that resides in a vehicle as shown in  FIG. 2 . The air may be heated in a sequence as shown in  FIG. 3 . A method for heating the air is shown in  FIG. 4 . 
     Referring to  FIG. 1 , internal combustion engine  10 , comprising a plurality of cylinders, one cylinder of which is shown in  FIG. 1 , is controlled by electronic engine controller  12 . The controller  12  receives signals from the various sensors of  FIG. 1  and employs the various actuators of  FIG. 1  to adjust engine operation based on the received signals and instructions stored on a memory of the controller. 
     Engine  10  includes combustion chamber  30  and cylinder walls  32  with piston  36  positioned therein and connected to crankshaft  40 . Cylinder head  13  is fastened to engine block  14 . Combustion chamber  30  is shown communicating with intake manifold  44  and exhaust manifold  48  via respective intake valve  52  and exhaust valve  54 . Each intake and exhaust valve may be operated by an intake cam  51  and an exhaust cam  53 . Although in other examples, the engine may operate valves via a single camshaft or pushrods. The position of intake cam  51  may be determined by intake cam sensor  55 . The position of exhaust cam  53  may be determined by exhaust cam sensor  57 . Intake poppet valve  52  may be operated by a variable valve activating/deactivating actuator  59 , which may be a cam driven valve operator (e.g., as shown in U.S. Pat. Nos. 9,605,603; 7,404,383; and 7,159,551 all of which are hereby fully incorporated by reference for all purposes). Likewise, exhaust poppet valve  54  may be operated by a variable valve activating/deactivating actuator  58 , which may a cam driven valve operator (e.g., as shown in U.S. Pat. Nos. 9,605,603; 7,404,383; and 7,159,551 all of which are hereby fully incorporated by reference for all purposes). Intake poppet valve  52  and exhaust poppet valve  54  may be deactivated and held in a closed position preventing flow into and out of combustion chamber  30  for one or more entire engine cycles (e.g. two engine revolutions), thereby deactivating combustion chamber  30 . Flow of fuel supplied to combustion chamber  30  may also cease when combustion chamber  30  is deactivated. 
     Fuel injector  68  is shown positioned in cylinder head  13  to inject fuel directly into combustion chamber  30 , which is known to those skilled in the art as direct injection. Fuel is delivered to fuel injector  68  by a fuel system including a fuel tank  26 , fuel pump  21 , fuel pump control valve  25 , and fuel rail (not shown). Fuel pressure delivered by the fuel system may be adjusted by varying a position valve regulating flow to a fuel pump (not shown). In addition, a metering valve may be located in or near the fuel rail for closed loop fuel control. A pump metering valve may also regulate fuel flow to the fuel pump, thereby reducing fuel pumped to a high pressure fuel pump. 
     Engine air intake system  9  may include an upstream throttle  63 , intake manifold  44 , central throttle  62 , grid heater  16 , turbocharger compressor  162 , and air filter  42 . Intake manifold  44  is shown communicating with optional central throttle  62  which adjusts a position of throttle plate  64  to control air flow from intake boost chamber  46 . Upstream throttle  63  may be operated in a similar way. Electrically driven compressor  162  draws air from air filter  42  when upstream throttle is open to supply boost chamber  46 . Compressor vane actuator  84  adjusts a position of compressor vanes  19 . Electric machine (e.g., motor)  165  may rotate vanes  19  to pressurize air entering engine  10 . Further, an optional grid heater  16  may be provided to warm air entering combustion chamber  30  when engine  10  is being cold started. Compressor speed may be adjusted via adjusting an amount of current that is provided to electric machine  165 . Compressor recirculation valve  158  allows compressed air at the outlet  15  of compressor  162  to be returned to the inlet  17  of compressor  162 . Alternatively, a position of compressor variable vane actuator  78  may be adjusted to change the efficiency of compressor  162 . In this way, the efficiency of compressor  162  may be increased or reduced so as to affect the flow of compressor  162  and reduce the possibility of compressor surge. Further, by returning air back to the inlet of compressor  162 , work performed on the air may be increased, thereby increasing the temperature of the air. Electric machine  165  may rotate compressor  162  when engine  10  is not rotating or when engine  10  is rotating. Air flow through the engine, when the engine is not rotating before an engine cold start, is indicated in the direction of arrows  5 . 
     Flywheel  97  and ring gear  99  are coupled to crankshaft  40 . Starter  96  (e.g., low voltage (operated with less than 30 volts) electric machine) includes pinion shaft  98  and pinion gear  95 . Pinion shaft  98  may selectively advance pinion gear  95  to engage ring gear  99  such that starter  96  may rotate crankshaft  40  during engine cranking. Starter  96  may be directly mounted to the front of the engine or the rear of the engine. In some examples, starter  96  may selectively supply torque to crankshaft  40  via a belt or chain. In one example, starter  96  is in a base state when not engaged to the engine crankshaft. An engine start may be requested via human/machine interface (e.g., key switch, pushbutton, remote radio frequency emitting device, etc.)  69  or in response to vehicle operating conditions (e.g., brake pedal position, accelerator pedal position, battery SOC, etc.). Low voltage battery  8  may supply electrical power to starter  96 . High voltage battery  7  may supply electrical power to electric machine  165 . Controller  12  may monitor battery state of charge. 
     Combustion is initiated in the combustion chamber  30  when fuel automatically ignites via combustion chamber temperatures reaching the auto-ignition temperature of the fuel that is injected to cylinder  30 . Alternatively, in petrol engines a fuel-air mixture may be ignited via a spark plug (not shown). The temperature in the cylinder increases as piston  36  approaches top-dead-center compression stroke. In some examples, a universal Exhaust Gas Oxygen (UEGO) sensor  126  may be coupled to exhaust manifold  48  upstream of emissions device  71 . In other examples, the UEGO sensor may be located downstream of one or more exhaust after treatment devices. Further, in some examples, the UEGO sensor may be replaced by a NOx sensor that has both NOx and oxygen sensing elements. 
     At lower engine temperatures optional glow plug  66  may convert electrical energy into thermal energy so as to create a hot spot next to one of the fuel spray cones of an injector in the combustion chamber  30 . By creating the hot spot in the combustion chamber  30  next to the fuel spray, it may be easier to ignite the fuel spray plume in the cylinder, releasing heat that propagates throughout the cylinder, raising the temperature in the combustion chamber, and improving combustion. Cylinder pressure may be measured via optional pressure sensor  67 , alternatively or in addition, sensor  67  may also sense cylinder temperature. 
     Engine exhaust gases may be processed via an exhaust system  11  that includes an electrically heated catalyst  35 , which alternatively may be a heater, emissions devices, EGR passage outlets, and an exhaust throttle  87 . Exhaust system  11  includes an emissions device  71  which may include an oxidation catalyst and it may be followed by a diesel particulate filter (DPF)  72  and a selective catalytic reduction (SCR) catalyst  73 , in one example. In another example, DPF  72  may be positioned downstream of SCR  73 . Temperature sensor  70  provides an indication of SCR temperature. 
     Exhaust gas recirculation (EGR) may be provided to the engine via high pressure EGR system  83 . High pressure EGR system  83  includes valve  80 , EGR passage  81 , and EGR cooler  85 . EGR valve  80  is a valve that closes or allows exhaust gas to flow from upstream of emissions device  71  to a location in the engine air intake system downstream of compressor  162 . EGR may be cooled via passing through EGR cooler  85 . EGR may also be provided via low pressure EGR system  75 . Low pressure EGR system  75  includes EGR passage  77  and EGR valve  76 . Low pressure EGR may flow from downstream of emissions device  71  to a location upstream of compressor  162 . Low pressure EGR system  75  may include an EGR cooler  74 , a cooler bypass passage  77   a , and a low pressure cooler bypass valve  78 . Low pressure cooler bypass valve  78  may be opened for gases to bypass cooler  74 . Exhaust throttle  87  may be opened when the engine is running and it may be fully closed when the engine is not rotating while emissions devices are being heated. 
     Controller  12  is shown in  FIG. 1  as a conventional microcomputer including: microprocessor unit  102 , input/output ports  104 , read-only memory (e.g., non-transitory memory)  106 , random access memory  108 , keep alive memory  110 , and a conventional data bus. Controller  12  is shown receiving various signals from sensors coupled to engine  10 , in addition to those signals previously discussed, including: engine coolant temperature (ECT) from temperature sensor  112  coupled to cooling sleeve  114 ; a position sensor  134  coupled to an accelerator pedal  130  for sensing accelerator position adjusted by human foot  132 ; a measurement of engine manifold pressure (MAP) from pressure sensor  121  coupled to intake manifold  44  (alternatively or in addition sensor  121  may sense intake manifold temperature); boost pressure from pressure sensor  122  exhaust gas oxygen concentration from oxygen sensor  126 ; an engine position sensor from a Hall effect sensor  118  sensing crankshaft  40  position; a measurement of air mass entering the engine from sensor  120  (e.g., a hot wire air flow meter); and a measurement of throttle position from sensor  58 . Barometric pressure may also be sensed (sensor not shown) for processing by controller  12 . In a preferred aspect of the present description, engine position sensor  118  produces a predetermined number of equally spaced pulses every revolution of the crankshaft from which engine speed (RPM) can be determined. 
     During operation, each cylinder within engine  10  typically undergoes a four stroke cycle: the cycle includes the intake stroke, compression stroke, expansion stroke, and exhaust stroke. During the intake stroke, generally, the exhaust valve  54  closes and intake valve  52  opens. Air is introduced into combustion chamber  30  via intake manifold  44 , and piston  36  moves to the bottom of the cylinder so as to increase the volume within combustion chamber  30 . The position at which piston  36  is near the bottom of the cylinder and at the end of its stroke (e.g. when combustion chamber  30  is at its largest volume) is typically referred to by those of skill in the art as bottom dead center (BDC). During the compression stroke, intake valve  52  and exhaust valve  54  are closed. Piston  36  moves toward the cylinder head so as to compress the air within combustion chamber  30 . The point at which piston  36  is at the end of its stroke and closest to the cylinder head (e.g. when combustion chamber  30  is at its smallest volume) is typically referred to by those of skill in the art as top dead center (TDC). In a process hereinafter referred to as injection, fuel is introduced into the combustion chamber. In some examples, fuel may be injected to a cylinder a plurality of times during a single cylinder cycle. 
     In a process hereinafter referred to as ignition, the injected fuel is ignited by compression ignition resulting in combustion. During the expansion stroke, the expanding gases push piston  36  back to BDC. Crankshaft  40  converts piston movement into a rotational torque of the rotary shaft. Finally, during the exhaust stroke, the exhaust valve  54  opens to release the combusted air-fuel mixture to exhaust manifold  48  and the piston returns to TDC. Note that the above is described merely as an example, and that intake and exhaust valve opening and/or closing timings may vary, such as to provide positive or negative valve overlap, late intake valve closing, or various other examples. Further, in some examples a two-stroke cycle may be used rather than a four-stroke cycle. 
     Referring now to  FIG. 2 , engine  10  is shown included within vehicle  200 . A vehicle door position sensor  204  provides an indication of a position of vehicle door  202  to controller  12 . Controller  12  may use a door position indication that is provided by door position sensor  204  to pre-heat after treatment devices (e.g.,  71  and  72  shown in  FIG. 1 ). In particular, controller  12  may activate an electrically heated catalyst or a heater when engine  10  is not rotating in response to an indication of an open door. In addition, controller  12  may activate an electrically heated catalyst or a heater when engine  10  is not rotating in response to a signal from a remote device  206 . Remote device (e.g., key fob, phone, tablet, etc.) may transmit a signal  208  that it is desired to start engine  10  or that a vehicle operator is proximate to the location of vehicle  200 , which may be indicative of a pending engine start. 
     The system of  FIGS. 1 and 2  provides for an engine system, comprising: a diesel engine including an electrically driven compressor, a low pressure exhaust gas recirculation (EGR) valve, and an exhaust system including an electrically heated catalyst; and a controller including executable instructions stored in non-transitory memory that cause the controller to open the low pressure EGR valve, activate the electrically driven compressor, and activate the electrically heated catalyst in response to an indication that a start of the diesel engine is imminent. The engine system further comprises additional instructions to close the low pressure EGR valve in response to a request to start the engine. The engine system further comprises an upstream throttle and a central throttle. The engine system further comprises additional instructions to fully close the upstream throttle and fully open the central throttle in response to the indication that the start of the diesel engine is imminent. The engine system further comprises additional instructions to fully open the upstream throttle in response to an engine start request. The engine system further comprises additional instructions to not open the EGR valve in response to less a battery state of charge being less than a threshold. 
     Referring now to  FIG. 3 , an example prophetic engine operating sequence for an engine is shown. The operating sequence of  FIG. 3  may be produced via the system of  FIG. 1  executing instructions of the method described in  FIG. 4 . The plots of  FIG. 3  are aligned in time and occur at the same time. Vertical markers at t 0 -t 4  indicate times of particular interest during the sequence. 
     The first plot from the top of  FIG. 3  represents engine state versus time. Trace  302  represents engine state and the engine is off when trace  302  is at a low level near the horizontal axis. The engine is on and receiving fuel combusting the fuel or at least attempting to combust the fuel via compression ignition when trace  302  is at a higher level near the vertical axis arrow. The vertical axis represents engine state. The horizontal axis represents time and time increases from the left side to right side of the figure. 
     The second plot from the top of  FIG. 3  represents an engine pre-start state versus time. Trace  304  represents the engine pre-start state. The vertical axis represents engine pre-start state and an engine pre-start is active when trace  304  is at a higher level near the vertical axis arrow. The engine pre-start is not active when trace  304  is at a lower level near the horizontal axis. The engine pre-start sequence may include activating an electrically heated catalyst, adjusting engine throttles, activating a compressor, and adjusting a position of an exhaust gas recirculation (EGR) valve. The pre-start sequence may heat up one or more exhaust after treatment devices in preparation for an impending engine start so that engine emissions may be converted sooner, thereby reducing tailpipe emissions. The horizontal axis represents time and time increases from the left side to right side of the figure. 
     The third plot from the top of  FIG. 3  represents an operating state of the engine&#39;s central throttle versus time. Trace  306  represents the operating state of the central throttle. The vertical axis represents the state of the central throttle and the central throttle is open when trace  306  is at a higher level near the vertical axis arrow. The central throttle is fully closed when trace  306  is at a lower level near the horizontal axis. The horizontal axis represents time and time increases from the left side to right side of the figure. 
     The fourth plot from the top of  FIG. 3  represents an operating state of the engine&#39;s upstream throttle versus time. Trace  308  represents the operating state of the upstream throttle. The vertical axis represents the state of the upstream throttle and the upstream throttle is open when trace  308  is at a higher level near the vertical axis arrow. The upstream throttle is fully closed when trace  308  is at a lower level near the horizontal axis. The horizontal axis represents time and time increases from the left side to right side of the figure. 
     The fifth plot from the top of  FIG. 3  represents an operating state of the engine&#39;s exhaust throttle versus time. Trace  310  represents the operating state of the exhaust throttle. The vertical axis represents the state of the exhaust throttle and the exhaust throttle is open when trace  310  is at a higher level near the vertical axis arrow. The exhaust throttle is fully closed when trace  310  is at a lower level near the horizontal axis. The horizontal axis represents time and time increases from the left side to right side of the figure. 
     The sixth plot from the top of  FIG. 3  represents an operating state of the engine&#39;s EGR valve versus time. Trace  312  represents the operating state of the EGR valve. The vertical axis represents the state of the EGR valve and the EGR valve is open when trace  312  is at a higher level near the vertical axis arrow. The EGR valve is fully closed when trace  312  is at a lower level near the horizontal axis. The horizontal axis represents time and time increases from the left side to right side of the figure. 
     The seventh plot from the top of  FIG. 3  represents an operating state of the engine&#39;s electrically driven compressor versus time. Trace  314  represents the operating state of the electrically driven compressor. The vertical axis represents the state of the electrically driven compressor and the electrically driven compressor is activated or “ON” (e.g., rotating and compressing air) when trace  314  is at a higher level near the vertical axis arrow. The electrically driven compressor is deactivated of “OFF” when trace  314  is at a lower level near the horizontal axis. The horizontal axis represents time and time increases from the left side to right side of the figure. 
     The eighth plot from the top of  FIG. 3  represents an operating state of the electrically heated catalyst versus time. Trace  316  represents the operating state of the electrically heated catalyst. The vertical axis represents the state of the electrically heated catalyst and the electrically heated catalyst is activated or “ON” (e.g., being electrically heated) when trace  316  is at a higher level near the vertical axis arrow. The electrically heated catalyst is deactivated or “OFF” when trace  316  is at a lower level near the horizontal axis. The horizontal axis represents time and time increases from the left side to right side of the figure. 
     At time t 0 , the engine is stopped (not combusting and not rotating) and engine pre-starting is not asserted. The central throttle is fully closed and the upstream throttle is fully open. The exhaust throttle is fully open and the EGR valve is fully closed. The electrically driven compressor is deactivated and the electrically heated catalyst (ECAT) is not activated. Such conditions may be present when the engine is not running. 
     At the time t 1 , the engine pre-starting is asserted and the engine is not activated. The engine pre-starting may be asserted via a vehicle door being opened or via a signal from a remote device. The central throttle remains closed and the upstream throttle is fully open. The exhaust valve is fully open and the EGR valve is fully closed. The electrically driven compressor is not activated and the electrically heated catalyst is not activated. 
     At time t 2 , the engine pre-starting remains asserted and the engine is not activated. The central throttle is fully opened and the upstream throttle is fully closed in response to the pre-starting request. The exhaust valve is fully closed and the EGR valve is fully opened in response to the pre-starting request. The electrically driven compressor is activated and the electrically heated catalyst is activated in response to the pre-starting request. By closing the upstream throttle, closing the exhaust throttle, and opening the EGR valve, air may be pumped via the electrically driven compressor and repeatedly be recirculated back to the compressor. Thus, the same air may be heated and reheated via the compressor and the electrically heated catalyst. This operation may be referred to as compound heating of the air and it may increase temperatures of exhaust after treatment devices higher than if the air where only heated once and then ejected out of the vehicle&#39;s tailpipe. 
     At time t 3 , the engine is started and the pre-start state is exited. The engine may be started via input from a human driver/occupant or automatically. The central throttle remains fully open since this example is for a diesel engine; however, the central throttle may be fully closed at the time of engine start for petrol engines. The upstream throttle is fully opened and the exhaust throttle is fully opened in response to the engine start. Further, the EGR valve is fully closed in response to the engine start. The electrically drive compressor remains activated and the electrically heated catalyst remains activated. 
     At time t 4 , the engine is operating and the pre-start state is not asserted. The central throttle remains fully open and the upstream throttle is fully opened. The exhaust throttle remains fully opened and the EGR valve is fully closed. The electrically drive compressor remains activated and the electrically heated catalyst is deactivated in response to the catalyst reaching a threshold temperature. 
     In this way, pre-heating of exhaust system after treatment devices may be provided so that engine tailpipe emissions may be reduced. In addition, air within the engine may be heated several times during a pre-starting sequence so that after treatment device temperature may increase. 
     Referring now to  FIG. 4 , a method for operating an engine is shown. In particular, a flowchart of a method for operating an internal combustion engine is shown. The method of  FIG. 4  may be stored as executable instructions in non-transitory memory in systems such as shown in  FIGS. 1 and 2 . The method of  FIG. 4  may be incorporated into and may cooperate with the systems of  FIGS. 1 and 2 . Further, at least portions of the method of  FIG. 4  may be incorporated as executable instructions stored in non-transitory memory while other portions of the method may be performed via a controller transforming operating states of devices and actuators in the physical world. The controller may employ engine actuators of the engine system to adjust engine operation, according to the method described below. Further, method  400  may determine selected control parameters from sensor inputs. 
     At  402 , method  400  determines vehicle operating conditions. Vehicle operating conditions may include but are not limited to engine temperature, accelerator pedal position, ambient temperature, engine starting requests, ambient pressure, driver demand torque, and engine speed. Vehicle operating conditions may be determined via vehicle sensors and the engine controller described in  FIG. 1 . Method  400  proceeds to  404 . 
     At  404 , method  400  judges if the engine is off (e.g., not rotating and combusting fuel) and a temperature of an exhaust after treatment device start is less than a threshold temperature (e.g., a catalyst light off temperature). If method  400  judges that the engine is off and the temperature of the exhaust after treatment device is less than the threshold temperature, the answer is yes and method  400  proceeds to  406 . Otherwise, the answer is no and method  400  proceeds to exit. Method  400  may continue operating the engine in its present state if the answer is no. 
     At  406 , method  400  judges if there is an indication that the engine may be started in the near future. Method  400  may judge that there is an indication that the engine may be started in the near future if the vehicle&#39;s door is open or has been opened within a predetermined time. Method  400  may also judge that there is an indication that the engine may be started if the vehicle receives a signal to start the engine, prepare the engine for starting, or if a remote device has entered in close proximity to the vehicle (e.g., within 10 meters). If method  400  judges that there is an indication that the engine may start, the answer is yes and method  400  proceeds to  408 . Otherwise, the answer is no and method  400  proceeds to exit. Method  400  may continue operating the engine in its present state if the answer is no. 
     At  408 , method  400  may optionally fully close an upstream throttle, if an upstream throttle is present within the vehicle. By fully closing the upstream throttle, air may be recirculated from the compressor, through the engine, through the engine&#39;s exhaust system and EGR passage before returning back to the compressor. Fully closing the upstream throttle may prevent air from exiting the engine via the engine&#39;s air intake passage. Method  400  proceeds to  410 . 
     At  410 , method  400  fully opens a central throttle, if a central throttle is present within the vehicle. By fully opening the central throttle, air may pass from the compressor and through the engine&#39;s cylinders where intake and exhaust valves may be simultaneously open. In addition, intake and exhaust poppet valves of one or more cylinders may be opened to allow air flow through the engine&#39;s cylinders if intake and exhaust valve overlap is small. The poppet valve may be opened via a decompression control device or via variable valve actuators. Alternatively, or in addition, method  400  may open a high pressure EGR valve (e.g.,  80 ) to direct air around engine  10  and to electrically heated catalyst  35 . In such cases, the air may also be directed around an EGR cooler, if present. Method  400  proceeds to  412 . 
     At  412 , method  400  may optionally fully close an exhaust throttle, if an exhaust throttle is present within the vehicle. By fully closing the exhaust throttle, air may be returned to the compressor without flowing from the exhaust system so that the air may be reheated. Reheating the air may increase after treatment device temperatures and reduce an amount of energy used to heat the after treatment device. Method  400  proceeds to  414 . 
     At  414 , method  400  fully opens a low pressure EGR valve (e.g.,  78  of  FIG. 1 ). By fully opening the low pressure EGR valve, air may be returned from the engine&#39;s exhaust manifold to the engine&#39;s compressor without flowing from the exhaust system so that the air may be reheated. Method  400  proceeds to  416 . 
     At  416 , method  400  activates the electrically heated catalyst (e.g.,  35  of  FIG. 1 ). By activating the electrically heated catalyst, a temperature of the catalyst and other after treatment devices may be increased, thereby increasing their efficiencies. Method  400  proceeds to  418 . 
     At  418 , method  400  activates the electrically driven compressor (e.g.,  162  of  FIG. 1 ). By activating the electrically driven compressor, heated air may be continuously be recirculated in the engine before the engine is started and rotating. Method  400  proceeds to  420 . 
     At  420 , method  400  judges if an engine start is requested or if a temperature of an after treatment device is greater than a threshold temperature. Method  400  may judge that there is an engine start request if a human driver requests an engine start or of there is a request to start the engine automatically. If method  400  judges that there is an indication that the engine may be started in the near future. Method  400  may judge that an engine start is requested or that a temperature of an after treatment device is greater than a threshold, then the answer is yes and method  400  proceeds to  422 . Otherwise, the answer is no and method  400  returns to  420 . 
     At  422 , method  400  optionally fully closes the central throttle. If the engine is a diesel engine, the central throttle may be held fully or partially open. If the engine is a petrol engine, the central throttle may be fully closed so that engine torque may be controlled. Method  400  proceeds to  424 . 
     At  424 , method  400  fully opens the upstream throttle. The upstream throttle is fully opened to allow fresh air to enter the engine. Method  400  proceeds to  426 . 
     At  426 , method  400  fully opens the exhaust throttle. The exhaust throttle is fully opened to allow exhaust to exit the engine. Method  400  proceeds to  428 . 
     At  428 , method  400  fully closed the low pressure EGR valve. The low pressure EGR valve is fully closed to reduce charge dilution during engine starting so that engine starting may be improved. Method  400  proceeds to  430 . 
     At  430 , method  400  starts the engine. The engine may be started via rotating the engine via a starter and supplying fuel to the engine. Method  400  proceeds to  432 . 
     At  432 , method  400  judges if a temperature of a catalyst is greater that a threshold temperature (e.g., a catalyst light off temperature). If so, method  400  proceeds to  434 . Otherwise, method  400  returns to  432 . In this way, the electrically heated catalyst may continue to heat the after treatment devices so that emissions reductions may be provided. 
     At  434 , method  400  deactivates the electrically heated catalyst to reduce power consumption. Method  400  proceeds to exit. 
     In this way, warm air may be circulated within an engine and the engine&#39;s exhaust system to warm after treatment devices sooner. By warming the after treatment devices sooner, engine emissions may be reduced sooner. 
     In some examples, method  400  may heat after treatment devices without compound heating of the air. For example, method  400  may activate the electrically heated catalyst, activate the compressor and flow air to the exhaust passage, open the high pressure EGR valve and/or engine poppet valves, close the low pressure EGR valve, open the exhaust throttle, open the central throttle, and open the upstream throttle. Thus, fresh air may flow from the engine intake to the electrically heated catalyst and from the electrically heated catalyst to other after treatment devices. 
     Thus, method  400  provides for an engine operating method, comprising: activating an electrically heated catalyst and opening an exhaust gas recirculation (EGR) valve in response to an indication that an engine start request is imminent. The engine method includes where the indication that the engine start request is imminent is provided via a vehicle door position sensor. The engine method includes where the indication that the engine start request is imminent is provided via a device that is remote from a vehicle, the device transmitting a signal. The engine method further comprises closing an exhaust throttle in response to the indication that the engine start request is imminent. The engine method includes where the EGR valve is fully opened and where the EGR valve is a low pressure EGR valve. The engine method further comprises activating an electrically driven compressor in response to the indication that the engine start request is imminent. The engine method further comprises closing the EGR valve in response to an engine start request. The engine method further comprises opening an exhaust throttle in response to the engine start request, the exhaust throttle positioned in an exhaust system downstream of an emissions control device. 
     Method  400  also provides for an engine operating method, comprising: activating an electrically heated catalyst, opening an exhaust gas recirculation (EGR) valve, and closing an upstream throttle in response to an indication that an engine start request is imminent. The engine method includes where the upstream throttle is fully closed. The engine method further comprises opening a central throttle in response to the indication that the engine start request is imminent. The engine method further comprises fully opening the upstream throttle and closing the EGR valve in response to a request to start the engine. The engine method further comprises closing an exhaust throttle in response to the indication that the engine start request is imminent. The engine method further comprises not activating an electrically heated catalyst, not opening an exhaust gas recirculation (EGR) valve, and not closing an upstream throttle in response to the indication that the engine start request is imminent and battery state of charge being less than a threshold. 
     Note that the example control and estimation routines included herein can be used with various engine and/or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and may be carried out by the control system including the controller in combination with the various sensors, actuators, and other engine hardware. Further, portions of the methods may be physical actions taken in the real world to change a state of a device. The specific routines described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various actions, operations, and/or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example examples described herein, but is provided for ease of illustration and description. One or more of the illustrated actions, operations and/or functions may be repeatedly performed depending on the particular strategy being used. Further, the described actions, operations and/or functions may graphically represent code to be programmed into non-transitory memory of the computer readable storage medium in the engine control system, where the described actions are carried out by executing the instructions in a system including the various engine hardware components in combination with the electronic controller. One or more of the method steps described herein may be omitted if desired. 
     It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific examples are not to be considered in a limiting sense, because numerous variations are possible. For example, the above technology can be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein. 
     The following claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.