Detection of leaks and blockages in a vehicle exhaust system

Methods and systems are provided for diagnosing a source of degradation in an exhaust system of a vehicle. In one example, a method may include actuating an electric turbocharger to rotate in a first direction to evaluate integrity of an exhaust pipe of the exhaust system and rotation the turbocharger in a second direction to assess an exhaust manifold of the exhaust system, after an engine of the vehicle is turned off. Pressures generated in the exhaust system are compared to thresholds based on barometric pressure and/or turbocharger speed.

FIELD

The present description relates generally to methods and systems for detecting leaks and/or blockages in a vehicle exhaust system.

Combustion of air-fuel mixtures at the cylinders of a vehicle engine generates torque to power a propulsion of the vehicle. The process of combustion produces exhaust gas that is evolved at the cylinders and channeled into an exhaust management system of the vehicle. The exhaust gas may be composed of a mixture of by-products including nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbons, and particulate matter. Release of such materials into the atmosphere is undesirable and current exhaust management systems are configured to remove these chemicals from the exhaust gas prior to emission.

Treatment of exhaust gas may include removal of NOx, CO, and hydrocarbons by one or more three-way catalytic converters (TWCs) and particulate matter by a gas particulate filter (GPFs), where both devices are positioned between an exhaust manifold of the engine and an outlet of an exhaust pipe of the vehicle. The TWC and GPF are effective systems for removal of combustion by-products but may become degraded over time. For example, components of the exhaust system that are frequently exposed to outdoor elements, such as the TWC housing and the exhaust pipe, and temperature changes, such as the exhaust manifold, may rust or crack, leading to leakage of untreated exhaust gas. In addition, accumulation of particulate matter in gas flow pathways of the exhaust system may occur, resulting in blockages that degrade engine performance due to back pressure in the exhaust system. Thus, methods to diagnose leaks and blockages in the exhaust system soon after the leaks and blockages are formed may allow the system to be repaired before degradation increases and adversely affects engine performance.

Attempts to address detection of degradation to the exhaust system include operating an electrical supercharger to diagnose vehicle components. One example approach is shown by Bauerle et al. in U.S. Pat. No. 6,688,104. Therein, an electrical supercharger is activated after a vehicle is stopped and diagnostic methods to assess an intake manifold and an exhaust system of the vehicle are conducted. For example, an exhaust gas recirculation (EGR) valve operation may be evaluated based on measured changes in pressure or correct functioning of an exhaust temperature sensor may be determined by comparing a temperature signal to a pre-set reduction in temperature resulting from a cooling effect of the active electrical supercharger.

However, the inventors herein have recognized potential issues with such systems. As one example, the method of U.S. Pat. No. 6,688,104 does not include monitoring the exhaust system for leaks or blockages. Degradation of specific exhaust components such as the EGR valve or exhaust temperature sensor may not be indicative of leak formation in the exhaust manifold. If the diagnosed parts are deemed to be in satisfactory condition in spite of the presence of a source of degradation, operation of the vehicle may proceed with the leak or blockage unnoticed until degradation of other exhaust system elements or decreased engine performance occurs.

In one example, the issues described above may be addressed by a method for, upon engine shutdown, operating an electric turbocharger to draw air into an exhaust system and indicating degradation of the exhaust system based on a comparison of a pressure in the exhaust system measured during operating the electric turbocharger to a threshold pressure that is based on a barometric pressure. In this way, leaks and blockages in an exhaust system may be detected using elements already present in a vehicle engine system.

As one example, a throttle and one or more cylinder valves may be closed to create a closed system upstream of a turbine of an electric turbocharger. The electric turbocharger may be actuated after the engine is turned off and spun in a direction opposite of a direction when the turbocharger is operated when the engine is on (e.g., a reverse direction). The reverse spinning of the turbine may pull air, in reverse through an exhaust passage and into the exhaust manifold. A comparison of the pressure in the exhaust manifold, while running the turbocharger in reverse, to a threshold pressure that is determined based on barometric pressure is conducted to determine if a leak is present. In another example, the electric turbocharger may be spun in a forward direction, opposite of the reverse direction, with the engine off and throttle and the intake and exhaust valves of the cylinders in open positions to allow airflow through the cylinders and into the exhaust system. An exhaust tuning valve in an exhaust pipe may be closed to restrict air flow out of the exhaust pipe, allowing pressure to accumulate when air is pumped into the exhaust pipe, from upstream to downstream of the turbine. Pressures in the exhaust pipe and exhaust manifold may be measured and compared to a set of thresholds calculated as functions of barometric pressure to determine if the exhaust system is degraded.

DETAILED DESCRIPTION

The following description relates to systems and methods for diagnosing leaks and blockages in an exhaust system of a vehicle. The vehicle may comprise an engine system with an engine coupled to an exhaust system and an electric turbocharger, as shown inFIG. 1. When the engine is turned off, the electric turbocharger may be activated to spin in a first, forward direction, to force air into an exhaust pipe from an intake passage of the engine system, as shown inFIG. 2A, arranged downstream of a turbocharger turbine. The electric turbocharger may also be spun in a second, reverse direction when the engine is off to pump air into an exhaust manifold of the engine, located upstream of the turbine, from an exhaust pipe of the vehicle. Spinning the electric turbocharger in the first or second direction while the engine is off may be included in example routines for determining if leaks or blockages are present in the exhaust system, as shown inFIG. 3. Upon diagnosis of degradation to the exhaust system, a leak or blockage in the exhaust pipe may be determined by a routine executable by an engine controller, as depicted inFIG. 4. Similarly, the engine controller may conduct a routine, as shown inFIG. 5, to detect a presence of a leak in the exhaust manifold.FIGS. 6 and 7shows example operations for the detection of a leak or blockage in the exhaust pipe and a leak in the exhaust manifold, respectively.

A vehicle may include an engine system comprising an engine coupled between an intake system and an exhaust system and an electric turbocharger including a compressor arranged in the intake system and a turbine arranged in the exhaust system. The engine includes an intake manifold coupled with a remainder of the intake system and an exhaust manifold coupled with a remainder of the exhaust system. Additionally, the exhaust system may include an exhaust pipe adapted to expel combusted gas from the engine system, downstream of the turbocharger turbine. An example of a vehicle with such components is shown inFIG. 1.FIG. 1depicts an example of a cylinder of internal combustion engine10included by engine system7of vehicle5. Engine10may be controlled at least partially by a control system including controller12and by input from a vehicle operator130via an input device132. In this example, input device132includes an accelerator pedal and a pedal position sensor134for generating a proportional pedal position signal PP. Cylinder14(which may be referred to herein as a combustion chamber) of engine10may include combustion chamber walls136with piston138positioned therein. Piston138may be coupled to crankshaft140so that reciprocating motion of the piston is translated into rotational motion of the crankshaft. Crankshaft140may be coupled to at least one drive wheel of the passenger vehicle via a transmission system. Further, a starter motor (not shown) may be coupled to crankshaft140via a flywheel to enable a starting operation of engine10.

Cylinder14can receive intake air via a series of intake air passages142,144, and146. Intake air passage146can communicate with other cylinders of engine10in addition to cylinder14.FIG. 1shows engine10configured with an electric turbocharger175including a compressor174arranged between intake passages142and144, and an exhaust turbine176arranged along the exhaust system between exhaust manifold148and exhaust pipe158. In some examples, compressor174may be adapted with a compressor recirculation passage202, as shown inFIGS. 2A-2B, which recirculates compressed air from downstream of compressor174and a charge air cooler160to upstream of compressor174. Flow through compressor recirculation passage202may be controlled by adjusting an opening of a continuously variable compressor recirculation valve (CCRV)204. CCRV204may be a continuously variable valve and increasing the opening of the CCRV204may include actuating (or energizing) a motor or solenoid to open the valve. In some embodiments, CCRV204may be partially open during boosted engine operation to provide a surge margin and the opening of the CCRV204may be increased in response to an indication of surge.

Compressor174may be at least partially powered by exhaust turbine176via a shaft180. In one example, shown inFIG. 1, electric motor177is also coupled to shaft180and may also rotate compressor174when it is supplied with electrical power via an energy recovery system, such as battery58. During events where a likelihood of turbo lag is increased, such as immediately after engine start-up or an increase in torque demand after a period of idling, exhaust turbine176may not spin fast enough due to an insufficient amount of exhaust gas to power the rotation of exhaust turbine176. Thus, controller12may command electric motor177to rotate compressor174to compress air entering engine10. A speed of compressor174may be regulated by electric motor177and/or wastegate181, arranged in an exhaust system of the engine system7.

In another example, electric motor177may be directly coupled to turbine176, as shown inFIGS. 2A-2B. Power is similarly supplied to electric motor177by battery58and an amount of power commanded by controller12. Rotation of turbine176by electric motor177may also result in rotation of compressor174due to mechanical coupling by shaft180. Thus, if turbine176rotates in a first direction, compressor174may spin in the first direction at a similar speed. If the turbine176spins in a second, opposite direction, the compressor174may spin in the second direction. Herein, the first direction may refer to a forward direction and the second direction may refer to a reverse direction. The first direction may include the compressor174flowing boosted air from the compressor, to the engine10, thereby increasing a manifold absolute pressure (MAP). The second direction may include pumping air from the exhaust pipe158to the exhaust manifold148, such that pressure in the exhaust manifold148increases if flow through cylinder14is blocked. The direction and speed of rotation may be initiated by the electric motor177and turbo lag may be mitigated by electrically powering turbine176until exhaust pressure has accumulated sufficiently to spin turbine176at a desired speed.

Wastegate181may be opened via controller12to allow exhaust gases to bypass turbine176via bypass passage179. Controller may increase compressor speed by increasing an electric current supplied to electric motor177and/or closing wastegate181. Conversely, compressor speed may be decreased by reducing the electric current and/or opening wastegate181. When exhaust gas pressure increases enough to spin turbine176at a speed that meets the boost demand, electric motor177may be deactivated and compressor174driven exclusively by mechanical coupling with turbine176via shaft180.

A charge air cooler (CAC)160may be positioned in intake passage142downstream of compressor174and upstream of a throttle162. The CAC160may be an air-to-air CAC or a liquid-cooled CAC, configured to cool and increase a density of air compressed by the compressor174. The cooled air may be delivered to the engine10and combusted at cylinder14.

Throttle162, including a throttle plate164, may be provided along an intake passage of the engine for varying the flow rate and/or pressure of intake air provided to the engine cylinders. For example, throttle162may be positioned downstream of compressor174as shown inFIG. 1, or alternatively may be provided upstream of compressor174.

Each cylinder of engine10may include one or more intake valves and one or more exhaust valves. For example, cylinder14is shown including at least one intake poppet valve150and at least one exhaust poppet valve156located at an upper region of cylinder14. In some examples, each cylinder of engine10, including cylinder14, may include at least two intake poppet valves and at least two exhaust poppet valves located at an upper region of the cylinder.

Intake valve150may be controlled by controller12via actuator152. Similarly, exhaust valve156may be controlled by controller12via actuator154. During some conditions, controller12may vary the signals provided to actuators152and154to control the opening and closing of the respective intake and exhaust valves. The position of intake valve150and exhaust valve156may be determined by respective valve position sensors (not shown). The valve actuators may be of the electric valve actuation type or cam actuation type, or a combination thereof. The intake and exhaust valve timing may be controlled concurrently or any of a possibility of variable intake cam timing, variable exhaust cam timing, dual independent variable cam timing or fixed cam timing may be used. Each cam actuation system may include one or more cams and may utilize one or more of cam profile switching (CPS), variable cam timing (VCT), variable valve timing (VVT) and/or variable valve lift (VVL) systems that may be operated by controller12to vary valve operation. For example, cylinder14may alternatively include an intake valve controlled via electric valve actuation and an exhaust valve controlled via cam actuation including CPS and/or VCT. In other examples, the intake and exhaust valves may be controlled by a common valve actuator or actuation system, or a variable valve timing actuator or actuation system.

In some examples, each cylinder of engine10may be configured with one or more fuel injectors for providing fuel thereto. As a non-limiting example, cylinder14is shown including two fuel injectors166and170. Fuel injectors166and170may be configured to deliver fuel received from fuel system8. Fuel system8may include one or more fuel tanks, fuel pumps, and fuel rails. Fuel injector166is shown coupled directly to cylinder14for injecting fuel directly therein in proportion to the pulse width of signal FPW-1received from controller12via electronic driver168. In this manner, fuel injector166provides what is known as direct injection (hereafter referred to as “DI”) of fuel into combustion cylinder14. WhileFIG. 1shows injector166positioned to one side of cylinder14, it may alternatively be located overhead of the piston, such as near the position of spark plug192. Such a position may improve mixing and combustion when operating the engine with an alcohol-based fuel due to the lower volatility of some alcohol-based fuels. Alternatively, the injector may be located overhead and near the intake valve to improve mixing. Fuel may be delivered to fuel injector166from a fuel tank of fuel system8via a high pressure fuel pump, and a fuel rail. Further, the fuel tank may have a pressure transducer providing a signal to controller12.

Fuel injector170is shown arranged in intake passage146, rather than in cylinder14, in a configuration that provides what is known as port fuel injection (hereafter referred to as “PFI”) into the intake port upstream of cylinder14. Fuel injector170may inject fuel, received from fuel system8, in proportion to the pulse width of signal FPW-2received from controller12via electronic driver171. Note that a single driver168or171may be used for both fuel injection systems, or multiple drivers, for example driver168for fuel injector166and driver171for fuel injector170, may be used, as depicted.

In an alternate example, each of fuel injectors166and170may be configured as direct fuel injectors for injecting fuel directly into cylinder14. In still another example, each of fuel injectors166and170may be configured as port fuel injectors for injecting fuel upstream of intake valve150. In yet other examples, cylinder14may include only a single fuel injector that is configured to receive different fuels from the fuel systems in varying relative amounts as a fuel mixture, and is further configured to inject this fuel mixture either directly into the cylinder as a direct fuel injector or upstream of the intake valves as a port fuel injector.

Fuel may be delivered by both injectors to the cylinder during a single cycle of the cylinder. For example, each injector may deliver a portion of a total fuel injection that is combusted in cylinder14. Further, the distribution and/or relative amount of fuel delivered from each injector may vary with operating conditions, such as engine load, knock, and exhaust temperature, such as described herein below. The port injected fuel may be delivered during an open intake valve event, closed intake valve event (e.g., substantially before the intake stroke), as well as during both open and closed intake valve operation. Similarly, directly injected fuel may be delivered during an intake stroke, as well as partly during a previous exhaust stroke, during the intake stroke, and partly during the compression stroke, for example. As such, even for a single combustion event, injected fuel may be injected at different timings from the port and direct injector. Furthermore, for a single combustion event, multiple injections of the delivered fuel may be performed per cycle. The multiple injections may be performed during the compression stroke, intake stroke, or any appropriate combination thereof.

Herein, operation of intake valve150may be described in greater detail. For example, the intake valve150may be moved from a fully open position to a fully closed position, or to any position therebetween. For all conditions being equal (e.g., throttle position, vehicle speed, pressure, etc.), the fully open position allows more air from the intake passage146to enter the cylinder14than any other position of the intake valve150. Conversely, the fully closed position may prevent and/or allow the least amount of air from the intake passage146to enter the cylinder14than any other position of the intake valve150. Thus, the positions between the fully open and fully closed position may allow varying amounts of air to flow between the intake passage146to the cylinder14. In one example, moving the intake valve150to a more open position allows more air to flow from the intake passage146to the cylinder14that its initial position.

Fuel injectors166and170may have different characteristics. These include differences in size, for example, one injector may have a larger injection hole than the other. Other differences include, but are not limited to, different spray angles, different operating temperatures, different targeting, different injection timing, different spray characteristics, different locations etc. Moreover, depending on the distribution ratio of injected fuel among injectors170and166, different effects may be achieved.

Fuel tanks in fuel system8may hold fuels of different fuel types, such as fuels with different fuel qualities and different fuel compositions. The differences may include different alcohol content, different water content, different octane, different heats of vaporization, different fuel blends, and/or combinations thereof etc. One example of fuels with different heats of vaporization could include gasoline as a first fuel type with a lower heat of vaporization and ethanol as a second fuel type with a greater heat of vaporization. In another example, the engine may use gasoline as a first fuel type and an alcohol containing fuel blend such as E85 (which is approximately 85% ethanol and 15% gasoline) or M85 (which is approximately 85% methanol and 15% gasoline) as a second fuel type. Other feasible substances include water, methanol, a mixture of alcohol and water, a mixture of water and methanol, a mixture of alcohols, etc.

As the mixture of intake air and fuel is combusted at cylinder14, exhaust valve156may be commanded to open and flow exhaust gas from cylinder14to exhaust manifold148. The opening of the exhaust valve156may be timed to open before intake valve150is fully closed so that there is a period of overlap when both valves are at least partially open. The overlap may generate a weak vacuum that accelerates the air-fuel mixture into the cylinder, e.g., exhaust scavenging. The period of valve overlap may be timed in response to engine speed, camshaft valve timing, and configuration of the exhaust system. Exhaust manifold148can receive exhaust gases from other cylinders of engine10in addition to cylinder14. The exhaust gas channeled from cylinder14to exhaust manifold148may flow to turbine176or bypass turbine176via bypass passage179and wastegate181.

Exhaust gas that is directed to turbine176may drive the rotation of turbine176when wastegate181is closed, thereby spinning compressor174when compressor174is not spun by electric motor177. Alternatively, when wastegate181is at least partially open, e.g., adjusted to a position between fully closed and fully open, or fully open, a portion of the exhaust gas may be diverted around turbine176through bypass passage179. Shunting exhaust flow through bypass passage179may decrease the rotation of turbine176, thereby reducing the amount of boost provided to intake air in intake passage142by compressor174. Thus during events where a rapid decrease in boost is desired, e.g., an tip-out at input device132, turbine176may be decelerated by opening wastegate181and reducing the amount of exhaust gas directed to turbine176.

Wastegate181is disposed in bypass passage179which couples exhaust manifold148, downstream exhaust gas sensor128, to an exhaust pipe158, between turbine176and emission control device178. Spent exhaust gas from turbine176and exhaust gas routed through bypass passage181may convene in exhaust pipe158upstream of emission control device178before catalytic treatment at emission control device178.

Exhaust gas sensor128is shown coupled to exhaust manifold148upstream of turbine176and a junction between bypass passage179and exhaust manifold148. Sensor128may be selected from among various suitable sensors for providing an indication of exhaust gas air/fuel ratio such as a linear oxygen sensor or UEGO (universal or wide-range exhaust gas oxygen), a two-state oxygen sensor or EGO (as depicted), a HEGO (heated EGO), a NOx, HC, or CO sensor, for example, before treatment at emission control device178. Emission control device178may be a three way catalyst (TWC), NOx trap, various other emission control devices, or combinations thereof, configured to remove undesirable chemicals from the exhaust gas prior to atmospheric release.

Emission control device (ECD)178may also include a gasoline particulate filter (GPF) for removing particulate matter such as soot from the exhaust gas. In one example, as shown inFIG. 1, the GPF may be integrated into ECD178so that the GPF is arranged downstream of the TWC, enclosed within an outer housing of ECD178, and functioning as a final treatment stage in ECD178. In other examples, the GPF may be integrated into ECD178upstream of the TWC, or configured as a separate component upstream or downstream of ECD178.

Exhaust pipe158may also include an exhaust tuning valve (ETV)185, arranged downstream of ECD178. The ETV185may restrict flow out of the exhaust pipe158when an opening of the ETV185is decreased, thereby increasing back pressure in the exhaust pipe158. During engine operation, the ETV185may be fully opened to allow maximum flow through the exhaust pipe158. When in a fully closed position, the ETV815may not block flow through the exhaust pipe158but instead reduce flow sufficiently to allow pressure to accumulate in the exhaust system. The ETV may be closed during low flow engine operations to provide noise attenuation in areas near residents and pedestrians, and be opened at higher flows for increased power and fuel economy from less pressure restriction. Optionally, the ETV may be maintained open for improved performance at a track, or alternatively maintained closed under most vehicle operations for maximum noise attenuation.

The valves described above and other actuatable components of vehicle5may be controlled by controller12. Controller12is shown inFIG. 1as a microcomputer, including microprocessor unit106, input/output ports108, an electronic storage medium for executable programs and calibration values shown as non-transitory read only memory chip110in this particular example for storing executable instructions, random access memory112, keep alive memory114, and a data bus. Controller12may receive various signals from sensors16, as shown inFIGS. 2A-2B, coupled to engine10, in addition to those signals previously discussed, including measurement of inducted mass air flow (MAF) from mass air flow sensor122; engine coolant temperature (ECT) from temperature sensor116coupled to cooling sleeve118; a profile ignition pickup signal (PIP) from Hall effect sensor120(or other type) coupled to crankshaft140; throttle position (TP) from a throttle position sensor; and absolute manifold pressure signal (MAP) from sensor124. Engine speed signal, RPM, may be generated by controller12from signal PIP. Manifold pressure signal MAP from a manifold pressure sensor may be used to provide an indication of vacuum, or pressure, in the intake manifold. Exhaust manifold pressure may be measured by a pressure sensor182and pressure in the exhaust pipe158measured by another pressure sensor184. Controller12may infer an engine temperature based on an engine coolant temperature.

As described above,FIG. 1shows only one cylinder of a multi-cylinder engine. As such, each cylinder may similarly include its own set of intake/exhaust valves, fuel injector(s), spark plug, etc. It will be appreciated that engine10may include any suitable number of cylinders, including 2, 3, 4, 5, 6, 8, 10, 12, or more cylinders. Further, each of these cylinders can include some or all of the various components described and depicted byFIG. 1with reference to cylinder14.

In some examples, vehicle5may be a hybrid vehicle with multiple sources of torque available to one or more vehicle wheels55. In other examples, vehicle5is a conventional vehicle with only an engine. In the example shown, vehicle5includes engine10and an electric machine52. Electric machine52may be a motor or a motor/generator. Crankshaft140of engine10and electric machine52are connected via a transmission54to vehicle wheels55when one or more clutches56are engaged. In the depicted example, a first clutch56is provided between crankshaft140and electric machine52, and a second clutch56is provided between electric machine52and transmission54. Controller12may send a signal to an actuator of each clutch56to engage or disengage the clutch, so as to connect or disconnect crankshaft140from electric machine52and the components connected thereto, and/or connect or disconnect electric machine52from transmission54and the components connected thereto. Transmission54may be a gearbox, a planetary gear system, or another type of transmission. The powertrain may be configured in various manners including as a parallel, a series, or a series-parallel hybrid vehicle.

Electric machine52receives electrical power from an energy storage device58(herein, battery58) to provide torque to vehicle wheels55. Electric machine52may also be operated as a generator to provide electrical power to charge battery58, for example during a braking operation. In some examples, the electric machine52may be coupled to the turbine176, as will be described in greater detail below.

The controller12receives signals from the various sensors ofFIG. 1and employs the various actuators ofFIG. 1, depicted inFIGS. 2A-2Bby sensors16and actuators81(as described further below), to adjust engine operation based on the received signals and instructions stored on a memory of the controller. For example, adjusting a rotational speed and direction of the turbine176may include adjusting a signal provided to an actuator, such as actuator208ofFIGS. 2A-2B, of the turbine176sent by the controller12. In some examples, the rotational speed of the turbine176is adjusted in response to one or more of a cold-start and pressures of the intake and exhaust passages. Thus, the turbine176, and therefore the compressor174, may be rotated in forward and reverse directions, wherein the forward direction results in boost flowing to the engine10and where the reverse direction results in increased exhaust backpressure and manifold pressure decreasing.

Elements included in an exhaust system of a vehicle may affect a fuel efficiency and power output of an engine. Furthermore, the exhaust system may remove undesirable constituents of exhaust gas, such as CO, NOx, hydrocarbons, and particulate matter by channeling the exhaust gas through an after treatment device before releasing the gas to the atmosphere. Formation of blockages in an exhaust pipe (e.g., passage) of the exhaust system may result in increased exhaust backpressure, decreasing engine performance. Prolonged and excessive accumulation of debris clogging passageways of the exhaust system may lead to engine backfire. In addition, undetected leakages in the exhaust system may release undesirable chemicals to the atmosphere and also degrade combustion efficiency. For example, in vehicles with exhaust gas recirculation (EGR), fuel injection and spark timing may be calculated based on an expected amount of exhaust gas recirculated to an intake manifold of the engine. A leak in the exhaust system may decrease a flow of EGR, causing the air-to-fuel ratio at combustion chambers of the engine to deviate from stoichiometry. Thus, a method to regularly and efficiently diagnose the exhaust system for leaks and blockages may address the issues described above.

A system for diagnosing leaks and blockages in an exhaust system of an engine system200is illustrated inFIGS. 2A and 2B. Specifically,FIG. 2Aillustrates a first embodiment230for operating the engine system200to detect a leak or blockage in an exhaust pipe of the engine system200, downstream of the turbine, andFIG. 2Billustrates a second embodiment250for operating the engine system200to detect a leak in an exhaust manifold of the exhaust system200. Components in common with those ofFIG. 1are similarly numbered and will not be re-introduced. The turbocharger175is illustrated as an electric turbocharger wherein the turbine176is directly coupled to an electric motor206configured to power (e.g., drive rotation of) the turbine176when receiving power from battery58. It will be appreciated that the electric motor206may be used similarly to electric motor177ofFIG. 1without departing from the scope of the present disclosure. Power supply from battery58to the electric motor206may be adjusted via a power actuator208. The controller12may signal to the power actuator208when and how much power to direct from the battery58to the electric motor206. By sending power to the electric motor206, the turbine176may spin and/or rotate in a particular direction. Specifically, the power actuator208may be adapted to actuate the motor206to spin in each of a forward and a reverse direction, thereby rotating the turbine176in the forward and reverse direction, based on control signals received from the controller12.

As described above forFIG. 1, rotation of the turbine176may result in similar rotation of the compressor174due to the shaft180mechanically coupled therebetween. The turbine176may spin in the first, or forward direction, directing gas flow through the engine cylinders, through the turbine16, and to the exhaust pipe158and causing the pressure in the exhaust pipe158to increase when the ETV185is closed. In contrast, rotation of the turbine176in the second, reverse direction draws air into the exhaust system through the exhaust pipe158and to the exhaust manifold148, thereby increasing the pressure in the exhaust manifold148when there is no valve overlap between the cylinder intake and exhaust valves (such that air does not flow from the exhaust manifold to the intake manifold via the cylinders). Flow is channeled entirely through the turbine176when wastegate181is closed, whereas when wastegate181is at least partially open, a portion of the flow may be diverted from the turbine176and through the bypass179.

Turning now toFIG. 2A, the first embodiment230for operating the electric turbocharger175to detect degradation in the exhaust pipe158, downstream of the turbine176, by spinning the turbine176in the first direction (e.g., forward direction) is shown. The engine may be turned off and a period of time allowed to elapse for engine components, such as a crankshaft, to stop spinning. The controller12may adjust the rotation of the crankshaft so that the final crankshaft position results in the intake valves and exhaust valves of a plurality of cylinders210, which may each be cylinder14ofFIG. 1, overlapping so that intake passage146is fluidly coupled to exhaust manifold148via the plurality of cylinders210. In other words, both the intake valves and exhaust valves may be partially open so that air may flow from the intake passage146, to the exhaust manifold148, via the plurality of cylinders210. The throttle162may be adjusted to an at least partially open position and the ETV185closed to restrict flow out of the exhaust pipe158. The barometric pressure may be measured by the pressure sensor182in the exhaust manifold148when the engine is stationary and the valves of the plurality of cylinders210adjusted to be open to gas flow. The controller12may also command the wastegate181in the bypass passage179to close.

The turbine176is rotated in the first direction by the electric motor206, pulling air into the intake passages142,144,146, through the throttle162and cylinders30, and to the exhaust manifold148, as indicated by arrows212. A speed of a turbine176may be accelerated and maintained at a pre-set speed. Air passing through the cylinders210flows into the exhaust system, building pressure in the exhaust system due to the flow restriction imposed by the closing of the ETV185. The spinning of the turbine176may stabilize after a brief period of time, such as two seconds. After the spinning has stabilized, the pressure in the exhaust pipe158may be measured by the pressure sensor184, arranged immediately upstream of the ECD178. In other embodiments, pressure sensor184may be positioned inside or integrated into the ECD178. As one example, the pressure sensor184may be a pressure sensor of a particulate filter included as or as part of the ECD178. Specifically, in one example, the pressure sensor184may be a gasoline particulate filter (GPF) gage pressure sensor adapted to measure a pressure of air in the exhaust pipe.

The measured pressure in the exhaust pipe158, as determined by the output of the pressure sensor184, may be compared to a first threshold pressure, which may be a function of the measured barometric pressure, to evaluate whether a leak or a blockage in the exhaust pipe158is present. For example, the first threshold may be an expected final pressure in the exhaust pipe based on a calculated rise in pressure upon actuation of the turbine in the first direction when the ETC185is closed. The increase in pressure relative to the barometric pressure as a starting value may be determined. Thus, a measured pressure in the exhaust pipe158that is higher than the first threshold may indicate that a blockage is present in the exhaust pipe158and impeding air flow more than expected by the closed ETV158. A measured pressure in the exhaust pipe that is lower than a second threshold may indicate a leak is present in the exhaust pipe158and releasing pressure from the exhaust pipe158. The second threshold may also be a function of the measured barometric pressure and may be a lower boundary of an expected pressure range of the exhaust pipe158for a blockage-free and leak-free system while the turbine is spinning in the first direction. If, however, the pressure in the exhaust pipe158matches the second threshold or is between the first and second thresholds, the exhaust pipe158may be deemed intact. If diagnosis of the exhaust system is initiated due to an indication that the exhaust system is degraded, the exhaust manifold may additionally be evaluated for a leak. Alternatively, if the controller is configured to diagnose the exhaust system as a routine check, the exhaust manifold may also be assessed.

The second embodiment250for operating the electric turbocharger175, shown inFIG. 2B, may be used to detect a leak in the exhaust manifold148, upstream of the turbine176, by spinning the turbine176in the second direction (e.g., reverse direction). The engine may be turned off and allowed to come to a standstill. The controller12may adjust the crankshaft so that the intake valves and exhaust valves of the plurality of cylinders210, which may each be cylinder14ofFIG. 1, do not overlap. In other words, one of or both the intake valve or the exhaust valve is closed so that flow through the plurality of cylinders210, between the intake and exhaust manifolds, is blocked. The throttle162may be adjusted to a fully closed position and the ETV185adjusted to an open position. The barometric pressure may be measured by the pressure sensor182in the exhaust manifold148when the engine is stationary and the intake and exhaust valves are closed to gas flow. The controller12may also command the wastegate181in the bypass passage179to close or maintain the wastegate181closed.

The turbine176is rotated by the electric motor206in the second direction at a fixed, pre-set speed, pumping air from the opening of the exhaust pipe158, through the ECD178and turbine176, into the exhaust manifold148. Air flow through the exhaust system is indicated by arrows214, travelling in an opposite direction with respect to exhaust gas flow during engine operation and terminating at the plurality of cylinders210. The exhaust manifold pressure increases and the pressure is measured again by pressure sensor182after a period of time during which the spinning of the turbine176stabilizes. For example, the pressure may be measured a threshold duration after turbine rotation is initiated (e.g., two seconds, in one example). The measured pressure may be compared to a third threshold pressure to determine if a leak is present in the exhaust manifold148.

Similar to the first threshold, the third threshold may be calculated as an expected pressure in the exhaust manifold148as function of the barometric pressure and turbine speed. A measured exhaust manifold pressure that is lower than the third threshold may indicate a leak in the exhaust manifold148. If the measured pressure in the exhaust manifold148is equal to the third threshold, the exhaust manifold148may be deemed leak-free. It may be noted that development of a blockage in the exhaust manifold148is unlikely due to higher flow rates through the exhaust manifold148versus the exhaust pipe158during engine operation, thus diagnosis of the exhaust manifold148for blockages is not described. However, in other examples, rotating the turbine176in the second direction may be similarly used to detect blockages in the exhaust manifold148.

In one embodiment, the operations described above forFIGS. 2A-2Bmay be used every time the engine is turned off as a relatively fast and convenient method to diagnose the exhaust system for leaks and blockages without adding parts or controls to the engine system, during engine operation. Once engine key-off occurs, the method may be initiated after a period of time elapses to allow engine components, such as the crankshaft, to become stationary and/or pressures in the exhaust system to stabilize. Furthermore, the methods for detecting leaks upstream of the turbine176and leaks and blockages downstream of the turbine176may be employed independently, if a region of the exhaust system, e.g., the exhaust manifold148or the exhaust pipe158, has been identified as intact. The methods may also be used cooperatively as a set of regular diagnostic operations or if degradation is suspected and location of the leak or blockage is desired.

For example, after the engine is turned off and the crankshaft is stationary, the turbine176may be rotated in the first direction to determine if a leak or blockage is present in the exhaust pipe158. The turbine176may then be rotated in the second direction to evaluate if a leak is present in the exhaust manifold148. In one example, the exhaust pipe may be diagnosed first to confirm the present of a leak or blockage. The exhaust manifold may then be tested regardless of the results of the exhaust pipe test for leaks because the results of the exhaust pipe test may not rule out a leakage in the exhaust manifold. For example, if degradation in the exhaust system is detected and the exhaust pipe diagnosis confirms that the issue is not in the exhaust pipe, the exhaust manifold may be tested. However, if a leak is detected in the exhaust manifold, it is desirable to also test the exhaust manifold for a leak as both regions may have concurrent leaks.

In addition, if a blockage is detected in the exhaust pipe, it may not be useful to subsequently test for a leak in the exhaust manifold. Restricted flow through the exhaust pipe due to the blockage may decrease air flow into the exhaust manifold while the turbine is spinning in the second direction. Thus, pressure in the exhaust manifold may not increase as calculated and lead to a false positive, e.g., identification of a leak, upon diagnosis.

FIG. 3shows a method300for diagnosing an engine system, including an engine coupled to an exhaust system, for leaks and blockages in the exhaust system. Method300may include determining whether there is a leak or blockage in an exhaust pipe of the exhaust system, the exhaust pipe arranged downstream of a turbine of an electric turbocharger, as depicted in routine400ofFIG. 4and/or determining whether there is a leak in an exhaust manifold of the exhaust system, the exhaust manifold arranged upstream of the turbine, as depicted in method500ofFIG. 5. Methods300,400, and500may be initiated by the operator, for example, by turning on a switch or button to prompt a controller, such as controller12ofFIGS. 1-2B, to initiate the routine. Alternatively, methods300,400, and500may be performed routinely and automatically, via the controller, every time the engine is turned off. The exhaust system may comprise an exhaust manifold, electric turbocharger turbine, and an exhaust pipe (such as the exhaust manifold148, electric turbocharger175, and exhaust pipe158ofFIGS. 1-2B). The turbine of the electric turbocharger may be actuated by an electric motor, such as the turbine176ofFIGS. 1-2B, and configured to spin in a first, forward direction, and a second, reverse direction (e.g., two different directions). An emissions control device (ECD) and an exhaust tuning valve (ETV) arranged downstream of the ECD, e.g., the ECD178and ETV185ofFIGS. 2A-2B, may be positioned in line with the path of gas flow in the exhaust pipe. The ECD may be configured with an integrated gas particulate filter (GPF) in addition to a three-way catalyst. The ETV may be configured to remain fully open position during engine operation unless instructed to close. When closed, the ETV may be adapted to restrict gas flow through the tailpipe but not block flow. Instructions for carrying out methods300,400,500and the rest of the methods included herein may be executed by the controller, based on instructions stored on a memory of the controller and in conjunction with signals received from sensors of the engine system, such as the sensors described above with reference toFIG. 1. The controller may employ engine actuators of the engine system to adjust engine operation, according to the methods described below.

At302, the method includes estimating and/or measuring the operating conditions of the engine. These may include, for example, engine speed, engine torque, boost pressure, a manifold absolute pressure, barometric pressure, an exhaust manifold pressure measured by a pressure sensor such as pressure sensor182ofFIGS. 1-2B, and oxygen content of exhaust gas detected by an exhaust gas sensor, such as exhaust gas sensor128ofFIG. 1, etc. Other estimated or measured operating conditions may include positions of intake and exhaust valves at combustion chambers as determined by position sensors, a position of an exhaust wastegate, such as the wastegate181ofFIGS. 2A-2B, and a position of the ETV.

The method may include determining at304whether the torque supplied by the engine meets a torque demand. The torque demand may be a driver-initiated torque demand indicated by a signal from an input device, such as the accelerator pedal132ofFIG. 1. A shortfall in torque supply relative to the demand may indicate that more boost and thus higher boost pressure at the engine intake is desired. However, the comparison of torque supply to torque demand may also provide detection of a potential issue in engine performance due to degradation of a component in the engine system. For example, a leak in the exhaust system may result in the air-to-fuel ratio at the combustion chambers to deviate from stoichiometry. A blockage in the exhaust system may generate backpressure in the exhaust system and reduce a power output of the engine. If the torque supply is not less than the torque demand, e.g., the supply meets the demand, the method proceeds to306to continue vehicle operation with the current engine conditions. If a torque shortfall is detected, the method continues to307to determine if the shortfall may be met by increasing engine boost. Boost may be increased by closing (or decreasing an opening of) an exhaust wastegate, thereby directing exhaust gas from exhaust valves of all engine cylinders to the turbine. The increased flow of gas to the turbine increases a rotational speed of the turbine, resulting in an increase in compressor speed and boost pressure. If the operations described above to increase boost pressure provides sufficient torque to meet the torque demand, the method proceeds to306to continue vehicle operation with the current engine conditions (e.g., with the increased boost pressure supplied by the faster speed of the turbocharger). If increasing turbine flow does not compensate for the torque shortfall, the method continues to308to confirm if the engine is turned off.

If the engine is on, the method may activate an indicator at310, such as an indicator light or signal on a dashboard of the vehicle, to notify an operator that the diagnosis for a leak in the exhaust manifold will be performed when the engine is deactivated. Alternatively, the method at310may include setting a diagnostic code in the controller so that once the engine is turned off, the controller may automatically initiate the leak detection routine described herein. Once engine key-off occurs, the method may proceed to312. If the engine is already off, the method continues directly to312from308to evaluate a presence or absence of a source of degradation in the exhaust pipe of the exhaust system. The method400ofFIG. 4may be conducted to assess whether a leak or blockage is detected in the exhaust pipe.

Continuing toFIG. 4, at402, the method400includes adjusting the intake and exhaust valves of each cylinder to overlap so that air may flow through the combustion chambers. Adjusting the positions of the valves may include the controller commanding an actuator of a crankshaft, which may drive rotation of a camshaft coupled to the intake and exhaust valves, to rotate until the intake valves and the exhaust valves are in an at least partially open position, e.g., a position between fully open and fully closed, or until the intake valves and exhaust valves are both fully open. In this way, air may pass between the intake manifold and exhaust manifold of the engine, via the open cylinder intake and exhaust valves. A throttle, such as throttle162ofFIGS. 1-2B, in an intake passage upstream of the intake manifold is commanded to open at404to fluidly couple the intake passage to the intake manifold. The controller commands the ETV to close at406to restrict flow out of the exhaust pipe and a barometric pressure is measured at408by the pressure sensor in the exhaust manifold and the measured pressure is stored in the memory of the controller. At410, the controller commands the wastegate to close to block flow through a turbine bypass passage arranged around the turbine. An electric motor, powered by a battery, such as battery58ofFIGS. 1-2B, actuates the rotation of the turbine in a first direction (e.g., forward direction) at412.

Spinning the turbine in the forward direction drives air from the engine intake, through the combustion chambers, into the exhaust manifold, and to the exhaust pipe, as shown inFIG. 2A. Pressure may rise in the exhaust pipe due to the flow restriction imposed by the ETV. The turbine may be spun at a pre-set speed that has been determined to increase pressure by a calculated amount in the exhaust pipe. For example, the turbine speed may be adapted to increase pressure by 25% or by 50% in the exhaust pipe. The pressure may be measured by a pressure sensor, such as pressure sensor184ofFIGS. 1-2B, arranged upstream of the ECD in the exhaust pipe or integrated into the ECD, for example. In another example, the pressure in the exhaust pipe may be measured by a GPF pressure gauge. At414of the method, the exhaust pipe pressure is compared to a first threshold and a second threshold, or a threshold range of pressure for the expected exhaust pipe pressure. Comparing the exhaust pipe pressure to the first threshold and/or second threshold at414may include first spinning the turbine for a period of time, e.g., 2 seconds, after the rotational speed of the turbine reaches a pre-set speed to allow the speed of the turbine to stabilize. After the period of time for stabilization passes, the pressure in the exhaust manifold may be measured by a pressure sensor, such as pressure sensor184ofFIGS. 1-2B, arranged upstream of the ECD in the exhaust pipe or integrated into the ECD.

The method at414may further include, first determining the first threshold based on the barometric pressure measured at408. The first threshold may be a function of the measured barometric pressure and based on the amount of expected pressure increase due to turbine rotation at the pre-set speed. In one example, the controller may refer to look-up tables, which may be based on mapped data of exhaust pipe pressure according to barometric pressure, stored in the memory of the controller where the measured barometric pressure is the input and the first threshold (or expected pressure after running the turbine forward at the pre-set speed for the threshold duration or period of time) is the output. As another example, the controller may be configured to calculate a theoretical, final pressure in the exhaust pipe, which may be used as the first threshold, as a function of barometric pressure, turbine speed, and/or temperature. A measured pressure in the exhaust pipe that is higher than the first threshold may indicate that a blockage is present in the exhaust pipe while a pressure that is lower than the first threshold may indicate that either the exhaust pipe is blockage-free or that exhaust gas may be escaping from the exhaust system via a leak in the exhaust pipe. The method may return to method300ofFIG. 3to determine, at314, if the pressure in the exhaust manifold is higher than the first threshold.

If the pressure in the exhaust pipe is higher than the first threshold, the method proceeds to316to set a diagnostic trouble code (DTC) to notify an operator that a blockage in the exhaust pipe is present. The method at316may further include indicating to the operator, via a signal sent to an indicator light, alarm, or other type of notifying device, that a blockage in the exhaust pipe is present. The DTC may also be set in the controller memory and be readable by a technician. If the pressure in the exhaust pipe is not higher than the first threshold, the method continues to318to determine if the pressure in the exhaust pipe is lower than a second threshold.

The second threshold may be a function of the measured barometric pressure and based on a range of pressures expected in the exhaust pipe when the exhaust pipe is blockage- and leak-free. The second threshold may be equivalent to a lower boundary of the range of pressures and thus may be set at a lower pressure than the first threshold. In some examples, the second threshold may be similar to or within a threshold range of the first threshold. In one example, the controller may refer to look-up tables, which may be based on mapped data of exhaust pipe pressure according to barometric pressure, stored in the memory of the controller where the measured barometric pressure is the input and the first threshold (or expected pressure range after running the turbine forward at the pre-set speed for the threshold duration or period of time) is the output. As another example, the controller may be configured to calculate a theoretical pressure range in the exhaust pipe, which may be used to determine the second threshold, as a function of barometric pressure, turbine speed, and/or temperature. A measured pressure in the exhaust pipe that is lower than the first threshold may indicate that a blockage is present in the exhaust pipe while a pressure equal to or higher than the second threshold may indicate that exhaust pipe is leak-free.

If the exhaust pipe pressure is lower than the second threshold, the method continues to320to set a DTC notification that a leak is present in the exhaust pipe. The method at320may further include indicating to the operator, via a signal sent to an indicator light, alarm, or other type of notifying device, that a leak in the exhaust pipe is present. The DTC may also be set in the controller memory and be readable by a technician. The method proceeds to322to diagnose the exhaust manifold for a leak.

The method also proceeds to322if the exhaust pipe pressure is not lower than the second threshold. Thus, the exhaust pipe pressure is between the first and second thresholds and may be leak- and blockage-free. As such, the exhaust manifold may be a source of degradation resulting in the torque shortfall. To check for a leak in the exhaust manifold, the method continues to method500ofFIG. 5.

Looking atFIG. 5, at502, the method includes adjusting the intake and exhaust valves of the engine cylinders to block flow through the combustion chambers. Adjusting the positions of the valves may include the controller commanding the actuator of the crankshaft, which may control rotation of the camshaft coupled to the intake and exhaust valves, to rotate until either the intake valves or the exhaust valves are in a fully closed position, or so that both the intake and exhaust valves and closed so that no airflow passes between the intake manifold and exhaust manifold. As one example, if the crankshaft is already stationary prior to starting method500, the crankshaft may be rotated via rotational input from a motor/generator coupled with the crankshaft (e.g., electric machine52shown inFIG. 1) and then stopped to achieve the lack of opening overlap between the intake and exhaust valves. The throttle is commanded to close at504to block flow between the intake passage and the intake manifold. The barometric pressure is measured at506by the pressure sensor in the exhaust manifold and stored in the memory of the controller. The controller commands the ETV to open and the wastegate to remain closed at508to continue blocking flow through a turbine bypass passage. The electric motor may stop the rotation of the turbine, if the turbine is still spinning in the first direction, and then actuate the rotation of the turbine in the second direction (e.g., reverse direction) at410. Alternatively, if the turbine is stationary, the electric motor initiates the reverse rotation.

Spinning the turbine in the reverse direction drives air flow in an opposite direction through the exhaust system compared to flow during engine operation. Air may flow into the exhaust pipe, through the ECD, through the turbine, and into the exhaust manifold, as shown inFIG. 2B. Since flow through the combustion chambers is blocked, pressure may accumulate in the exhaust manifold if the exhaust system is leak-free.

The turbine may be spun at a pre-set speed that has been determined to increase pressure by a calculated amount in the exhaust manifold. For example, the turbine speed may be adapted to increase pressure by 25% or by 50% in the exhaust manifold. At512of the method, the pressure is compared to a third threshold. Comparing the exhaust manifold pressure to the third threshold may include first spinning the turbine for a period of time, e.g., 2 seconds, after the turbine speed reaches a pre-set speed to allow the speed of the turbine to stabilize. After the period of time for stabilization passes, the pressure in the exhaust manifold may be measured.

The method at512may further include first determining the third threshold based on the barometric pressure measured at506. The third threshold may be a function of the measured barometric pressure and based on the amount of expected pressure increase due to turbine rotation at the pre-set speed. In one example, the controller may refer to look-up tables, which may be based on mapped data of exhaust manifold pressure according to barometric pressure, stored in the memory of the controller where the measured barometric pressure is the input and the first threshold (or expected pressure after running the turbine in the reverse direction at the pre-set speed for the threshold duration or period of time) is the output. As another example, the controller may be configured to calculate a theoretical, final pressure in the exhaust manifold, which may be used as the third threshold, as a function of barometric pressure, turbine speed, and/or temperature. A measured pressure in the exhaust manifold that is lower than the third threshold may indicate that exhaust gas may be escaping from the exhaust system via a leak in the exhaust manifold. The method may return to method300to determine, at324, if the pressure in the exhaust manifold is lower than the second threshold.

If the pressure in the exhaust manifold is lower than the third threshold, the method proceeds to326to set a diagnostic trouble code (DTC) to notify an operator that a leak in the exhaust manifold is present. The method at326may further include indicating to the operator, via a signal sent to an indicator light, alarm, or other type of notifying device, that a leak in the exhaust manifold is present. The DTC may also be set in the controller memory and be readable by a technician. If the exhaust manifold pressure is not lower than the second threshold, the routine is terminated and other diagnostic tests to evaluate other engine components for sources of degradation may be conducted. Repair of leaks or blockages indicated by DTCs may be addressed.

FIGS. 6 and 7show example operational timing maps600and700, respectively, for diagnosing an exhaust system of a vehicle engine system for leaks and blockages automatically upon engine shutdown and/or when degradation of the exhaust system is detected. The exhaust system (such as the exhaust system shown inFIGS. 1, 2A, and 2B) includes an exhaust manifold and an exhaust pipe, configured with pressure sensors in both regions of the exhaust system and timing map600depicts processes for evaluating leaks and blockages in the exhaust pipe while timing map700illustrates processes for detecting leaks in the exhaust manifold. Commencement of the example operations shown inFIGS. 6 and 7may be initiated by an operator activated switch or the operations may be configured to occur routinely and automatically when the engine is turned off. An electrically driven turbine is positioned in the exhaust system between the exhaust manifold and the exhaust pipe.

As depicted inFIG. 6, an engine status is shown at plot602, a throttle position is shown at plot604, a position of an exhaust tuning valve (ETV) located at an end of the exhaust pipe (proximate to atmosphere) is shown at plot606, a position of a wastegate arranged in a bypass passage that bypasses the turbine is shown at plot608, and positions of intake and exhaust valves of combustion cylinders of the engine are shown at plots609and610, respectively. Positions of the intake and exhaust valves may be adjusted between fully open and fully closed positions and any position in between.

A direction of rotation of the turbine is shown at plot612. Pressure in the exhaust pipe is shown at plots616,618, and620, depicting three possible scenarios, and may be measured by a gas particulate filter pressure sensor (e.g., gage pressure sensor) arranged in the exhaust pipe downstream of the turbine and immediately upstream of an ECD (which includes the GPF) or integrated into the ECD. The exhaust pipe pressure is compared to a first threshold shown at plot614and a second, lower threshold shown at plot615. Elements inFIG. 7that are common toFIG. 6are similarly numbered. InFIG. 7, pressure in the exhaust manifold is shown, instead of in the exhaust pipe, at plots704and706, and compared to a second threshold702. Pressure in the exhaust manifold may be measured by a pressure sensor arranged in the exhaust manifold.

Prior to t1, the engine is running (602) but the vehicle may be stopped and the throttle closed (604). The ETV is open (606), and the wastegate (608) is in a partially open position to moderate turbine speed. The intake valve is closed (610) and the turbine (612) is spinning in a forward direction. The pressure in the exhaust pipe may be relatively high (616) if a blockage is present, relatively low (620) if a leak is present, or at a pressure in between (618) if no degradation to the exhaust pipe is present.

At t1, the engine is turned off and moving engine components (e.g., crankshaft) decelerate to a stop between t1and t2. During this interval the throttle remains closed and the ETV and wastegate are maintained open. The position of the intake and exhaust valves is also adjusted so that the intake valves are closed at t2. The rotational speed of the turbine decreases and comes to a halt between t1and t2, resulting in a decrease in the exhaust pipe pressure. As the crankshaft decelerates, the controller commands an adjustment in deceleration of the crankshaft to adjust a camshaft position to close (or maintain closed) the intake and exhaust valves, thereby blocking air flow through the engine cylinders. The engine is stationary by t2.

At t2, the throttle is opened and both the wastegate and the ETV are closed. The crankshaft is rotated to a position where intake and exhaust valves begin to open at t2. Adjusting the crankshaft while the engine is off may include rotating the crankshaft by an electrical motor powered by an energy storage device, such as an electrical motor and a battery of a hybrid engine system. However, if the engine is not a hybrid engine, the engine may be rotated by the starter motor briefly to allow the intake and exhaust valves to be opened before testing of the exhaust manifold commences. Pressure in the exhaust pipe is at a minimum (e.g., at atmospheric pressure). A barometric pressure measurement is obtained from the exhaust manifold. The rotation of the turbine is actuated in the forward direction after a brief period to allow the adjustments of the throttle, wastegate, and ETV to be completed. Between t2and t3, which may be a period of at least 2 seconds, the throttle opening increases and the turbine speed increases until a pre-set speed is reached. The exhaust pipe pressure increases while positions of the various valves are maintained.

At t3, the rotation of the turbine stabilizes and the pressure in the exhaust pipe plateaus. Positions of all the valves are maintained. After t3the pressure in the exhaust pipe is compared to a first threshold pressure (614) that is calculated as a function of the measured barometric pressure and the speed of the turbine. If the exhaust pipe pressure (616) is higher than the first threshold (614), a DTC is set, indicating a blockage in the pipe. If the exhaust pipe pressure is lower than the first threshold (e.g.,618and620), then the exhaust pipe pressure is compared to the second threshold (615). An exhaust pipe pressure (620) that is lower than the second threshold (615) leads to setting a DTC to indicate a leak in the pipe, and operations continue to timing map700ofFIG. 7. If the exhaust pipe pressure (618) is at the second threshold (615), the exhaust pipe is deemed leak-free and operations according to timing map700are performed.

The engine is maintained off and the wastegate maintained closed throughout the operations of timing map700. At t1, the throttle is adjusted to a fully closed position and the ETV is opened. The crankshaft is adjusted so that the intake valves and exhaust valves are closed. Adjusting the crankshaft while the engine is off may include rotating the crankshaft by an electrical motor powered by an energy storage device, such as an electrical motor and a battery of a hybrid engine system. However, if the engine is not a hybrid engine, the engine may be rotated by the starter motor briefly to allow the intake and exhaust valves to be closed before testing of the exhaust manifold commences.

The electric motor driving rotation of the turbine is deactivated at t1and the turbine decelerates, becoming briefly stationary between t1and t2before spinning in the reverse direction is initiated. The barometric pressure is measured in the exhaust manifold during the period when the turbine is still. The pressure in the exhaust manifold is initially at atmospheric pressure until the turbine begins rotating in the reverse direction. Thereafter, pressure in the exhaust manifold increases.

At t2, the turbine rotation is stabilized and exhaust manifold pressure stabilizes. If the pressure (704) is equal to a third threshold (702), also calculated as a function of the barometric pressure and speed of the turbine, the exhaust manifold is intact. However, if the exhaust manifold pressure is lower (706) than the third threshold, a DTC is set, indicating a leak in the exhaust manifold.

In this way, an exhaust system of a vehicle may be diagnosed for leaks and blockages and a source of the degradation in the exhaust system may be identified. The methods described herein for the diagnosis may be requested by an operator or configured to be performed as a routine maintenance check, automatically when an engine of the vehicle is turned off. By rotating an electrically driven turbine of a turbocharger when the engine is off, the rotation in a first direction may allow evaluation of an exhaust pipe for leaks and blockages by comparing a measured pressure in the exhaust pipe to first and second predetermined threshold pressures. Rotating the turbine in a second direction provides detection of leaks in an exhaust manifold by similarly comparing a measured pressure in the exhaust manifold to a third predetermined threshold pressure. The diagnosis may be conducted without additional parts beyond already existing components in the vehicle and provides a reliable testing method by using thresholds that are functions of measured barometric pressure. The technical effect of using the electric turbocharger to generate pressure in targeted regions of the exhaust system is that leaks and blockages may be identified with equal integrity for each test trial, and without adding additional sensors or controls that may complicate engine control during engine operation and/or increase engine costs.

As one embodiment, a method includes upon engine shutdown, operating an electric turbocharger to draw air into an exhaust system and indicating degradation of the exhaust system based on a comparison of a pressure in the exhaust system measured during operating the electric turbocharger to a threshold pressure that is based on a barometric pressure. In a first example of the method the barometric pressure is measured in an exhaust manifold of the exhaust system before operating the electric turbocharger, following engine shutdown. A second example of the method optionally includes the first example, and further includes wherein operating the electric turbocharger includes spinning a turbine of the electric turbocharger in a first, forward direction and wherein the pressure in the exhaust system is a measured exhaust pipe pressure measured via a pressure sensor arranged directly upstream of or at a particulate filter arranged in an exhaust pipe of the exhaust system, downstream of the turbine. A third example of the method optionally includes one or more of the first and second examples, and further includes, upon engine shutdown and prior to spinning the turbine in the forward direction and measuring the pressure in the exhaust system, adjusting a stopping position of a crankshaft so that opening of intake and exhaust valves of each engine cylinder are overlapping so that air flows through the engine cylinders during the operating the electric turbocharger, and opening an intake throttle. A fourth example of the method optionally includes one or more of the first through third examples, and further includes, wherein indicating degradation includes indicating a leak in the exhaust pipe in response to the measured exhaust pipe pressure being less than a first threshold pressure, the first threshold pressure based on the barometric pressure and indicating a blockage in the exhaust pipe in response to the measured exhaust pipe pressure being greater than a second threshold pressure, the second threshold pressure based on the barometric pressure. A fifth example of the method optionally includes one or more of the first through fourth examples, and further includes, wherein operating the electric turbocharger includes spinning a turbine of the electric turbocharger in a second, reverse direction while an intake throttle is closed. A sixth example of the method optionally includes one or more of the first through fifth examples, and further includes, upon engine shutdown and prior to spinning the turbine in the reverse direction and measuring the pressure in the exhaust system, adjusting a stopping position of a crankshaft so that opening of intake and exhaust valves of each engine cylinder are not overlapping so that no air flows through the engine cylinders during the operating the electric turbocharger. A seventh example of the method optionally includes one or more of the first through sixth examples, and further includes, wherein the pressure in the exhaust system is an exhaust manifold pressure measured in an exhaust manifold, the exhaust manifold arranged in the exhaust system, upstream of the turbine, and wherein indicating degradation includes indicating a leak in the exhaust system, upstream of the turbine, in response to the measured pressure in the exhaust system being less than a third threshold pressure, the third threshold pressure based on the barometric pressure.

As another embodiment, a method includes following an engine key-off event and after a crankshaft of an engine stops spinning, electrically driving rotation of a turbine disposed in an exhaust system of the engine in a first, forward direction and pumping air from an intake system of the engine into an exhaust pipe of the exhaust system arranged downstream of the turbine and measuring a first pressure in the exhaust pipe, electrically driving rotation of the turbine in a second, reverse direction and pumping air from the exhaust pipe into an exhaust manifold of the exhaust system and measuring a second pressure in the exhaust manifold, and indicating degradation of one or more of the exhaust pipe and the exhaust manifold of the exhaust system based on the first pressure and the second pressure relative to a barometric pressure. In a first example of the method, wherein the first pressure is measured by a first pressure sensor arranged between the turbine and an emission control device positioned at a downstream end of the exhaust pipe and the second pressure is measured by a second pressure sensor positioned in the exhaust manifold. A second example of the method optionally includes the first example, and further includes prior to electrically driving rotation of the turbine in the first direction, adjusting a position of the crankshaft so that opening of an intake valve and an exhaust valve of each engine cylinder overlap to allow airflow through each engine cylinder and opening an intake throttle. A third example of the method optionally includes one or more of the first and second examples, and further includes, prior to electrically driving the turbine in the first direction, closing an exhaust tuning valve positioned in the exhaust pipe, downstream of an emission control device and upstream of an outlet of the exhaust pipe. A fourth example of the method optionally includes one or more of the first through third examples, and further includes, wherein indicating degradation includes indicating a blockage in the exhaust pipe in response to the first pressure being higher than a first threshold pressure, the first threshold determined as a function of the barometric pressure and turbine speed of the turbine during the electrically driving rotation of the turbine in the first direction. A fifth example of the method optionally includes one or more of the first through fourth examples, and further includes, wherein indicating degradation includes indicating a leak in the exhaust pipe in response to the first pressure being lower than a second threshold pressure that is determine as a function of the barometric pressure and turbine speed of the turbine during the electrically driving rotation of the turbine in the first direction. A sixth example of the method optionally includes one or more of the first through fifth examples, and further includes, prior to electrically driving rotation of the turbine in the second direction, adjusting a position of the crankshaft so that opening of an intake valve and an exhaust valve of each engine cylinder do not overlap to prevent airflow through each engine cylinder. A seventh example of the method optionally includes one or more of the first through sixth examples, and further includes, wherein indicating degradation includes indicating a leak in the exhaust manifold in response to the second pressure being lower than a third threshold pressure, the third threshold pressure determined as a function of the barometric pressure and turbine speed of the turbine during the electrically driving rotation of the turbine in the second direction.

As another embodiment, a system for a vehicle includes a controller with computer readable instructions stored on non-transitory memory that, when executed during an engine-off condition, cause the controller to obtain a barometric pressure after an engine stops spinning and determine one or more pressure thresholds based on the barometric pressure, drive rotation of an electric turbocharger in a direction to draw air into an exhaust system, measure an exhaust system pressure in an exhaust system of the engine, and indicate degradation of the exhaust system in response to the measured exhaust system pressure being outside of the one or more pressure thresholds. In a first example of the system a first pressure sensor is disposed in the exhaust system, downstream of a turbine of the electric turbocharger and directly upstream of a particulate filter disposed in the exhaust system, wherein the direction that the electric turbocharger is driven to rotate is a first, forward direction which draws air into the exhaust system from an intake system of the engine, and wherein the measured exhaust system pressure is measured via the first pressure sensor. A second example of the system optionally includes the first example and further includes a second pressure sensor disposed in an exhaust manifold of the engine, upstream of a turbine of the electric turbocharger, wherein the direction that the electric turbocharger is rotated is a second, reverse direction which draws air into the exhaust system from outside of the exhaust system, and wherein the measured exhaust system pressure is measured via the second pressure sensor.