Method for controlling a motor vehicle powertrain incorporating a spark-ignition internal combustion engine and associated control system
The method addresses false cylinder imbalance detections in spark-ignition engines by using oil dilution, torque deviation, and temperature metrics to adjust fuel injection, ensuring accurate engine diagnostics and reduced emissions.
Patent Information
- Application Number
- FR2024001462
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2024-02-15
- Publication Date
- 2026-01-02
- Estimated Expiration
- 2044-02-15
AI Technical Summary
Existing OBD diagnostic systems in spark-ignition engines falsely detect cylinder imbalance due to the presence of blow-by gases, leading to unnecessary maintenance and component replacement, as they cannot distinguish between torque dispersion caused by blow-by gases and actual engine component failures.
A method and system for controlling a powertrain that includes determining oil dilution rate, maximum torque deviation, and oil temperature to identify and compensate for torque dispersion caused by blow-by gases, adjusting fuel injection to rebalance cylinder mixtures, and implementing compensation when specific conditions are met.
This approach accurately distinguishes torque dispersion due to blow-by gases from engine component failures, preventing false detections and reducing pollutant emissions by maintaining optimal fuel mixture balance across cylinders.
Smart Images
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Abstract
Description
Title of the invention: Method for controlling a motor vehicle powertrain incorporating a spark-ignition internal combustion engine and associated control system
[0001] The present invention relates, in general, to the control of the mixture of an internal combustion engine with spark ignition of a motor vehicle and, more particularly, to the control of the mixture of an internal combustion engine with spark ignition of a motor vehicle in the presence of engine crankcase gases, known as "blow-by" gases.
[0002] More specifically, the invention relates to a method of controlling a powertrain incorporating a spark-ignition internal combustion engine, to a control system for implementing such a method, and to a motor vehicle incorporating such a control system.
[0003] In an effort to reduce polluting emissions, car manufacturers are required to equip motor vehicles with an on-board diagnostic device, known as an "OBD" device, an acronym for the Anglo-Saxon terms "On-Board Diagnosis", intended for monitoring the operating condition of the engine.
[0004] In order to meet the new pollutant emission requirements, the OBD device must, in particular, include an on-board diagnostic of cylinder imbalance, known in English as "Cylinder imbalance". This consists of detecting torque balance problems between the different engine cylinders that could lead to exceeding emission limits.
[0005] Conventionally, spark-ignition engines are equipped with a proportional oxygen sensor, mounted at the engine exhaust and upstream of a three-way catalyst, and allowing the oxygen content of the exhaust gases to be measured.
[0006] This oxygen content control system monitors the engine's fuel mixture, which is set in a closed loop to a target value that is generally equal to 1. This represents a stoichiometric air-fuel mixture that ensures optimal breakdown of the three pollutants CO, HC, and NOx. The target value is adjusted by modifying the fuel injection duration through the injectors, i.e., by changing the injector opening time.
[0007] However, this mixture setting is an average mixture setting, the fuel injection duration by the different fuel injectors being the same in all the engine cylinders.
[0008] Consequently, when one of the fuel injectors malfunctions, for example partially blocked, it injects a much lower quantity of fuel than the expected quantity corresponding to the commanded opening duration, resulting in an unbalanced average fuel mixture across the cylinders. This leads to the cylinder receiving less fuel running "lean," meaning its fuel mixture ratio is less than 1, while the other cylinders run "rich," meaning their fuel mixture ratio is greater than 1, resulting in higher pollutant emissions from the exhaust.
[0009] The "Cylinder Imbalance" diagnostic function of the OBD diagnostic tool allows for the detection of malfunctions in engine components, such as fuel injectors. The detection of a component malfunction is called "Good Detection" and allows for the correction of imbalances in parameters such as the resulting fuel mixture.
[0010] In the event that the OBD diagnostic device manages to highlight that an injector is delivering too little fuel, it is known to rebalance the fuel mixtures of the engine cylinders by specifically increasing the injection duration of the malfunctioning injector, i.e. by adopting a distinct injection duration compared to the other functional cylinders.
[0011] In some cases, the mixtures between the cylinders can be very dispersed without this resulting from a malfunction of an engine component.
[0012] In particular, crankcase gases, known as blow-by gases, generated in the cylinder crankcase of an internal combustion engine are likely to disturb the air-fuel ratio.
[0013] Fig. 1 represents an existing powertrain 1 comprising an internal combustion engine 2 with spark ignition, an air intake circuit 3 and an exhaust circuit 4.
[0014] The engine 2 comprises three cylinders Cl, C2 and C3, and a fuel supply circuit, not visible, comprising fuel injectors, each of which is capable of injecting fuel into one of the three cylinders Cl, C2 and C3.
[0015] The air intake circuit 3 includes an intake manifold 5 supplying air to the cylinders.
[0016] The engine 2 is supercharged by the compressor C of a turbocharger 6.
[0017] The exhaust circuit 4 includes an exhaust manifold 7, a turbine T of the turbocharger 6, a treatment device 8 and a proportional oxygen sensor R.
[0018] The treatment device 8 comprises a three-way catalyst which continuously oxidizes unburned hydrocarbons (HC) and carbon monoxide (CO) and reduces nitrogen oxides (NOx) present in the exhaust gases. The treatment device further comprises a particulate filter which enables The system stores the fine particles emitted by the engine and then burns them when the stockpile reaches a certain threshold. The proportional oxygen sensor R is mounted at the inlet of the three-way catalytic converter and allows the air-fuel mixture to be regulated to a set value in a closed loop by adjusting the injection duration of all injectors to the same value.
[0019] The powertrain 1 incorporates an OBD diagnostic device.
[0020] As illustrated in [Fig.2], during its operation, the engine 2 generates leaks of unburned combustion gases which escape beyond the piston rings of cylinders Cl, C2 and C3, penetrating into the cylinder casing 9, above an oil bath 10 for lubricating the engine 2. The oil bath 10 then gradually becomes charged with fuel.
[0021] The blow-by gases, some of which have evaporated from the oil bath 10, rise to the cylinder head 11 where they are cleared of oil using a separator, before being re-admitted via a recirculation circuit 12 into the air intake circuit 3 of the engine 2. The blow-by gases are admitted at a point P of the air intake circuit 3 located on the intake manifold 5.
[0022] The blow-by gas recirculation circuit 12 is connected to the intake manifold 5 of the air intake circuit 3, which supplies fresh air to each of the engine cylinders 2, so as to minimize flow dispersion between the cylinders. However, given the architectural constraints and the internal aerodynamics of the intake manifold 5, this distribution is generally not ideal, so that design-related blow-by flow dispersions form between the cylinders.
[0023] When fuel evaporated from the oil bath is re-admitted via the blow-by gas recirculation circuit 12, the mixture is regulated via the oxygen sensor R so that the average mixture Rmoy of the cylinders returns to a value equal to 1. This results in an individual mixture of each cylinder that is highly dispersed between the cylinders.
[0024] Figures 3A and 3B, representing respectively the torque and richness dispersions generated by the presence of blow-by gases in the three cylinders Cl, C2 and C3 of engine 2, show the consequences of a low flow of blow-by gases on the first cylinder Cl where the richness is less than 1 and of a high flow on the second and third cylinders C2 and C3 where the richness is greater than 1.
[0025] The dispersions of richness have a direct consequence on the torque generated by each of the cylinders, which will deviate in the same way from an average torque Cmoy generated individually by each of the cylinders in the absence of blow-by gas and failure of engine components 2.
[0026] Or, classically, the OBD diagnostic device for cylinder imbalance "Cylinder imbalance" is activated according to torque dispersion information. In particular, the OBD diagnostic is activated when the torque of one of the cylinders deviates from the average torque Cmoy by a predetermined deviation e, in percentage %, beyond which the level of exhaust emissions is considered to become critical, as is the case for the first and third cylinders Cl and C3 on the [Fig.3B].
[0027] Such an activation of the OBD diagnostic linked to the presence of blow-by gas in the cylinders of engine 2 is problematic since it leads to a "False Detection", i.e. to an activation which is not linked to a faulty component.
[0028] The invention therefore aims to remedy these drawbacks and to propose a solution enabling the detection at a lower cost of torque dispersions due to the presence of blow-by gas in the cylinder block of an internal combustion engine with spark ignition, in order to be able to distinguish such a dispersion from a torque dispersion due to a failure of an engine component.
[0029] A method for controlling a powertrain is therefore proposed, comprising a spark-ignition internal combustion engine incorporating a plurality of cylinders and a cylinder block containing oil, an air intake circuit for the cylinders, a blow-by gas recirculation circuit from the cylinder block connected to the air intake circuit, and a fuel supply circuit for the cylinders, the method comprising the following steps:
[0030] a) the determination of a rate of oil dilution by the fuel,
[0031] b) determining a maximum difference between a maximum torque generated by one of the cylinders and an average torque generated by all the cylinders,
[0032] c) determining the oil temperature, and
[0033] d) the implementation of compensation for torque dispersion between the cylinders, step d) being activated when the following conditions are met:
[0034] - the oil dilution rate by the fuel determined in step a) is greater than a predetermined threshold value,
[0035] - the maximum torque deviation determined in step b) is greater than a threshold value predetermined, and
[0036] - the oil temperature determined in step c) is greater than a threshold value predetermined.
[0037] Preferably, step d) includes adjusting the amount of fuel injected into at least one of the cylinders to rebalance the mixtures between the cylinders.
[0038] Advantageously, the adjustment of the quantity of fuel can be achieved by increasing the duration of fuel injection into the cylinders where the richness of the air and fuel mixture is less than a setpoint value, preferably the setpoint value being equal to 1.
[0039] Preferably, the fuel quantity adjustment is performed using a model based on the maximum deviation of the maximum cylinder torque and the torque average generated by all the cylinders.
[0040] Preferably, the powertrain further includes a device for diagnosing a failure of an engine component, the predetermined threshold value of the maximum torque deviation being less than a predetermined threshold value of a maximum torque deviation from the average torque generated by all cylinders from which the device for diagnosing a failure of an engine component is activated.
[0041] Preferably, the predetermined threshold value of oil temperature is between 40 and 50°C.
[0042] In one embodiment, the value of the oil temperature determined in step c) may be a value calculated from a model.
[0043] Preferably, the value of the oil dilution rate determined in step a) by the fuel is a value calculated from a model.
[0044] The invention also relates to a powertrain control system comprising a spark-ignition internal combustion engine incorporating a plurality of cylinders and a cylinder block containing oil, an air intake circuit for the cylinders, a blow-by gas recirculation circuit from the cylinder block connected to the air intake circuit, and a fuel supply circuit for the cylinders, the control system comprising a control device capable of:
[0045] - determine a rate of oil dilution by the fuel,
[0046] - determine a maximum difference between a maximum torque generated by one of the cylinders and an average torque generated by all the cylinders,
[0047] - determine an oil temperature, and
[0048] - implement compensation for torque dispersion between cylinders when the following conditions are met:
[0049] - the determined oil dilution rate by the fuel is greater than a value predetermined threshold,
[0050] - the maximum determined torque deviation is greater than a predetermined threshold value, And
[0051] - the determined oil temperature is above a predetermined threshold value Done.
[0052] Preferably, the control device is capable of adjusting the quantity of fuel injected into at least one of the cylinders to rebalance the mixtures between the cylinders.
[0053] Advantageously, the control device may be able to adjust the quantity of fuel from a model according to the maximum deviation of the maximum torque of the cylinders and the average torque generated by all the cylinders.
[0054] Advantageously, the control device can be configured to adjust the amount of fuel injected by increasing the duration of fuel injection into the cylinders where the air-fuel mixture richness is less than a setpoint value, preferably the setpoint value being equal to 1.
[0055] Advantageously, the control system may include an oil temperature sensor for measuring the temperature of the oil present in the cylinder block.
[0056] Advantageously, the control device may include a model adapted to calculate the temperature of the oil present in the cylinder crankcase.
[0057] Advantageously, the control device may include a model adapted to calculate the maximum torque deviation.
[0058] Advantageously, the control device may include a model adapted to calculate the rate of oil dilution by the fuel.
[0059] Preferably, the powertrain further includes a device for diagnosing a failure of an engine component, the predetermined threshold value of the maximum rate of torque dispersion between the cylinders being less than a predetermined threshold value of the rate of torque dispersion between the cylinders from which the device for diagnosing a failure of an engine component is activated.
[0060] The invention also relates to a motor vehicle comprising:
[0061] an internal combustion engine with spark ignition comprising a plurality of cylinders, a cylinder block containing oil, an air intake circuit for the cylinders, a blow-by gas recirculation circuit from the cylinder block connected to the air intake circuit, and a fuel supply circuit for the cylinders, and
[0062] a control system as previously described. Brief description of the drawings
[0063] Other purposes, advantages and features will become apparent from the following description, given for illustrative purposes only and made with reference to the accompanying drawings on which:
[0064] [Fig. 1] is a motor vehicle powertrain incorporating a prior art internal combustion and spark-ignition engine.
[0065] [Fig.2] represents a blow-by gas recirculation circuit of the motor vehicle powertrain of [Fig.1].
[0066] [Fig.3A] and [Fig.3B] represent, respectively, the richness and torque of each of the three cylinders of the engine of [Fig.1].
[0067] [Fig.4] illustrates a motor vehicle powertrain incorporating a spark-ignition internal combustion engine according to an embodiment of the invention.
[0068] [Fig.5] is a logic diagram illustrating a method of controlling an internal combustion engine with spark ignition according to an embodiment of the invention.
[0069] [Fig.6A] and [Fig.6B] represent, respectively, the richness and torque of each of the three cylinders of the engine of the [Fig.4] dispersed by the presence of blow-by gas.
[0070] [Fig.7A] and [Fig.7B] represent, respectively, the richness and torque of each of the three cylinders of the engine of [Fig.4] after compensation of the torque dispersions between the cylinders using a control method according to the invention. Detailed description
[0071] In what follows, the bounds of a domain of values are included in that domain, in particular in the expression "between".
[0072] Furthermore, the expression "at least one" used in this description is equivalent to the expression "one or more".
[0073] Figure 4 illustrates a motor vehicle powertrain 101 comprising a spark-ignition internal combustion engine 102, an air intake circuit 103 and an exhaust circuit 104.
[0074] The illustrated engine 102 comprises three cylinders Cl, C2 and C3, and a fuel supply circuit, not shown, comprising fuel injectors, each of which is capable of injecting fuel into one of the three cylinders Cl, C2 and C3.
[0075] The air intake circuit 103 includes an air inlet A, an air filter F, the compressor C of a turbocharger 106, a cooler RG for the intake gases supercharged by the compressor C, a throttle body B and an intake manifold 105 supplying fresh air to cylinders Cl, C2 and C3.
[0076] The engine 102 also includes a cylinder block 109 surmounted by a cylinder head, not visible, and an oil bath 110 for lubricating the engine 102 in the cylinder block 109.
[0077] The exhaust circuit 104 includes an exhaust manifold 107, a turbine T of the turbocharger 106, a treatment device 108 and a proportional oxygen sensor R.
[0078] The illustrated treatment device 108 includes a three-way catalyst 114 that oxidizes unburned hydrocarbons HC and carbon monoxide CO and reduces nitrogen oxides NOx present in the exhaust gases. It further includes a particulate filter 113 that stores fine particles emitted by the engine 102 and burns them when the stock reaches a threshold. The proportional oxygen sensor R is mounted at the inlet of the three-way catalyst 114 and regulates the RCi of the air-fuel mixture introduced into cylinders C1, C2, and C3 to a setpoint value, in a closed loop, by adjusting the injection duration of all the in- fuel injectors on the same value.
[0079] The powertrain 101 further includes a blow-by gas recirculation circuit 112 connecting the cylinder block 109 to the air intake circuit 103 of the engine 102. The blow-by gases are admitted at a point P of the air intake manifold 105 located on the intake manifold 105.
[0080] The powertrain 101 further incorporates a control system for controlling the powertrain 101.
[0081] The control system includes a control device 115 capable of:
[0082] determine the dilution rate of the oil in the oil bath 110 by the fuel,
[0083] determine a maximum difference, expressed as a percentage (%), between a maximum torque generated by one of the cylinders Cl, C2, C3 and an average torque Cmoy generated by all the cylinders Cl, C2, C3,
[0084] determine an oil temperature Th of the oil bath 110, and
[0085] implement compensation for torque dispersion between cylinders Cl, C2, C3 when the following conditions are met:
[0086] - the determined oil dilution rate by the fuel is greater than a value predetermined threshold,
[0087] - the maximum determined torque deviation is greater than a predetermined threshold value x, and
[0088] - the determined oil temperature Th is greater than a predetermined threshold value Done.
[0089] Preferably, the control system further integrates a fault diagnostic device 116 for a component of the engine 102, such as a fuel injector.
[0090] The fault diagnostic device 116, or OBD diagnostic device, is intended to detect torque balance problems between the different cylinders Cl, C2, C3 of the engine 102 which may lead to exceeding the pollutant emission limits.
[0091] With reference to [Fig. 5], the invention also relates to a method for controlling the powertrain 101 comprising the following steps:
[0092] a) determining the dilution rate of the oil in the oil bath 110 by fuel,
[0093] b) determining a maximum difference between the torque generated by one of the cylinders Cl, C2, C3 and the average torque Cmoy generated by all the cylinders,
[0094] c) the determination of the temperature of the oil Th of the oil bath 110, and
[0095] d) the implementation of compensation for torque dispersion between cylinders Cl, C2, C3, step d) being activated when the following conditions are met:
[0096] the oil dilution rate by the fuel determined in step a) is greater than a predetermined threshold value,
[0097] the maximum torque deviation determined in step b) is greater than a predetermined threshold value x, and
[0098] the oil temperature Th determined in step c) is greater than a predetermined threshold value.
[0099] The control process is implemented by the control system which incorporates all the hardware and software means for the implementation of this control process.
[0100] The oil dilution rate by the fuel determined in step a) is advantageously a value calculated from a model.
[0101] For example, the rate of oil dilution by fuel can be determined from a model such as described in document EP2520785.
[0102] Preferably, the predetermined threshold value of the oil dilution rate by the fuel is less than or equal to 10%.
[0103] In step b), the individual torque generated by each of the cylinders Cl, C2, C3 is determined so as to identify the cylinder whose rate of variation between its individual torque and the average torque Cmoy generated by all the cylinders is the most important compared to the other cylinders Cl, C2, C3.
[0104] The individual torque generated by each of the cylinders Cl, C2, C3 and therefore the maximum torque gap can be calculated.
[0105] The control system may include a torque meter for determining the individual torque generated by each of the cylinders Cl, C2, C3 and connected to the control device 115.
[0106] Advantageously, the maximum torque deviation can be determined from a method known as a "software torque meter", as described in document FR2757945 or document FR2818740, based on the use of a torque meter and on the analysis of the instantaneous speed of the engine 102, and which makes it possible to know the individual torque developed in a cylinder on a combustion cycle.
[0107] Preferably, the predetermined threshold value x of the maximum torque dispersion deviation is greater than or equal to 5%.
[0108] In one embodiment, the value of the oil temperature determined in step c) may be a value calculated from a model.
[0109] Advantageously, the control device 115 of the control system is capable of determining the value of the oil temperature of the oil bath 110 from a model.
[0110] According to an alternative, the value of the oil temperature determined in step c) can be a value measured from a temperature sensor.
[0111] The control system may include a temperature measurement sensor connected to the control device 115 and intended for determining, in step c), the value of the temperature of the oil in the oil bath 110 in the cylinder block 109.
[0112] The predetermined threshold value of the oil temperature is preferably between 40 and 50°C. Beyond this range of values, the fuel present in the oil evaporates.
[0113] Preferably, steps a), b) and c) are carried out simultaneously.
[0114] Moreover, the three aforementioned conditions are cumulative so that the implementation of the compensation of the torque dispersion between cylinders Cl, C2, C3 in step d) is activated only when all three conditions are met.
[0115] Preferably, steps a), b) c) and d) are carried out continuously during the operation of the engine 102 so as to regulate, in a closed loop, the dispersions of richness and therefore of torques between the cylinders Cl, C2, C3.
[0116] Figures 6A and 6B represent, respectively, the richness and torque generated individually by each of the three cylinders Cl, C2 and C3 of engine 102 at a time t.
[0117] It can be seen that the blow-by gas intake into the air intake circuit 103 disturbs the richness of the air and fuel mixture so that the torque difference Displ, Disp3 of the first and third cylinders Cl and C3 is greater than the predetermined threshold value x.
[0118] In the third cylinder C3, a maximum torque deviation is generated relative to the average torque Cmoy.
[0119] When, cumulatively to the determination of the maximum torque deviation greater than the predetermined threshold value x, the oil dilution rate by the fuel and the oil temperature Th are greater than their predetermined threshold value, a situation of disturbance of the richness of cylinders Cl, C2, C3 by the presence of blow-by gas is identified.
[0120] The control device 115 then triggers the implementation of a compensation of torque dispersions between the cylinders.
[0121] Advantageously, the quantity of fuel Qinj_i injected into each of the cylinders Cl, C2, C3 is adjusted using a model based on the maximum torque deviation determined and the average torque Cmoy generated by all the cylinders.
[0122] Preferably, the setpoint value for the richness of the air and fuel mixture in each of the cylinders Cl, C2, C3 is equal to 1. The coefficients before perturbation are therefore, preferably, set to a value equal to 1.
[0123] The control device 115 applies coefficients Fac_Qinj_i to each of the quantities of fuel Qinj_i to be injected in order to rebalance the mixtures between the cylinders so that each of the cylinders returns to the setpoint value which, in the illustrated example, is equal to 1.
[0124] For example, when a cylinder lacks torque, such as the first cylinder Cl, the quantity injected into that cylinder Cl is increased, and when a cylinder generates too much torque, such as the third cylinder C3, the quantity injected on this cylinder C3 is reduced in order to decrease the maximum torque gap in cylinders Cl, C2, C3.
[0125] In this regard, the control device 115 is advantageously connected to the fuel injectors in cylinders Cl, C2, C3 in order to control the adjustment of the quantity of fuel.
[0126] Advantageously, the activation of the fault diagnostic device 116 also relies on torque dispersion information, calculated for example by the torque meter.
[0127] Advantageously, the fault diagnostic device 116 of a component of the engine 102 is activated when the maximum torque deviation, relative to the average torque generated by all cylinders, is greater than a predetermined threshold value e.
[0128] The predetermined threshold value x of the maximum deviation between the torque generated by one of the cylinders and the average torque Cmoy generated by all the cylinders, determining the activation of step d) is less than the predetermined threshold value e of the maximum torque deviation triggering the activation of the fault diagnostic device 116.
[0129] After compensation of torque dispersions in step d), we will therefore return to a conforming situation as shown in Figures 7A and 7B, avoiding a critical quantity of pollutant emission and avoiding a false detection of the fault diagnostic device 116.
[0130] Advantageously, the control method includes a step of deactivating step d) when at least one of the activation conditions of step d) is no longer met.
[0131] The coefficients Fac_Qinj_i are all reset to 1 by the control device 115.
[0132] Such a control method makes it possible, at a lower cost, to detect a dispersion of torque between the plurality of cylinders Cl, C2, C3 of engine 102 due to the presence of blow-by gas in the cylinder block 109 of engine 102 so as to prevent false detection of failure of an engine component by the fault diagnostic device 116 and avoid unjustified maintenance and replacement of the components concerned.
Claims
Demands
1. A method for controlling a powertrain comprising a spark-ignition internal combustion engine (102) incorporating a plurality of cylinders (C1, C2, C3) and a cylinder block (109) containing oil, an air intake circuit (103) into the cylinders, a blow-by gas recirculation circuit (112) from the cylinder block connected to the air intake circuit, and a fuel supply circuit to the cylinders, the method comprising the following steps: a) determining a fuel dilution ratio of the oil, b) determining a maximum deviation between the torque generated by one of the cylinders and the average torque (Cavg) generated by all the cylinders, c) determining an oil temperature, and d) implementing compensation for torque variations between the cylinders.step d) being activated when the following conditions are met: - the oil dilution rate by the fuel determined in step a) is greater than a predetermined threshold value, - the maximum torque deviation determined in step b) is greater than a predetermined threshold value (x), and - the oil temperature (Th) determined in step c) is greater than a predetermined threshold value.
2. A method according to claim 1, wherein step d) includes adjusting the amount of fuel injected into at least one of the cylinders to rebalance the mixtures between the cylinders.
3. A method according to claim 2, wherein the adjustment of the quantity of fuel is achieved by increasing the duration of fuel injection into the cylinders where the richness of the air and fuel mixture is less than a setpoint value, preferably the setpoint value being equal to 1.
4. A method according to claim 2 or 3, wherein the adjustment of the quantity of fuel is carried out from a model based on the maximum deviation of the torque of the cylinders and the average torque (Cmoy) generated by the set of cylinders (Cl, C2, C3).
5. A method according to any one of the preceding claims, wherein the powertrain further comprises a device for fault diagnosis (116) of an engine component (102), the predetermined threshold value (x) of the maximum torque deviation being less than a predetermined threshold value (e) of a maximum torque deviation from the average torque (Cmoy) generated by all cylinders from which the fault diagnosis device (116) of an engine component (102) is activated.
6. A method according to any one of the claims, wherein the predetermined threshold value of the oil temperature is between 40 and 50°C.
7. A method according to any one of the claims, wherein the value of the oil temperature (Th) determined in step c) is a value calculated from a model.
8. A method according to any one of the claims, wherein the value of the oil dilution rate determined in step a) by the fuel is a value calculated from a model.
9. A powertrain control system comprising a spark-ignition internal combustion engine (102) incorporating a plurality of cylinders (C1, C2, C3) and a cylinder block (109) containing oil, an air intake circuit (103) into the cylinders, a blow-by gas recirculation circuit (112) from the cylinder block (109) connected to the air intake circuit (103), and a fuel supply circuit to the cylinders, the control system comprising a control device (115) capable of: - determining a fuel-oil dilution ratio, - determining a maximum difference between the torque generated by one of the cylinders and an average torque (Cavg) generated by all the cylinders, - determining an oil temperature (Th), and - implementing compensation for torque variations between the cylinders (C1, C2,C3) when the following conditions are met: - the determined oil dilution rate by the fuel is greater than a predetermined threshold value, - the determined maximum torque deviation is greater than a predetermined threshold value (x), and - the determined oil temperature (Th) is greater than a predetermined threshold value.
10. Motor vehicle comprising: an internal combustion engine with spark ignition (102) comprising a plurality of cylinders (Cl, C2, C3), a cylinder block (109) containing oil, an air intake circuit (103) into the cylinders, a blow-by gas recirculation circuit (112) from the cylinder block (109) connected to the air intake circuit (103), and a fuel supply circuit for the cylinders, and a control system according to claim 9.