Method for analysing the actual energy consumption of a motor vehicle on a journey

Abstract

Method (10) for analysing an actual energy consumption of a motor vehicle, comprising : • - a step (13) of calculating an instantaneous consumption penalty (Pen_cons_inst) per litre per second as a function of an ignition advance efficiency (Rend_Av), a richness efficiency (Rend_Rich) of said efficiencies (Rend_Av, Rend_Rich) and an instantaneous fuel consumption (Consjnst) of the engine in litre per second; • - a step (14) of checking whether or not the various strategies (S) affecting ignition advance and / or richness on-board the engine computer are activated; and • - a step (15) of calculating, over a journey (T), a consumption penalty (Pen_cons_S_T) linked to the active strategy (S) as a function of the instantaneous consumption penalty (Pen_cons_inst) calculated for each active strategy (S).

Description

[0001] DESCRIPTION

[0002] TITLE: Method for analysing the actual energy consumption of a motor vehicle on a journey

[0003] This invention relates to the field of internal combustion engines, and in particular to spark-ignition engines.

[0004] More specifically, the invention relates to the analysis of the actual fuel consumption of the internal combustion engine of the motor vehicle.

[0005] Current standards require diagnostics to be carried out on internal combustion engines, and in particular on-board fuel consumption monitoring. Current regulations require information on the vehicle's actual fuel consumption to be made available on a diagnostic socket, including average consumption in litres per 100 km, absolute consumption in litres, etc .

[0006] The aim of these regulations is to compare the actual fuel consumption of motor vehicles with that approved on a regulatory reference cycle known as the "Worldwide Harmonized Light Vehicles Test Cycle" (WLTC).

[0007] Actual fuel consumption is generally estimated by the vehicle's engine control system from the quantity injected by the fuel injection system. This actual consumption must be accurate to within plus or minus 5 % of the regulatory cycle. This is checked when the vehicle is approved on a test bench.

[0008] When actual fuel consumption is very different from the measurement taken on the regulatory cycle, it may be worthwhile for the car manufacturer to analyse such a discrepancy and to be able to explain it with a view to rectifying it.

[0009] It is known to analyse the type of driving carried out by the vehicle in terms of the time split between City, Highway and Motorway or dual carriageway, known as the "VRA" . The VRA is calculated by the engine control system. It is available on the diagnostic socket and can be retrieved by the manufacturer's computer servers, in particular via a telemetry system.

[0010] The WLTC-approved reference cycle is a mixture of city, road and motorway driving. When the motor vehicle's actual fuel consumption is very different from the approved reference consumption, and the VRA is very different from the WLTC approved reference cycle, the difference in fuel consumption can be explained by this difference in the type of driving carried out by the vehicle. However, such an analysis is generally not sufficient to provide an exhaustive explanation of the differences between actual fuel consumption and certified fuel consumption.

[0011] US 2015 / 0314789 - A l also describes a process for analysing the causes of a vehicle's energy consumption in order to reduce it. The causes of energy consumption are linked in particular to driver behaviour and environmental factors .

[0012] However, this document does not aim to analyse excess fuel consumption due to specific operating modes of an internal combustion engine that are not present in the approved reference cycle.

[0013] There is a need to analyse excess fuel consumption due to specific operating modes of an internal combustion engine that are not present in the approved reference cycle.

[0014] The purpose of this invention is to analyse the actual fuel consumption of a motor vehicle when said actual consumption is very far from the approved consumption and to deduce the causes of the excess fuel consumption.

[0015] The object of the present invention is a method of analysing the actual energy consumption of a motor vehicle on a journey, the method being intended to be implemented in part by an electronic control unit on board a computer of a spark-ignition internal combustion engine of a motor vehicle, characterised in that the method comprises :

[0016] - a step for determining an ignition advance efficiency;

[0017] - a step for determining a richness efficiency;

[0018] - a step for calculating a penalty in terms of instantaneous consumption in litres per second, as a function of the said efficiencies and of an instantaneous fuel consumption of the engine in litres per second; -

[0019] - a step of checking whether or not the various strategies on-board the engine computer and selected from the group comprising at least strategies that affect ignition advance and strategies that affect richness are activated; and

[0020] - a step of calculating, over a journey, a consumption penalty linked to the active strategy, both in absolute value in litres and in relative value as a percentage with respect to the total consumption as a function of the instantaneous consumption penalty calculated in the step for each active strategy.

[0021] The process analyses actual fuel consumption and identifies fuel consumption penalties relative to optimal operation using engine control variables .

[0022] Advantageously, the method comprises a step of recording in the memory of the engine computer the consumption penalties calculated in the calculation step for a plurality of journeys, and of calculating the average values over this plurality of journeys, with i between 1 and 20, preferably equal to the number 20, a step of synthesising the data recorded during the recording step in a comparative table and a step of comparing said data synthesised in the comparative table with reference values of an approved cycle to determine the origin of the excess fuel consumption.

[0023] In this way, we can determine the origins of any excess fuel consumption based on the consumption penalties of the strategies activated.

[0024] Advantageously, the consumption penalty linked to the ignition advance is calculated according to the following equation : [Math 2]

[0025] Pen_cons_inst = (1 — Rend_AV). Consjnst

[0026] Advantageously, the richness consumption penalty is calculated according to the following equation : [Math 3]

[0027] Pen_cons_inst = (1 — Rend_Rich). Consjnst

[0028] Advantageously, the consumption penalty Pen_cons_S_T linked to the active strategy (S) is calculated according to the following equations :

[0029] [Math 4]

[0030] [Math 5]

[0031] Pen cons SJ' (litre)

[0032] P en_cons _S _T (%) = 100.

[0033] Cons_T (litre) For example, the ignition advance efficiency Rend_Av is calculated according to the following equation: [Math 1 ]

[0034] RendAV= l - k. (Avopt- Avappi)2with : k, a coefficient derived from a map present in the engine control system; Av_opt, the optimum value of ignition advance, or optimum advance ; Av_appl, the actual value of ignition advance, or advance actually applied. For example, the ignition advance efficiency Rend_Av reflects the difference in engine efficiency linked to the difference between the applied advance Av_appl and the optimum advance Av_opt. It is therefore equal to 1 at optimum advance and less than 1 for lower advances . The response as a function of feed rate is parabolic, with a coefficient k mapped in the engine control system on the basis of tests. It depends on engine speed and load. For example, the richness efficiency Rend_Rich translates the difference in engine efficiency linked to the difference between the applied richness R and the optimum richness 1. It is therefore 1 for a richness equal to 1 and less than 1 for richnesses greater than 1 , i.e. a rich mixture. This law is calibrated in the engine control system on the basis of tests.

[0035] Preferably, the strategies affecting the ignition timing include at least: a strategy for heating up an engine pollution control catalyst, a strategy for reserving torque at ralenti, an anti-knock strategy and an anti-cliquetisation strategy.

[0036] The catalyst heating strategy, in particular a three-way engine catalyst, in the case of a spark ignition engine, is activated after the engine has been cold started in order to heat the catalyst quickly so that it can process the pollutant gas emissions (carbon monoxide CO, unburnt hydrocarbons HC, nitrogen oxides NOx) as quickly as possible. To achieve this, the ignition advance is greatly reduced compared with the optimum values, so that efficiency is degraded and high exhaust gas temperatures are obtained. Once the catalyst is primed, i.e. at a temperature sufficient to treat the pollutants with at least a predetermined minimum efficiency, this strategy is deactivated. Depending on the type of engine and the architecture of the exhaust line, this strategy can last between 20s and 120s . There is therefore a penalty in terms of fuel consumption for the entire time during which this catalyst heating strategy is activated.

[0037] The so-called at ralenti torque reserve strategy is activated to ensure precise regulation of the at ralenti speed, typically to within + / - lOrpm, and which is robust when engine consumers such as an air conditioning compressor are activated. To do this, the nominal advance is reduced compared with the optimum values in order to quickly provide extra torque by temporarily increasing the advance when necessary, for example when the air conditioning is activated, so as to avoid a sharp drop in speed. In the same way, this reduction in advance makes it possible to avoid a sharp drop in speed in other circumstances, in particular during a take-off manoeuvre due to rapid clutching. This variation in torque by modifying the advance is generally referred to as "fast" torque because it can be modulated cycle by cycle, i.e. from one engine combustion cycle to the next, whereas the variation in torque obtained by modifying the flow of air entering the engine is referred to as "slow" torque, because the response time is much longer, being conditioned by the movement of an engine intake flap. The intake flap does not allow the torque to be modulated as quickly as necessary. There is therefore a penalty in terms of fuel consumption when this at ralenti torque reserve strategy is activated.

[0038] The anti-knock strategy is used to limit the jolts and speed oscillations that occur during transient manoeuvres on the vehicle's accelerator pedal, typically when putting the foot down or lifting the foot. It can include a preventive part (avoiding jerking) and a curative part (eliminating residual oscillations) . To do this, the engine control will modulate the torque generated by the engine in relation to the driver's torque demand as expressed by the pedal depression (or alternatively the effort applied to the pedal), by reducing the ignition advance to a greater or lesser extent. Typically, if the torque demanded by the driver were to be delivered immediately when the pedal is depressed by adjusting the ignition advance to the optimum setting, this would create a jolt associated with the engine tilting and the impact on its suspension pads on the body. To avoid this, the ignition advance is temporarily reduced to gradually tilt the engine and avoid the impact. Once the engine has settled on its buffers, the optimum ignition advance is applied. There is therefore a fuel consumption penalty when this anti-knock strategy is activated.

[0039] The anti-cliquetisation strategy makes it possible to avoid and deal with the abnormal combustion phenomenon known as knocking, which can be destructive for the piston. The way to reduce or even eliminate knocking is to reduce the ignition advance compared with the optimum values. This generally comprises a preventive part (advance values are reduced in advance in conditions where knocking is more prevalent than at rated values, such as in a very hot environment) and a curative part (advance values applied are reduced rapidly to suppress the appearance of knocking detected by a knock sensor fitted to the engine) . There is therefore a consumption penalty when this anti-cliquetisation strategy is active.

[0040] For example, the strategies affecting richness include at least: a start-up strategy, a richness regulation strategy, a strategy for managing the quantity of oxygen present in an engine depollution catalyst and an intrusive richness diagnosis strategy.

[0041] The start-up strategy is activated during cold start phases, when the mixture is enriched, i.e. the richness R is strictly greater than 1 , in order to ensure optimum combustion, particularly in the case of low volatility fuel, which has more difficulty evaporating and therefore ensuring optimum combustion. There is therefore a consumption penalty during these start-up phases .

[0042] The richness regulation strategy adjusts the quantity injected in real time so that the richness R of the air-fuel mixture is equal to a set value (generally stoichiometry, i.e. 1 ) . However, during very transient phases of operation, the richness control is not perfect and it can therefore happen that the actual richness is temporarily higher than the set value, for example with a richness of 1.05 for a target equal to 1. There is therefore a penalty in terms of consumption when this is the case.

[0043] The strategy of managing the quantity of oxygen present in the catalyst, or oxygen storage in Anglo-Saxon terms, can also be used. For example, see FR-A 1 -3101673 : the aim of this strategy is to place the level of oxygen OS stored in the catalyst within an optimum window for the treatment of both NOx and CO pollutants. In fact, if the OS exceeds a given maximum threshold value, which can be predetermined by tests, it treats NOx inefficiently. Conversely, if the OS falls below a given minimum threshold value, which can be predetermined by tests, it does not treat CO very effectively. This strategy therefore consists of defining a setpoint value between the said minimum threshold and the said maximum threshold and regulating the OS on the setpoint value. If the OS is too high in relation to the target, the system will enrich the air-fuel mixture, with a set richness greater than 1 , to consume oxygen in the catalyst and return to the optimal OS level for treating pollutants . These enrichment phases occur, for example, during acceleration following a long deceleration, for example when the vehicle is on a downhill slope and the driver takes his foot off the accelerator pedal: during this last downhill phase, fuel injection is cut off. Pure air is sent to the exhaust, saturating the catalytic converter with oxygen, which is then unable to treat the NOx during re-acceleration. The catalyst will therefore be enriched from the start of the re-acceleration phase to rapidly lower the OS and return to the optimum value for treating the pollutants (in this case NOx in particular) . In the end, therefore, there is a consumption penalty when these enrichments are activated.

[0044] The purpose of the intrusive richness diagnostic strategy is to diagnose the state of catalyst ageing. OBD diagnostic strategies need to generate richness slots of a few seconds . Typically a richness window at 1.07 instead of 1 , which also leads to a fuel consumption penalty. See for example publication FR-A 1 -3057022 which describes such a process.

[0045] According to a second aspect, the invention relates to a motor vehicle comprising a spark-ignition internal combustion engine, an engine control unit and an electronic control unit on-board the engine control unit and capable of partly implementing the method as described above.

[0046] Other aims, characteristics and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which : [Fig 1 ] shows the synoptic diagram of a process for analysing the actual energy consumption of a motor vehicle and determining the causes of any over- con sumption;

[0047] [Fig 2A] , [Fig 2B] illustrate curves representing the evolution of the feed efficiency and richness efficiency respectively; and [Fig 3] is a table summarising the actual values of the parameters of several journeys, the fuel consumption on each of these journeys and the consumption penalties based on reference values on an approved cycle.

[0048] As illustrated in Figure 1 , the method 10 for analysing the actual energy consumption of a motor vehicle and determining the origins of any over- consumption is intended to be implemented in part by an electronic control unit (not shown) on-board a computer of the spark-ignition internal combustion engine of a motor vehicle (not shown).

[0049] Process 10 enables actual fuel consumption to be analysed and fuel consumption penalties to be identified in relation to optimum operation using engine control variables .

[0050] Method 10 comprises a step 1 1 of determining the ignition advance efficiency Rend_Av according to the following equation:

[0051] [Math 1 ]

[0052] Rend_AV = 1 — k. Av_opt — Av_appl~)2

[0053] With : k, a coefficient derived from a map present in the engine control system; Av_opt, the optimum value of the ignition advance, or optimum advance; and Av_appl, the actual value of ignition advance, or advance actually applied.

[0054] Process 10 also includes a step 12 for determining the richness efficiency Rend_Rich as shown in Figure 2B .

[0055] In a spark-ignition engine, optimal operation is defined by :

[0056] - in relation to the ignition advance: optimum operation is at the so-called optimum advance Av_opt. Anything that leads to operation with a degraded advance, i.e. lower than the optimum advance, penalises consumption.

[0057] - in relation to the richness of the air-fuel mixture: optimum operation is when the richness is equal to 1 , i.e. stoichiometric. Anything that leads to operating with a rich mixture, i.e. with a richness strictly greater than 1 , reduces fuel consumption.

[0058] Two main variables are used in the engine control software:

[0059] -the ignition advance efficiency Rend_Av: this reflects the difference in mo.teur efficiency linked to the difference between the applied advance Av_appl and the optimum advance Av_opt. It is therefore equal to 1 at the optimum feedrate and less than 1 for lower feedrates. The response as a function of feed rate is parabolic, with a coefficient k mapped in the engine control system on the basis of tests . It depends on engine speed and load.

[0060] - the richness efficiency Rend_Rich: this reflects the difference in engine efficiency linked to the difference between the applied richness R and the optimum richness 1. It is therefore equal to 1 for a richness equal to 1 and is less than 1 for richnesses greater than 1 , i.e. a rich mixture. This law is calibrated in the engine control system on the basis of tests.

[0061] From of the yields Rend_Av, Rend_Rich , a penalty in instantaneous consumption Pen_cons_inst per litre / s is calculated in step 13 according to the following equations:

[0062] Consumption penalty linked to ignition advance :

[0063] [Math 2]

[0064] Pen_cons_inst = (1 — Rend _AV). Cons _Inst

[0065] Richness-related consumption penalty :

[0066] [Math 3]

[0067] Pen_cons_inst = (1 — Rend_Rich~). Consjnst

[0068] With :

[0069] Cons_Inst , the engine's instantaneous fuel consumption in litres per second

[0070] The aim is to identify the contributions of the different strategies to the total consumption penalty calculated for a journey T.

[0071] Method 10 also includes a step 14 to check whether or not the various strategies S present in the engine control software have been activated.

[0072] For each of the strategies S, the method determines, via the motor control, when it is active by means of a Boolean Activ_S which changes to 1 instead of 0 when the strategy is active.

[0073] The strategies S present in the engine control software are such as to affect ignition advance or richness and are chosen from the group comprising at least the strategies affecting ignition advance and the strategies affecting richness .

[0074] Strategies based on ignition timing include at least : - a strategy for heating a pollution control catalytic converter: this strategy is activated after the engine has been cold-started in order to rapidly heat the catalytic converter, in particular a three-way catalytic converter, in the case of a spark-ignition engine, so that it can process the pollutant gas emissions (HC, CO, NOx) as quickly as possible. To achieve this, the ignition advance is greatly reduced compared with the optimum values, so that efficiency is degraded and high exhaust gas temperatures are obtained. Once the catalyst is primed, i.e. at a temperature sufficient to treat the pollutants, this strategy is deactivated. Depending on the type of engine and the architecture of the exhaust line, this strategy can take between 20 seconds and 120 seconds . There is therefore a penalty in terms of fuel consumption for all the time during which this catalyst heating strategy is activated.

[0075] - a torque reserve at ralenti strategy: this strategy is activated to ensure precise regulation of the at ralenti speed, typically at + / - lOrpm, and is robust when engine consumers, such as an air conditioning compressor, are activated. To do this, the nominal advance is reduced compared with the optimum values in order to quickly provide extra torque by temporarily increasing the advance when necessary, for example when the air conditioning is activated. This strategy can also be used in other situations where there is a risk of a sharp drop in engine speed, such as during a takeoff manoeuvre due to rapid clutch engagement. This variation in torque by modifying the advance is generally referred to as "fast" torque because it can be modulated cycle by cycle by modifying the ignition advance from one engine combustion cycle to the next, whereas " slow" torque has a much longer response time because it is conditioned by the mass of air admitted to the engine by adjusting the opening position of an intake flap. The intake flap does not allow the torque to be modulated as quickly as necessary because of the duration of its movements . There is therefore a fuel consumption penalty when this at ralenti torque reserve strategy is activated.

[0076] - an anti-knock strategy: this strategy limits the jerks and oscillations in engine speed that occur during transient manoeuvres on the accelerator pedal, typically when putting the foot down and lifting the foot. It generally comprises a preventive part (avoiding jerking) and a curative part (eliminating residual oscillations) . To do this, the engine control system modulates the torque generated by the engine in relation to the driver's demand by reducing the ignition advance to a greater or lesser extent. Typically, if the torque demanded by the driver were supplied immediately when the vehicle is put down, using the optimum advance, this would create a jolt linked to the tilting of the engine and the impact on its suspension buffers on the body. To avoid this, the ignition advance is temporarily reduced to gradually tilt the engine and avoid the impact. Once the engine has settled on its buffers, the optimum ignition advance is applied. There is therefore a fuel consumption penalty when this anti-knock strategy is activated.

[0077] - an anti-cliquetisation strategy: this strategy makes it possible to avoid and deal with the abnormal combustion phenomenon known as knocking, which can be destructive for the piston. The way to reduce or even eliminate knocking is to reduce ignition advance compared with optimum values . This strategy generally comprises a preventive part (basic reduction in advance in conditions where knocking is more prevalent than at nominal, such as in a very hot environment) and a curative part (rapid reduction in advance applied to suppress the appearance of cliqueting detected by the cliquetisation sensor) . There is therefore a consumption penalty when this anti- cliquetisation strategy is active.

[0078] Strategies that play on richness include at least :

[0079] - a start-up strategy: during cold start-up phases, the mixture is enriched, i.e. the richness R is greater than 1 , to ensure optimum combustion, particularly in the case of "heavy" fuel, i.e. with low volatility, which has more difficulty evaporating and therefore ensuring optimum combustion. There is therefore a penalty in terms of fuel consumption during these start-up phases .

[0080] - a richness regulation strategy: this strategy adjusts the quantity injected in real time so that the air-fuel mixture is at a given richness set-point value (generally stoichiometry, so richness R is equal to 1 ) . However, during very transient phases of operation, control of the richness is not perfect and it can therefore happen that the actual richness is temporarily higher than the set value, for example with a richness of 1.05 for a target of 1. There is therefore a penalty in consumption when this is the case. - a strategy for managing the quantity of oxygen present in the catalyst, or oxygen storage: the aim of this strategy is to place the OS level within an optimum window for the treatment of NOx and CO pollutants, and more precisely to regulate the quantity of oxygen OS to a setpoint value within the said range. If the OS is too high in relation to the setpoint, the system will enrich the mixture, by imposing a richness setpoint greater than 1 determined as a function of the difference between the actual quantity of oxygen and the oxygen quantity setpoint, in order to consume oxygen in the catalyst and return to the optimum OS level for treating the pollutants . These enrichment phases occur, for example, during an acceleration that follows a long deceleration: during the deceleration phase, which takes place, for example, when the vehicle is on a downhill slope and the driver takes his foot off the accelerator pedal, fuel injection is cut off and pure air is sent to the engine exhaust. If the deceleration is long enough, the catalytic converter ends up saturated with oxygen and is no longer capable of treating the NOx during re-acceleration. The catalyst will therefore be enriched from the start of the re-acceleration phase to rapidly lower the OS and return to the optimum value for treating the pollutants (more particularly NOx in this case) . In the end, therefore, there is a consumption penalty when these enrichments are activated. See for example publication FR-A 1 -3101673 which describes such a process .

[0081] - an intrusive richness diagnostic strategy: the aim of this strategy is to diagnose the state of catalyst ageing. OBD diagnostic strategies need to generate richness windows of a few seconds . Typically, a rich slot has a richness equal to 1.07 instead of 1 , which also leads to a consumption penalty. Reference is made, for example, to publication FR-A 1 -3057022 which describes such a process .

[0082] The method 10 also includes a step 15 for calculating, over a journey T, a consumption penalty linked to the active strategy S, both in absolute value in litres and in relative value in percentage with respect to the total consumption Cons_T in litres according to the following equations :

[0083] [Math 4] [Math 5]

[0084] Pen_cons_S_T(%) = 100.

[0085] With :

[0086] Pen_cons_S_T , the consumption penalty in litres for strategy S on route T ; Pen_cons_S_T(%), the consumption penalty as a percentage of the total fuel consumption of strategy S on route T ; t_start_journeyT, the start time of path T, in seconds ; t_end_journeyT, the time at which path T ends, in seconds ;

[0087] Pen_cons_inst_S, the instantaneous consumption penalty in litres per second of strategy S ;

[0088] Activ_S, a Boolean for activating strategy S , equal to 1 if the strategy is activated, equal to 0 if the strategy is not activated; dt, the integration time step, in seconds; and

[0089] Cons_T (litre), the fuel consumption of the engine in litres over the distance T calculated according to the following equation :

[0090] [Math 6]

[0091] The method 10 also comprises a step 16 of storing in the engine computer memory the consumption penalties calculated in step 15 for a plurality of journeys Ti, and calculating the average values over said plurality of journeys Ti, in particular with i between 1 and 20.

[0092] In step 17, the data recorded in step 16 is summarised in a comparative table and, in step 18 , said recorded data is compared with of the reference values of a WLTC approved cycle to determine the origin of the excess fuel consumption .

[0093] Such a comparative table is illustrated in Figure 3.

[0094] In this example, for which three journeys were considered, average fuel consumption (l / 100km) was significantly higher than the approved figure of 1.1 litres per 100km. The first point that differs from the vehicle's use is the high proportion of use in town, which averages 93 % compared with 20% on a WLTC-approved cycle, on short journeys, averaging 4.3km compared with 23.3km on a WLTC- approved cycle.

[0095] To begin with, we can see that this vehicle's fuel consumption is penalised because the engine operates on low load zones with lower efficiency and more with a cold / lukewarm water temperature (<90°C), which also penalises fuel consumption. The calculated consumption penalties complete this initial macroscopic analysis .

[0096] In the first place, we find a much higher contribution from catalyst heating, because the short journeys mean that the duration of activation of the catalyst heating strategy relative to the total journey time is greater. This is necessary for vehicle pollution control and can therefore be justified.

[0097] The other thing that emerges from these typical 'city' journeys is the greater penalty of the torque reserve strategy at ralenti, as there are many phases when the vehicle is stopped (traffic lights, traffic jams, etc.) .

[0098] It then appears that the user is driving quite dynamically, as we see a high penalty for the Anti-knock strategy, which involves a lot of acceleration and deceleration, and gearbox ratio changes with very firm pressure on the accelerator pedal. This highly dynamic or transient driving also results in a high penalty on the OS management strategy, which very often has to reset the catalyst to the correct OS level, given the multiple deceleration phases that saturate the catalyst with oxygen. This can also be justified for pollution control purposes .

[0099] For other penalties, the differences are not very significant.

[0100] Overall, the total fuel consumption penalty is on average 5.5% higher in absolute terms than in the WLTC-approved reference cycle.

[0101] The analysis of these penalties has therefore made it possible to pinpoint the origins of the excess consumption in relation to an initial macroscopic analysis, and will enable the manufacturer to enrich its arguments with the authorities.

[0102] Such a process for analysing actual fuel consumption and determining the causes of any over-consumption is easy to install on board the engine control unit (ECU), since it uses variables already present in the ECU. Thanks to the invention, it is easy to explain the origin of the differences in real-life vehicle fuel consumption compared with that approved on the WLTC cycle.

Claims

CLAIMS1. Method ( 10) for analysing an actual energy consumption of a motor vehicle on a journey (T), the method being intended to be implemented in part by an on-board electronic control unit in a computer of a sparkignition internal combustion engine of a motor vehicle, characterised in that the method ( 10) comprises:- a step ( 1 1 ) of determining an ignition advance efficiency (Rend_Av) ;- a step ( 12) of determining a richness efficiency (Rend_Rich) ;- a step ( 13) of calculating an instantaneous consumption penalty (Pen_cons_inst), in litre per second, as a function of said efficiencies (Rend_Av, Rend_Rich) and of an instantaneous fuel consumption (Cons_Inst) of the engine in litre per second;- a step ( 14) of checking whether or not the various strategies (S) on-board the engine computer and selected from the group comprising at least strategies that affect ignition advance and strategies that affect richness are activated; and- a step ( 15) for calculating, over a journey (T), a consumption penalty (Pen_cons_S_T) linked to the active strategy (S), both in absolute value in litres and in relative value in percentage with respect to the total consumption (Cons_T (litre)) as a function of the instantaneous consumption penalty (Pen_cons_inst) calculated in step ( 13) for each active strategy (S).

2. Method according to claim 1 , comprising a step ( 16) of recording in the memory of the engine computer the consumption penalties (Pen_cons_S_T) calculated in the calculation step ( 15) for a plurality of journeys (Ti), and of calculating the average values over the said plurality of journeys (Ti), in particular with i between 1 and 20, a step ( 17) of synthesising the data recorded during the recording step ( 16) in a comparative table and a step ( 18) of comparing said synthesised data in the comparative table with reference values of a WLTC approved cycle to determine the origin of the excess fuel consumption.

3. Method according to claim 1 or 2, in which the consumption penalty linked to the ignition advance is calculated according to thefollowing equation:[Math 2] Pen_cons_inst = (1 — Rend_AV}. Consjnst.

4. A method according to any one of the preceding claims, wherein the richness-related consumption penalty is calculated according to the following equation:[Math 3] Pen_cons_inst = (1 — RendJUch . Consjnst.

5. Method according to any one of the preceding claims, in which the consumption penalty (Pen_cons_S_T) linked to the active strategy (S) is calculated according to the following equations :[LMath 4]JPen>, . . , > , „ „[Math 5 ]Pen_cons_S_T(% 7 = 100.

6. A method ( 10) according to any one of the preceding claims, wherein the ignition advance efficiency (Rend_Av) is calculated according to the following equation:[Math 1 ] Rend_AV = 1 — k. (Av_opt — Av_appl2where: k, a coefficient derived from a map present in the engine control system;Av_opt, the optimum value of ignition advance; andAv_appl, the actual value of ignition advance.

7. A method according to any one of the preceding claims, in which the strategies (S) affecting ignition advance comprise at least: a strategy for heating an engine pollution control catalyst, a strategy for reserving torque at ralenti, an anti-knock strategy and an anti-cliquetisation strategy.

8. A method according to any one of the preceding claims, in which the strategies (S) affecting richness comprise at least: a starting strategy, a richness regulation strategy, a strategy for managing the quantity of oxygen present in an engine depollution catalyst and an intrusive richness diagnosis strategy.

9. Motor vehicle comprising a spark-ignition internal combustion engine, an engine control unit and an electronic control unit on-board the engine control unit and capable of implementing the method ( 10) according to any one of the preceding claims.

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