METHOD AND DEVICE FOR CONTROLLING A MULTI-CYLINDER INTERNAL COMBUSTION ENGINE

Abstract

A method for controlling a multi-cylinder spark-ignition engine (10) including a monitored cylinder (11) and a plurality of unmonitored cylinders (12, 13, 14), wherein an in-cylinder pressure sensor (15) is arranged in the monitored cylinder (11), the method comprising: Monitoring the internal cylinder pressure for the monitored cylinder (11) during a combustion event for the monitored cylinder (11) via the pressure sensor (15); Determining a first ignition timing (209) for the monitored cylinder (11) based on a desired ignition timing (211) and the internal cylinder pressure; Controlling the ignition timing for the monitored cylinder (11) based on the first ignition timing (209); Monitoring the engine speed and the crankshaft speed via a rotational position sensor associated with the monitored cylinder (11) and the non-monitored cylinders (12, 13, 14); Determining a modal coefficient for the non-monitored cylinders (12, 13, 14) based on the engine speed and the crankshaft speed pulsations; Determining coefficient errors for the unmonitored cylinders (12, 13, 14) based on the modal coefficients; performing a compensation control to determine an ignition timing setting for each of the unmonitored cylinders (12, 13, 14) based on the coefficient error; Determining final ignition times for the non-monitored cylinders (12, 13, 14) based on the desired ignition timing (211) and the respective ignition timing setting; and Controlling the ignition timing for each of the non-monitored cylinders (12, 13, 14) based on the respective final ignition timing.

Description

[0001] The present invention relates to a method for controlling a multi-cylinder spark-ignition engine and a correspondingly designed multi-cylinder spark-ignition engine. INTRODUCTION

[0002] The operation of an internal combustion engine is advantageous because it balances combustion between the cylinders.

[0003] For general background information, reference is made to the documents EP 2 431 595 A1 and DE 10 2008 054 690 A1. SUMMARY

[0004] A multi-cylinder spark-ignition engine is described, including a monitored cylinder and a plurality of unmonitored cylinders, a plurality of pistons disposed within the monitored cylinder and the unmonitored cylinders and coupled to a crankshaft, a pressure sensor disposed within the monitored cylinder to monitor the in-cylinder pressure, a rotational position sensor disposed within the crankshaft to monitor the rotational position of the crankshaft, a spark-ignition system having a spark controller in communication with a plurality of spark igniters disposed within the monitored cylinder and the plurality of unmonitored cylinders, and a controller. The controller is in communication with the pressure sensor, the rotational position sensor, and the spark controller.The controller includes a set of instructions executable to monitor, via the pressure sensor, the in-cylinder pressure for the monitored cylinder during a combustion event for the monitored cylinder and to determine an initial spark timing for the monitored cylinder based on a desired spark timing and the in-cylinder pressure. The spark control is arranged to control the spark timing for the monitored cylinder based on the final spark timing. The controller monitors, via the rotational position sensor, the engine speed and crankshaft speed pulsations associated with the monitored cylinder and the unmonitored cylinders and determines a modal coefficient for the unmonitored cylinders from the engine speed and crankshaft speed pulsations.

[0005] One aspect of the disclosure includes performing a principal component analysis to determine the modal coefficient for the unmonitored cylinders based on engine speed and crankshaft speed pulsations.

[0006] Another aspect of the disclosure includes monitoring the in-cylinder pressure for the monitored cylinder during a combustion event for the monitored cylinder via the pressure sensor and determining a combustion parameter for the combustion event for the monitored cylinder based on the in-cylinder pressure.

[0007] Another aspect of the disclosure includes determining a combustion parameter for the combustion event for the monitored cylinder based on the in-cylinder pressure, determining a first error term based on the combustion parameter and a desired state for the combustion parameter, determining a checkpoint for the combustion parameter based on the first error term, determining the desired spark timing for the monitored cylinder based on an engine operating point, and determining the final spark timing for the monitored cylinder based on the desired spark timing and the checkpoint for the combustion parameter.

[0008] Another aspect of the disclosure includes determining a combustion parameter that includes determining a crank angle associated with a parameter associated with a mass combustion breakpoint for the cylinder charge.

[0009] Another aspect of the disclosure includes the parameter associated with the mass combustion breakpoint for the cylinder charge being a crank angle associated with a 50% mass combustion breakpoint for the cylinder charge.

[0010] Another aspect of the disclosure includes a method for controlling a multi-cylinder spark ignition engine including a monitored cylinder and a plurality of unmonitored cylinders, wherein a pressure sensor is arranged to monitor the in-cylinder pressure in the monitored cylinder.

[0011] The above features and advantages, as well as other features and advantages of the present teachings, will become more apparent from the following detailed description of some of the best modes and other embodiments for carrying out the present teachings, as defined in the appended claims, with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In the following, one or more embodiments are described by way of example with reference to the accompanying drawings, in which: Fig. 1 schematically illustrates a multi-cylinder direct fuel injection spark ignition internal combustion engine and the associated engine control according to the disclosure; Fig. Figure 2 schematically shows a spark control routine for controlling the ignition timing in an embodiment of the multi-cylinder positive ignition internal combustion engine described with reference to Fig. 1, wherein combustion is monitored via a single cylinder pressure sensor and a crankshaft rotational position sensor according to the disclosure; Fig. Figure 3 graphically illustrates the crankshaft speed with respect to the crank angle of the engine over 720 degrees of crankshaft rotation, wherein the magnitude of the crankshaft speed with respect to the crankshaft speed in connection with the operation of an embodiment of the engine described with reference to Fig. 1 is specified according to the disclosure; Fig. Figure 4 graphically illustrates a magnitude of the delta crankshaft speed with respect to the crank angle of the engine in connection with the operation of an embodiment of the engine described with reference to Fig. 1, according to the disclosure; Fig. 5 graphically illustrates a plurality of principal component vectors based on the delta crankshaft speeds for the individual cylinders as a function of engine crank angle according to the disclosure; Fig. 6 graphically illustrates the target modal principal component (PC-1) coefficients for the monitored cylinder and the unmonitored cylinders based on the magnitude of the principal component vectors according to the disclosure; and Fig. 7 graphically illustrates a relationship between the target modal principal component coefficients (PC-1) with respect to a corrected state of the combustion parameters for each of the cylinders according to the disclosure.

[0013] It should be understood that the accompanying drawings are not necessarily to scale and present a somewhat simplified representation of various preferred features of the present disclosure as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes. Details pertaining to such features will be determined in part by the particular intended application and use environment. DETAILED DESCRIPTION

[0014] With reference to the drawings, wherein like reference numerals correspond to the same or similar components in the various figures, Fig. 1 schematically illustrates, in accordance with embodiments disclosed herein, a multi-cylinder direct fuel injection spark-ignition internal combustion engine (engine) 10 and the associated engine controller 20 that may be arranged to provide motive power to a vehicle. The vehicle may include a mobile platform in the form of a commercial vehicle, industrial vehicle, agricultural vehicle, passenger car, aircraft, watercraft, train, off-road vehicle, personal mobility device, robot, and the like to fulfill the purposes of the present disclosure.

[0015] The engine 10 includes a plurality of cylinders, including cylinder 1 11, cylinder 2 12, cylinder 3 13, and cylinder 4 14. The engine 10 is arranged in an inline configuration as shown, but may be configured in a V configuration, a W configuration, or other configuration. Each of the cylinders 11, 12, 13, and 14 includes an in-cylinder fuel injector arranged to inject fuel into a corresponding combustion chamber. The injected fuel is combined with intake air and recirculated exhaust gas to form a cylinder charge. Each of the cylinders 11, 12, 13, and 14 includes an in-cylinder igniter electrically connected to an ignition controller 22 and arranged to ignite the respective cylinder charge. Each of the cylinders 11, 12, 13, and 14 has a piston slidably disposed therein, the piston being coupled to a rotatable crankshaft 16 via a connecting rod.A rotational position, and thus the rotational speed, of the crankshaft 16 is monitored by a rotational position sensor 18. The rotational position sensor 18 may be an encoder device, e.g., a Hall-effect sensor, that generates a signal for a direction of rotation of the crankshaft 16. In one embodiment, the encoder signal is associated with a rotational degree of six degrees of the crankshaft 16.

[0016] A pressure sensor 15 is arranged to dynamically monitor the in-cylinder pressure generated in one of the cylinders, i.e., cylinder 11, during each combustion event as a result of the ignition of the cylinder charge, and is referred to herein as the "monitored cylinder." The in-cylinder pressure of the other cylinders, e.g., cylinders 12, 13, and 14, is not monitored, and these other cylinders are referred to herein as "unmonitored cylinders." The spark controller 22, the rotational position sensor 18, and the pressure sensor 15 are connected to the controller 20.

[0017] The term "controller" and related terms such as control module, module, controller, control unit, processor, and similar terms refer to one or various combinations of application-specific integrated circuits (ASICs), electronic circuit(s), central processing unit(s), e.g., microprocessor(s), and associated non-transitory storage component(s) in the form of memory and storage devices (read-only memory, programmable read-only memory, random access memory, hard disk, etc.). The non-transitory storage component is capable of storing machine-readable instructions in the form of one or more software or firmware programs or routines, combinational logic circuit(s), input / output circuit(s) and devices, signal conditioning and buffer circuit(s), and other components accessible by one or more processors to provide a described functionality.Input / output circuitry and devices include analog-to-digital converters and related devices that monitor sensor inputs at a predetermined polling frequency or in response to a trigger event. Software, firmware, programs, instructions, control routines, code, algorithms, and similar terms refer to sets of instructions executable by a control unit, such as calibrations and look-up tables. Each controller executes one or more control routines to provide desired functions. The routines may be executed at regular intervals, such as every 100 microseconds during operation. Alternatively, routines may be executed in response to a trigger event.Communication between controllers and communication between controllers and actuators and / or sensors may be via a direct wired connection, a networked communications bus, a wireless connection, or any other suitable communications link. Communication involves the exchange of data signals by any suitable means, including, for example, electrical signals through a conductive medium, electromagnetic signals through the air, optical signals through fiber optics, and the like. Data signals may include discrete, analog, or digitized analog signals representing inputs from sensors and actuator commands, as well as communication signals between control units. The term "signal" refers to a physically perceivable indication that conveys information and may be a suitable waveform (e.g.,electrical, optical, magnetic, mechanical or electromagnetic), such as direct current, alternating current, sine waves, triangular waves, square waves, vibration and the like, which can pass through a medium.

[0018] The term "model" refers to processor-based or processor-executable code and associated calibration that simulates the physical existence of a device or physical process. As used herein, the terms "dynamic" and "in a dynamic manner" describe steps or processes that are performed in real time and are characterized by monitoring or otherwise determining parameter states and regularly or periodically updating parameter states when executing a routine or between iterations of executing the routine. The terms "calibration," "calibrating," and related terms refer to a result or procedure that compares an actual or standard measurement associated with a device with a sensed or observed measurement or a commanded position.A calibration described herein may be reduced to a storable parametric table, several executable equations, or any other suitable form.

[0019] A parameter is defined as a measurable quantity representing a physical property of a device or other element, detectable by one or more sensors and / or a physical model. A parameter can have a discrete value, such as "1" or "0," or can be continuously adjustable.

[0020] Fig. Figure 2 schematically illustrates a control routine 200 for controlling the ignition timing in an embodiment of the system described with reference to Fig. 1, including a single monitored cylinder, e.g., cylinder 11, and a plurality of unmonitored cylinders, e.g., cylinders 12, 13, and 14, wherein combustion is monitored via cylinder pressure sensor 15 and rotational position sensor 18. Control routine 200 includes monitoring the in-cylinder pressure during a combustion event for the monitored cylinder (202) via pressure sensor 15. The pressure sampling rate occurs at a relatively high sampling rate, e.g., once per degree of rotation of crankshaft 16. The in-cylinder pressure represents the heat release of combustion during the combustion of a cylinder charge and can therefore be analyzed to determine mass combustion breakpoints for the combustion event (204).An actual mass combustion breakpoint may be an actual CA50 point, which represents a crank angle at which 50% of the mass combustion fraction of the cylinder charge has been reached in the individual monitored cylinder, e.g., cylinder 11. The CA50 point is an example of a combustion parameter that can be dynamically determined during engine operation. The concepts are described herein with respect to the state of a combustion parameter in terms of the CA50 point. Note that other combustion parameters may be used.

[0021] Engine operating conditions and desired engine performance are simultaneously monitored to determine an engine operating point 205, and a desired CA50 point for the individual monitored cylinder, e.g., cylinder 11, may be determined based thereon (206). The engine operating point 205 preferably includes parameter conditions such as engine speed, engine load, and similar parameters. In one embodiment, a CA50 error 207 may be determined, which is a difference between the actual CA50 point and the desired CA50 point. The CA50 error term 207 is used in a control routine 208 to determine a first spark timing command 209 based thereon. Concurrently, the engine operating point 205 is used in an engine spark calibration routine (210) to responsively determine a desired spark timing 211 for operation of the engine 10.The engine ignition calibration routine (210) may consist of a calibration array stored in a memory device and including an ignition timing for the engine operating point 205 that achieves minimum brake-specific fuel consumption. The desired ignition timing 211 and the ignition timing command 209 are arithmetically combined to determine a final ignition timing command for the individual monitored cylinder 215, e.g., cylinder 11, which is communicated to the ignition controller 22 for implementation during the next engine cycle.

[0022] At the same time, the rotational position sensor 18 monitors the rotational position and thus the rotational speed of the crankshaft 16, which is sampled at a relatively low frequency, e.g., every 6 angles of rotation of the crankshaft 16 (222), whereby crankshaft speed pulsations are generated and input into an analysis routine (224). Exemplary data are described with reference to Fig. 3, which graphically depicts crankshaft speed relative to engine crank angle over 720 degrees of crankshaft rotation, i.e., a single engine cycle, and is described with further reference to the internal combustion engine 10. The magnitude of the crankshaft speed is displayed on the vertical axis 320, and the crankshaft speed is displayed on the horizontal axis 310. The data displayed includes the crankshaft speed for engine operation with unbalanced cylinders 315 and the crankshaft speed for engine operation with balanced cylinders 325.Crankshaft speed points associated with engine operation with unbalanced cylinders 315 include a crankshaft speed measured at the beginning of combustion in cylinder 1 11 301, a crankshaft speed measured at the end of combustion in cylinder 1 11 302, a crankshaft speed measured at the beginning of combustion in cylinder 2 12 303, a crankshaft speed measured at the end of combustion in cylinder 2 12 304, a crankshaft speed measured at the beginning of combustion in cylinder 3 13 305, a crankshaft speed measured at the end of combustion in cylinder 3 13 306, and a crankshaft speed measured at the beginning of combustion in cylinder 4 14 307, and a crankshaft speed measured at the end of combustion in cylinder 4 14 308.

[0023] The analysis routine (224) uses principal component analysis (PCA) techniques to determine coefficients (PCM-1 coefficients) associated with each of the cylinders based on the crankshaft speed and the crankshaft speed variations between cylinders. PCA is a mathematical procedure that transforms a large number of potentially correlated variables into a smaller number of uncorrelated variables called principal components. The PCA technique first involves determining crankshaft speed deviations for individual cylinders with respect to an average crankshaft speed over an engine cycle. This is represented graphically in terms of Fig. 4, which includes a magnitude of the delta crankshaft speed 420 on the vertical axis relative to the engine crank angle 410 indicated on the horizontal axis for an embodiment of the engine 10 described with reference to Fig. 1. Delta crankshaft speeds for the individual cylinders include a first delta speed 411 associated with cylinder 1 11, a second delta speed 412 associated with cylinder 2 12, a third delta speed 413 associated with cylinder 3 13, and a fourth delta speed 414 associated with cylinder 4 14.

[0024] The analysis routine (224) executes the PCA to determine principal component vectors based on the delta crankshaft speeds for the individual cylinders, as described with respect to Fig. 4. This is shown graphically in relation to Fig. 5, which includes the modal vectors 520 on the vertical axis relative to the engine crank angle 510. The principal component vectors PCM1 511, PCM2 512, and PCM3 513 are associated with the unmonitored cylinders, e.g., cylinders 12, 13, and 14, and represent factors associated with individual torque fluctuations from the individual monitored cylinder, e.g., cylinder 11.

[0025] The principal component vectors PCM1 511, PCM2 512, and PCM3 513 can be used to determine the target modal principal component (PC-1) coefficients for the monitored cylinder and the unmonitored cylinders based on the magnitude of the modal vector. Examples of the target PC-1 coefficients are described with reference to Fig. 6, which graphically illustrates the magnitude of the PC-1 coefficients 620 on the vertical axis with respect to the modal number 610 on the horizontal axis, including a first target PC-1 coefficient 611 for the monitored cylinder and the target PC-1 coefficients 612, 613, and 614 for the respective unmonitored cylinders, respectively. The initial values ​​for the target PC-1 coefficients include a first initial value 621 for the first target PC-1 coefficient 611 for the monitored cylinder and the initial values ​​622, 623, and 624 for the target PC-1 coefficients 612, 613, and 614 for the respective unmonitored cylinders. For each of the unmonitored cylinders, error terms are determined for the PC-1 coefficients compared to the PC-1 coefficient for the monitored cylinder (225).

[0026] The error terms for the PC-1 coefficients are used in a scale routine 228 which determines a corrected CA50 point for each of the unmonitored cylinders based on the associated error term for the respective PC-1 coefficient.

[0027] Fig.Figure 7 graphically illustrates a relationship used in the scale routine 228, including a corrected CA50 point relative to a magnitude of a PC-1 coefficient, with the magnitude of CA50 point 720 relative to the magnitude of PC-1 coefficient 710, which is plotted relative to the horizontal axis, being plotted on the vertical axis. The recorded values ​​include a corrected CA50 point for each of the cylinders, including a corrected CA50 point 711 for the monitored cylinder and the corrected CA50 points 712, 713, and 714 for the unmonitored cylinders. The corrected CA50 point 711 for the monitored cylinder and the corrected CA50 points 712, 713, and 714 for the unmonitored cylinders form a straight line that can be reduced to an algorithm and incorporated into the scale routine 228.

[0028] The corrected CA50 point 711 for the monitored cylinder and the corrected CA50 points 712, 713, and 714 for the unmonitored cylinders are provided as input to a control routine. The control routine determines the spark timing settings 229 for the unmonitored cylinders based on the corrected CA50 point 711 and the corrected CA50 points 712, 713, and 714, respectively. The respective spark timing settings 228 are arithmetically combined with the desired spark timing 211 to determine the respective final spark timing commands 235 for the unmonitored cylinders, e.g., cylinders 12, 13, and 14, which are communicated to the ignition controller 22 for implementation in the next engine cycle.

[0029] By using a cylinder pressure sensor measurement, the CA50 point of the monitored cylinder can be controlled to the desired value, and the ignition timing for each of the cylinders can be compensated based on the engine speed and the desired CA50 point, which is determined based on the engine operating point 205. This approach can reduce the number of combustion pressure sensors to a single sensor while reducing the computational load.

[0030] The flowchart and block diagrams in the flowcharts illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowcharts or block diagrams may represent a module, segment, or portion of code that includes one or more executable instructions for implementing the specified logical function(s). It should also be understood that each block of the block diagrams and / or flowchart representations and combinations of blocks in the block diagrams and / or flowchart representations may be implemented by special-purpose hardware-based systems that perform the specified functions or operations, or combinations of special-purpose hardware and computer instructions.These computer program instructions may also be stored in a computer-readable medium that can direct a controller or other programmable data processing device to function in a particular manner such that the instructions stored in the computer-readable medium produce an article of manufacture, including instructions that implement the function / operation specified in the flowchart and / or block diagram block or blocks.

Claims

[1] A method for controlling a multi-cylinder spark-ignition engine (10) including a monitored cylinder (11) and a plurality of unmonitored cylinders (12, 13, 14), wherein an in-cylinder pressure sensor (15) is arranged in the monitored cylinder (11), the method comprising: Monitoring the internal cylinder pressure for the monitored cylinder (11) during a combustion event for the monitored cylinder (11) via the pressure sensor (15); Determining a first ignition timing (209) for the monitored cylinder (11) based on a desired ignition timing (211) and the internal cylinder pressure; Controlling the ignition timing for the monitored cylinder (11) based on the first ignition timing (209); Monitoring the engine speed and the crankshaft speed via a rotational position sensor associated with the monitored cylinder (11) and the non-monitored cylinders (12, 13, 14); Determining a modal coefficient for the non-monitored cylinders (12, 13, 14) based on the engine speed and the crankshaft speed pulsations; Determining coefficient errors for the unmonitored cylinders (12, 13, 14) based on the modal coefficients; performing a compensation control to determine an ignition timing setting for each of the unmonitored cylinders (12, 13, 14) based on the coefficient error; Determining final ignition times for the non-monitored cylinders (12, 13, 14) based on the desired ignition timing (211) and the respective ignition timing setting; and Controlling the ignition timing for each of the non-monitored cylinders (12, 13, 14) based on the respective final ignition timing. [2] The method of claim 1, comprising performing a principal component analysis to determine the modal coefficient for the unmonitored cylinders (12, 13, 14) based on the engine speed and the crankshaft speed pulsations. [3] The method of claim 1, further comprising determining a combustion parameter for the combustion event for the monitored cylinder (11) based on the in-cylinder pressure. [4] The method of claim 3, wherein determining a first ignition timing (209) for the monitored cylinder (11) based on a desired ignition timing (211) and the cylinder internal pressure comprises: Determining a first error term based on the combustion parameter and a desired state for the combustion parameter; Determining a control point for the combustion parameter based on the first error term; Determining the desired ignition timing (211) for the monitored cylinder (11) based on an engine operating point; and Determining the first ignition timing (209) for the monitored cylinder (11) based on the desired ignition timing (211) and the combustion parameter checkpoint. [5] The method of claim 3, wherein determining the combustion parameter for the combustion event for the monitored cylinder (11) comprises determining a crank angle associated with a parameter associated with a mass combustion breakpoint for a cylinder charge. [6] The method of claim 5, wherein the parameter associated with the mass combustion breakpoint for the cylinder charge comprises a crank angle associated with a 50% mass combustion breakpoint for the cylinder charge. [7] A method for controlling a multi-cylinder positive-ignition internal combustion engine (10) including a monitored cylinder (11) and a plurality of unmonitored cylinders (12, 13, 14), wherein a pressure sensor (15) is arranged to monitor the in-cylinder pressure in the monitored cylinder (11), the method comprising: Monitoring the internal cylinder pressure for the monitored cylinder (11) during a combustion event for the monitored cylinder (11) via the pressure sensor (15); Determining a first ignition timing (209) for the monitored cylinder (11) based on a desired ignition timing (211) and the internal cylinder pressure; Controlling the ignition timing for the monitored cylinder (11) based on the first ignition timing (209); Monitoring the engine speed and the crankshaft speed via a rotational position sensor associated with the monitored cylinder (11) and the non-monitored cylinders (12, 13, 14); Determining modal coefficients for the non-monitored cylinders (12, 13, 14) based on the engine speed and the crankshaft speed pulsations; Determining coefficient errors for the unmonitored cylinders (12, 13, 14) based on the modal coefficients; performing a compensation control to determine an ignition timing setting for each of the unmonitored cylinders (12, 13, 14) based on the coefficient error; Determining a final ignition timing for each non-monitored cylinder (12, 13, 14) based on the desired ignition timing (211) and the respective ignition timing setting; and Controlling the ignition timing for each of the non-monitored cylinders (12, 13, 14) based on the respective final ignition timing. [8] A method according to claim 7, comprising performing a principal component analysis to determine the modal coefficients for the unmonitored cylinders (12, 13, 14) based on the engine speed and the crankshaft speed pulsations. [9] The method of claim 7, wherein determining a final ignition timing for the monitored cylinder (11) based on a desired ignition timing (211) and the cylinder internal pressure comprises: Determining a combustion parameter for the combustion event for the monitored cylinder based on the in-cylinder pressure; Determining a first error term based on the combustion parameter and a desired state for the combustion parameter; Determining a control point for the combustion parameter based on the first error term; Determining the desired ignition timing (211) for the monitored cylinder (11) based on an engine operating point; and Determining the final ignition timing for the monitored cylinder (11) based on the desired ignition timing (211) and the combustion parameter checkpoint. [10] Multi-cylinder positive ignition internal combustion engine (10) comprising a monitored cylinder (11) and a plurality of unmonitored cylinders (12, 13, 14); a plurality of pistons arranged in the monitored cylinder (11) and the unmonitored cylinders (12, 13, 14), the pistons being coupled to a crankshaft; a pressure sensor (15) arranged to monitor the internal cylinder pressure in the monitored cylinder (11); a rotational position sensor arranged to monitor the rotational position of the crankshaft; a spark ignition system including a spark controller in communication with a plurality of spark igniters disposed in the monitored cylinder (11) and the plurality of unmonitored cylinders (12, 13, 14); a controller in communication with the pressure sensor (15), the rotational position sensor and the radio control, the controller including a set of instructions executable via the pressure sensor (15) for: Monitoring the in-cylinder pressure for the monitored cylinder (11) during a combustion event for the monitored cylinder (11); Determining a first ignition timing (209) for the monitored cylinder (11) based on a desired ignition timing (211) and the internal cylinder pressure; Controlling the ignition timing for the monitored cylinder (11) based on the final ignition timing via the spark control; Monitoring the engine speed and the crankshaft speed via the rotational position sensor associated with the monitored cylinder (11) and the non-monitored cylinders (12, 13, 14); Determining a modal coefficient for the non-monitored cylinders (12, 13, 14) based on the engine speed and the crankshaft speed pulsations; Determining coefficient errors for the unmonitored cylinders (12, 13, 14) based on the modal coefficients; performing a compensation control to determine an ignition timing setting for each of the unmonitored cylinders (12, 13, 14) based on the coefficient error; Determining final ignition times for the non-monitored cylinders (12, 13, 14) based on the desired ignition timing (211) and the respective ignition timing setting; and Controlling the ignition timing for each of the non-monitored cylinders (12, 13, 14) based on the respective final ignition timing via the spark control.

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