GB2527103A

GB2527103A - A method and system for a spark ignition engine

Info

Publication number: GB2527103A
Application number: GB1410466.5A
Authority: GB
Inventors: James Fraser Andrew Donald; Paul Witton; Peter Deakin; Mike Rowland; Martyn Ball
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2014-06-12
Filing date: 2014-06-12
Publication date: 2015-12-16
Anticipated expiration: 2034-06-12
Also published as: CN105275650A; RU2689888C2; CN105275650B; GB201410466D0; RU2015122737A3; RU2015122737A; GB2527103B; DE102015108864A1

Abstract

A method for a spark ignition internal combustion engine comprising energising a common ignition coil 10 to simultaneously actuate a first spark plug 11 coupled to a first cylinder and a second spark plug 12 coupled to a second cylinder, the spark event in only one of the cylinders initiating combustion with the spark event in the other cylinder being wasted, and selectively delaying an intake valve opening and/or fuel injection for the other cylinder so as to prevent backfire into an intake manifold of the engine. Preferably, the method further comprises adjusting a timing of the ignition coil energisation based on operational conditions of the engine. The method may also comprise determining a likelihood of backfire. Also claimed is an engine ignition system. The method is particularly suitable for stopping misfire in engines comprising variable valve timing in which there is an overlap between a wasted spark event and the start of an intake stroke.

Description

I

A METHOD AND SYSTEM FOR A SPARK IGNITION ENGINE

The present disclosure relates a method and system for a spark ignition engine and particularly but not exclusively relates to a method and system for preventing an intake backfire event.

Background

Internal combustion engines typically comprise intake and exhaust valves to control the flow of gases into and out of a combustion chamber respectively. The performance of the internal combustion engine is at least partially determined by the timing of the valves opening and closing and the extent to which the valves are opened. Typically, the opening and closing of the valves is determined by camshafts, which are constrained to rotate at a fixed ratio of the engine crankshaft speed. With such a system the relative valve timing must be the same for all engine speeds and conditions and as a result compromises are necessary. However, to overcome this constraint, an engine may be provided with a variable valve timing actuation system and/or a variable valve lift actuation system, thereby allowing performance to be improved over the engine operating range.

Whether a variable valve actuation system is provided or not, there may be a period when both the intake and exhaust valves are open at the same time. In particular, the valves may be timed so the intake valve opens slightly before the piston reaches Top Dead Centre (TDC) on the exhaust stroke, Likewise, the exhaust valve may be timed to close just after the piston starts down on the intake stroke. Such an overlap in the opening of the valves may create a siphon effect with the exhaust flow drawing further charge air into the combustion chamber. With a variable valve actuation system this siphon effect may be tailored over the engine operating range.

In addition to the above described valve overlap, early intake valve opening may reduce emissions. Opening the intake valve early may result in some of the inert exhaust gas flowing out of the cylinder via the intake valve, where it may cool in the intake manifold. This inert gas may then enter the cylinder in the subsequent intake stroke, which aids in controlling the temperature of the cylinder and thus the nitrogen oxide emissions. Again, with a variable valve actuation system this effect may be tailored over the engine operating range.

Furthermore, wasted spark ignition systems are commonplace on four stroke spark ignition engines. These systems make use of the fact that exhaust stroke and compression stroke are aligned on pairs of cylinders. With such systems one ignition coil can supply two spark plugs, which are fired together at the timing that is required by the fuelled cylinder, with the spark in the other cylinder being "wasted". Such ignition systems are desirable since they reduce the number of ignition coils required.

The inventors behind the present disclosure have realised that with a variable valve actuation system, which may take advantage of the early intake valve opening scenarios described above, there can be significant overlap between a wasted spark event and the start of the intake stroke. For port injected systems, emission constraints often lead to fuel injection while the intake valve is still closed. As a result, when the intake valve is opened and the wasted spark occurs, an ignitable mixture may be present in the cylinder and the flame may propagate, e.g. backfire, to the intake manifold.

Statements of Invention

According to a first aspect of the present disclosure there is provided a method for a spark ignition internal combustion engine, wherein the method comprises: energising a common ignition coil to simultaneously actuate a first spark event at a first spark plug coupled to a first cylinder of the engine and a second spark event at a second spark plug coupled to a second cylinder of the engine, the engine being configured such that for a particular ignition coil energisation the spark event in only one of the first and second cylinders is intended to initiate combustion with the spark event in the other of the first and second cylinders being wasted; and selectively delaying an intake valve opening and/or fuel injection for the other of the first and second cylinders so as to prevent backfire into an intake manifold of the engine.

The method may further comprise adjusting a timing of the ignition coil energisation based on operational conditions of the engine. The operational conditions may comprise one or more of inlet charge temperature, fuel octane, engine speed and intake manifold pressure.

The method may further comprise determining the scheduled intake valve lift for the other of the first and second cylinders at the spark event The method may further comprise delaying the intake valve opening and/or fuel injection for the other of the first and second cylinders if the scheduled intake valve lift at the spark event for the other of the first and second cylinders is greater than or equal to a maximum tolerated intake valve lift for the other of the first and second cylinders at the spark event.

The method may further comprise determining the maximum tolerated intake valve lift for the other of the first and second cylinders at the spark event. The maximum tolerated intake valve lift at the spark event may be a fixed value, e.g. zero, or may be a function of when the spark event is scheduled to occur.

The method may further comprise delaying the intake valve opening so that the intake valve lift for the other of the first and second cylinders at the spark event is equal to or less than the maximum tolerated intake valve lift for the other of the first and second cylinders at the spark event. Alternatively or additionally, the method may further comprise delaying the fuel injection so that not all of the fuel to be injected is in the other of the first and second cylinders when the spark event occurs. For example, the method may further comprise delaying the fuel injection so that the fuel arrives in the cylinder after the wasted spark event occurs.

The method may further comprise determining a likelihood of backfire into the intake manifold of the engine based on ignition coil energisation timing and intake valve timing.

The method may further comprise determining whether to delay the intake valve opening and/or fuel injection for the other of the first and second cylinders. The method may further comprise adjusting the length of the delay of the intake valve opening and/or the fuel injection as a function of the timing of the ignition coil energisation. The method may further comprise carrying out the determining whether to delay the intake valve opening and/or fuel injection for the other of the first and second cylinders as the engine is operating.

The method may further comprise limiting the opening of the intake valve for the other of the first and second cylinders when the spark event occurs after first and second crank pins associated with the first and second cylinders pass through Top Dead Centre (TDC). The method may further comprise limiting the opening of the intake valve for the other of the first and second cylinders when the spark event occurs after first and second crank pins associated with the first and second cylinders pass through TOC to an amount less than if the spark event occurs before the first and second crank pins pass through TDC.

The method may further comprise limiting the opening of the intake valve to a value less than or equal to 1 mm (e.g. approximately 1 mm), for example when the spark event in the other of the first and second cylinders occurs after first and second crank pins associated with the first and second cylinders pass through Top Dead Centre.

The method may further comprise limiting the opening of the intake valve to a value greater than 1 mm (e.g. greater than approximately 1 mm), for example when the spark event in the other of the first and second cylinders occurs before first and second crank pins associated with the first and second cylinders pass through Top Dead Centre.

(The intake valve opening value may correspond to a distance between a valve closure and a corresponding valve seat, in other words the gap between the valve closure and valve seat.) For the particular ignition coil energisation a first piston in the first cylinder may be in a compression stroke and a second piston in the second cylinder may be in an expansion stroke. In other words, first and second cranks pins associated with the first and second pistons respectively may be aligned, although the first and second pistons may perform different strokes of an engine cycle, such as a four-stroke cycle.

For a subsequent ignition coil energisation, the spark event in the other of the first and second cylinders may be intended to initiate combustion and the spark event in the one of the first and second spark events may be wasted. The method may further comprise selectively delaying the intake valve opening and/or fuel injection for the one of the first and second cylinders so as to prevent backfire into the intake manifold of the engine.

The method may further comprise energising a further common ignition coil to simultaneously actuate a third spark event at a third spark plug coupled to a third cylinder of the engine and a fourth spark event at a fourth spark plug coupled to a fourth cylinder of the engine. The engine may be configured such that for a particular energisation of the further ignition coil the spark event in only one of the third and fourth cylinders is intended to initiate combustion with the spark event in the other of the third and fourth cylinders being wasted. The method may further comprise selectively delaying an intake valve opening and/or fuel injection for the other of the third arid fourth cylinders so as to prevent backfire into the intake manifold of the engine.

According to a second aspect of the present disclosure there is provided an engine ignition system for a spark ignition internal combustion engine, the engine comprising: a first spark plug for initiating a first spark event in a first cylinder of the engine; a second spark plug for initiating a second spark event in a second cylinder of the engine; a common ignition coil coupled to each of the first and second spark plugs; wherein the engine ignition system comprises one or more engine controllers configured to activate the ignition coil to simultaneously energize each of the first and second spark plugs so that the first and second spark events occur concurrently; such that for a particular ignition coil energisation the spark event in only one of the first and second cylinders is intended to initiate combustion with the spark event in the other of the first and second cylinders being wasted; and wherein the engine controllers are further configured to selectively delay opening an intake valve and/or fuel injection for the other of the first and second cylinders so as to prevent backfire into an intake manifold of the engine.

The engine ignition system may further comprise the first and second spark plugs and/or the common ignition coil. The engine may further comprise the intake valve and/or a fuel injector. The fuel injector may inject fuel into an intake manifold in the region of the intake valve.

The one or more controllers may be further configured to carry out any of the above- mentioned methods. An engine control unit may comprise, at least in part, the above-mentioned controllers.

Software which when executed by a computing apparatus may cause the computing apparatus to perform any of the above-mentioned methods. The one or more engine controllers may be provided with computer readable instructions on non-transitory memory for carrying out any of the above-mentioned methods.

A vehicle or engine may comprise the above-mentioned engine ignition system for a spark ignition internal combustion engine.

Brief Description of the Drawings

For a better understanding of the present disclosure, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 shows an engine ignition system for a spark ignition internal combustion engine according to examples of the present disclosure; Figure 2 shows a method for a spark ignition internal combustion engine according to

examples of the present disclosure;

Figure 3 is a graph showing how the intake valve lift may vary with crank angle and the delayed intake valve lift according to a first example of the present disclosure; Figure 4 is a graph showing how the intake valve lift delay may be varied depending on the spark event timing; and Figure 5 is a graph showing how intake valve lift may vary with crank angle and the delayed fuel injection according to a second example of the present disclosure.

Detailed Description

With reference to Figure 1, the present disclosure relates to an engine ignition system for a spark ignition internal combustion engine. The engine comprises a common ignition coil 10 which is electrically coupled to both first and second spark plugs 11, 12.

The first spark plug 11 may initiate a first spark event in a first cylinder of the engine.

Similarly, the second spark plug 12 may initiate a second spark event in a second cylinder of the engine.

The engine ignition system 100 may comprise an engine controller 30. The engine controller 30 may comprise one or more modules for controlling the engine. In particular, the engine controller 30 may be configured to activate the common ignition coil 10, which is coupled to the first and second spark plugs 11, 12. For example, the engine controller 30 may selectively connect a battery 40 to the common ignition coil 10, Accordingly, the engine controller 30, via the common ignition coil 10, may simultaneously energise each of the first and second spark plugs 11, 12, so that the first and second spark events occur concurrently. The engine may operate in a mode in which, at a particular point in the engine cycle, either of the first or second spark events in the respective cylinder is intended to result in a combustion event. By contrast, the other of the first and second spark events in the respective cylinder may not be intended to result in a combustion event and as such may be wasted. At a subsequent point in the engine cycle the combustion event and wasted spark event may swap cylinders. It will be appreciated that the first and second pistons in the respective first and second cylinders may operate in a four stroke regime with the first and second pistons moving together but on different strokes of the cycle.

Referring still to Figure 1, the engine may further comprise a further common ignition coil 20 electrically coupled to both third and fourth spark plugs 21, 22. The third spark plug 21 may initiate a third spark event in a third cylinder of the engine. Similarly, the fourth spark plug 22 may initiate a fourth spark event in a fourth cylinder of the engine.

As for the common ignition coil 10, the further common ignition coil 20 may simultaneously energise each of the third and fourth spark plugs 21, 22 so that the third and fourth spark events occur concurrently. The further common ignition coil 20 may be activated by the engine controller 30, which may selectively connect the battery 40 to the further common ignition coil 20. Only one of the third and fourth spark events in the respective cylinder may be intended to initiate combustion. The other of the third and fourth spark events in the respective cylinder may not be intended to initiate combustion and as a result may be wasted. The combustion event and wasted spark event may swap cylinders for a subsequent ignition coil energisation. Third and fourth pistons in the third and fourth cylinders may also operate in a four stroke cycle with the third and fourth pistons moving together, albeit on different strokes of the cycle.

It will be appreciated that the first, second, third and fourth pistons and respective cylinders may form a four cylinder engine with each piston being arranged to perform a different stroke of the cycle, namely intake, compression, power and exhaust (e.g. expansion) strokes. The first and second pistons may be out of phase with the third and fourth pistons. In other words the first and second pistons may be connected to the crankshaft at a point that is 180° apart from a point on the crankshaft at which the third and fourth pistons are connected. Although a four piston engine has been described above, it will be appreciated that further pistons and cylinders may be provided.

The engine controller 30 or at least a module of the engine controller 30, may be configured to selectively delay opening an intake valve for a cylinder in which a wasted spark event is about to occur. Alternatively or additionally, the engine controller 30, or at least a module thereof, may be configured to selectively delay the injection of fuel into a cylinder or an intake port of the cylinder for which a wasted spark event is about to occur. By delaying the intake valve opening or injection of fuel, the likelihood of the wasted spark event initiating combustion may be reduced.

With reference to Figure 2 a method 200 for a spark ignition internal combustion engine according to an example of the present disclosure will now be described. The method may be carried out in respect of a cylinder in which a wasted spark event is scheduled to occur. The method 200 may be carried out for each wasted spark event in each cylinder or the method 200 may be carried out at any other frequency.

In a first step 210, the engine controller 30, or at least a module thereof, may determine at what point (e.g. crank angle) in the engine cycle the spark event is to occur. The engine controller 30 may also calculate the optimum timing of the spark event based on operational conditions of the engine, such as the inlet charge temperature, fuel octane, engine speed and intake manifold pressure. The timing of the spark event may be adjusted whilst the engine is running and may be adjusted in real time, for example in response to changes in the operational conditions. The first step 210 may comprise such adjustment of the spark timing. However, the spark timing may be adjusted by a different controller or module, in which case the first step 210 may simply obtain the spark timing from such a different controller or module.

In a second step 220 the amount of lift, L, of the intake valve that is scheduled to occur at the spark event may be determined. As for the first step 210, the second step 220 may comprise calculating the optimal intake valve timing. However, the optimal valve timing may be calculated by a different controller or module, in which case the second step 220 may simply obtain the intake valve timing from such a different controller.

With the intake valve timing, the second step 220 may determine the amount of lift that the intake valve is scheduled to have when the wasted spark event occurs.

In a third step 230, the maximum tolerated intake valve lift, Lmax, at the spark event may be determined. The maximum tolerated intake valve lift at the spark event may be a fixed value, for example zero, or it may be a variable value, which may depend on when the spark event occurs. For example, a greater amount of intake valve lift may S be tolerated if the wasted spark event is scheduled to occur before the piston reaches Top Dead Centre (TDC), since the pressure and temperature of the gases in the combustion chamber may be lower. By contrast, if the wasted spark event is scheduled to occur after the piston reaches TDC, the maximum tolerated intake valve lift may be lower due to the higher pressure and temperature of the gases in the combustion chamber. In this respect, the third step 230 may refer to a look-up table which may be stored on the engine controller 30 or a separate memory module. The third step 230 may further comprise interpolating between data points from such a look-

up table.

In a fourth step 240 the amount of intake valve lift, L, that is scheduled to occur at the wasted spark event, which was obtained in the second step 220, is compared with the maximum tolerated intake valve lift, Lmax, at the wasted spark event, which was obtained in the third step 230. If the amount of intake valve lift, L, scheduled to occur at the wasted spark event is greater than the maximum tolerated intake valve lift, Lmax, at the wasted spark event, then the method 200 proceeds to a fifth step 250. However, if the amount of valve lift, L, scheduled to occur at the wasted spark event is less than the maximum tolerated intake valve lift, Lmax, at the wasted spark event then the method 200 proceeds to a sixth step 260 and the fifth step 250 is bypassed.

In the fifth step 250 the controller 30 may delay the intake valve opening so that the intake valve lift at the wasted spark event is less than or equal to the maximum tolerated intake valve lift, Lmax, which was determined in the third step 230.

Alternatively or additionally, the fifth step 250 may delay the injection of fuel, for example by the controller 30 sending a signal to adjust the fuel injection timing. In either case, the amount of time delay required may be calculated within the fifth step 250. The likelihood of a backfire into an intake manifold of the engine may be reduced since there is less air and/or fuel in the combustion chamber when a wasted spark event occurs.

In the sixth step 260 the engine controller 30 may energise one of the ignition coils 10, 20, thereby causing a spark event in the corresponding cylinders. The method 200 may then be repeated, for example for a subsequent spark event or in response to a change in the spark timing.

Although the method 200 has been described above with reference to a number of steps, it will be appreciated that the steps may be carried out in a different order.

Furthermore, two or more of the steps may be carried out concurrently, for example, the second and third steps 220, 230 may be carried out in parallel.

With reference to Figures 3 and 4 a first example of the present disclosure will now be described. In the graph shown in Figure 3, the vertical axis 310 corresponds to the amount of intake valve lift, whUst the horizontal axis 320 corresponds to the crank angle with zero degrees being Top Dead Centre (TDC) for a particular cylinder and piston.

(BTDC denotes Before Top Dead Centre and ATDC denotes After Top Dead Centre.) The unadjusted scheduled intake valve lift profile is denoted by line 340. The timing of the wasted spark event is denoted by 330. In the second step 220 of the method 200, the intake valve lift at the scheduled spark event 330 is determined. In the fifth step 250, the opening of the intake valve may be delayed so as to reduce the lift of the intake valve at the spark event. The delayed intake valve profile is denoted by reference numeral 350. By delaying the intake valve opening the amount of intake valve lift has been reduced from L to L2d, which may be equal to or less than Lmax. The amount of air (and optionally fuel) in the cylinder of the wasted spark event has been reduced and as a result the likelihood of the wasted spark event initiating combustion has also been reduced. Although Figure 3 shows the entire profile for the intake valve opening being delayed, in an alternative arrangement the opening of the intake valve may be delayed, but the closing of the intake valve may remain unchanged or delayed by a different amount. In such circumstances, to compensate for a reduced intake of air, the intake valve may open by a greater amount once the wasted spark event has occurred.

Referring now to Figure 4, an example of how the maximum tolerated intake valve lift, Lmax, at the wasted spark event may vary with respect to the timing of the spark event is shown. The vertical axis 410 corresponds to the intake valve lift and the horizontal axis 420 corresponds to the crank angle at which the wasted spark event is scheduled to occur. The relationship between the maximum tolerated intake valve lift, Lmax, and the timing of the spark event is denoted by line 430. As is shown the maximum tolerated intake valve lift may reduce as the wasted spark event is scheduled to occur later in the engine cycle. The reduction in the maximum tolerated intake valve lift may level off for wasted spark events that are scheduled to occur after Top Dead Centre. The maximum tolerated intake valve lift may level off to an intake valve lift value of approximately 1mm. It has been found that the likelihood of a flame propagating through a gap of 1mm or less is low. Therefore, an intake valve lift value of approximately 1mm or less may be tolerated when a wasted spark event occurs at or after TDC. By contrast, if the wasted spark event is scheduled to occur before TDC then a greater intake valve lift may be tolerated because the pressures and temperatures in the combustion chamber may be lower and the likelihood of a wasted spark event initiating combustion is lower.

The relationship depicted in Figure 4 is merely one example of the functional relationship between the maximum tolerated intake valve lift, Lmax, and the wasted spark event timing. It will be appreciated that this functional relationship may take other forms, for example the maximum tolerated intake valve lift, [max, may be a constant value, such as 1mm or even zero mm. The form of the relationship between the maximum tolerated intake valve lift and the timing of the wasted spark event may be determined by experiment or by calculation. The relationship between the maximum tolerated intake valve lift and the timing of the wasted spark event may be stored in a memory module associated with the engine controller 30, for example in the form of a look-up table comprising a number of discrete points from line 430, which may be interpolated between.

Tuming now to Figure 5, a second example of the present disclosure will be described.

The graph shown in Figure 5 is similar to that shown in Figure 3 in that vertical axis 510 represents the amount of intake valve lift, horizontal axis 520 represents the crank angle and line 530 denotes the timing of the wasted spark event. Furthermore, the scheduled amount of lift for the intake valve as a function of the crank angie is denoted by reference numeral 540. As described above, in the fifth step 250 the timing of the fuel injection may be delayed. In this respect, Figure 5 depicts the unadjusted fuel injection timing 550 with the Start Of Injection (SQl) being denoted by 552 and the End Of Injection (EOl) being denoted by 554. In a particular example, the fuel may be injected into an intake port which is upstream of the intake valve, however, it is also envisaged that the fuel may be injected directly into the cylinder. In the particular example of the fuel being injected into the intake pod, there may as a result be a delay in the fuel reaching the cylinder since the fuel may not flow into the cylinder until the intake valve has been opened. The fuel transport delay in the case of the fuel injection timing being unadjusted is denoted by 556 and as depicted the fuel may have entered the cylinder shortly after the intake valve has opened.

In the event that the fourth step 240 determines that the scheduled intake valve lift at the wasted spark event is greater than the maximum tolerated intake valve lift, the injection of the fuel may be delayed. The timing of the delayed fuel injection is denoted by 560 with the start of the adjusted injection being denoted by 562 and the end of the adjusted injection being denoted by 564. Since the fuel injector may be upstream of the intake valve there may be a transport delay for the fuel to enter the cylinder and this delay is denoted by reference numeral 566 in the event that the fuel injection is delayed by a fifth method step 250. The fuel transport delay 566 may apply from the start of the adjusted injection 562 because the start of the adjusted injection 562 may occur after the intake valve has opened. As a result, the injected fuel may be immediately carried up by the flowing intake air rather than having to wait for the opening of the intake valve. Accordingly the fuel transport delay 566 is depicted as starting from the start of the adjusted injection 562.

As depicted, the fuel injection may be adjusted so that the fuel arrives in the cylinder after the wasted spark event occurs. The start of the adjusted injection 562 may thus occur before the wasted spark event occurs taking into account the transport delay 566. With the fuel arriving in the cylinder after the wasted spark event has occurred the likelihood of the wasted spark event initiating combustion has been reduced. Although Figure 5 depicts the fuel arriving after the wasted spark event has occurred, it is also envisaged that the adjusted fuel injection may allow some fuel to arrive before the wasted spark event occurs, for example provided that the concentration of the fuel in the cylinder when the spark event occurs is sufficiently low such that the likelihood of the wasted spark event igniting combustion is also low.

It will be appreciated that the functional relationship between the maximum tolerated intake valve lift and the wasted spark event timing, e.g. as depicted in Figure 4, may apply equally to the second example of the present disclosure. In other words, the fuel injection may be delayed if the scheduled intake valve lift at the wasted spark event exceeds the maximum tolerated intake valve lift.

The method and systems described herein may be applied to an engine that comprises valve actuators that may vary the timing and/or extent of the valve opening. For example, the intake valve lift may be adjusted with a variable lift control device or via variable camshaft timing with a fixed lift profile.

It will be appreciated that the one or more controllers may comprise further modules configured to carry out any of the above-mentioned methods. For example, the controllers may determine which of the operational modes the internal combustion engine operates in. It will also be appreciated that the controllers may comprise pre- existing controllers that have been re-programmed to carry out any of the above-mentioned methods. Furthermore, the method and system described herein require no extra hardware and can thus be readily deployed with little additional cost. It could also be retrofitted to existing vehicles if required.

It has been discovered that the likelihood of a backfire event occurring may be greatest when the wasted spark occurs after TDC (e.g. due to a combination of a high compression ratio, high intake temperature) and/or if there is more than 1 mm of intake valve lift (e.g. as such a gap may allow a flame to propagate through the valve). The present disclosure advantageously realises these factors and reduces the likelihood of the backfire event from occurring.

It will be appreciated by those skilled in the art that although the invention has been described by way of example with reference to one or more examples, it is not limited to the disclosed examples and that alternative examples could be constructed without departing from the scope of the invention as defined by the appended claims.

Claims

Claims 1. A method for a spark ignEtion internal combustion engine, wherein the method comprises: energising a common ignition coil to simultaneously actuate a first spark event at a first spark plug coupled to a first cylinder of the engine and a second spark event at a second spark plug coupled to a second cylinder of the engine, the engine being configured such that for a particular ignition coil energisation the spark event in only one of the first and second cylinders is intended to initiate combustion with the spark event in the other of the first and second cylinders being wasted; and selectively delaying an intake valve opening and/or fuel injection for the other of the first and second cylinders so as to prevent backfire into an intake manifold of the engine.
2. The method of claim I further comprising: adjusting a timing of the ignition coil energisation based on operational conditions of the engine.
3. The method of claim I or 2 further comprising: determining the scheduled intake valve lift for the other of the first and second cylinders at the spark event.
4. The method of claim 3 further comprising: delaying the intake valve opening and/or fuel injection for the other of the first and second cylinders if the scheduled intake valve lift at the spark event for the other of the first and second cylinders is greater than or equal to a maximum tolerated intake valve lift for the other of the first and second cylinders at the spark event.
5. The method of claim 4 further comprising: determining the maximum tolerated intake valve lift for the other of the first and second cylinders at the spark event.
6. The method of claim 4 or 5 further comprising: delaying the intake valve opening so that the intake valve lift for the other of the first and second cylinders at the spark event is equal to or less than the maximum tolerated intake valve lift for the other of the first and second cylinders at the spark event.
7. The method of any of claims 4 to 6 further comprising: delaying the fuel injection so that not all of the fuel to be injected is in the other of the first and second cylinders when the spark event occurs.
8. The method of any of the preceding claims further comprising: determining a likelihood of backfire into the intake manifold of the engine based on ignition coil energisation timing and intake valve timing.
9. The method of any of the preceding claims further comprising: determining whether to delay the intake valve opening and/or fuel injection for the other of the first and second cylinders.
10. The method of any of the preceding claims further comprising: adjusting the length of the delay of the intake valve opening and/or the fuel injection as a function of the timing of the ignition coil energisation.
11. The method of claim 9 or 10 further comprising: carrying out the determining whether to delay the intake valve opening and/or fuel injection for the other of the first and second cylinders as the engine is operating.
12. The method of any of the preceding claims wherein for the particular ignition coil energisation a first piston in the first cylinder is in a compression stroke and a second piston in the second cylinder is in an expansion stroke.
13 The method of any of the preceding claims wherein for a subsequent ignition coil energisation the spark event in the other of the first and second cylinders is intended to initiate combustion and the spark event in the one of the first and second spark events is wasted; the method further comprising: selectively delaying the intake valve opening and/or fuel injection for the one of the first and second cylinders so as to prevent backfire into the intake manifold of the engine.
14. The method of any of the preceding claims further comprising: energising a further common ignition coil to simultaneously actuate a third spark event at a third spark plug coupled to a third cylinder of the engine and a fourth spark event at a fourth spark plug coupled to a fourth cylinder of the engine, the engine being configured such that for a particular energisation of the further ignition coil the spark event in only one of the third and fourth cylinders is intended to initiate combustion with the spark event in the other of the third and fourth cylinders being wasted; and selectively delaying an intake valve opening and/or fuel injection for the other of the third and fourth cylinders so as to prevent backfire into the intake manifold of the engine.
15. An engine ignition system fora spark ignition internal combustion engine, the engine comprising: a first spark plug for initiating a first spark event in a first cylinder of the engine; a second spark plug for initiating a second spark event in a second cylinder of the engine;and a common ignition coil coupled to each of the first and second spark plugs; wherein the engine ignition system comprises one or more engine controllers configured to activate the ignition coil to simultaneously energize each of the first and second spark plugs so that the first and second spark events occur concurrently; such that for a particular ignition coil energisation the spark event in only one of the first and second cylinders is intended to initiate combustion with the spark event in the other of the first and second cylinders being wasted; and wherein the engine controllers are further configured to selectively delay opening an intake valve and/or fuel injection for the other of the first and second cylinders so as to prevent backfire into an intake manifold of the engine.
16. The engine ignition system of claim 15, wherein the one or more engine controllers are further configured to carry out the method of any of claims 2 to 14.
17. Software which when executed by a computing apparatus causes the computing apparatus to perform the method of any of claims I to 14.
18. A vehicle or engine comprising the engine ignition system for a spark ignition internal combustion engine of claim 15 or 16.
19. A method for a spark ignition internal combustion engine substantially as described herein with reference to and as shown in Figures 2 to 5.
20. An engine ignition system for a spark ignition internal combustion engine substantially as described herein with reference to and as shown in Figures 1 and 3 to 5.Amendments to the claims have been filed as follows Claims 1. A method for a spark ignition internal combustion engine, wherein the method comprises: energising a common ignition coil to simultaneously actuate a first spark event at a first spark plug coupled to a first cylinder of the engine and a second spark event at a second spark plug coupled to a second cylinder of the engine, the engine being configured such that for a particular ignition coil energisation the spark event in only one of the first and second cylinders is intended to initiate combustion with the spark event in the other of the first and second cylinders being wasted; determining the scheduled intake valve lift for the other of the first and second cylinders at the spark event; and selectively delaying an intake valve opening and/or fuel injection for the other of the first and second cylinders so as to prevent backfire into an intake manifold of the engine.2. The method of claim 1 further comprising: 0 adjusting a timing of the ignition coil energisation based on operational conditions LCD of the engine.3. The method of claim 1 or 2 further comprising: delaying the intake valve opening and/or fuel injection for the other of the first and second cylinders if the scheduled intake valve lift at the spark event for the other of the first and second cylinders is greater than or equal to a maximum tolerated intake valve lift for the other of the first and second cylinders at the spark event.4. The method of claim 3 further comprising: determining the maximum tolerated intake valve lift for the other of the first and second cylinders at the spark event.5. The method of claim 3 or4 further comprising: delaying the intake valve opening so that the intake valve lift for the other of the first and second cylinders at the spark event is equal to or less than the maximum tolerated intake valve lift for the other of the first and second cylinders at the spark event.6. The method of any of daims 3 to 5 further comprising: delaying the fuel injection so that riot aD of the fuel to be injected is in the other of the first and second cylinders when the spark event occurs.7. The method of any of the preceding claims further comprising: determining a likelihood of backfire into the intake manifold of the engine based on ignition coil energisation timing and intake valve timing.8. The method of any of the preceding claims further comprising: determining whether to delay the intake valve opening and/or fuel injection for the other of the first and second cylinders.9. The method of any of the preceding claims further comprising: adjusting the length of the delay of the intake valve opening and/or the fuel injection as a function of the timing of the ignition coil energisation.co 10. The method of claim 8 or 9 further comprising: o carrying out the determining whether to delay the intake valve opening and/or LI) fuel injection for the other of the first and second cylinders as the engine is operating. o 2011. The method of any of the preceding claims wherein for the particular ignition coil energisation a first piston in the first cylinder is in a compression stroke and a second piston in the second cylinder is in an expansion stroke.12. The method of any of the preceding claims wherein for a subsequent ignition coil energisation the spark event in the other of the first and second cylinders is intended to initiate combustion and the spark event in the one of the first and second spark events is wasted; the method further comprising: selectively delaying the intake valve opening and/or fuel injection for the one of the first and second cylinders so as to prevent backfire into the intake manifold of the engine.13. The method of any of the preceding claims further comprising: energising a further common ignition coil to simultaneously actuate a third spark event at a third spark plug coupled to a third cylinder of the engine and a fourth spark event at a fourth spark plug coupled to a fourth cylinder of the engine, the engine being configured such that for a particuiar eriergisation of the further ignition coil the spark event in only one of the third and fourth cylinders is intended to initiate combustion with the spark event in the other of the third and fourth cylinders being wasted; and selectively delaying an intake valve opening and/or fuel injection for the other of the third and fourth cylinders so as to prevent backfire into the intake manifold of the engine.14. An engine ignition system for a spark ignition internal combustion engine, the engine comprising: a first spark plug for initiating a first spark event in a first cylinder of the engine; a second spark plug for initiating a second spark event in a second cylinder of the engine; and a common ignition coil coupled to each of the first and second spark plugs; wherein the engine ignition system comprises one or more engine controllers configured to activate the ignition coil to simultaneously energize each of the first and second spark plugs so that the first and second spark events occur concurrently; such that for a particular ignition coil energisation the spark event in only one of the first and o second cylinders is intended to initiate combustion with the spark event in the other of LCD the first and second cylinders being wasted; and o 20 wherein the engine controllers are further configured to determine the scheduled intake valve lift for the other of the first and second cylinders at the spark event and selectively delay opening an intake valve and/or fuel injection for the other of the first and second cylinders so as to prevent backfire into an intake manifold of the engine.15. The engine ignition system of claim 14, wherein the one or more engine controllers are further configured to carry out the method of any of claims 2 to 13.16. Software which when executed by a computing apparatus causes the computing apparatus to perform the method of any of claims ito 13.17. A vehicle or engine comprising the engine ignition system for a spark ignition internal combustion engine of claim 14 or 15.18. A method for a spark ignition internal combustion engine substantially as described herein with reference to and as shown in Figures 2 to 5.19. An engine ignition system for a spark ignition interna combustion engine substantiaHy as described herein with reference to and as shown in Figures 1 and 3 to 5. IC)CO IC)