JPH07139359A - Intake system of multiple cylinder engine - Google Patents

Abstract

PURPOSE:To smoothly propagate a positive pressure wave through a communicating passage and through between independent intake passages in a multiple cylinder engine intake system having a butterfly shutter valve in the vicinity of the junction of each independent intake passage with a communicating passage which mutually communicates independent intake passages on the way. CONSTITUTION:A communicating passage consists of a second volume chamber 8b and a second passage 13. A shutter valve 14 is installed in the vicinity of the junction of the second passage 13 with an independent intake passage 6. The shutter valve 14 turns, when it opens, in such a direction that the downstream edge of the independent intake passage of the shutter valve 14 moves toward the independent passage 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an intake system for a multi-cylinder engine which utilizes the dynamic effect of intake air to improve output.

[0002]

2. Description of the Related Art Conventionally, in an intake system of an engine, a negative pressure wave (pressure wave of negative pressure) generated at the start of intake is reflected at the atmosphere on the upstream side of the intake passage or at the open end to the intake expansion chamber and a positive pressure wave ( The pressure wave of positive pressure) is returned to the intake port, and the positive pressure wave reaches the intake port just before closing the intake valve and pushes the intake air into the combustion chamber. It is known to increase the charging efficiency of intake air by the effect. When such a technique is used, if the shape of the intake passage is constant, the vibration cycle of the pressure wave generated in the intake passage and the opening / closing cycle of the intake valve are matched to enhance the intake inertia effect. Limited to specific rotation range.

Therefore, in the past, Japanese Patent Laid-Open No. 56-11581 has been used.
As disclosed in Japanese Patent Publication No. 9, the length of the intake passage is changed according to the number of revolutions of the engine. For example, the intake passage for each cylinder is bifurcated in the upstream portion to form a long passage and a short passage. And the upstream ends of these passages are opened to the intake expansion chamber and the like, and a control valve is provided in a short passage so that the effective length of the intake passage is shortened by opening this control valve in the high rotation range. (See FIG. 6 of the above publication) is proposed, and the intake device of the engine can enhance the inertial effect of intake air in the low rotation range and the high rotation range.

[0004]

Immediately after the intake valve of the engine is closed, the inertia of the intake air compresses the intake air, and a compression wave (positive pressure wave) is generated in the vicinity of the intake port.

Therefore, the inventors of the present invention connect the middle portions of the independent intake passages for each cylinder to each other through the communication passages, and make butterfly shutters near the confluence of the communication passages and the individual intake passages. A valve is provided, and in a high rotation range, a positive pressure wave generated immediately downstream of the intake valve of one cylinder on the downstream side of the independent intake passage of the cylinder (in the vicinity of the intake port) is introduced into the intake passage through the communication passage. The invention has been invented to propagate to the independent intake passage of another cylinder at the final stage (immediately after closing the valve), and improve the intake charging efficiency by the pushing action (supercharging action) of the intake due to this positive pressure wave.

However, as a result of various studies using the intake system of the engine having the above structure, the present inventors have found that the intake charging efficiency greatly differs depending on the rotating direction of the shutter valve.

In view of the above, according to the present invention, the positive pressure wave is smoothly propagated between the communication passage and each of the independent intake passages by limiting the rotating direction of the shutter valve.
The purpose is to improve the charging efficiency of intake air.

[0008]

In order to achieve the above-mentioned object, the invention of claim 1 provides a communication passage for connecting the midway portions of the independent intake passages for introducing intake air to each cylinder, and the communication passage. And a butterfly-type shutter valve that is provided in the vicinity of the confluence of each of the independent intake passages and that opens and closes the communication passage, and the shutter valve has an end portion on the downstream side of the independent intake passage when the independent intake passage is opened. The structure is provided so as to rotate to the side.

Further, according to the invention of claim 2, the length of the communication passage is made as short as possible. Therefore, in the structure of claim 1, the shutter valve has the end portion on the downstream side of the independent intake passage when the shutter valve is opened. A structure is provided in which the end portion on the upstream side of the independent intake passage that is advanced inside is retracted into the communication passage.

Further, according to the invention of claim 3, the positive pressure wave is propagated more smoothly between the communication passage and each of the independent intake passages. Therefore, in the structure of claim 1 or 2, the communication passage and the independent intake passage are connected to each other. A configuration is added in which the merging portion is formed so that the intersecting angle of each of the communication passage and the independent intake passage in the intake flow direction is an acute angle.

[0011]

According to the structure of the first aspect of the present invention, the butterfly shutter valve is provided so that the end portion on the downstream side of the independent intake passage is rotated to the independent intake passage side when the valve is opened, so that the intake valve is closed. Immediately after that, the positive pressure wave generated near the intake port smoothly propagates from the end of the shutter valve on the downstream side of the independent intake passage to the inside of the communication passage along the surface on the communication passage side, and then to the independent intake passage of the intake stroke. The shutter valve provided in the vicinity of the junction with the communication passage smoothly propagates into the independent intake passage along the surface on the communication passage side.

According to the invention of claim 2, when the shutter valve is opened, the downstream end of the independent intake passage advances into the independent intake passage, while the upstream end of the independent intake passage communicates with the continuous valve. Since it is provided so as to be retracted into the passage, the length of the communication passage can be shortened, and the intake resistance of the independent intake passage is reduced despite the structure in which the end of the shutter valve advances into the independent intake passage when the valve is opened. Can be suppressed.

Further, according to the structure of the third aspect of the present invention, the merging portion of the communication passage and the independent intake passage is formed such that the intersecting angle of each of the communication passage and the independent intake passage in the intake flow direction is an acute angle. The positive pressure wave propagates more smoothly between the communication passage and the independent intake passage.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings.

1 to 4 show an embodiment in which the present invention is applied to a 4-cylinder 4-cycle engine. In the figure,
Reference numeral 1 denotes an engine body including a cylinder block 2 and a cylinder head 3, and the like. The engine body 1 has first to fourth four cylinders 4, 4, ... Each cylinder 4 has a combustion chamber 5
Are formed.

Reference numeral 6 denotes an independent intake passage provided independently of each other for each cylinder, and each independent intake passage 6 is formed in the cylinder head 3 and constitutes an intake port forming a downstream end portion of the independent intake passage 6. It opens to the combustion chamber 5 of each cylinder 4 via 7. The reference numeral 8 designates an intake expansion chamber composed of a substantially rectangular tubular tank extending parallel to the longitudinal direction of the engine. The intake expansion chamber 8 is vertically partitioned by a partition plate 9 and has a relatively large volume on the upper side. It is divided into a volume chamber 8a and a second volume chamber 8b having a relatively small volume on the lower side. The upstream ends of the independent intake passages 6, 6 ... Are connected to the first volume chamber 8a of the intake expansion chamber 8 with substantially the same passage length. An intake air introducing pipe 10 for introducing outside air is connected to one end surface of the first volume chamber 8a, and a throttle valve 11 for controlling an intake air amount is provided in the intake air introducing pipe 10.
The intake air introduced into the first volume chamber 8a by the intake introduction pipe 10 is supplied to the combustion chamber 5 of each cylinder 4 through each independent intake passage 6. An intake valve 12 is provided in the intake port 7.

Further, a second passage 13 is branched from an intermediate portion of each of the independent intake passages 6, and each of the second passages 13,
The other ends of 13 ... Are connected to the second volume chamber 8b of the intake expansion chamber 8 with substantially the same passage length, whereby the independent intake passages 6 are formed by the second volume chamber 8b and the second passages 13. , 6 ... communicate with each other, and the second
The volume chamber 8b and the second passage 13 form a communication passage. In this case, as shown in FIG. 1, the second passage 13 joins the independent intake passage 6 at an acute intersection angle.

A butterfly type shutter valve 14 for opening and closing the second passage 13 is provided in the vicinity of the opening of each of the second passages 13. Each shutter valve 14 extends in the longitudinal direction of the intake expansion chamber 8. It is rotatably supported by a valve shaft 15 extending in parallel with. In this case, as shown by the alternate long and short dash line in FIG. 1, one end of the shutter valve 14 advances into the independent intake passage 6 while the other end of the shutter valve 14 retreats into the second passage 13 and one end thereof is a shutter. It is provided so as to be located on the downstream side in the intake air inflow direction with respect to the rotation axis of the valve 14. Shutter valve 1
4 is provided, the intake air flowing through the independent intake passage 6 flows downstream along the surface of the butterfly shutter valve on the independent intake passage side, so that one end of the shutter valve 14 enters the independent intake passage 6 when the valve is opened. Despite the advance, it is possible to suppress the increase in intake resistance as much as possible.

Although not shown, each shutter valve 14 is controlled to be opened / closed via an actuator by a control circuit that receives an output of engine speed detecting means or the like, and each independent intake passage 6 by the second volume chamber 8b. , 6 ... Controls communication between each other according to the engine operating state, and is controlled so as to be closed in a low speed range where the engine speed is lower than a set value and opened in a high speed range where the engine speed is higher than the set value. It It should be noted that the opening / closing operation of the shutter valve 14 according to the engine speed as described above may be performed at least during high load when output is required, and when the load is low, the shutter valve 14 is opened or closed. It may be kept.

In such an intake system, 16 is the intake expansion chamber 8 and each of the independent intake passages 6 and 6.
, And each of the second passages 13, 13 ..., which is an intake system structure, and the structure 16 is a tank that constitutes the intake expansion chamber 8 (first volume chamber 8a and second volume chamber 8b). The part 17 and a part of the constituent wall, that is, the side wall and the lower wall, which extend around the periphery of the tank part 17 from the upper side of the side opposite to the engine side of the tank part 17 to the side and the lower side. The integral intake pipe integrally forming the upstream side portions 6a, 6a ... Of the independent intake passages 6, 6 ... so that the upstream ends thereof open to the upper side of the side of the tank portion 17 (first volume chamber 8a). .. and the respective integral intake pipe portions 18, 1
8 ... Branches from the lower side toward the engine side for each cylinder, and extends downstream from the independent intake passages 6, 6 ...
6b, and the lower wall of the constituent walls of the tank portion 17 (second volume chamber 8b) in the vicinity of the branch intake pipe portion 19 of each of the integral intake pipe portions 18 described above. Then, the communicating pipe portions 20, 2 integrally forming the second passage 13 communicating with the second volume 8b in the middle of each independent intake passage 6
0 and a flange portion 21 that connects the tip portions of the branch intake pipe portions 19, 19 to each other, and the flange portion 21 connects the branch intake pipe portion 19 to the engine body 1 downstream of the independent intake passage. The side portions 6b are fixed to the engine body 1 by inserting and tightening the bolts 22 from the side while the side portions 6b are fitted to the intake ports 7 of the cylinders 4.
The upper part of the side of the tank portion 17 on the engine side is formed so as to bulge toward the engine side.
The volume of a is secured sufficiently.

Further, the independent intake passage downstream side portion 6b of each branch intake pipe portion 19 and each intake port 7 extend in a substantially straight line from diagonally above toward the combustion chamber 5 and open into the combustion chamber 5. Has been formed. An injection valve mounting hole 23 is formed in the upper portion of the branch intake pipe portion 19 near the downstream end of the independent intake passage downstream side portion 6b.
4 has its tip injection port portion inserted and fixed in the mounting hole 23 via a seal ring 23a. This mounting hole 23
The fuel injection valve 24 is mounted so that the fuel from the injection valve 24 is injected toward the intake valve 12 of the combustion chamber 5, and the fuel injection valves 24, 24 ... Are arranged in the longitudinal direction of the engine. The fuel supply pipes 25 arranged in parallel are communicatively connected. As a result, the fuel injection valve 24 is mounted in a lying state substantially along the branch intake pipe portion 19, and the intake expansion chamber 8 (tank portion 17 is provided on the extension line 1 of the center line of the fuel injection valve 24). ) Is located close to the fuel injection valve 24 and the fuel supply pipe 25.

Further, the second passage 13 of each of the communicating pipe portions 20.
Is provided with the shutter valve 14, and the intake expansion chamber 8 (tank portion 17) is provided with a center extension line l of the fuel injection valve 24.
Since it is located above, the intake system structure 16 has the intake expansion chamber 8 in the tank portion 17 at a position lower than the center extension line 1 and including the second passages 13, 13.
Of the second volume chamber 8b and the first volume chamber 8 of the intake expansion chamber 8
It is formed by dividing the upper and lower parts of the tank part 17 and each integral intake pipe part 18 at a position of the partition plate 9 between a and a by a dividing surface along the longitudinal direction of the intake expansion chamber 8. , 18 ... Upper half 1 integrally formed with the upper half part
6a, the lower half of the tank portion 17, the integrated intake pipe portions 18, 1
8 is composed of a lower half part, branch intake pipe parts 19, 19 ..., communication pipe parts 20, 20 ... and a lower part 16b integrally formed with a flange part 21, and both parts 16a, 16b.
Are joined via the partition plate 9, and the bolts 26, 26 ...
Are tightly connected by inserting from below and tightening.

Further, as shown in detail in FIG. 4, each of the second passages 13 is formed in the lower wall of the tank portion 17 (second volume chamber 8b).
Of the shutter valve 14 are rotatably supported by the boss portions 27, 27, ... Between the openings of the second volume chamber 8b and both ends thereof. Rib portions 28, 28 ... Which are annularly raised so as to continuously connect the boss portions 27, 27 are integrally formed on the valve seat portion on which the valve body 14a of the valve 14 is seated. Intake expansion chamber 8 is formed by bosses 27, 27 ...
The rigidity of the (tank part 17) in the longitudinal direction of the engine is increased.

Further, as shown in FIG. 4, the second passage 13 is drilled from the second volume chamber 8b side by a drill. The connection portion of the second passage 13 with the independent intake passage is smoothed.
Formed in the second portion 13 to suppress the change of the passage cross-sectional area of the second passage 13 to be small and gentle, and to prevent the flow resistance from the second volume chamber 8b to the independent intake passage 6 via the second passage 13 and its change. Is kept small. Further, 29 is a rib portion which is formed along the boss portion 27 and which connects the annular rib portions 28, 28 around the opening of the second passage 13 to each other.

Next, the operation of the above embodiment will be described. When the shutter valves 14 are closed and the second passage 13 is closed, the communication between the independent intake passages 6, 6 ... By the second volume chamber 8b is cut off. In this state, the negative pressure wave generated in the intake stroke of each cylinder 4 propagates to the first volume chamber 8a and is reflected there, that is, the negative pressure wave and its reflected wave propagate through a relatively long passage, so that the low pressure wave is reduced. In the rotation range, the vibration cycle of such a pressure wave matches the intake valve opening / closing cycle, the inertia effect of intake air in the low rotation range is enhanced, and the intake charging efficiency is enhanced.

On the other hand, in a state where the shutter valves 14 are opened, the second passage 13 is opened, and the independent intake passages 6, 6 ... Are communicated with each other by the second volume chamber 8b, The negative pressure wave generated in the intake stroke is reflected by the second volume chamber 8b through the second passage 13 and the passage length used for propagating the negative pressure wave and the reflected wave is shortened. The inertial effect is enhanced, and the pressure wave propagating from other cylinders in this operating range also receives the second volume chamber 8b.
Thus, the filling efficiency in the high rotation range is significantly improved. Therefore, at least when the load is high, at a predetermined rotational speed corresponding to an intermediate rotational speed of each rotational speed at which the intake inertia effect of the low rotational speed and the high rotational speed is obtained,
By closing the shutter valve 14 on the lower rotation side and opening the shutter valve 14 on the higher rotation side than this, the intake charging efficiency can be increased and the output can be improved in the entire rotation range. In particular, the intake charge efficiency in the high engine speed range is further enhanced by the pressure propagation action between the cylinders, as compared with the conventional case where the intake passage is simply shortened to increase the inertia effect. .

Further, when the intake stroke ends and the intake valve 12 closes the intake port of the combustion chamber 5, the pressure wave is transmitted to the intake port 7 of the independent intake passage 6 by the propagation of the reflected wave, but the pressure wave is intaken. After being reflected by the valve 12, the second passage 1
3 and the second volume chamber 8b to be propagated and introduced into the independent intake passage 6 in the intake stroke. In this case, since the second passage 13 merges with the independent intake passage 6 with an acute angle of intersection, the pressure wave is transmitted from the independent intake passage 6 after the intake stroke to the middle of the independent intake passage 6. After being smoothly introduced into the second passage 13 that opens in the section, the second volume chamber 8b and the second passage 13 that opens in the middle of the independent intake passage 6 in the intake stroke smoothly into the independent intake passage 6 in the intake stroke. be introduced. Therefore, the pressure wave is efficiently transmitted to the intake port 7 of the independent intake passage 6, so that the intake charging efficiency is improved.

The sizes of the first and second volume chambers 8a and 8b suitable for effectively exhibiting the above-mentioned action are as follows: the first volume chamber 8a has a capacity of 0.5 times the displacement or more. It is desirable that the volume of the second volume chamber 8b be 1.5 times or less the displacement. Further, the second volume chamber 8b
It is desirable to make the volume smaller than that of the first volume chamber 8a, and make the cross-sectional area of the second volume chamber 8b larger than the cross-sectional area of each independent intake passage 6.

In this case, the intake expansion chamber 8 (the first volume chamber 8a and the second volume chamber 8b in the intake system structure 16).
), An integral intake pipe portion 18 that constitutes the upstream portion 6a of each independent intake passage 6, a branch intake pipe portion 19 that constitutes the downstream portion 6b of each independent intake passage 6, and each second passage. 13 and the communication pipe portion 20 constituting each unit 13, the individual intake passages 6 bypass the periphery of the intake expansion chamber 8 and are integrally formed by utilizing a part of the constituent wall of the intake expansion chamber 8 (tank portion 17). Since the second passages 13 are formed integrally with a part of the constituent wall of the intake expansion chamber 8 (second volume chamber 8b), the required length of the independent intake passage 6 and the intake air are increased. The first and second volume chambers 8a, 8 of the expansion chamber 8
In obtaining each required volume of b, these intake systems can be made compact and small, so that the required length and required volume can be sufficiently secured in a limited space (engine room). Therefore, the vehicle mountability can be improved.

Further, in this case, the fuel injection valve 24 is near the downstream end of the branch intake pipe portion 19, that is, on the downstream side of the independent intake passage 6, and the injected fuel is responsive to the combustion chamber 5 with good atomization. The tank portion 17 (the intake expansion chamber 8) of the intake system structure 16 is located close to the center extension line 1 of the fuel injection valve 24 because it is mounted toward the combustion chamber 5 for supply. , And it is necessary to dispose the shutter valve 14 in each of the second passages 13. Therefore, the intake system structure 16 in the tank portion 17 is located below the center extension line 1, that is, on the side of the branch intake pipe portion 19 and at the position of the partition plate 9 along the longitudinal direction of the intake expansion chamber 8. Upper divided body 16a and lower divided body 1 vertically
6b and the two divided bodies 16a, 16b are joined together via the partition plate 9, so that the lower divided body 16b is attached to the engine body 1 by the flange portion 21 of the bolt 2 from the side.
After mounting by tightening with 2, the lower divided body 16
Each fuel injection valve 24 is attached by inserting the fuel injection valve 24 into the injection valve mounting hole 23 of each branch intake pipe portion 19 of b from the direction of the center extension line 1 and fixing the fuel supply pipe 25 to the lower split body 16b. At the same time, the shutter valve 14 is inserted into the second passage 13 of each communication pipe portion 20 of the lower divided body 16b from above.
Is fixed to the valve shaft 15, and then the upper divided body 16a is joined to the lower divided body 16b with the partition plate 9 interposed therebetween, and the bolts 26 are tightened from below so that both 16a and 16b are joined together. By integrally connecting the shutter valve 14 and the fuel injection valve 24, it is possible to secure good moldability and easily assemble the upper and lower split bodies 16a and 16b. Can be performed easily, and good assembling property can be secured.

Moreover, since the upper divided body 16a and the lower divided body 16b are coupled by tightening the bolts 26 from below, the tank portion 17 is secured as described above while ensuring good assembling. There is also an advantage that a bulge can be formed in the upper part of the side of the intake expansion chamber 8 on the engine side, and a sufficient volume of the intake expansion chamber 8, especially the first volume chamber 8a, can be secured. The second volume chamber 8b is arranged in parallel with the first volume chamber 8a by vertically dividing the tank portion 17 of the intake system structure 16 by the partition plate 9, and a part of the wall of the first volume chamber 8a. Since the (partition plate 9) is formed in common, the intake system can be made more compact.

Further, the tank portion 17 (second volume chamber 8)
The valve shaft 14 of each shutter valve 14 is fixed to the lower wall of b), and the valve shaft 1 extends parallel to the longitudinal direction of the engine.
The boss portions 27, 27, ... Which rotatably support the 5 are integrally formed, and the boss portions 27, 27.
Annular ribs 28, 2 formed integrally around the opening of the
8 ... Because it is connected in series, the intake expansion chamber 8
The rigidity strength of the (tank portion 17) in the longitudinal direction of the engine is enhanced. Therefore, the vibrational deformation of the tank portion 17 due to the engine vibration is suppressed as much as possible, and the smooth opening / closing operation is stably ensured without interfering with the opening / closing of the shutter valve 14 as in the conventional case. Therefore, it is possible to ensure the above-mentioned intake inertia effect. Further, by integrally forming the boss portion 27 and the rib portion 28 on the constituent wall of the tank portion 17, the structure can be made compact and simplified.

The present invention is not limited to the four-cylinder engine as in the above embodiments, but can be applied to other multi-cylinder engines, for example, a five-cylinder engine and a six-cylinder engine.

[0034]

As described above, according to the first aspect of the invention, the butterfly shutter valve provided in the vicinity of the junction of the communication passage and the independent intake passage is provided with the end of the independent intake passage on the downstream side. Since the part is provided so as to rotate to the independent intake passage side when the valve is opened, the positive pressure wave generated near the intake port immediately after the intake valve is closed is smoothly propagated into the communication passage,
Since it is propagated in the independent intake passage of the intake stroke, the pushing action of the intake air works effectively, and the intake air charging efficiency is improved.

Further, according to the second aspect of the present invention, when the shutter valve is opened, the end portion on the downstream side of the independent intake passage advances into the independent intake passage, while the end portion on the upstream side of the independent intake passage inside the communication passage. Since it is provided so as to be retracted to, it is possible to suppress an increase in the intake resistance of the independent intake passage even when the length of the communication passage is shortened. Therefore, according to the second aspect of the present invention, it is possible to achieve both improvement of the engine output and downsizing of the engine.

Further, according to the third aspect of the present invention, the merging portion of the communication passage and the independent intake passage is formed such that the intersecting angle of each of the communication passage and the independent intake passage in the intake flow direction is an acute angle. Since the positive pressure wave is smoothly propagated between the communication passage and the independent intake passage, the intake charging efficiency is further improved and the engine output is improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view taken along the line I-I of FIG. 3, showing an intake system for a multi-cylinder engine according to an embodiment of the present invention.

FIG. 2 shows the intake system of the multi-cylinder engine, which is shown in FIG.
It is a vertical side view in the II-II line.

FIG. 3 is a plan view in which a part of the intake device of the multi-cylinder engine is cut away.

FIG. 4 shows the intake system of the multi-cylinder engine, which is shown in FIG.
FIG. 4 is an enlarged sectional view taken along line IV-IV.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine main body 4 ... Cylinder 6 ... Independent intake passage 8 ... Intake expansion chamber 8a ... 1st volume chamber 8b ... 2nd volume chamber 13 ... 2nd passage 14 ... Shutter valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Hanabusa 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Motor Corporation

Claims (3)

[Claims] 1. A communication passage that connects midway portions of each independent intake passage for introducing intake air to each cylinder, and a communication passage that is provided near a confluence of the communication passage and each independent intake passage. A multi-cylinder engine, characterized in that the shutter valve is provided such that the end of the shutter valve on the downstream side of the independent intake passage is turned to the independent intake passage side when the valve is opened. Intake device. 2. The shutter valve is provided such that, when the shutter valve is opened, an end portion on the downstream side of the independent intake passage advances into the independent intake passage, while an end portion on the upstream side of the independent intake passage retracts into the communication passage. The intake system for a multi-cylinder engine according to claim 1, wherein the intake system is provided. 3. The merging portion of the communication passage and the independent intake passage is formed such that an intersection angle of the communication passage and the independent intake passage in an intake flow direction is an acute angle. An intake system for a multi-cylinder engine according to 1 or 2.