CN111852683A

CN111852683A - Cylinder head cooling structure, engine cooling structure and engine

Info

Publication number: CN111852683A
Application number: CN201910365038.1A
Authority: CN
Inventors: 李米龙; 杨春玲; 陈涛; 张永静; 邸金瑞
Original assignee: Great Wall Motor Co Ltd
Current assignee: Great Wall Motor Co Ltd
Priority date: 2019-04-30
Filing date: 2019-04-30
Publication date: 2020-10-30

Abstract

The invention provides a cylinder head cooling structure, an engine cooling structure and an engine, wherein the cylinder head cooling structure is arranged on an engine cylinder head, an exhaust manifold is integrated on the engine cylinder head, and the cylinder head cooling structure comprises a main water jacket capable of cooling a cylinder head main body of the engine and a manifold water jacket capable of cooling the exhaust manifold; and a plurality of groups of cylinder cover cooling liquid inlets are formed on the engine cylinder cover corresponding to the positions of the combustion chambers on the engine cylinder cover, each cylinder cover cooling liquid inlet comprises a plurality of water inlets which are arranged in parallel, each water inlet is communicated with the main body water jacket, and at least one water inlet is communicated with the manifold water jacket. The cylinder cover cooling structure of the invention can have better cooling effect on the cylinder cover of the engine.

Description

Cylinder head cooling structure, engine cooling structure and engine

Technical Field

The invention relates to the technical field of vehicle parts, in particular to a cylinder cover cooling structure. The invention also relates to an engine cooling structure provided with the cylinder head cooling structure, and an engine provided with the engine cooling structure.

Background

In order to better cool the exhaust manifold, the cooling structure of the engine cylinder head generally comprises a body water jacket for cooling the engine cylinder head body, particularly the combustion chamber, and a manifold water jacket for cooling the exhaust manifold. In the prior art, coolant for cooling an engine cylinder head generally flows into a main body water jacket and then flows into a manifold water jacket, and the temperature of the coolant flowing into the manifold water jacket through the main body water jacket is generally high, so that the exhaust manifold is not well cooled. And a water inlet structure of a common engine cylinder cover usually has only one water inlet, and the cooling effect on the position with higher temperature on the engine cylinder cover is also poor.

Disclosure of Invention

In view of the above, the present invention is directed to a cylinder head cooling structure, so as to provide a better cooling effect for a cylinder head of an engine.

In order to achieve the purpose, the technical scheme of the invention is realized as follows: a cylinder head cooling structure disposed on an engine cylinder head with an exhaust manifold integrated thereon, the cylinder head cooling structure comprising a body water jacket configured to cool a cylinder head body of the engine, and a manifold water jacket configured to cool the exhaust manifold; and a plurality of groups of cylinder cover cooling liquid inlets are formed on the engine cylinder cover corresponding to the positions of the combustion chambers on the engine cylinder cover, each cylinder cover cooling liquid inlet comprises a plurality of water inlets, each water inlet is communicated with the main body water jacket, and at least one water inlet is communicated with the manifold water jacket.

Furthermore, the main body water jacket comprises a nose bridge area water channel arranged between exhaust channels of the engine cylinder cover, the coolant inlet comprises a main water inlet and branch water inlets positioned on two sides of the main water inlet, and the main water inlet is communicated with the nose bridge area water channel and the manifold water jacket.

Furthermore, the manifold water jacket comprises an upper water jacket and a lower water jacket which are communicated and respectively arranged on the upper side and the lower side of the exhaust manifold, and at least one of the water inlets is communicated with the upper water jacket or the lower water jacket.

Further, the upper water jacket has an outer convex portion that protrudes outward toward the outlet of the engine cylinder head exhaust passage.

Furthermore, a plurality of diversion holes penetrating through the lower water jacket are formed in the lower water jacket, and each diversion hole can form a guide for the circulation of the cooling liquid in the lower water jacket.

Compared with the prior art, the invention has the following advantages:

according to the cylinder cover cooling structure, the cylinder cover cooling liquid inlet is formed to comprise the plurality of water inlets which are arranged in parallel, each water inlet is communicated with the main body water jacket, at least one water inlet is communicated with the manifold water jacket, so that cooling liquid can enter the main body water jacket and the manifold water jacket from each water inlet simultaneously, the engine cylinder cover main body and the manifold water jacket are cooled by the cooling liquid with lower temperature, and a good cooling effect can be achieved on the engine cylinder cover main body and the exhaust manifold. Meanwhile, the arrangement of the water inlets can preferentially cool a plurality of places with higher temperature on the engine cylinder cover so as to further improve the cooling effect on the engine cylinder cover body.

Another object of the present invention is to provide an engine cooling structure disposed on an engine, the engine including an engine block, an engine cylinder head, and a cylinder head gasket provided between the engine block and the engine cylinder head, the engine cooling structure including a block water jacket configured on the engine block, and a cylinder head water jacket configured on the engine cylinder head, characterized in that: the cylinder head water jacket adopts the cylinder head cooling structure.

Furthermore, a plurality of groups of water inlet units and water return units are formed on the cylinder head gasket corresponding to the positions of each combustion chamber of the engine, the water inlet units can form the inflow of the cooling liquid from the cylinder body water jacket to the cylinder head water jacket, the water return units can form the backflow of the cooling liquid from the cylinder head water jacket to the cylinder body water jacket, and the water return units have different flow cross-sectional areas.

Further, the block water jacket includes an exhaust side water jacket adjacent to the exhaust passage of the engine cylinder head, and an intake side water jacket adjacent to the intake passage of the engine cylinder head, and a block water jacket coolant inlet port, which forms a coolant inflow to the block water jacket, communicates with the exhaust side water jacket.

Further, the engine includes four combustion chambers in-line with the block jacket coolant inlet being proximate the combustion chamber at the end of the engine; along the direction that is close to cylinder body water jacket water inlet, the ratio of each return water mouth circulation cross-sectional area is 1.2 ~ 1.7: 0.8-1.2: 1.1-1.6: 1.

in addition, the invention also provides an engine, and the engine cooling structure is arranged on the engine.

The engine of the present invention has substantially the same advantages as the engine cooling structure described above, and will not be described herein again.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 is an overall schematic view of a cylinder head cooling structure according to a first embodiment of the present invention;

FIG. 2 is a schematic view of the underside water jacket according to the first embodiment of the present invention;

FIG. 3 is a schematic structural view of an upper water jacket according to a first embodiment of the present invention;

fig. 4 is an overall schematic view of an engine cooling structure according to a second embodiment of the invention;

Fig. 5 is an enlarged view of a portion a in fig. 4.

Description of reference numerals:

1-a main body water jacket, 11-a main body water jacket unit, 111-a nose bridge area water path, 112-an exhaust valve guide pipe cooling water path, 113-a main body water jacket water outlet, 2-a manifold water jacket, 21-an upper side water jacket, 211-an outer convex part, 22-a lower side water jacket, 2201-a diversion hole, 221-an outer convex unit, 23-a communication passage, 24-a manifold water jacket water outlet, 3-a cylinder cover cooling liquid inlet, 31-a main water inlet, 32-a water dividing port, 4-a cylinder body water jacket, 41-an exhaust side water jacket, 42-an air inlet side water jacket, 43-a circulation passage, 5-a cylinder body water jacket cooling liquid inlet, 6-a cylinder cover gasket, 61-an water inlet unit and 62-a water.

Detailed Description

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

Example one

The present embodiment relates to a cylinder head cooling structure that is disposed on an engine cylinder head with an exhaust manifold integrated thereon, the cylinder head cooling structure including a body water jacket 1 that can constitute a cooling of an engine cylinder head body, and a manifold water jacket 2 that can constitute a cooling of the exhaust manifold; corresponding to the position of each combustion chamber on the engine cylinder cover, a plurality of groups of cylinder cover cooling liquid inlets 3 are formed on the engine cylinder cover, each cylinder cover cooling liquid inlet 3 comprises a plurality of water inlets which are arranged in parallel, each water inlet is communicated with the main body water jacket 1, and at least one water inlet is communicated with the manifold water jacket 2.

In the present embodiment, as shown in fig. 1 to fig. 3, the manifold water jacket 2 includes an upper water jacket 21 disposed on an upper side of the exhaust manifold and a lower water jacket 22 disposed on a lower side of the exhaust manifold, and the upper water jacket 21 is communicated with the lower water jacket 22, and by arranging the manifold water jacket 2 according to the above structure, compared with a full-wrapping form of the manifold water jacket on the exhaust manifold in the prior art, the exhaust manifold can be cooled while the water temperature of the vehicle is prevented from rising too slowly due to excessive cooling of the exhaust manifold under a low-speed and low-load working condition of the vehicle.

As shown in fig. 1 and 2, the lower water jacket 22 is in a sheet shape, and a plurality of baffle holes 2201 penetrating the lower water jacket 22 are formed in the lower water jacket 22, and by providing the baffle holes 2201, the lower water jacket 22 can be divided into a plurality of water jacket branches having a small cross-sectional area, and the water jacket branches have a small cross-sectional area, so that a high flow velocity can be obtained, and the cooling effect of the lower water jacket 22 on the exhaust manifold can be improved. Meanwhile, the arrangement of the diversion holes 2201 reduces the contact area between the lower water jacket 22 and the exhaust manifold, and can reduce the problem that the water temperature rises too slowly when the vehicle runs at low speed and under small load.

In addition, the inventor finds that the heat at the outlet of the exhaust passage of the cylinder head is concentrated, so that the temperature at the outlet of the exhaust passage is higher, while the existing manifold water jacket 2 is far away from the outlet of the exhaust passage, and if the whole flow cross section area of the manifold water jacket 2 is increased, the cooling effect on the exhaust manifold is influenced, and the strength of the cylinder head of the engine is also influenced. Therefore, in the embodiment, the convex unit 221 which protrudes towards the outlet of the exhaust passage is formed on the lower water jacket 22, and by arranging the convex unit 221, the temperature at the outlet of the exhaust passage can be effectively reduced and the thermal deformation at the outlet of the exhaust passage can be reduced under the condition of not influencing the integral cooling of the exhaust manifold and the integral strength of the cylinder cover of the engine.

The upper water jacket 21 is configured as shown in fig. 1 and 3 in a strip shape, and a communication passage 23 on the exhaust manifold side is provided between the upper water jacket 21 and the lower water jacket 22, and the communication passages 23 are two in the longitudinal direction of the upper water jacket 21 at intervals, and the coolant entering the lower water jacket 22 can enter the upper water jacket 21 from the communication passage 23. In the present embodiment, as shown in fig. 1 and 3, an outer protrusion 211 protruding outward toward the exhaust port outlet and having a zigzag shape is formed on the upper water jacket 21, so that the exhaust port outlet can be further cooled.

The above-described body water jacket 1 is structured as shown in fig. 1, and includes body water jacket units 11 arranged corresponding to the respective combustion chambers on the engine cylinder head, each body water jacket unit 11 having a nose bridge region water passage 111 configured to cool a nose bridge region of the engine cylinder head, and an exhaust valve guide cooling water passage 112 configured to cool an exhaust valve guide.

The structure of the cylinder head coolant inlet 3 is shown in fig. 1, and the cylinder head coolant inlet 3 is arranged in one-to-one correspondence with each main body water jacket unit 11, in this embodiment, the number of water inlets included in the cylinder head coolant inlet 3 is three, and specifically, the cylinder head coolant inlet includes a main water inlet 31 located in the middle, and two branch water inlets 32 located on both sides of the main water inlet 31, the coolant flowing into the main water inlet 31 can simultaneously enter the main body water jacket 1 and the manifold water jacket 2, and the coolant flowing into the branch water inlets 32 can enter the main body water jacket 1, wherein the main water inlet 31 is specifically communicated with the nose bridge area water channel 111 and the lower side water jacket 22, and the branch water inlets 32 are specifically communicated with the.

By arranging the cylinder cover cooling liquid inlet 3 according to the structure, the cooling liquid entering the cylinder cover cooling structure from the cylinder cover cooling liquid inlet 3 can enter the main body water jacket 1 and the manifold water jacket 2 simultaneously, namely, the parallel arrangement of the main body water jacket 1 and the manifold water jacket 2 is formed, compared with the prior art that the main body water jacket 1 and the manifold water jacket 2 are arranged in series, the cooling liquid flows into the manifold water jacket 2 after flowing through the main body water jacket 1, and the temperature of the cooling liquid entering the manifold water jacket 2 is lower in the embodiment, so that the cooling effect on the manifold water jacket 2 is better.

In addition, each cylinder cover cooling liquid inlet 3 is provided with a plurality of water inlets, and a plurality of areas with higher temperature on the engine cylinder cover, such as a nose bridge area between two exhaust passages on the engine cylinder cover and an exhaust valve guide pipe, can be preferentially cooled, so that the cooling effect on the engine cylinder cover is further improved. Meanwhile, the water inlet in the middle is set to simultaneously convey cooling liquid to the manifold water jacket 2 and the main body water jacket 1, and the arrangement of the water inlet on the engine cylinder cover is facilitated.

In the present embodiment, as shown in fig. 1, a manifold water jacket outlet 24 is configured at the tail of the upper water jacket 21, and a body water jacket outlet 113 is configured at the side of the body water jacket 1 away from the water inlet.

With the structure, the cooling liquid entering the cylinder head water jacket from the cylinder head cooling liquid inlet 3 has a path as shown by arrows in fig. 1 to 3, 1, enters the nose bridge area water path 111 from the main water inlet 31, flows to one side of the main water jacket close to the cylinder head air inlet channel, and then flows out from the main water jacket water outlet 113; 2. flows into the lower water jacket 22 from the main water inlet 31, then flows through the upper water jacket 21, and is discharged through the manifold water jacket water outlet 24 arranged at the tail end of the upper water jacket 21; 3. enters the exhaust valve guide cooling water channel 112 from the water inlet 32, flows to one side of the main water jacket close to the cylinder head air inlet channel, and then flows out from the main water jacket water outlet 113. Because the cooling liquid flowing through the bridge area water path 111 and the exhaust valve guide pipe cooling water path 112 can be merged in the water path around the exhaust passage of the cylinder cover, the cylinder cover combustion chamber is cooled together, and therefore the cooling effect on the engine combustion chamber is better.

Example two

The present embodiment relates to an engine cooling structure that is disposed on an engine including an engine block, an engine cylinder head, and a head gasket 6 provided between the engine block and the engine cylinder head. As shown in fig. 4, the engine cooling structure includes a block water jacket 4 configured on the engine block, and a head water jacket configured on the engine cylinder head, wherein the head water jacket adopts the cylinder head cooling structure according to the first embodiment. In the present embodiment, the engine cooling structure will be described by taking a four-cylinder engine, that is, an engine with four combustion chambers as an example, and an engine with other number of combustion chambers, for example, a three-cylinder engine, has the same principle as the four-cylinder engine, and will not be described herein again.

In the present embodiment, the block water jacket 4 is structured as shown in fig. 4, and includes an intake-side water jacket 42 on the side close to the cylinder-head intake port, and an exhaust-side water jacket 41 on the side close to the cylinder-head exhaust port, respectively. For convenience of description, the four combustion chambers from left to right illustrated in fig. 4 are referred to as a first combustion chamber, a second combustion chamber, a third combustion chamber, and a fourth combustion chamber, respectively, in this embodiment. The intake side water jacket 42 and the exhaust side water jacket 41 respectively comprise four arc-shaped cylinder water jacket units which are arranged in a connecting way corresponding to four combustion chambers on an engine cylinder, and the cylinder water jacket units on the intake side water jacket 42 and the cylinder water jacket units on the exhaust side water jacket 41 are arranged oppositely and can surround the periphery of each combustion chamber, so that the cooling of each combustion chamber on the engine cylinder can be well formed.

In the present embodiment, the intake side water jacket 42 is provided so as to be separated from the exhaust side water jacket 41, and specifically, as shown in fig. 4 and 5, the intake side water jacket 42 is provided at an interval from the exhaust side water jacket 41 on the peripheral side of the first combustion chamber so that one ends of the intake side water jacket 42 and the exhaust side water jacket 41 are separated; meanwhile, on the peripheral side of the fourth combustion chamber, the intake side water jacket 42 and the exhaust side water jacket 41 are also provided with an interval therebetween, so that the other ends of the intake side water jacket 42 and the exhaust side water jacket 41 are also blocked, so that the coolant can flow from the exhaust side water jacket 41 into the head water jacket, and flow from the head water jacket back into the intake side water jacket 42. However, in order to ensure that the coolant can flow from the exhaust side water jacket 41 into the intake side water jacket 42 to circulate, in the present embodiment, a flow passage 43 is provided between the exhaust side water jacket 41 and the end of the intake side water jacket 42 near the fourth combustion chamber, so that the coolant can be ensured to flow in a special case.

In the present embodiment, the block jacket coolant inlet 5, which constitutes the inflow of external coolant into the block jacket 4, communicates with the exhaust side water jacket 41, and the coolant outlet, which constitutes the return of coolant from the block jacket 4 to the outside, communicates with the intake side water jacket 42. Through the arrangement, in the working process of the engine, the temperature of exhaust gas generated by combustion in the combustion chamber is very high and is far higher than the temperature of air inlet, and high-temperature exhaust gas is exhausted through the exhaust passage of the cylinder cover, so that the temperature of one side, close to the exhaust passage, of the cylinder cover of the engine is higher than the temperature of one side, close to the air inlet passage, of the cylinder cover of the engine. And a cooling liquid inlet is arranged on the exhaust side water jacket 41, so that cooling liquid with lower temperature can preferentially enter one side of the cylinder block water jacket close to the exhaust passage, the temperature gradient between one side of the cylinder head close to the exhaust passage and one side of the cylinder head close to the air inlet passage is obviously reduced, and the integral deformation of the cylinder head of the engine is reduced.

As shown in fig. 4, the aforementioned cylinder head gasket 6 is configured with water inlet units 61 arranged in one-to-one correspondence with the respective combustion chambers, and each water inlet unit 61 is provided specifically in correspondence with the head coolant inlet 3. And the cylinder head gasket 6 is provided with water return units 62 which are arranged corresponding to the combustion chambers one by one, and each water return unit 62 is specifically arranged corresponding to the water outlet 113 of the main body water jacket. The coolant that has entered the exhaust-side water jacket 41 may enter the cylinder head water jacket through each water intake unit 61, and the coolant that has entered the cylinder head water jacket may flow back into the intake-side water jacket 42 through the water return unit 62.

When the cooling performance of each combustion chamber of the engine is studied, the inventors found that a large difference in temperature between the respective combustion chambers on the peripheral side thereof means that the cooling of each combustion chamber is not uniform, and the performance of the engine is affected. The inventor further researches and discovers that the reason for uneven cooling of each combustion chamber is as follows: the pressure of the cooling liquid is not uniform at all places in the engine cooling structure. In order to improve the cooling effect of each combustion chamber, the inventors tried to improve the cooling effect of each combustion chamber by adjusting the structure of the cylinder head water jacket or the block water jacket 4, but adjusting the structure of the cylinder head water jacket and the block water jacket 4 was troublesome. In the course of research, the inventors have unexpectedly found that the uniformity of cooling of each combustion chamber can be improved by adjusting the flow cross-sectional area of the water inlet unit 61 or the water return unit 62, but further research by the inventors has found that the cooling of the exhaust manifold can be adversely affected by adjusting the flow cross-sectional area of the water inlet unit 61, although the uniformity of cooling of each combustion chamber can be improved.

The flow cross section area of each water return unit 62 is adjusted, so that the cooling of each combustion chamber is uniform, the cooling effect of the engine is effectively improved, the cooling effect of other structures cannot be influenced, and the flow cross section area of each water return unit 62 is adjusted simply and is easy to realize. In the embodiment, from the water return unit 62 corresponding to the fourth combustion chamber to the water return unit 62 corresponding to the first combustion chamber, the ratio of the flow cross-sectional areas of the water return units 62 is 1.2-1.7: 0.8-1.2: 1.1-1.6: 1, preferably 1.4: 1: 1.3: 1. it should be noted that, in the present embodiment, each water returning unit 62 has a different cross-sectional flow area, which means that the cross-sectional flow area of at least one water returning unit 62 in each water returning unit 62 is different from the cross-sectional flow areas of the other water returning units 62, and each water returning unit 62 in the present embodiment includes a plurality of water returning holes, and the cross-sectional flow area of each water returning unit 62 refers to the total cross-sectional flow area of the included water returning holes.

It should be noted that, in the present embodiment, reference may be made to the prior art for parts that are not mentioned in the engine cooling structure, and detailed description thereof is omitted here.

In conclusion, the engine cooling structure of the embodiment can effectively improve the cooling uniformity of each combustion chamber on the engine and effectively improve the cooling effect of the engine.

EXAMPLE III

The present embodiment relates to an engine to which the engine cooling structure according to the second embodiment is applied.

The engine of the embodiment can improve the cooling effect of the engine and prolong the service life of the engine by applying the engine cooling structure in the first embodiment.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A cylinder head cooling structure that is disposed on an engine cylinder head and on which an exhaust manifold is integrated, characterized in that: the cylinder head cooling structure includes a body water jacket (1) configured to cool the engine cylinder head body, and a manifold water jacket (2) configured to cool the exhaust manifold; and a plurality of groups of cylinder cover cooling liquid inlets (3) are formed on the engine cylinder cover corresponding to the positions of the combustion chambers on the engine cylinder cover, each cylinder cover cooling liquid inlet (3) comprises a plurality of water inlets, each water inlet is communicated with the main body water jacket (1), and at least one water inlet is communicated with the manifold water jacket (2).

2. The cylinder head cooling structure according to claim 1, wherein: the main body water jacket (1) comprises a nose bridge area water channel (111) arranged between exhaust passages of the engine cylinder cover, the cooling liquid inlet (3) comprises a main water inlet (31) and branch water inlets (32) positioned on two sides of the main water inlet (31), and the main water inlet (31) is communicated with the nose bridge area water channel (111) and the manifold water jacket (2).

3. The cylinder head cooling structure according to claim 1, wherein: the manifold water jacket (2) comprises an upper water jacket (21) and a lower water jacket (22) which are communicated with each other and respectively arranged on the upper side and the lower side of the exhaust manifold, and at least one of the water inlets is communicated with the upper water jacket (21) or the lower water jacket (22).

4. The cylinder head cooling structure according to claim 1, wherein: the upper water jacket (21) has an outer convex portion (211) that protrudes outward toward the outlet of the engine cylinder head exhaust passage.

5. The cylinder head cooling structure according to claim 1, wherein: the lower water jacket (22) is provided with a plurality of diversion holes (2201) which penetrate through the lower water jacket (22), and each diversion hole (2201) can form a guide for the circulation of cooling liquid in the lower water jacket (22).

6. An engine cooling structure arranged on an engine, and the engine including an engine block, an engine cylinder head, and a cylinder head gasket (6) provided between the engine block and the engine cylinder head, the engine cooling structure including a block water jacket (4) configured on the engine block, and a cylinder head water jacket configured on the engine cylinder head, characterized in that: the cylinder head water jacket employs the cylinder head cooling structure as claimed in any one of claims 1 to 5.

7. The engine cooling structure according to claim 6, characterized in that: the cylinder head gasket (6) is provided with a plurality of groups of water inlet units (61) and water return units (62), wherein the water inlet units (61) can form the inflow of the coolant from the cylinder head water jacket (4) to the cylinder head water jacket, the water return units (62) can form the backflow of the coolant from the cylinder head water jacket to the cylinder head water jacket (4), and the water return units (62) have different flow cross-sectional areas.

8. The engine cooling structure according to claim 6 or 7, characterized in that: the block water jacket (4) comprises an exhaust side water jacket (41) close to an exhaust passage of the engine cylinder head and an intake side water jacket (42) close to an intake passage of the engine cylinder head, and a block water jacket coolant inlet (5) forming coolant flowing into the block water jacket (4) is communicated with the exhaust side water jacket (41).

9. The engine cooling structure according to claim 8, characterized in that: the engine comprises four combustion chambers in-line, and the block water jacket coolant inlet (5) is close to the combustion chamber at the end of the engine; along the direction that the water inlet of the cylinder body water jacket (4) is close to, the ratio of the flow cross-sectional area of each backwater opening is 1.2 ~ 1.7: 0.8-1.2: 1.1-1.6: 1.

10. an engine, characterized in that: an engine cooling structure according to any one of claims 6 to 9 provided on the engine.