1 The inv ention re l ates genera l l y to an interna l

2 combustion angina.

3 In a particu l ar aspect this inv ention re l ates to an

4 engine part pro v iding an auxi l iary combus ion chamber f or

5 spark ignition internal combustion engines. In an exemplary S a pp l ica tion , th e engin e pa r t i s a n a ccesso ry t o a 7 conventional four cycle internal combustion engine with the 3 auxil iary combustion chamber prov iding a pre-co bustion 9 chamber, and it wil l be convenient to hereinafter describe 0 preferred engine parts in relation to that application. 1 Pre-comb u s tion ch amb e rs w er e f i r st described for 2 conventional spark Ignition f our cyc le engines during the 3 mid 1960's and ref erence is made to Austra l ian Patent 4 Spe if i a ion No. 459,698. In that engine type , each 5 cyl inder had a main combustion chamber and an additiona l 8 auxi l iary combustion chamber equipped with a spark p l ug. 7 The main combustion chamber mas prov ided wi h an intake 8 valve for combustion fuel/air mixtures, and an exhaust valve 9 for products of the combustion process, while the auxiliary 0 chamber u a 3 prov ided with an inl et va l v e. The auxi liary 1 chamber was in co munication with its respecti ve main 2 chamber through a smal l port. A relatively lean combustion 3 uel/air ■ mixture was supplied to the main combustion chamber 4 through the intake va l ve and a rel ativ e l y rich combustion 5 fuel/air mixture was supplied to the auxiliary combustion 8 chamber through the Inl et va l v e. This pro v ided f or ready ignition of the rich mixture in the auxiliary chamber by the spark p l ug , and resu l ting b l ast of f l ams ignited the relatively lean mixture in the main combustion chamber. An advantage that the auxiliary chamber provided was to r educ e t he emis sion o f unwanted ga s e s a s p ar t o f th e exhausted combustion products. Those gases include the oxide s o f n i g t rogen , u nb urnt hy droc arb on s and carb o n monoxide in the exhaust gases. Consumption of those gasβa was general ly increased as the engine was adapted to burn a l eaner mixture of fuel /air. As a resu l t, a more comp lete burning of the fuel occurred. A f urther adv antage was that greater fue l economy

occurred as a result. However, previously known internal combustion engines of that type have a disadvantage that the auxiliary combustion cha ber formed an integral part of the engine head. Thus the chamber could not be included or removed after manufacture of the engine. Further βaid small port was particulary prone to corrosion and erosion. The present invention seeks to provide an engine part.. The engine part of the present invention would be particularly useful in association with internal combustion engines that include at least a main cylinder. The main cylinder of the engine will typically have a main combustion chamber in which a piston is slidably mounted. The or each main combustion chamber is provided with at least one inlet valve controlling the intake of a fuel/air mixture to the chamber, and at least one exhaust valve for emission of products from the combustion process. The fuel/air mixture may be supplied to the main combustion chamber from a fuel and air supply in any known manner, such as via a carburettor or electronic fuel injection systems. The main cylinder will have a spark plug socket for inclusion of a spark plug. The spark plug would under normal operating circumstances be included so as to provide a spark igniting gases within the main combustion chamber. The present invention provides for an engine part for an internal combustion engine. The engine part may broadly include a body portion defining an auxiliary combustion chamber having a valve controlled inlet port, an outlet port and means for the inclusion of an ignition means. The internal combustion engine may be a four cycle internal combustion engine of the type as described above. An engine part of this invention may be associated with each main cylinder of an engine. In this respect each cylinder of the engine may have associated with it at least one of such engine parts. The engine part may also include connecting means for connection of the part to the main cylinder. The connecting means may be in association with the body portion defining

the auxiliary combustion chamber. The connecting means preferably is adapted so as to utilise an axis ting spark plug socket of a main cylinder, once the existing spark plug has bean removed. The connecting means may be provided in a form that is in common with the connecting means that the spark plug may have assumed. Thi3 may in one form comprise a "screw-in ^*1 facility. The connecting means may also define the outlet port for the auxiliary combustion chamber. In one f orm, the out l et port may be comprised of a bore through the connecting means, leading from the auxiliary combustion chamber to the main combustion chamber of a main cyl inder. The outlet port may be of any dimension, but such that it is ab l e to direct a f l ame discharge f rom the auxi l iary combustion chamber to the main combustion chamber. In a preferred aspect, the present invention provides an engine part having connecting means for connecting the engine part to a spark plug hole in a head of an internal combustion engine, which engine having a combustion chamber (hereinafter called "said main combustion chamber") a chamber defining an auxiliary combustion chamber for the engine, an outlet passage extending through said connecting means and in use putting the auxiliary combustion chamber and said main combustion chamber in communication, a bore passing from the auxiliary engine part and for receiving a spark plug, and an inl et passage to the auxiliary combustion chamber adapted to be provided with a fuel rich fuel-air mixture. Preferably the connecting means includes a screw threaded portion adapted to be received into said spark plug hole. Preferably the connecting means is such as to permit the auxiliary chamber to be located at a selected rotated position with respect thereto. Preferably there is included director means to direct a

flame produced in auxiliary combustion chamber towards the outlet passage into said main combustion chamber. The shape and volume of the auxiliary combustion chamber is not criticial and may vary. The variation in the shape and volume will depend at least to some extent upon the type of engine in which it is to be used. The larger the volume of the auxiliary combustion chamber, the less the compression ratio will be for the combined main and auxiliary combustion chambers. Hence, the volume of the auxiliary combustion chamber can be varied according to need . Preferably the volume of the auxiliary combustion chamber is from about 5 % to 12 % the total combined volume of the auxiliary combustion chamber and the main combustion chamber of the main cylinder measured when the piston is at the top dead center. The shape of the auxiliary combustion chamber may be such that when the gases in the chamber ignite, the resulting f lame will be directed toward the outlet port of the chamber and such that the flame will be capable of igniting gases in the main combustion chamber. As previously indicated, the body portion of the engine part includes means for the inclusion of an ignition means. This ignition means may generally comprise a spark plug. The ignition means is such that an ignition mechanism is in contact with the fuel/air mixture in the auxiliary combustion chamber. In the preferred case of the spark plug, the means far inclusion may be adapted in a conventional manner for a spark plug, such as a conventional spark plug socket, so as to provide for easy insertion and removal of the spark plug. The spark plug ignition may then be timed in any conventional manner, such as by the distributor timed by the cam shaft or by an electronic ignition means. As previously indicated, the body portion of the engine part includes an inlet port for the auxiliary combustion chamber. The inlet port is in communication with an inlet passage to supply an fuel/air mixture to the auxiliary combustion chamber. The inlet port enables fuel/air mixture

to be delivered to the auxiliary combustion chamber. Preferab ly the inlet passage is associated i h at least ana val ve to contro l fuel/air mixture through the inlet passage to the auxiliary combustion chamber. The val ve may be positioned to control the flow of fuel/air mixture at the junction of the inlet passage opening and the auxiliary combustion chamber. The val ve is preferably actuab l e to open and c l ose in the in l et passage in accordance with engine piston movement and the valves of the main chamber. In particular, the valve is preferably timed to open the inlet pasage 30 as to al low the passage of fuel/air mixture into the auxiliary combustion chamber during a fuel/air mixture induction stroke of the engine piston. The valve will preferably then generally close the inlet passage for compression, work and exhaust strokes of the piston. Timed actuation of the v al v e to the auxil iary combustion chamber may be achieved in any suitable manner, and in particular by either the same mode, or an indepeπdant mode to the val ves of the main cylinder. This may be by way of any conventional actuating mechanism such as actuating a solenoid driven by switch gear on the cam shaft , directly off the crank shaft or may be independently electrical ly timed . However, the inventor has also found that such an actuating mechanism may be difficult to engineer, expensive or prone to difficulties particularly in the case of the use of solenoids. As a result of tests, the inventor has found that such an actuating mechanism is not essential and that effective opening and closing of the valve can be effected in response to pressure in said engine. Thus, preferably, the inlet valve i3 biased towards a closed position but is adapted to open solely under vacuum induced during an induction stroke of said engine. At least one inlet manifold may be associated with the inlet passage of the auxiliary combustion chamber and the main combustion chamber. Th e manifo l d wi l l b e in

communica ion in use with a fuel/air source, and may be arranged so as to direct a prede e ined fuel/air ratio mixtures to one or each of the main combustion chamber and the auxiliary combustion chamber. The manifold may be variable to accαmodate different engine constructions. The inlet manifold may be arranged so as to direct a relatively rich fuel/air mixture to the auxiliary combustion chamber, and a relatively leaner fuel/air mixture to the main combustion chamber. This is preferably achieved through the use of seperate manifolds for the auxiliary and the main combustion chambers. The provision of different fuel/air mixtures to the auxiliary and main combustion chambers can be achieved in a number of conv entional manners inc luding making odifications to an existing carburettor system of the engine. Such modifications may include adjustment so as to direct a separate predeter ined fuel/air mixture to the manifolds supplying each respective chamber, such that a richer fuel/air mixture is supplied to the auxiliary combustion chamber and a leaner fuel/air mixture supplied to the main combustion chamber. Electronic fuel ignition systems may also be similarly modified to achieve that. The fuel/air mixture leading into the auxiliary combustion chamber may be preheated. This preheating step can be carried out in any conventional manner. Such manner may involve transferring at least some of the heat of the exhausted combustion products to preheat the mixture leading into the auxiliary combustion chamber. This may be achieved by routing the combustion products passed the fuel/air mixture . The engine part of the invention Itself may be cooled by any conventional means, such as air or liquid cooling by using or modifying the existing cooling system of the engine . A baffle may also be included in the engine part and may be arranged so as to direct the jet of flame in the auxiliary combustion chamber toward the deepest part of the main combustion chamber. The baffle may also assist in

avoiding swirling of the fuel/air mixtures during the compression stroke of the engine piston. The baffle may be included in any conventional manner, preferably in or near the outlet passage of the auxiliary combustion chamber. By making appropriate modifications to the existing engine, the engine part as described in this invention may be arranged for use in turbo charged systems, super charged systems, as well as normally aspirated and electronicall fuel injected systems. The engine part may a lso be a benefit when unl eaded fuel is used. The more complete burning of the fuel in the main combustion chamber, may reduce the need for catalytic oonvertors to be fitted. Specific constructions in accordance with th is invention wil l now be described with reference to the accompanying drawings in whichs- Fig 1 is a cross-sect iona 1 view of a first engine part installed in an existing engine. Fig 2 is a perspective view of a second engine part, and Fig 3 is a vertical cross -sect iona 1 view of the second engine part. In Fig 1 drawing, there is illustrated the engine part P, including an auxiliary combustion chamber 1 , having a predeter ined volume, defined by body portion 2. A screw-in connecting means 3 is arranged to fit In an existing spark p lug socket 4 of a main cyl inder of an engine E, so as to mount the body portion 2 on the engine E. An outlet port 5 for the auxiliary combustion chamber 1 leads from the auxiliary combustion chamber 1 into a main combustion chamber 6 of the main cylinder. The outlet port 5 is directed so that flame produced in the auxiliary combustion chamber 1 is directed toward and into the main combustion chamber 6. An ignition means 7 of a spark plug 8 is able to ignite fuel/air mixtures within the auxiliary combustion chamber 1 to produce that flame. The body portion 2 has a spark plug socket 9 for mounting the spark plug 8 thereon.

In operation of engine part P, a relatively rich fuel/air mixture is directed to the auxiliary combustion chamber 1 by flowing along an inlet passage 10 through an inlet port 13 and past an inlet valve 11. In this form, the valve 11 is controlled by a solenoid 12 which may be driven by a switch gear on an existing cam shaft (not illustrated). The valve 11 is positioned to control flow of fuel/air mixtures at an Inlet port 13. A relatively lean fuel/air mixture is directed into the main combustion chamber 6 of the main cylinder along the inlet passage 14 and through an inlet valve 15. Both valve 11 and valve 15 open during an induction stroke of a piston 16 drawing fuel/air mixtures into the auxiliary and main combustion chambers 1 and δ. Combustion products from both chambers 1 and 6 are subsequently exhausted through an exhaust outlet 17 when an exhaust valve 18 opens. In order to direct the jet of flame through the outlet port 5 to the deepest part of the main combustion chamber 6, and also to reduce the swirling and excess mixing of the fuel/air mixtures of the combustion chambers 1 and 6, during the compression stroke of the piston 16, a baffle 19 may be positioned near the outlet port 5 of the auxiliary combustion chamber 1. The engine part 51 shown in Figs 2 and 3 comprises a tubular member 52 having a screw threaded end 53 for being received in a spark plug hole of a head of an internal combustion engine having a combustion chamber (hereinafter called "said main combustion chamber"). Within the tubular member 52 is a baffle 55. Located on the outside of the tubular member 52 is a housing 53 provided with a water cooling bore 54 and spigots 56 at each end of the bore 54 for connection to a source of cooling water. The housing 53 also has a bore 57 which is threaded at 58 and within which can be received, as shown, a conventional spark plug 59. At the end of the tubular member 51 opposite the end 53 is a valve carrier 51 comprising a body 62, an inlet passage

S3, a val ve 54, an inlet port 65 defined by the val ve 64 and a seat 57, a va l ve spring 68, a val ve spring retainer 89 and an inlet spigot 70. The inlet spigot 70 is connected in use to a source of a rich fuel/air mixture such as by means of a tubular manifold part 71. V a r i α u 3 seal members 72, 73, 74 and 75 are provided for creating seals. The tubular member 52 is apertured at 81 to communicate the interior 82 of the tubu l ar member with the bore 57 and which interior 82 and bore 57 together def ine an auxi l iary combustion chamber 85 hav ing an outl et 87 which , in use, will be communication with said main combustion chamber. In use, the engine part 51 wil l operate in simil ar manner to the engine part described with respect to Fig 1 but the fol lowing differences are to be noted. Firstly, the baff le 55 wil l restrict dilution of a rich fuel/air mixture in the auxiliary combustion chamber 86 by a l ean fue l/air mixture in said main combustion chamber and wil l further tend to direct f lame initiated in the auxiliary combustion chamber to exit via the outlet 87 rather than to travel towards the valve 64. The val ve 64 is not opened by any mechanical coupling or by app l ication of interna l f orce -but instead opens to a l l ow in l et of a rich fue l /air mixture into the auxi l iary combustion chamber 86 in consequence only of vacuum induced during an induction stroke of the engine. Th e c l a im s f orm p a r t o f th e d i s c l o s u r e o f t h i s specification. It is to bs understood that v arious mo if ications and/or alterations may be made to the engine parts disclosed abov e without departing f rom the ambit of the present invention disclosed herein.