BACKGROUND OF THE INVENTION The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge in any country.

The use of liquid gas to run internal combustion engines has become more prevalent because of perceived advantages that arise from such use. Those advances include improved economy for the user and equally importantly, decreased pollution in use. In order to reap the benefits of such use, many conventional petrol and diesel powered engines have been converted to run on liquid petroleum gas ("LPG") liquefied natural gas ("LNG") or other suitable gaseous fuels.

Many petrol engines have been converted to run on LPG or similar to obtain low operating costs and reduced combustion emissions. The conversion of diesel engines, particularly heavy-duty diesel engines, has not been as successful as conversion of less powerful petrol engines. Yet the cost savings are potentially greater for heavy-duty engines as they consume more fuel.

When a heavy-duty diesel engine is converted to operate on a liquefied gas fuel

such as LPG, the liquid fuel must first be converted to gaseous form for delivery into the engine cylinders. Currently, the most common method of converting the liquid fuel to gaseous form and delivering it to the engine is through the use of gas converters and gas valves. However, these conventional methods are unsuitable for use in heavy-duty engines as they will not deliver sufficient gas vapour to meet demand in such engines when operating at high power. Additionally, the conventional devices are usually relatively complex incorporating many moving parts.

The transition to gas fuels has encountered a number of technological hurdles.

The use of LPG, LNG and similar gas sources creates difficulties in all engines including diesel engines and in particular high performance diesel engines for commercial vehicles such as prime movers. Due to the high compression produced in such engines and the heat generated by combustion, the use of volatile flammable gases may lead to early detonation in combustion chambers with resulting interference to orderly and controlled combustion in the motor. This may lead to inefficiency in operation and defective running of an engine.

Additionally, it is a clear and real risk that detonation of the compressed gases at an inappropriate stage of the combustion cycle may lead to physical damage to the cylinder, piston rings or valves.

It would be advantageous to provide a system including a heat exchanger for converting liquid fuel into gaseous form suitable for use with gas engines and in particular high powered gas engines.

It would also be of considerable advantage to provide a means of cooling the intake air or the mixture of air and fuel prior to or on delivery to a combustion chamber to thereby reduce the risk of mistimed detonation.

SUMMARY OF THE INVENTION Throughout this specification, unless the context requires otherwise, the word "comprise", or variations such as"comprises"or"comprising", will be understood to imply the inclusion of a stated element or integer or group of elements or integers but not the exclusion of any other element or integer or group of elements or integers.

In one broad form, the present invention provides a conversion system to convert liquid fuel to gaseous form for use in an internal combustion engine, said conversion system comprising: heat exchange means for transferring heat from a liquid heat source to the liquid fuel ; and valve means adapted to control the flow of the liquid heat source to the heat exchange means; wherein operation of the valve means is dependent on the temperature of the liquid fuel.

The liquid fuel may be any suitable fuel source such as LPG, LNG or Propane.

The heat exchange means preferably comprises a heat exchanger having: a first inlet for receiving fuel in liquid form, and a first outlet for delivering the fuel in gaseous form; a second inlet for receiving the liquid heat source and a second outlet for delivering the liquid heat source; and the heat exchanger being configured to provide thermal exchange between the fuel therein and the liquid heat source to thereby convert the liquid fuel to gaseous form.

The liquid heat source is preferably coolant liquid from the engine which is

returned to the engine after passing through the heat exchanger.

In a preferred embodiment, the heat exchanger comprises a series of small- diameter spaced stainless steel tubes extending longitudinally within a large diameter stainless steel outer tube. Coolant flows in the large tube around the small tubes which carry the fuel. The inlet ends of the small tubes communicate with a manifold in an end cap at one end of the large tube. The outlet ends of the small tubes also communicate with a manifold in an end cap at the other end of the large tube. The end caps are connected into the fuel line. Coolant is introduced into the large tube by a radial opening at one end, and removed through a radial opening at the other end. The openings are suitably provided with threaded coupling that can be connected into the engine cooling system by flexible hoses.

The valve means is suitably a thermostat valve which is designed to open whenever the temperature of the input liquid fuel is below a predetermined temperature. For example, if LPG is being used as the fuel, the valve would normally open whenever the temperature is below-27°C. (The LPG in the storage tank is usually around-37°C). The valve may open at any suitable temperature which is selected to avoid icing up or freezing of the liquid coolant.

Unlike thermostat operation in normal internal combustion engines in which fans and other cooling mechanisms are activated when engine temperature rises above a certain value, the thermostat value used with the heat exchanger of this invention opens when temperature is below a predetermined value. Thus, additional heat from the engine coolant is applied to the liquid fuel to convert it to gaseous form.

The valve means may have a simple open/closed operation leading to full flow of coolant when open and complete obstruction of flow when closed. Preferably, however, the valve means has a variable response for varying the flow rate between open and closed according to the temperature of the liquid fuel. The flow

rate may be adapted to maintain the outside temperature of the heat exchanger in the range of 20°C to 100°C. Preferably the range is 60°C to 90°C. The most preferred range is 70°C to 80°C and in particular 75°C.

Preferably the system includes an intake fuel pressure regulator means located upstream of the heat exchange means. The intake fuel pressure regulator means may comprise an intake pressure regulator. The intake fuel pressure regulator may be set to maintain pressure at 100 pounds per square inch ("psi") or less.

Preferably the intake fuel pressure regulator includes a variable pressure setting to permit alteration of the set pressure.

The conversion system may also include an outlet fuel pressure regulation means.

The outlet fuel pressure regulation means may suitably comprise an outlet fuel pressure regulator. Preferably, the outlet fuel pressure regulator is adapted to maintain outlet fuel at a pressure between 40 psi to 400 psi. The outlet fuel pressure regulator may include a variable pressure setting to permit alteration of the set pressure.

The conversion system may further include direct gas delivery means adapted to provide direct gas delivery into each individual cylinder of the internal combustion engine. The direct gas delivery means may comprise one or more gas delivery tubes for each cylinder. The one or more gas delivery tubes may suitably be formed of flexible hose material.

The direct gas delivery means may also include at least one gas injector for the engine. The at least one injector may comprise: a curved tubular member having a channel terminating in an outlet ; and a connecting member adjacent the tubular member having a passage which is continuous with the channel to form a fluid path through the injector.

The injector may further comprise a flange.

The flange, may have at least one aperture to receive a fixing member. The connecting member may be externally threaded. Two or more of the curved tubular member, the connecting member and the flange may be formed integrally.

Due to the configuration of the heat exchanger, a high throughput of fuel can be obtained at high and regulated pressure. The heat exchanger arrangement thereby eliminates the need for depressurisation which often causes severe icing up of the fuel rail, and consequently engine shutdown.

The conversion system may further include an intake air cooling device for the gas combustion engine, the device comprising : a conduit for passage of a liquid fuel, the conduit having a thermal exchange surface; and a chamber for passage of charge air for delivery to a combustion chamber of the engine; wherein the conduit is disposed in the chamber such that the charge air may contact the thermal exchange surface.

The conduit may be formed as at least one tubular coil. The thermal exchange surface may be metallic and preferably stainless steel or aluminium and may form the wall of the conduit. The conduit may be formed of multiple tubular members in fluid connection with an intake manifold and an outlet manifold.

The chamber may be located within an air intake manifold of the engine. The walls of the chamber may be formed by or, alternatively, separate from the walls of the air intake manifold of the engine.

Alternatively, the intake air may pass through the conduit and the liquid fuel may pass through the chamber.

In a further aspect the invention resides in a method of converting liquid fuel to

gaseous fuel for an internal combustion engine, the method comprising the steps of: passing the liquid fuel through a heat exchanger wherein the liquid fuel is converted to gaseous fuel due to transfer of heat from an engine coolant ; and varying the flow of engine coolant to the heat exchanger depending on the temperature of the liquid fuel.

Varying the flow of engine coolant may comprising providing full flow of engine coolant below a set temperature or preventing flow of engine coolant to the heat exchanger above the set temperature. Preferably varying the flow of engine coolant includes providing a range of flow rates between full flow and nil flow over a suitable temperature range. Most preferably the range of flow rates may be infinitely variable over the suitable temperature range.

The method may include the step of providing full flow of engine coolant to the heat exchanger when the liquid fuel is LPG at a temperature below-27°C and preventing engine coolant flow to the heat exchanger when the temperature is- 27°C or more. The flow rate may be adapted to prevent icing up of the heat exchanger. Suitably the flow rate may be adapted to maintain the average temperature of the heat exchanger in the range of 20°C to 100°C, preferably 60°C to 90°C, most preferably 70°C to 80°C.

The method may include the step of using an intake pressure regulator to control the intake pressure of liquid fuel delivered to the heat exchanger. The intake pressure regulator may be set to maintain pressure around a level of 100 psi or less.

The method preferably further includes the step of using an outlet pressure regulator to control the pressure of outlet gas delivered from the heat exchanger.

The outlet pressure regulator may be set to maintain pressure of outlet gas at a level of between 100 psi and 400 psi.

The method may further include the step of delivering outlet gaseous fuel directly into each individual cylinder of an internal combustion engine. Delivery of gaseous fuel may include the step of using flexible hose members to transfer gas into each cylinder of the engine.

The outlet gaseous fuel is preferably delivered into the cylinder adjacent an inlet valve. The method may further use electronically controlled fuel injectors to control the dose of gaseous fuel to each cylinder.

The method may include the step of cooling charge air for delivery to the engine comprising the step of cooling the charge air by locating liquid fuel and the charge air in heat-exchanging proximity. Charge air in this specification refers to air provided to the cylinders of the engine for combustion with fuel.

Preferably the liquid fuel and charge air are separated by a heat conducting membrane. The heat conducting membrane is preferably a tubular wall. The heat conducting membrane may be formed of metal. Suitably the metal is stainless steel or aluminium.

The method may include the steps of: pumping liquid fuel through a tubular structure, the walls of which form the heat exchanging membrane; and directing the charge air around the tubular structure.

The cooling of the charge air may suitably take place in an intake manifold of the engine.

The method may further include the step of providing a curved injector for delivery of gaseous fuel into a cylinder of the engine.

In another aspect, the invention resides in an intake air cooling device for the gas combustion engine, the device comprising:

a conduit for passage of a liquid fuel, the conduit having a thermal exchange surface; and a chamber for passage of charge air for delivery to a combustion chamber of the engine; wherein the conduit is disposed in the chamber such that the charge air may contact the thermal exchange surface to provide heat exchange between the fuel and charge air.

The conduit may be formed as at least one coil. The thermal exchange surface may be metallic and preferably stainless steel or aluminium and may form the wall of the conduit. The conduit may be formed of multiple tubular members in fluid connection with an intake manifold and an outlet manifold.

The chamber may be located within an air intake manifold of the engine. The walls of the chamber may be formed by or, alternatively, separate from the walls of the air intake manifold.

Alternatively, the intake air may pass through the conduit and the liquid fuel may pass through the chamber.

In yet another aspect, the invention resides in a gas injector for an engine, said injector comprising: a curved tubular member having a channel terminating in an outlet ; and a connecting member adjacent the tubular member having a passage which is continuous with the channel to form a fluid path through the injector.

The injector may further comprise a flange.

The flange, may have at least one aperture to receive a fixing member. The connecting member may be externally threaded. Two or more of the curved tubular members, the connecting member and the flange may be formed

integrally.

In another aspect, the invention resides in a kit for use in conversion of liquid fuel to gaseous fuel, for an internal combustion engine. The kit comprising a heat exchanger for conversion of liquid fuel to gaseous fuel through the transfer of heat from an engine coolant ; and an inline thermostatically controlled valve for controlling the flow rate of engine coolant to the heat exchanger depending on the temperature of the liquid fuel.

The kit may include an intake liquid fuel pressure regulator and an outlet gaseous fuel pressure regulator. Preferably the regulators are fully adjustable.

The kit may also include individual delivery hose members for providing a fluid path for delivery of gaseous fuel directly into individual cylinders.

The kit may further include one or more injectors as described above. Further the kit may include an intake air cooling device as described above.

In order that the invention may be more fully understood and put into practice, a preferred embodiment thereof will now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic diagram illustrating an embodiment of a fuel conversion system of the present invention.

Figure 2 is a schematic diagram illustrating the position of the thermostat valve relative to a fuel delivery system and coolant delivery system.

Figure 3 is a schematic elevation of a preferred embodiment of a heat exchanger

of Figures 1 and 2.

Figure 4 is an enlarged sectional elevation of the end portion of the heat exchanger of Figure 3.

Figure 5 is a sectional end view of the heat exchanger of Figure 3 through section plane A.

Figure 6 is a schematic representation of a fuel line for an engine incorporating a fuel conversion system of the present invention including an air cooling arrangement.

Figure 7 is a schematic representation of a second embodiment of a fuel line featuring a conversion system of the present invention, including an air cooling arrangement.

Figure 8 is a perspective view of a gas injector for the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS As shown in Figure 1, fuel gas, such as LPG or LNG, is stored in liquid form under pressure in a fuel tank 10. The liquid fuel is fed via a fuel line 11 to a heat exchanger 12 where it is converted to gaseous form. The pressurised gas then passes to the intake manifold 14 of an engine. While it is acceptable to deliver the gaseous fuel to a manifold, this method may on occasion encounter some difficulties. One of the problems that may arise is the presence of a mixture of gaseous fuel and air in the manifold, the mixture being susceptible to ignition in the event of an engine backfire. Detonation of the mixture may result in damage to the manifold and associated components. In a preferred embodiment, the gaseous fuel may be delivered internally into the cylinder through individual electronically controlled fuel injectors. A fluid pathway is then provided to deliver a gaseous fuel dose directly into a cylinder. The dose of fuel is preferably delivered

in the vicinity of an inlet valve of the combustion chamber. This method avoids mixture of the gaseous, fuel and air before entry into the cylinder.

The liquid fuel passes through an intake pressure regulator 15 which may be an adjustable regulator. A suitable range of pressure control may be set at a level of 100 psi or less so as to provide a steadily pressurised fuel supply. The pressure controlled liquid fuel is then provided to the heat exchanger 12 via fuel line 11.

On exit of gas fuel from the heat exchanger 12, an outlet pressure regulator 20 is provided to control gas supply pressure. The gas regulator is preferably an adjustable regulator and may be set within the range of 40 psi to 400 psi. For simplicity, pressure gauges, valve switches and similar components have been omitted from Figure 1 but may be applied. The pressure regulators 15,20 are of types well known to a skilled addressee.

As can be seen in Figure 1 and Figure 2, the heat exchanger 12 has an inlet 16 adapted to receive coolant fluid from the engine (not shown). Typically, inlet 16 is connected to the discharge side of the water pump of the engine to receive some of the coolant water being circulated via the water pump. The heat exchanger also has an outlet 17 for returning the coolant water to the suction side of the engine water pump. The inlet 16 and outlet 17 are suitably provided with threaded coupling that are connected to the engine cooling water system by way of flexible hoses.

A thermostat valve 18 is located in the coolant line having a temperature sensor 19 located in the fuel line 11. (In Figure 1, the valve 18 is shown on the coolant discharge side of the heat exchanger, but it could alternatively be located on the inlet side). Operation of the valve 18 is dependent upon the temperature of the fuel passing from fuel line 11 to the heat exchanger 12, as sensed by a temperature sensor 19. The thermostat valve 18 may have a simple open/closed operation so that around or below a certain threshold temperature, the valve 18 may open to provide engine coolant to the heat exchanger. This temperature may

be selected at a level below which the device may inadequately gasify the fuel or provide gas at too low a temperature. Flow of the liquid coolant provides an increased heat supply leading to increased efficiency of the heat exchanger function with improved gas production.

The thermostat valve 18 may also be set to close the valve and interrupt flow of liquid coolant to the heat exchange, at or above the threshold temperature. If the gas produced becomes too heated, the quality of the product as a fuel source may be adversely affected. One possible effect is the production of oil residue with a potential clogging effect on fuel injectors further downstream.

It may however be preferable to have a response to temperature changes in the liquid fuel so that the flow rate of liquid coolant may be varied according to variation in a temperature range for the liquid fuel. For example, in the case of LPG, a suitable range may commence with full flow of liquid coolant to the heat exchanger below-37°C and may gradually decrease to interrupted or nil flow at any suitable temperature selected to prevent overheating of the gaseous fuel. In general, the lower threshold temperature is selected to avoid icing up of the heat exchanger. The upper temperature is selected to provide a gasified fuel. The inventor has found a suitable effect may be obtained if the outer surface of the heat exchanger is in the range of 70°C to 80°C, although a range of 20°C to 100°C may be acceptable in certain circumstance. The appropriate temperature range may be easily established by a person skilled in the art, without any inventive input.

The addition of heat from the engine coolant is also important to prevent icing up of the heat exchanger due to delivery of the cold liquid fuel and the energy absorbed during the change of state to gas.

The construction of a suitable heat exchanger 12 is shown in more detail in Figures 3-5. The heat exchanger 12 comprises an elongate stainless steel tube 21 in which the radial inlet 16 and radial outlet 17 are suitably joined at opposite

ends. The tube 21 is provided with end caps at its opposite ends in which inlet 23 and outlet 24 are formed, respectively. The inlet 23 and outlet 24 are suitably provided with threaded coupling for connection to the fuel lines 11,13 respectively. The tube 21 is typically a 60mm (outer diameter tube).

The tube 21 also contains a plurality of smaller diameter tubes 25, typically 6mm (outer diameter) stainless steel tubes, extending longitudinally inside the tube 21 and spaced generally evenly within the tube. In the illustrated embodiment, there are 15 of the smaller diameter tubes, five being equally spaced circumferentially around the longitudinal axis of the heat exchanger, surrounded by the remaining ten small diameter tubes which are also spaced equally circumferentially.

The small diameter tubes 25 have their opposite ends fixed to manifold plates 26, 27 located at respective opposite ends of the tube 21. In this manner, the inlet of each small diameter tube communicates directly with the inlet 23 to the heat exchanger, and the outlet of each small diameter tube 25 communicates directly with the outlet 24 of the heat exchanger.

If the fuel is LPG, it would normally be stored at around-37°C in the fuel storage tank 10. The valve 18 may be designed to be open whenever the temperature of the fuel in fuel line 11, as sensed by sensor 19, is below-27°C. Thus, when the LPG is flowing to the heat exchanger, the valve 18 will normally be open to enable the coolant fluid to circulate through heat exchanger 12. The configuration of the small diameter tubes 25 carrying the fuel in the heat exchanger 12 promotes good thermal exchange with the surrounding coolant liquid in the heat exchanger, thereby heating the liquid fuel and causing it to vaporise.

If, for any reason, the temperature of the LPG rises above-27°C, the valve 18 will shut off to stop the flow of coolant to the heat exchanger. (At that temperature, the liquid fuel may vaporise without additional heat).

The heat exchanger of this invention enables liquid fuel to vaporise at a high rate

without substantial loss of pressure, thereby satisfying the demand of heavy duty engines. The addition of pressure regulation also provides a steady supply of gaseous fuel under controlled pressure for delivery to combustion chambers. The effect of the present system is enhanced by the addition of individual direct intra- cylinder delivery of gaseous fuel. The present invention provides a great advantage in the provision of gaseous fuel to internal combustion engines, particularly modified diesel or petrol engines. The system is mechanically simple and substantially devoid of moving parts, thus providing a reliable and low maintenance arrangement.

Referring to Figure 6 there is seen a general schematic representation of a fuel line conversion system for providing cooled charge air for an engine (not shown).

A fuel tank 30 acts as a reservoir for combustible matter which in this case is LPG fuel. The liquid gas is delivered through a fuel inlet line 31 to a first heat exchanger 32 in the form of cooling core 34 which may be formed from any suitable material known to a skilled addressee. One particularly suitable structural material is in the form of metal and more particularly stainless steel. The cooling core may be as basic as a single line located in a chamber 35 which may be defined by outer walls 36. The inlet line 31 as previously described may deliver liquid fuel to the cooling core 34 and an outlet line 37 may provide a pathway for delivery of exiting liquid fuel from the cooling core for further application in combustion. Shading in the drawing represents charge air.

The preferred configuration of the cooling core 34 involves maximising surface area of the core 34 to provide the most efficient exchange of heat between air in the chamber 35 and fluid in the cooling core 34. While any suitable configuration may be utilised, a system with coiled tubes may provide an advantage in operation.

Alternatively, the cooling core may be formed by multiple tubular conduits which may be connected to an inlet manifold for delivery of liquid fuel and connected at an opposite end to an outlet manifold for collection of liquid fuel for subsequent

use in combustion.

In operation, heat from the intake air is transferred to the liquid fuel causing cooling of the air and warming of the liquid fuel. This warming may serve as a beneficial pre-conditioning of the liquid fuel prior to delivery to the vaporising heat exchanger 39.

The outer walls 36 describe chamber 35 and may be located in any suitable position. One of the most effective sites for location of the cooling core is in the air inlet manifold of a motor. In this circumstance, a quantity of charge air awaiting utilisation in the cylinders of the motor may be cooled immediately prior to delivery to the cylinders of the engine, and mixing with the particular fuel of the engine.

The existing walls of a vehicle manifold may then form the walls of the cooling chamber.

In such a circumstance, the inventor has found that the tuning of the motor may be best achieved using at least one butterfly throttle 33 for delivery of a required amount of air to the intake manifold and hence cooling chamber of a diesel motor.

Preferably, throttle butterflies are individually tuned to a particular engine so that the settings may be calculated to provide the most precise and efficient use of fuel in the motor. The inlet through the throttle butterfly may be suitably sized to a particular engine.

Referring further to the schematic drawing of Figure 6, outlet gas is subsequently delivered to an intake pressure regulator 38 by fuel line 37. The liquid petroleum gas or other liquid fuel supply may then be passed through a thermostat valve 46 and to a vaporising heat exchanger 39 to render it into suitable gaseous form for mixing with air and combustion. The vaporising heat exchanger 39 may suitably be formed and operate as described above. The gaseous fuel may then be delivered to an outlet pressure regulator 40 to ensure the consistency of gas supply. The operation of this arrangement of regulators and vaporiser is substantially as described above and will not be further outlined. Gas may be

passed through a filter 41 prior to delivery through fuel line 42 which is in fluid communication with line 37. The gaseous fuel is ultimately delivered to a fuel rail 43 to be passed through injectors 44 into the cylinders of the engine (not shown) for combustion.

Figure 7 schematically highlights the interaction of the fuel supply system and the air cooling device. Liquid fuel is delivered to a first pressure regulator 45 and passes through a thermostat valve 46 before delivery to a vaporiser or heat exchanger 47. The thermostat valve 46 may be used to control the level of heat provided in the vaporiser to convert the liquid fuel into gaseous fuel prior to combustion. The thermostat valve 46 may control the amount of heating fluid delivered to the vaporiser as described above. Liquid fuel is converted to gaseous fuel in the vaporiser 47 before delivery to a second gas pressure regulator 48 which controls the delivery pressure of gas to the fuel side of the engine. The gas may be passed through a filter 49 and then delivered to the fuel rail block 50 and to the gas fuel injectors 51. The injectors 51 are preferably individually dedicated to each cylinder they supply. This arrangement allows for the exact metering of gas provided to the cylinder with subsequent precise control of quantity of fuel added to air in the cylinder. Most preferably, the system is computer controlled with a range of variability in the amount of gas delivered to the cylinders to reflect the operating conditions of an engine at any particular time. Charge air 52 is confined in the intake manifold 56 of the engine ready for cooling by passage around the cooling core 54 which may be located in its own cooling chamber or, as shown here, simply located in the intake manifold 56. The cooled air is delivered to the gas engine 53 for mixing with injected fuel from the injectors 51 prior to detonation. Preferably the gaseous fuel is injected directly into each cylinder.

This may be achieved using a port as described in relation to Figure 8. Liquid fuel exiting from the cooling core 54 is supplied to first regulator 45 for passage through the system for combustion.

Figure 8 shows a curved fuel distribution port 57 suitable for use with a diesel engine converted to run on gaseous fuel. The fuel distribution port 57 comprises a

flange 58 which supports a curved tubular delivery member 59 with a central channel 60 terminating in outlet 61. The central channel 60 is continuous with a central passage (not seen) in inlet spigot or tubular connecting member 62 which has a threaded end 63 for receiving a gas delivery line (not seen) which is preferably flexible. The flange 58 has two apertures 64 for receiving fixing members (not shown) to stably fix the fuel injector in place on an engine. The delivery member 57 preferably is located to provide the outlet 61 with a discharge area in the vicinity of the intake valve of an engine. In order to locate the fuel distribution port 57 it is necessary to drill an appropriate channel in the head of the engine or inlet manifold. Discharge is best described so that the fuel is sprayed at the back of the inlet valve of the engine. The use of the fuel distribution port 57 provides for very accurate control of fuel with effective mixing with air. The inlet spray into the cylinder may be controlled down to the level of around 4 milliseconds discharge under the control of a computer.

While a description of the heat exchanger has been provided with reference to the use of a liquid fuel supply it is clear that any other cold liquid may be used to cool the charge air prior to combustion. A compressor and system similar to that used in an automobile air conditioning system may be applied for the same purpose.

Clearly some modification in operation of such a cooling system would be required. This may particularly be the case when cooling systems using phase changes of liquids are harnessed to cool the charge air.

The advantages of the present invention including the air cooling arrangement are readily apparent. The cooled charged air decreases or avoids the risk of inappropriate detonation. This provides more generalised combustion in a cylinder and is particularly so when the engine is matched to a throttle for the delivery of an appropriate and precise amount of air to a cylinder. If a novel injector is used the amount of fuel delivered can be precisely matched to the operating conditions of the motor which will increase sufficiency and decrease pollution. It is known to use automatic sensors to monitor the level of oxygen in expelled gases from an engine and to thereby automatically vary the tuning of an engine through computer

controls. This variation may be precisely achieved with the present system. When using the liquid fuel supply as the cooling source, a high level of efficiency and energy conservation is obtained. In the absence of the cooling effect the gas produced from liquid fuel simply absorbs energy during its pre-ignition warming without beneficial effect. The combination of the above described integers provides an efficient and precisely controllable engine arrangement.

Although emphasis has been placed on diesel motors, it is clear that the above system and method can also be applied to petrol engines which are converted to run on liquid fuels.

Throughout the specification the aim has been to describe the preferred embodiments of the invention without limiting the invention to any one embodiment or specific collection of features. Those of skill in the art will therefore appreciate that, in light of the instant disclosure, various modifications and changes can be made in the particular embodiments exemplified without departing from the scope of the present invention. All such modifications and changes are intended to be included within the scope of the appendant claims.