BACKGROUND OF THE INVENTION Two-stroke engines generally employ an exhaust system using piping whose internal diameter varies over the length of the exhaust system.

This improves the efficiency of the engine. Generally, a cylindrical header is attached to the engine exhaust port of the combustion chamber. A diverging cone is secured to the downstream end of the header. This is followed by a larger diameter cylindrical mid-section which leads to a converging cone. The converging cone in turn leads to a cylindrical exhaust pipe which communicates with the atmosphere.

Improved efficiency resulting in increased power is a result of pressure waves in the exhaust gas. These act as follows. When the exhaust port opens, the gas pressure in the cylinder is greater than that in the exhaust system as the latter is open to the atmosphere. Due to the pressure difference, the exhaust gas flows from the cylinder and a pressure pulse is created to pass through the gas. When the pulse reaches the diverging cone after passing through the header, a negative pressure wave returns up the header to the exhaust port and, if timed correctly, arrives when the cylinder's intake port is in the open position. The length of the diverging cone as well as its angle from the axis of the pipe determine a profile of the negative wave.

As the pressure pulse travels down the pipe, it is reflected back from the converging cone. This pressure wave (or plugging pulse) travels back to the exhaust port just prior to its closing, pushing back into the cylinder the fresh charge that has entered through the intake port into the cylinder and part way down the header.

The angles of the diverging and converging cones are very important to the efficiency of the engine. They must be timed with the engine port timing so that pressure pulses arrive at the correct times. The larger diameter cylindrical mid-section is used to separate the diverging and converging cones to achieve this timing. The header length also assists in this respect.

Two-cycle engine exhaust systems have been refined over the years to the point where any increase in power achieved in a certain region of the power band results in a loss in power in another region. Adjusting the physical characteristics of such an exhaust system is often referred to as tuning.

In a tuned expansion chamber of the prior art, the broader the angle of a divergent cone, the stronger the plugging pulse. However, this occurs at the expense of the duration of the pulse. If too broad an angle is used, wave separation will occur."This separation is related to the mach number of the particle velocity more than the actual angle of the cone" (Design and Simulation of Two Stroke Engines, Chapter 2, G. P. Blair).

Reflected pressure pulses are also employed in four-stroke engines to increase engine efficiency, though to a lesser degree. Reflected pressure pulses are also employed to assist efficient gas flow on the intake side of internal combustion engines using similar principles.

SUMMARY OF THE INVENTION It is an aim of the present invention to overcome the limitations described above and to provide an exhaust system for an internal combustion engine which offers increased power without adversely affecting the engine's power band profile.

It is also an aim of the present invention to provide an engine intake system which improves engine efficiency.

The present invention comprises a gas flow splitter to be secured within a pipe associated with an internal combustion engine, the splitter to be oriented within the pipe for the purpose of dividing the flow of gas through the pipe over a predetermined distance. The present invention also comprises a gas flow splitter to be secured within a pipe associated with an internal combustion engine, whereby the power of the engine is increased and the power band of the engine is substantially undiminished.

The present invention also comprises a gas flow splitter to be secured within an exhaust pipe associated with a two-stroke internal combustion engine, whereby the length of the pipe may be reduced without substantially diminishing the power of the engine.

The present invention also comprises a fluid flow splitter to be located in a pipe whereby fluid pressure downstream of the splitter is reduced thereby permitting increased fluid flow.

Therefore, in accordance with the present invention, there is provided a pipe associated with an internal combustion engine in combination with a gas flow splitter, said splitter being provided within said pipe and extending axially therein over a predetermined distance, thereby dividing the flow of gas through said pipe.

Also in accordance with the present invention there is provided, in a pipe associated with an internal combustion engine, the improvement of providing a splitter adapted to be mounted within the pipe such as to extend axially therein over a predetermined distance, thereby dividing the flow of gas through the pipe.

Further in accordance with the present invention, there is provided a pipe in combination with a fluid flow splitter, said splitter being provided within said pipe and extending axially therein over a predetermined distance, thereby dividing the flow of a fluid through said pipe.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood by way of the following detailed description of preferred embodiments with reference to the appended drawings, in which : Figure 1 is an isometric view of a diverging cone of an exhaust system in accordance with an embodiment of the present invention ; Figure 2 is a sectional view of the diverging cone of Figure 1 ; Figure 3 is a graph demonstrating power generated at various engine speeds using the diverging cone of Figures 1 and 2, as compared to power generated without the splitter shown in those figures ; Figure 4 is an isometric view of a diverging cone of an exhaust system in accordance with a second embodiment of the present invention ; Figure 5 is a sectional view of the diverging cone of Figure 4 ; Figure 6 is a graph demonstrating power generated at various engine speeds using the diverging cone of Figures 4 and 5, as compared to power generated without the splitter shown in those figures ; Figure 7 is an isometric view of a header and a diverging cone of an exhaust system in accordance with a third embodiment of the present invention ; Figure 8 is a sectional view of the header and diverging cone of Figure 7 ; Figure 9 is a graph demonstrating power generated at various engine speeds using the header and diverging cone of Figures 7 and 8, as compared to power generated without the splitter shown in those figures ; Figure 10 is a representation of air flow through a pipe having opposed cones ; Figure 11 is a representation of air flow through a pipe having opposed cones and a splitter located therein ; Figure 12 is an isometric view of an intake port of an internal combustion engine in accordance with a third embodiment of the present invention ; Figure 13 is an end view of the inlet port of Figure 12 taken along line 13- 13 thereof Figure 14 is a representation of an expansion chamber in contact with an airflow bench ; and Figure 15 is a graph demonstrating pressure readings obtained at different locations in the expansion chamber of Figure 14.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The embodiment of the present invention shown in Figures 1 and 2 involves a splitter 10 in the form of a plate secured within a diverging cone 12 of a two-stroke engine exhaust system. The splitter 10 runs longitudinally between a header (not shown) at the inlet end 14 of the diverging cone 12 and a cylindrical mid-section (not shown) at the outlet end 16 of the diverging cone 12. The splitter 10 is located on the central axis through the axis of the diverging cone 12.

In testing, the addition of the splitter increased the power of the engine without substantial loss in any other region of the power band.

As can be seen in Figure 3, the output of the split cone was well above that of the normal cone. This output was as high as 6% more than the stock pipe. Output was higher and the power band was increased.

Figures 4 and 5 show a second embodiment of the present invention.

Here, a four-way splitter 20 is employed as with the first embodiment, the splitter is secured within a diverging cone 22 of a two-stroke engine exhaust system. The splitter 20 runs longitudinally between a header (not shown) at the inlet end 24 of the diverging cone 22 and a cylindrical mid- section (not shown) at the outlet end 26 of the diverging cone 22. The splitter 20 is located on the central axis of the diverging cone. The four-way splitter 20 comprises four arms 28.

Figure 6 shows a substantial increase in power at low engine speeds.

However, reduced power was shown in Figure 6 at high engine speeds.

The engine ran roughly, possibly due to interference with shock waves.

This may have been due to increased pressure of the returning plugging pulse.

Other types of splitters which have the effect of dividing gas flow through a diverging cone are contemplated. It is also contemplated that the splitter may have a different length and may be placed in other pipes associated with an internal combustion engine. For example, a splitter could be located within the header.

Tests were conducted by adding a splitter to the end of a header pipe as shown in Figures 7 and 8. A four-way splitter 30 is located in the header pipe 32 adjacent to diverging cone 34. Figure 9 demonstrates a small increase in peak power and a substantial increase in top end power.

Reynolds established that the transition from laminar to turbulent flow was a function of a single parameter that has since become known as the Reynolds Number. If the Reynolds Number, which is the product of velocity, fluid density and pipe diameter, divided by the fluid viscosity, is less than 2100, the pipe flow will always be laminar ; at higher values it will normally be turbulent.

Splitting the cone and/or header should help to keep the exhaust flow laminar. There will be an increase in friction because of the split, however the flow should remain laminar after the split.

Figures 10 and 11 show results of a test performed to compare flow in a cone that is split (Figure 11) and an unmodified or plain cone (Figure 10).

Air was extracted from cones (40 and 42) with a vacuum pump. Air entered cones (40 and 42) through tube (44) to establish laminar flow entering the cone (40 and 42). Flour was added to the incoming air so laminar and turbulent flow could be seen in cones (40 and 42). The only difference in the two tests was that a splitter (46) was added in Figure 11.

In Figure 10, turbulence started approximately of the way down the cone (42) and actually had a reverse air flow pattern at end of cone.

In Figure 11, turbulence did not start until after the splitter (46) in the cone (40), showing laminar flow through almost the entire length of the cone (40).

This may also be why the split cone of an expansion chamber has a higher power output and broader power range.

The number'of splits, the length of splits, and the location of splits all will have an effect on performance. The use of this invention is not limited to the exhaust but also on the intake as timing of its opening and closing is also critical to the length, volume, diameter and taper of the intake track.

Figures 12 and 13 demonstrate the use of the splitter of the present invention in the intake system of a four-stroke internal combustion engine. A splitter 50 is secured longitudinally within an intake port 52 in alignment with intake valve stem 54. Gas enters the intake port 52 from an intake manifold (not shown). The gas passes through inlet port 56 into combustion chamber 58. Valve stem 54 is attached to valve 60 which sits on valve seat 62 when closed. At appropriate times, valve 60 is opened to allow passage of gas into combustion chamber 58.

In testing, the addition of this intake splitter has resulted in increased engine power output without adversely affecting the power band profile.

It is hypothesized that the addition of a splitter in the intake side may have a similar effect in the opposite direction to the addition of a splitter on the exhaust side. The use of the splitter may also have the effect of reducing the Reynolds number of the pipe, thus reducing the turbulence of the gas entering the combustion chamber.

Another variation of the splitter is a twist. The twisted splitter is shaped such that adjacent airflow will be helical. It has been found that increasing the particle velocity by twisting the splitter will help to reduce wave separation from the diverging cone. It has also been found that, by twisting the splitter, the tuned length of the expansion chamber can be increased without physically increasing the length of the expansion chamber.

Referring to Figure 14, a test was performed using an expansion chamber 70 having an inlet 71 of 45 mm diameter expanding to 90 mm diameter over a length of 220 mm with a middle straight section 73 of 90 mm diameter. This expansion chamber was placed in contact with an airflow bench 72. Overall length from the inlet 71 to the airflow bench 72 was 505 mm. Pilot pressure sampling holes 74 were located at 45 mm, 101 mm, 152 mm, 205 mm and 250 mm from the inlet. Pilot pressure measurements were taken in mm of water starting at 45 mm from the inlet, as well as in the airflow bench.

Figure 15 presents the results of these measurements. These results show that particle velocity is increased by use of the twisted splitter. In addition, the overall mass flow rate has been improved.

A test of water flow through a nozzle was conducted using a 2-litre soft drink bottle with the bottom cut out. A splitter with a twist was inserted in the converging cone section of the bottle. The bottle was inverted and filled with 2 litres of water using a cork as a stopper. Twists of the splitter from 0° to 45° were tried. A stopwatch was started upon removal of the cork and stopped when all of the water had drained. Improvements of up to 0.3 seconds in drain time were recorded depending on the angle of the twist. This represents a time reduction of about 7 or 8%.

The above two tests show an improvement in mass flow rate. Where space is a concern, the problem can be overcome by use of a twisted splitter. The tuned length of an expansion chamber is more important than the volume.

The tuned length of an expansion chamber can be increased using twisted splitters. By the same principle, one could reduce the physical pipe length without reducing engine performance.

It should be understood that the embodiments specifically described herein are intended to be examples of the present invention and are not limitative. Various different sizes, locations and geometries of splitters, including splitters located off-axis or having geometries and locations which are variable with respect to engine speed or other criteria, can be employed provided they have the effect of increasing engine power without substantially diminishing power in another region of the engine's power band. Variable geometries of splitters could be achieved by direct mechanical means (e. g. displaced by an actuator controlled, for instance, by engine speed), or by some other means (e. g. fluid flow pressure).

In addition, opposite sides of a splitter need not meet within the pipe.

Instead, they could take the form of internal fins secured to the wall of the pipe but not meeting one another.

Furthermore, it is not necessary that a splitter be in contact with the pipe at any particular point either on the splitter or within the pipe.

Finally, a splitter for increasing fluid flow could be employed in environments other than an internal combustion engine. The same principle could be applied in other types of pipes having fluid flow.