CA2034928C - Secondary fuel modulating valve - Google Patents

Abstract

SECONDARY FUEL MODULATING VALVE
Abstract of the Disclosure A valve for controlling the flow of secondary fuel to a turbo-charged diesel engine. The valve incorporates a cylinder, a first inlet port which couples the cylinder to a secondary fuel reservoir, a second inlet port which couples the cylinder to the engine's turbo-charger, a discharge port which couples the cylinder to a secondary fuel inlet of the engine, and a piston which is slidably displaceable within the cylinder to controllably open and close the discharge port in response to changes in the turbo-charger's boost pressure. The piston moves between a closed position in which the piston blocks secondary fuel flow from the first inlet port to the discharge port, a first range of open positions in which the piston allows progressively increasing amounts of secondary fuel to flow from the first inlet port to the discharge port, and a second range of open positions in which the piston allows progressively decreasing amounts of secondary fuel to flow from the first inlet port to the discharge port.

Description

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SECONDARY FUEL MODULATING VALVE
Field of the Invention This application pertains to a valve for modulating the flow of a secondary fuel, such as propane, to a diesel engine in response to changing engine loads.

Background of the Invention Diesel engine fuel systems which utilize diesel fuel as the primary fuel and a secondary fuel such as propane are well known. Conventionally, dual fuel systems of this sort are employed to increase the horsepower output by the diesel engine.
As a general rule, it is undesirable to operate a diesel engine in excess of the maximum rated horsepower specified by the engine manufacturer, since this may cause damage to the engine and/or void the manufacturer's warranty coverage for the engine. Dual fuel systems are nevertheless desirable in that the price of the secondary fuel is typically less than the price of the primary diesel fuel. If a diesel engine can be operated efficiently and within the manufacturer's specifications with a dual fuel system, then significant cost savings may be realized over extended operating cycles when the combined cost of the primary and secondary fuels are taken into account.

United States Patent No. 4,953,515 issued 4 Septe~ber, 1990 for an invention of William Albert Fehr and Brian George Buck entitled "Diesel Engine Secondary Fuel Injection System", discloses a method of economically operating a dual fuel diesel engine in a manner which optimizes the engine's performance by continually varying the relative amounts of primary and secondary ~uel in~ected into the engine, as a function of one or more engine performance parameters such as turbo-charger boost pressure, whilst adhering to the manufacturer's specifications ~or operating the engine.

More particulary, the Patent a~oresaid discloses an apparatus ~or supplying a secondary fuel to a turbo-charged diesel engine. The apparatus incorporates a plurality of :'~ , , .: . .

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203492g adjustable pressure sensors which are coupled to the engine's turbo-charger. The sensors detect the boost pressure output by the turbo-charger and produce output signals representative thereof. An equal plurality of normally closed valves are coupled between the engine and a secondary fuel reservoir. The valves are electrically connected to corresponding ones of the pressure sensors, such that the valves open in response to the corresponding pressure sensor output signals, allowing the secondary fuel to flow to the engine. The sensors are adjusted to detect selected turbo-charger boost pressures distributed within a pre-defined boost pressure range. The plurality of sensors thus produces a corresponding range of output signals as the engine turbo-charger boost pressure increases, thereby sequentially opening or closing the valves to supply more or less secondary fuel to the engine as the turbo-charger boost pressure increases or decreases.

A disadvantage of the prior art apparatus described above is that premature detonation of the secondary fuel may occur if the engine is operated under high load at low R.P.M.
Secondary fuels such as propane are typically admitted into the engine's combustion chambers with air. Such admission occurs before the primary diesel fuel is injected into the combustion cham~er. If the engine is operated under high load at low R.P.M., its operating temperature may exceed the temperature required to ignite the secondary fuel. That is, the secondary fuel may be ignited before the primary diesel fuel is injected into the combu6tion chamber, adversely effecting engine perform-ance. The present invention overcomes the foregoing disadvan-tage.

Summarv of the Invention In acc~rdance with the preferred embodiment, theinvention provides a valve for controlling the flow of secondary fuel to a turbo-charged dieeel engine. The valve incorporates a cylinder, a fir~t inlet port which couples the cylinder to a secondary fuel reservoir, a second inlet port which couples the 2~34928 cylinder to the engine's turbo-charger, a discharge port which couples the cylinder to a secondary fuel inlet of the engine, and a piston which is slidably displaceable within the cylinder to controllably open and close the discharge port in response to changes in the turbo-charger's boost pressure.

The piston moves between a closed position in which the piston blocks secondary fuel flow from the first inlet port to the discharge port, a first range of open positions in which the piston allows progressively increasing amounts of secondary fuel to flow from the first inlet port to the discharge port, and a second range of open positions in which the piston allows progressively decreasing amounts of secondary fuel to flow from the first inlet port to the discharge port.
A conduit in the piston conveys secondary fuel through the piston, between an inlet and an outlet of the conduit. The conduit inlet overlaps the first inlet port during displacement of the piston between the closed position and the first and second ranges of open positions, thereby facilitating secondary fuel flow from the first inlet port into the conduit during the displacement of the piston. The conduit outlet is displaced away from the discharge port when the piston is in the closed position, thereby preventing secondary fuel flow from the conduit to the discharge port when the piston is in the closed position.
The conduit outlet overlaps the discharge port during displace-ment of the piston in the first and second ranges of open positions, thereby facilitating secondary fuel flow from the conduit to the discharge port during displacement of the piston in the ~irst and second ranges of open positions.

During slidable displacement of the piston through the ~irst range o~ open positions, the conduit outlet moves across the discharge port to progressively increase the overlap between the conduit outlet and the discharge port. During slidable displacement of the piston through the second range of open positions, the conduit outlet moves ~urther across the discharge ,, . - , -, : -: : ; , .......... .
., , . : : -port to progressively decrease the overlap between the conduit outlet and the discharge port.

Advantageously, biasing means are provided, to bias the piston towards the closed position. Preferably, the bias means is a spring having a spring tension selected to maximize the overlap between the conduit outlet and the discharge port upon application of a preselected turbo-charger boost pressure to the piston.
Limit means are advantageously provided to limit displacement of the piston in the second range of open positions, thereby limiting the minimum overlap between the conduit outlet and the discharge port in the second range of open positions.
The limit means may comprise a member threadably fastened through the cylinder to stop displacement of the piston at a pre-selected point.

Control means are preferably provided to control secondary fuel flow from the secondary fuel reservoir through the fir~t inlet port. The control means may comprise a second cylinder coupled to the second inlet port, a second piston elidably displaceable within the second cylinder, in response to changes in the turbo-charger boost pressure, controllable closure means for controllably closing the first inlet port, and coupling means for coupling the second piston to the closure means. An increase in the turbo-charger boost pressure causes a correspon-dlng displacement of the second piston, which in turn causes the coupling means to correspondingly displace the closure means relative to the first inlet port to increase the open cross-sectional area of the first inlet port. Similarly, a decrease in the turbo-charger boost pressure causes a corresponding displacement of the second piston, which in turn causes the coupling means to correspondingly displace the closure means relative to the first inlet port to decrease the open cross-sectlonal area o~ the ~irst inlet port.

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Alternatively, the control means may comprise a lever pivotally coupled between the second piston and the first inlet port, one end of the lever carrying a seal for sealingly engaging the first inlet port. In this case, an increase in the turbo-charger boost pressure causes a corresponding displacement of thesecond piston and the lever, which moves the seal away from the first inlet port to increase the open cross-sectional area of the first inlet port. Similarly, a decrease in the turbo-charger boost pressure causes a corresponding displacement of the second piston and the lever, which moves the seal toward the first inlet port to decrease the open cross-sectional area of the first inlet port.

Brief Description of the Drawinas Figure 1 is a block diagram of the basic components of a diesel engine propane injection system incorporating the invention.

Figures 2a through 2d are cross-sectional illustra-tions of a secondary fuel modulating valve constructed inaccordance with the preferred embodiment of the invention.

Figure 2a shows the modulating valve's piston in the closed position, blocking secondary fuel flow through the valve's ~uel discharge port.

Figure 2b shows the modulating valve's piston at the lower limit of its first range of open positions. Secondary fuel has just begun to flow through the valve's discharge port at this point.

Figure 2c shows the modulating valve's piston at the upper limit of its first range of open positions, which coincides with the lower limit of its second range of open positions.
Secondary fuel flow through the valve's discharge port is maximized at this point.

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Figure 2d shows the modulating valve's piston at the upper limit of its second range of open positions. Secondary fuel flow through the valve's discharge port is reduced at this point to avoid premature detonation of the secondary fuel.

Detailed Description of the Preferred Embodiment Figure 1 is a block diagram which illustrates the basic components of a diesel engine propane injection system incorpor-ating a secondary fuel modulating valve constructed in accordance with the preferred embodiment of the invention. A suitable secondary fuel such as liquid propane is stored in tank l and is supplied, through electric lock-off device 2, vaporizer/regulator valve 3 and fuel line 4 to secondary fuel modulating valve 5 in the form of vapour at a pressure of about .5 to about 3 pounds per square inch. Diesel engine 10 is equipped with a turbo-charger 12. Conduit 8 couples turbo-charger 12 to modulating valve 5, which controllably discharges secondary fuel through conduit 6 and orifice 7 into air intake pipe ll. Air intake pipe 11 delivers air from the engine's air cleaner (not shown), mixed with secondary fuel, to turbo-charger 12.

As shown in Figure 2, modulating valve 5 incorporates a cylinder 20 which contains a piston 22. Vaporized propane is supplied to cylinder 20 through first inlet port 24. More particularly, secondary fuel line 4 is threadably coupled to aperture 26. Vaporized propane flows through fuel line 4 into region 28, and i8 then controllably admitted into cylinder 20 through first inlet port 24, as hereinafter explained. Conduit 8 is threadably coupled to second inlet port 30 to supply pressurized air from turbo charger 12 to cylinder 20, against the base of piston 22. The turbo-charger boost air slidably displa¢es piston 22 within cylinder 20, controllably opening and closing discharge port 32 in response to changes in the turbo-charger boost pressure, as hereinafter explained in greater detail. Conduit 6 i8 threadably coupled to discharge port 32, thus coupling cylinder 20 to the secondary fuel inlet of engine 10 ~i.e. orifice 7 and air intake pipe 11).

As will now be explained, a progressive increase in the turbo-charger boost pressure slidably displaces piston 22 within cylinder 20 from a closed position (Figure 2a) in which piston 22 blocks secondary fuel flow from first inlet port 24 to discharge port 32, through a first range of open positions (Figures 2b & 2c) in which piston 22 allows progressively increasing amounts of secondary fuel to flow from first inlet port 24 to discharge port 32, and through a second range of open positions (Figures 2c & 2d) in which piston 22 allows progres-sively decreasing amounts of secondary fuel to flow from first inlet port 24 to discharge port 32.

A conduit 34 is machined in piston 22 to convey secondary fuel through piston 22, between inlet 36 and outlet 38 of conduit 34. A recess 40 is cut in piston 22, around conduit inlet 36. Recess 40 effectively enlarges conduit inlet 36, thus ensuring that the enlarged conduit inlet overlaps first inlet port 24 throughout the range of displacement of piston 22 between its closed position and its first and second ranges of open posi-tions, thereby facilitating secondary fuel flow from first inlet port 24 into conduit 34 regardless of the position of piston 22.

An annular recess 42 is cut around the circumference of piston 22, intersecting conduit outlet 38. Recess 42 remains beneath discharge port 32 when piston 22 is in its closed position, thus ensuring that conduit outlet 38 is displaced away from discharge port 32 when piston 22 is in its closed position, preventing secondary fuel flow from conduit 34 to discharge port 32 when piston 22 is in its closed position. However, recess 42 effectively enlarges conduit outlet 38, thus ensuring that, throughout the range of displacement of piston 22 in either of its firet or second ranges of open positions, the enlarged conduit outlet overlaps discharge port 32, thereby facilitating secondary fuel flow through conduit 36 to discharge port 32 throughout displacement o~ piston 22 in its first or second ranges of open positions.

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During slidable displacement of piston 22 through its first range of open positions, conduit outlet 38 moves across discharge port 32 from the lower limit depicted in Figure 2b to 5the upper limit depicted in Figure 2c, progressively increasing the overlap between conduit outlet 38 and discharge port 32, thus progressively increasing the quantity of secondary fuel passed through discharge port 32 to engine 10. During slidable displacement of piston 22 through its second range of open posi-10tions, conduit outlet 38 moves further across discharge port 32, from the lower limit depicted in Figure 2c to the upper limit depicted in Figure 2d, progressively decreasing the overlap between conduit outlet 38 and discharge port 32, thus progress-ively decreasing the quantity of secondary fuel passed through 15discharge port 32 to engine 10.

A "biasing means" namely, spring 44, is provided for biasing piston 22 towards the closed position. A vent hole 45 is drilled through the upper end of the casing enclosing cylinder 2020 to allow piston 22 to move without regard to air or gases trapped between the top of piston 22 and the inner walls of cylinder 20 above piston 22. The tension of spring 44 is selected to maximize the overlap between conduit outlet 38 and discharge port 32 upon application of a preselected turbo-25charger boost pressure to piston 22. That is, the spring tension i5 adjusted to maximize secondary fuel flow to engine 10 when turbo-charger 12 is generating a particular boost pressure.
Typically, maximum secondary fuel flow will be desired when engine 10 is operating in its mid horsepower or cruise range.
A "limit means", namely threaded member 46, is provided for setting the upper displacement limit of piston 22 in its second range of open positions. Member 46 is threadably fastened through the top o~ cylinder 20 to bear against the top of piston 3522 when piston 22 i5 at the upper limit o~ its second range of open positions. Member 46 thus stops upward displacement of piston 22 at a selected point which may be defined by threadably : - ': ' .

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advancing or retracting member 46 within cylinder 20. Member 46 accordingly prevents upward displacement of piston 22 from cutting off secondary fuel flow entirely, which would occur if piston 22 were displaced upwardly to the point that conduit outlet ~8 no longer overlapped discharge port 32. More particu-larly, member 46 limits the minimum overlap between conduit outlet 38 and discharge port 32 at the upper and of the second range of open positions. Lock nut 48 holds member 46 in place once it has been adjusted.

A suitable "control means" is provided for controlling secondary fuel flow from region 28 through first inlet port 24.
In the preferred embodiment, the control means incorporates a second cylinder 50 which is coupled to second inlet port 30 via passage 52. A second piston 54 is mounted for slidable displace-ment within second cylinder 50, in response to changes in the turbo-charger boost pressure. A "controllable closure means", namely seal 56 mounted on the end of lever 58, is provided for controllably closing first inlet port 24 as hereinafter de-scribed. Lever 58, which is pivotally connected to the body of valve 5 and to the rod of second piston 54, serves as a "coupling means" for coupling second piston 54 to seal 56.

If no pressurized turbo-charger boost air is supplied through passage 52, spring 60 biases second piston 54 toward the left, as viewed in Figure 2, which in turn forces the seal-carrying portion of lever 58 to the right, thus sealing first inlet port 24 and preventing secondary fuel flow from region 28 into conduit 34. An increase in the turbo-charger boost pressure causes corresponding displacement of second piston 54 (to the right, as viewed in Figure 2), overcoming the biasing action of spring 60, and causing lever 58 to correspondingly displace seal 56 away from ~irst inlet port 24 (to the left, as viewed in Figure 2), increasing the open cross-sectional area of first inlet port 24 and thus increasing the quantity of secondary fuel passing from region 28 into conduit 34. A decrease in the turbo-charger boost pressure allows spring 60 to corresponding . -.
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displace second piston 54 to the left, causing lever 58 to correspondingly displace seal 56 towards first inlet port 24, decreasing the open cross-sectional area of first inlet port 24 and thus decreasing the quantity of secondary fuel passing from region 28 into conduit 34.

In operation, when turbo charger 12 is not supplying pressurized boost air to engine 10 or to modulating valve 5, spring 44 holds piston 22 in its closed position and spring 60 biases second piston 54 and lever 58 to force seal 56 against first inlet aperture 24 (Figure 2a). Secondary fuel is thus prevented from entering conduit 34 and no secondary fuel flows to engine 10 through discharge port 32.

When turbo charger 12 begins to supply pressurized boost air to engine 10 and to modulating valve 5, piston 22 is displaced upwardly, overcoming the biasing action of spring 44 and moving piston 22 into the lower portion of its first range of operating positions (Figure 2b). At the same time, second piston 54 overcomes the biasing action of spring 60, pivoting lever 58 to move seal 56 slightly away from first inlet aperture 24. A small amount of secondary fuel is thus allowed to enter conduit 34 and flow to engine 10 through discharge port 32. As the turbo-charger boost pressure increases, piston 22 moves upwardly through its first range of operating positions; second piston 54 and lever 58 move seal 56 further away from first inlet port 24; and progressively larger amounts of secondary fuel enter conduit 34 and flow to engine 10 through discharge port 32.

When engine 10 reaches its mid horsepower or cruise operating range, turbo charger 12 supplies sufficient pressurized boost air to engine 10 and to modulating valve 5, to displace piston 22 upwardly into the upper portion of its first range of operating positions (Figure 2c). Second piston 54 concurrently moves to pivot lever 58 and move seal 56 still further away from first inlet aperture 24. A still larger amount of secondary fuel is thus allowed to enter conduit 34 and flow to engine 10 through , .

203~928 discharge port 32. It will be noted that the maximum amount of secondary fuel is supplied to engine 10 through discharge port 32 at this point, because outlet 38 entirely overlaps discharge outlet 38 and because second piston 54 has pivoted lever 58 to the maximum possible extent, thus moving seal 56 into its furthest position away from first inlet aperture 24 to maximize secondary fuel flow from region 28 into conduit 34.

When engine 10 operates above its mid horsepower or cruise range, turbo charger 12 supplies sufficient pressurized boost air to engine 10 and to modulating valve 5, to displace piston 22 upwardly into its second range of operating positions.
As described above, second piston 54 has already displaced lever 58 and seal 56 to the maximum possible extent, thus maximizing secondary fuel flow from region 28 into conduit 34. However, when piston 22 is in its second range of operating positions, the decreased overlap between outlet 38 and discharge outlet 32 reduces the flow of secondary fuel to engine 10 through discharge port 32, thus preventing premature detonation of the secondary fuel.

If engine 10 is operated to cause turbo-charger 12 to supply sufficient pressurized boost air to engine 10 and to modulating valve 5, to displace piston 22 upwardly to contact member 46 (Figure 2d), then the overlap between outlet 38 and discharge outlet 32 is held to a selected minimum (as opposed to having no overlap) thus allowing a further reduced amount of secondary fuel (as opposed to no secondary fuel) to flow to engine 10 through discharge port 32.
As will be apparent to those skilled in the art in the light of the ~oregoing disclosure, many alterations and modifica-tlons are possible in the practice o~ this invention without departing ~rom the spirit or scope thereof. For example, the invention may be adapted for use with engines having different horespower ratings by inserting orifices of varying diameters into aperture 26. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.

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Claims (17)

1. A valve for controlling the flow of secondary fuel to a turbo-charged diesel engine, said valve comprising:
(a) a cylinder;
(b) a first inlet port for coupling said cylinder to a secondary fuel reservoir;
(c) a second inlet port for coupling said cylinder to said engine turbo-charger;
(d) a discharge port for coupling said cylinder to a secondary fuel inlet of said engine; and, (e) a piston slidably displaceable within said cylinder, to controllably open and close said discharge port in response to changes in said turbo-charger boost pressure.

2. A valve as defined in claim 1, wherein said piston moves between:
(i) a closed position in which said piston blocks secondary fuel flow from said first inlet port to said discharge port;
(ii) a first range of open positions in which said piston allows progressively increasing amounts of secondary fuel to flow from said first inlet port to said discharge port; and, (iii) a second range of open positions in which said piston allows progressively decreasing amounts of secondary fuel to flow from said first inlet port to said discharge port.

3. A valve as defined in claim 2, further comprising a conduit in said piston for conveying secondary fuel through said piston, between an inlet and an outlet of said conduit.

4. A valve as defined in claim 3, wherein said conduit inlet overlaps said first inlet port during displacement of said piston between said closed position and said first and second ranges of open positions, thereby facilitating secondary fuel flow from said first inlet port into said conduit during said displacement of said piston.

5. A valve as defined in claim 4, wherein said conduit outlet:
(a) is displaced away from said discharge port when said piston is in said closed position, thereby preventing secondary fuel flow from said conduit to said discharge port when said piston is in said closed position; and, (b) overlaps said discharge port during displacement of said piston in said first and second ranges of open positions, thereby facilitating secondary fuel flow from said conduit to said discharge port during displacement of said piston in said first and second ranges of open positions.

6. A valve as defined in claim 5, wherein, during slidable displacement of said piston through said first range of open positions, said conduit outlet moves across said discharge port to progressively increase the overlap between said conduit outlet and said discharge-port.--

7. A valve as defined in claim 6, wherein, during slidable displacement of said piston through said second range of open positions, said conduit outlet moves further across said discharge port to progressively decrease the overlap between said conduit outlet and said discharge port.

8. A valve as defined in claim 7, further comprising biasing means for biasing said piston towards said closed position.

9. A valve as defined in claim 8, wherein said bias means is a spring and wherein said spring tension is selected to maximize the overlap between said conduit outlet and said discharge port upon application of a preselected turbo-charger boost pressure to said piston.

10. A valve as defined in claim 9, further comprising limit means for limiting the displacement of said piston in said second range of open positions, thereby limiting the minimum overlap between said conduit outlet and said discharge port in said second range of open positions.

11. A valve as defined in claim 10, wherein said limit means comprises a member threadably fastened through said cylinder to stop displacement of said piston at a pre-selected point.

12. A valve as defined in claim 5, further comprising control means for controlling secondary fuel flow from said secondary fuel reservoir through said first inlet port.

13. A valve as defined in claim 12, wherein said control means comprises:
(a) a second cylinder coupled to said second inlet port;
(b) a second piston slidably displaceable within said second cylinder, in response to changes in said turbo-charger boost pressure;
(c) controllable closure means for controllably closing said first inlet port; and, (d) coupling means for coupling said second piston to said closure means;
whereby:
(i) an increase in said turbo-charger boost pressure causes corresponding displacement of said second piston, causing said coupling means to correspon-dingly displace said closure means relative to said first inlet port, increasing the open cross-sectional area of said first inlet port; and, (ii) a decrease in said turbo-charger boost pressure causes corresponding displacement of said second piston, causing said coupling means to correspon-dingly displace said closure means relative to said first inlet port, decreasing the open cross-sectional area of said first inlet port.

14. A valve as defined in claim 12, wherein said control means comprises:
(a) a second cylinder coupled to said second inlet port;
(b) a second piston slidably displaceable within said second cylinder, in response to changes in said turbo-charger boost pressure;
(c) a lever pivotally coupled between said second piston and said first inlet port, one end of said lever carrying a seal for sealingly engaging said first inlet port;
whereby:
(i) an increase in said turbo-charger boost pressure causes corresponding displacement of said second piston and said lever, moving said seal away from said first inlet port to increase the open cross-sectional area of said first inlet port; and, (ii) a decrease in said turbo-charger boost pressure causes corresponding displacement of said second piston and said lever, moving said seal toward said first inlet port to decrease the open cross-sectional area of said first inlet port.

15. A valve for controlling the flow of secondary fuel to a turbo-charged diesel engine, said valve comprising:
(a) a cylinder;
(b) a first inlet port for coupling said cylinder to a secondary fuel reservoir;
(c) a second inlet port for coupling said cylinder to said engine turbo-charger;
(d) a discharge port for coupling said cylinder to a secondary fuel inlet of said engine;
(e) a piston slidably displaceable within said cylinder, to controllably open and close said discharge port in response to changes in said turbo-charger boost pressure;

(f) a conduit in said piston for conveying secondary fuel through said piston, between an inlet and an outlet of said conduit;
(g) a spring for biasing said piston towards said closed position; and, (h) stop means for stopping displacement of said piston at a pre-selected point.

16. A valve as defined in claim 15, further comprising:
(a) a second cylinder coupled to said second inlet port;
(b) a second piston slidably displaceable within said second cylinder, in response to changes in said turbo-charger boost pressure;
(c) controllable closure means for controllably closing said first inlet port; and, (d) coupling means for coupling said second piston to said closure means.

17. A valve as defined in claim 15, further comprising:
(a) a second cylinder coupled to said second inlet port;
(b) a second piston slidably displaceable within said second cylinder, in response to changes in said turbo-charger boost pressure; and, (c) a lever pivotally coupled between said second piston and said first inlet port, one end of said lever carrying a seal for sealingly engaging said first inlet port.