Internal combustion engine with programmed water injection into its exhaust system

An exhaust system for an internal combustion engine used in a marine propulsion system is provided with a water injection system by which water can be injected into the exhaust system. An engine control unit, which comprises a micro-processor, is used to select the rate of water injection into the exhaust system as a function of several predefined parameters. For example, engine speed and throttle position can be used by the micro-processor in the engine control unit to select a predefined rate of water flow into the exhaust system by selecting a predefined valve position, for an electronically controlled valve, that has been preselected and stored in the micro-processor.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention is generally related to injection of water into an 
exhaust system and, more particularly, a method by which a micro-processor 
controls the injection of predetermined amounts of water into an exhaust 
system based one or more conditions relating to the operation of the 
internal combustion engine. 
2. Description of the Prior Art 
It is well know that certain operational advantages can be achieved by 
injecting water into the exhaust system of an internal combustion engine. 
This concept is described in detail in U.S. Pat. No. 3,385,052, which 
issued to Holterman et al on May 28, 1968. The exhaust system described is 
operated according to a method which comprises the steps of discharging 
burned gases from a combustion chamber through an exhaust port to an 
exhaust passage in order to obtain timed return of a pressure wave to the 
exhaust port by injecting a liquid into the burned gases discharged from 
the combustion chamber. Also disclosed is an internal combustion engine 
having a means for timing the return to an exhaust port of a pressure wave 
in an exhaust passageway, including means for supplying a cooling liquid 
to the passageway. The engine includes an exhaust passageway which 
increases an internal cross section in the direction away from the exhaust 
port and terminates in a wall that is transversed to that direction. The 
passageway also includes a means for defining an opening which is located 
adjacent to the wall and which has a relatively small area as compared to 
the area of the wall. 
U.S. Pat. No. 3,813,880, which issued to Reid et al on Jun. 4, 1974, 
discloses an exhaust tuning system for a two stroke engine. The engine 
includes a pair of exhaust chambers having a common control wall and each 
of which is connected between a corresponding plurality of selected 
cylinders and a common exhaust passageway. The connection between each of 
the chambers and the passageway is defined by a tuning section which is 
constructed of sufficient length and a configuration to generate a 
negative pressure pulse to aid scavenging and reflected positive pulses 
from the fired cylinder. In addition, the next fired cylinder of each 
group establishes a super-charging of the engine. The common wall between 
the two tuned passageways is provided with a transfer port for 
transferring of a positive pressure signal from the one passageway into 
the opposite passageway which travels back toward the engine to provide a 
further positive super-charging pulse to the opposite exhaust chamber. The 
feedback pressure wave can be applied with a particular advantage to four 
and two cylinder engines. 
U.S. Pat. No. 5,746,054, which issued to Matte on May 5, 1998, describes a 
method and apparatus for a tuned pipe water injection. In an exhaust 
expansion chamber or tuned pipe of a two-cycle engine in a watercraft, 
variable amounts of water are injected, thus cooling the temperature 
within the expansion chamber and matching the sonic wave speed with that 
of the correct rpm of the motor. Thus, by regulating the temperature of 
the exhaust gases in the tuned pipe with water, the efficiency of the 
two-cycle engine at varying revolutions per minute is improved. 
U.S. Pat. No. 4,014,282, which issued to Kollman on Mar. 29, 1977, 
discloses an exhaust tube mounting apparatus for outboard motors. In an 
outboard motor, the engine exhausts through the drive shaft housing in 
which an exhaust tube directs the gases into a lower propeller unit 
secured to the housing. The exhaust tube has support legs on the opposite 
top sides. Bushings encircle each lug and they rest in receptacles on the 
upper interior portions of the housing. An adapter plate is secured to the 
housing, clamps the lugs in place and moves the lower end of the tube into 
sealing relationship within a lower bushing within the housing. The lower 
bushing is a rubber-like annular bushing having a projecting ledge aligned 
with the lower end of the exhaust tube. The inner wall of the bushing has 
an inwardly and downwardly extended lop deflected and sealing with the 
side of the exhaust tube. 
U.S. Pat. No. 3,808,807, which issued to Lanpheer on May 7, 1974, discloses 
a tuning arrangement for an outboard motor. The improvement in the exhaust 
system for a two cycle engine comprises one or more sets of three 
cylinders connected to the crankshaft 120.degree. apart, the exhaust ports 
of which communicate with a common exhaust chamber formed in association 
with the cylinder block. A diverging passage leading from the common 
exhaust chamber to a spacious exhaust tube enclosed within the drive shaft 
housing produces a negative pressure from the cylinder's positive exhaust 
pulse, which negative pressure aids in scavenging the cylinder. The 
geometry of the diverging passage and the exhaust tube are such that a 
positive pulse is created by the exit of the negative pulse from said 
diverging passage and propagates back through the diverging passages 
arriving at the exhaust ports of the cylinder simultaneously with a 
positive pulse from a subsequently fired cylinder to aid in supercharging. 
U.S. Pat. No. 4,920,745, which issued to Gilbert on May 1, 1990, describes 
an internal combustion engine which has a transfer port and an exhaust 
port in a cylinder which are opened and closed in a timed relationship by 
the reciprocating movement of a piston. The exhaust port communicates with 
an exhaust passage that is tuned to provide a pressure pattern in the 
exhaust passageway that will create at the exhaust port a predetermined 
pressure pattern while the exhaust port is opened. Coolant is supplied to 
the exhaust passage when the engine is subject to increasing transient 
load conditions, at engine speed below the tuned speed, and at a 
controlled rate to establish a tuned state in the exhaust passage during 
the transient condition. 
U.S. Pat. No. 5,378,180, which issued to Nakayama et al on Jan. 3, 1995, 
describes an exhaust system for outboard motors which have exhaust pipes 
and expansion chambers into which the exhaust pipes extend. A catalyst is 
positioned in the exhaust system downstream of the point where the exhaust 
pipe terminates in the expansion chamber so as to preclude interference 
with the exhaust timing. The catalyst bed is removable for ease of 
servicing without necessitating removal of the outboard motor from its 
attachment to the associated watercraft and a trap device is provided for 
precluding water from entering the engine through its exhaust ports. 
All of the patents described above are hereby expressly incorporated in the 
following description. 
As described above, it is well known that exhaust systems can be tuned to 
advantageously time the arrival of reflected pressure waves at the exhaust 
port of a cylinder. This is done for several reasons which are all well 
known to those skilled in the art. Proper tuning of the exhaust system can 
produce super charging within the combustion chambers of the engine. These 
techniques are also advantageous in preventing certain quantities of 
unburned hydrocarbons from being exhausted through the exhaust ports 
following a combustion event within the combustion chamber. The 
advantageous effect of this procedure is obtained by changing the 
temperature of the exhaust gases. The speed of sound is affected by the 
temperature within the exhaust system and, as a result, the effective 
length of the exhaust pipe is changed by changing the speed at which the 
pressure pulses move within the exhaust pipe. By cooling the exhaust 
gases, the speed of the pressure pulses is slowed. This has the effect of 
increasing the effective length of the exhaust pipe. At different speeds 
of engine operation, it would be theoretically advantageous to actually 
have different lengths of exhaust pipe. This being impractical, it has 
been discovered that changes in temperature of the exhaust gases has the 
same affect as dynamically changing the length of the exhaust pipe. 
In the prior art, many different techniques have been applied to control 
the rate at which water is injected into the exhaust pipe for these 
purposes of changing the speed of sound within the exhaust system. Certain 
mechanical systems, such as pressure responsive valves, have been used to 
change the rate at which water is injected into the exhaust system as a 
function of engine condition. 
It would be significantly advantageous if a system could be developed in 
which the amount of water injected into an exhaust system could be 
accurately controlled, not only as a function of engine speed and/or 
throttle position, but also as a function of the natural operating 
characteristics of the engine. In other words, certain engines require 
different amounts of injected water at various speeds than other engines 
do at those same speeds. In addition, different lengths of exhaust pipes 
are used with different engines and, therefore, the rate of water 
injection into the exhaust system is a function of engine speed and/or 
throttle position is different for each engine type and exhaust pipe 
length. 
SUMMARY OF THE INVENTION 
The present invention is directed to solve a long standing problem toward 
which many different techniques have previously been applied. It is 
intended to provide a way in which water can be injected into an exhaust 
system with increased preciseness to account for engine speed, throttle 
position, and other engine characteristics so that the proper amount of 
water injection can be applied under various operating conditions to 
maximize the performance of the engine. 
An apparatus for improving the operation of an internal combustion engine 
made in accordance with the present invention comprises an exhaust system 
having an exhaust pipe. It also comprises a water pump for pumping water 
through a first water conduit. A second conduit is connected in fluid 
communication between the first conduit and the exhaust system. An 
electrically controlled valve is connected to the second conduit for 
selectively allowing water to pass through the second conduit from the 
first conduit to the exhaust system. An engine control unit comprising a 
micro-processor is connected in signal communication with the electrically 
controlled valve. 
A preferred embodiment of the present invention further comprises a RPM 
measuring sensor, such as a tachometer or a gear tooth sensor, and the RPM 
measuring sensor provides a first signal output. A first input of the 
micro-processor is connected in signal communication with the first signal 
output of the RPM measuring sensor. The micro-processor controls the 
degree to which the electrically controlled valve allows water to pass 
through the second conduit from the first conduit to the exhaust system as 
a function of the RPM of the internal combustion engine. 
The micro-processor can contain a numerical table which stores a desired 
valve position for each of a plurality of engine speeds. In addition, the 
micro-processor could calculate a desired valve position for each of a 
plurality of engine speeds based on a predetermined mathematical 
relationship. 
The present invention can further comprise a throttle position sensor 
providing a second signal output and a second input to the micro-processor 
can be connected in signal communication with the second signal output of 
the throttle position sensor. As a result, the micro-processor can control 
the degree to which the electrically controlled valve allows water to pass 
through the second conduit from the first conduit to the exhaust system as 
a function of both the rpm of the internal combustion engine and the 
throttle position of the internal combustion engine. 
The present invention can be used in conjunction with the internal 
combustion engine of an outboard motor or a marine propulsion system 
comprising a stern drive unit.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Throughout the description of the preferred embodiment of the present 
invention, like components will be identified by like reference numerals. 
FIG. 1 is a highly schematic illustration which shows relative positions of 
an engine 10 and two adapter plates, 12 and 14. It should be understood 
that the components in FIG. 1 are not drawn to scale. 
The engine has an exhaust system 20 which connects the exhaust ports of 
three cylinders in fluid communication with a main exhaust pipe 24. 
Individual pipes, 31-33, connect the engine 10 to the exhaust pipe 24 
which, in turn, exhausts the gases into an expansion chamber 36. Arrows E 
represent the passage of exhaust gases from the engine 10 through the 
exhaust pipe 24 and into the expansion chamber 36. Many different 
configurations of exhaust pipes and expansion chambers are well known to 
those skilled in the art and have been applied to outboard motors. 
With continued reference to FIG. 1, the engine 10 is provided with an 
engine control unit 40 which typically comprises a micro-processor that 
receives inputs from various sensors and provides outputs that control the 
operation of the engine 10. In FIG. 1, the engine control unit 40 is shown 
being connected to an RPM measuring sensor such as a tachometer 44 and a 
throttle position sensor 46. These two sensors, 44 and 46, provide signal 
outputs that are connected to inputs of the engine control unit 40. This 
is represented by dashed lines in FIG. 1. 
Although the water pump is not shown in FIG. 1, it is well known to those 
skilled in the art that water cooled internal combustion engines require a 
continuous flow of water through cooling channels of the engine. This is 
typically accomplished by providing a water pump that is driven by an 
output shaft of the engine and which draws water from a body of water in 
which the marine propulsion unit is operated. The water is drawn from the 
body of water by the water pump and caused to flow through cooling 
channels of the engine. After cooling the engine, the water is then 
expelled back to the body of water in which the marine propulsion unit is 
operating. In FIG. 1, the first conduit 50 is connected in fluid 
communication with the cooling system of the engine 10 and the water 
passes in the direction represented by arrows W back toward the body of 
water in which the watercraft is operated. The first conduit 50 is 
provided with a restriction portion 52 which maintains a pressure within 
the first conduit 50 as a result of the pumping by the water pump and the 
restriction 52 at the exit portion of the first conduit 50. The present 
invention provides a second conduit 60 that is connected in fluid 
communication between the first conduit 50 and the exhaust system 20. An 
electrically controlled valve 70 is connected to the second conduit 60 for 
selectively allowing water to pass through the second conduit 60 from the 
first conduit 50 to the exhaust system 20. This selectively controlled 
passage of water flows in the direction represented by dashed line arrow 
74. The engine control unit 40 controls the operation of the electrically 
controlled valve 70, as represented by dashed line 76. 
In a preferred embodiment of the present invention, the engine control unit 
40 receives information, relating to the speed of the engine 10, from the 
RPM measuring sensor 44. In certain embodiments of the present invention, 
the engine control unit 40 also receives information relating to the 
throttle position from the throttle position sensor 46. Based on one or 
both of these inputs, the engine control unit selects a desired rate of 
water flow from the first conduit 50 to the exhaust system 20 through the 
second conduit 60. This flow is represented by dashed line 74 in FIG. 1. 
In a preferred embodiment of the present invention, a look-up table is 
used in which each predefined range of engine speeds is associated with a 
specific valve position that results in a particular water flow between 
the first conduit 50 and the exhaust system 20. This provides a 
preselected rate of cooling of the exhaust gases based on the engine speed 
and/or throttle position. If only the engine speed is used for these 
purposes, a one dimensional array can contain the various valve positions 
associated with the predefined engine speed ranges. Alternatively, if both 
engine speed and throttle position are used for these purposes, a two 
dimensional array, or MAP, can be stored in the micro-processor in which 
individual predefined ranges of engine speed and throttle position can be 
used to identify a specific valve position that is associated with that 
particular combination of engine speed and throttle position. These data 
storage techniques are known to those skilled in the art and have been 
used for many different purposes. 
In operation, the engine control unit 40 receives the engine speed signal 
from the RPM measuring sensor 44, receives the throttle position signal 
from the throttle position sensor 46, selects a predefined valve position 
for the valve 70, and then provides an output signal on line 76 to the 
valve 70 which sets the valve at that valve position to allow the 
predetermined magnitude of water flow through the second conduit 60 into 
the exhaust system 20. 
The primary advantage of the present invention is that it accurately 
selects the water flow through the second conduit 60 in a way that is 
unachievable through methods known to those skilled in the art which are 
disclosed in the prior art. The advantage of the present invention is the 
accuracy with which the valve positions can be preselected. 
It is anticipated that, in a typical application of the present invention, 
the engine will be empirically tested under various conditions and under 
various engine speeds and throttle positions. For each of these 
combinations, an optimal water flow magnitude through the second conduit 
60 could be empirically determined. Then each of these many predefined 
magnitudes would be stored in a table within the engine control unit 40 so 
that the engine control unit 40 can select the optimal water flow through 
the second conduit 60 for each combination of the defined parameters, such 
as engine speed and throttle position. The storage in the table and the 
application by the engine control unit 40 allows for a preciseness of 
water flow application previously unobtainable in known internal 
combustion engine systems. 
To illustrate the advantage of the present invention, FIG. 2 is a graphical 
representation of the actual power provided by an outboard motor, at 
various engine speeds, for both a standard engine and an engine with water 
injected into the exhaust system 20. Dashed line 81 represents the 
horsepower measured during an empirical test of an outboard engine at 
various speeds ranging from 3,000 rpm to 6,250 rpm. Solid line 82 
represents a similar test, but one that provided for water injection into 
the exhaust system 20 of the same engine. As can be seen, the horsepower 
of the engine is dramatically increased at the lower engine speeds, from 
3,000 rpm to approximately 5,000 rpm. As can be seen in FIG. 2, valuable 
horsepower can be added to the outboard motor during initial acceleration 
at low speeds if water is injected appropriately into the exhaust system 
20. 
FIG. 3 is related to the tests used to provide the data in FIG. 2, but 
shows the actual improvement, in horsepower, that the various engine 
speeds used in the empirical test. Line 83 in FIG. 3, measured against the 
right vertical axis in FIG. 3, shows the increase in horsepower of line 82 
in FIG. 2 compared to line 81. As can be seen, the line 83 in FIG. 3 
provides a significant horsepower increase at speeds below approximately 
5,250 rpm. The vertical bars in FIG. 3 represent the water injection, in 
gallons per minute, used during the test. It should be realized that the 
data relating to the water injection was determined in a manner that did 
not permit the water injection rate to be determined with extreme 
preciseness. Instead, the black bars 91 in FIG. 3 represent the low limit 
of a range of water injection rate at each of the identified engine speeds 
and the white bars 92 represent the high limit of water injected at those 
same speeds. However, the bars in FIG. 3 show that more water was injected 
at the extremely low engine speeds than at the higher engine speeds. It is 
intended that the rate of water injection would be higher at low speeds in 
a preferred embodiment of the present invention. The reason for this is 
that most engines would typically be tuned with an exhaust pipe 24 of a 
relatively short length that most closely maximizes the operation of the 
engine at wide open throttle (WOT). Therefore, at higher engine speeds, 
water injection is not needed for the purpose of increasing the effective 
length of the exhaust pipe 24. However, since the exhaust pipe is a fixed 
physical length, the water injection would typically be used at lower 
speeds in order to slow the speed of sound of the pressure pulses and, in 
effect, lengthen the shortened exhaust pipe 24 at those lower speeds. This 
would allow increased power to be provided by the engine at the low speeds 
and, as a result, would result in significant improvement in acceleration 
from a standing condition to a top speed condition. This improved 
horsepower and acceleration would provide a significant benefit in moving 
a watercraft from a standing position to a planing condition. FIG. 4 shows 
an outboard motor, shown in silhouette, to illustrate where the engine 10 
and exhaust system 20 are located. The individual pipes, 31-33, connect 
the engine 10 to the exhaust pipe 24. The exhaust pipe exhausts the gases 
into the expansion chamber 36. Also shown are the two adapter plates, 12 
and 14, and the first conduit 50 which extends through the adapter plates. 
The restriction portion 52 is shown at the bottom portion of the first 
conduit 50. The second conduit 60 connects the valve 70 with the first 
conduit 50 and also connects the valve 70 with the exhaust pipe 24. It can 
be seen that the arrangement in FIG. 4 is slightly different from the 
arrangement in FIG. 1 since the valve 70 and the second conduit 60 are 
both externally located with respect to the adapter plates, 12 and 14. 
It should be understood that the highly schematic embodiment of FIG. 1 and 
the embodiment shown in FIG. 4 both incorporate the concepts of the 
present invention. The basic advantage of the present invention is that an 
engine control unit (not shown in FIG. 4) controls the electrically 
controlled valve, as a function of engine speed, so that the 
micro-processor of the engine control unit can control the degree to which 
the electrically controlled valve allows water to pass through the second 
conduit from the first conduit to the exhaust system as a function of the 
speed of the internal combustion engine. This arrangement, shown 
schematically in FIG. 1 and also in FIG. 4, allows a significantly 
improved degree of accuracy in the rate at which water is provided to the 
exhaust system in order to more accurately and effectively tune the 
exhaust system. 
Although the present invention has been described to illustrate a 
particularly preferred embodiment, it should be understood that 
alternative embodiments are also within its scope.