System for controlling engine fueling according to vehicle location

A system for controlling fueling of an internal combustion engine based upon vehicle position includes a receiver associated with the vehicle that is capable of receiving position and altitude information. The vehicle includes a control computer that delivers control signals to an engine fueling system, as well as to a turbocharger control system. The control computer includes a module that receives the altitude information and uses that information to evaluate changes in ambient air pressure that might detrimentally affect turbocharger speed. In one embodiment, the control computer reduces the fueling signal to reduce engine speed in relation to a decrease in ambient air pressure accompanying an increase in vehicle elevation. In another embodiment, the control computer uses the highly accurate altitude information together with engine speed information provides signals to the turbocharger control system.

BACKGROUND OF THE INVENTION 
The present invention relates generally to systems and techniques for 
controlling fueling of an internal combustion engine, and more 
specifically to systems controlling engine fueling in accordance with 
information relating to vehicle location. A further aspect of the 
invention concerns a system and method for preventing an overspeed 
condition in a turbocharger when the engine is operating at higher 
altitude, lower ambient air pressure conditions. 
It is presently known in the internal combustion engine industry, and 
particularly in the medium and heavy duty truck industry, to select engine 
fueling strategies based on presumed geographic conditions, wherein the 
geographic conditions are presumed from certain engine and/or vehicle 
operational parameters. In one known system, engine acceleration is 
monitored, presumed geographic conditions are determined therefrom and an 
appropriate one of a pair of fueling strategies is selected based upon the 
presumed geographic conditions. For example, during periods of continuous 
accelerations (i.e. stop and go traffic), the vehicle is presumed to be 
operating in or near a city, and a low emissions engine fueling map is 
selected for operation in accordance therewith. Conversely, during periods 
of steady state engine operation, the vehicle is presumed to be operating 
on an open highway, and a fuel economic engine fueling map is selected for 
operation in accordance therewith. 
While engine fueling control systems of the foregoing type have been 
somewhat helpful in reducing emissions in areas designated by the 
Environmental Protection Agency (EPA) as non-attainment areas, they have 
several drawbacks associated therewith. For example, due to the engine 
acceleration-based determination of presumed geographic conditions, the 
foregoing system will typically select the fuel economic engine fueling 
map when driving on city freeways and beltways, thereby increasing vehicle 
emissions in or near low emissions urban areas. 
As another example drawback, engine fueling control systems of the 
foregoing type typically switch to the fuel economic engine fueling map 
only after prolonged periods of steady state engine operation. Thus, 
during stops in rural areas, such as at weigh stations and toll booths, 
such systems typically revert to the low emissions fueling map. The same 
result occurs when the vehicle is in operation and the vehicle operator is 
required to interrupt steady state engine operation, such as when 
downshifting to negotiate a steep grade or when slowing down the vehicle 
in construction areas. In either case, fuel economy unnecessarily 
deteriorates. 
As yet another drawback, known engine fueling control systems of the 
foregoing type provide for selection between only a fuel economic or a low 
emissions engine fueling map. However, either engine fueling map may be 
undesirable, or even counterproductive, under certain conditions requiring 
increased engine output (either via engine output power or engine output 
torque), such as when climbing steep grades. Increased engine output under 
such conditions would be advantageous in several respects. For example, 
vehicle operators would be grateful for increased engine output when 
driving through mountainous regions, and such increased output would 
reduce the need to down-shift, thereby reducing wear and tear on vehicle 
components. Moreover, such increased output would likely decrease transit 
time and allow vehicle operators to pass similarly rated vehicles while 
still maintaining good fuel economy. Further, vehicle purchasers could 
purchase lower rated engines and still get higher engine output when 
needed. The lower rated engines would resultantly last longer than the 
higher rated predecessor engines, and customer satisfaction would likely 
correspondingly increase. 
In some cases, a vehicle engine is provided with a turbocharger that 
increases the intake airflow to the engine. In a typical turbocharger, a 
turbine is driven by the engine exhaust. The turbine is linked to a 
compressor section so that the compressor rotates as the turbine is 
driven. The compressor section draws in and compresses ambient air, with 
the compressor output being fed to the engine air intake manifold. 
The rotational speed of the turbocharger is directly related to the flow 
rate of the engine exhaust, which is a function of engine speed. Since the 
turbocharger draws in ambient air, the speed of the device is also 
dependent upon the pressure of the air being drawn into the compressor 
section. For a given engine speed, the rotational speed of the 
turbocharger will increase as the pressure of the ambient air decreases. 
As with any rotating machinery, the turbocharger has a maximum operational 
speed. Exceeding this speed can lead to failure, often catastrophic, of 
the turbocharger as the yield strength of the rapidly rotating components 
is exceeded. Ordinarily this characteristic of turbochargers does not pose 
a problem since the turbocharger is calibrated to withstand operation at 
the maximum engine operating power at altitudes below 10,000 ft. 
However, problems arise when turbocharged engines are operated at high 
altitudes, where the ambient air pressure is less than at the sea level 
calibration pressure. At higher elevations, and consequently lower 
pressures, the turbocharger speed can exceed its limit speed when the 
engine is operating at or near its maximum rated power. Some known engine 
controllers rely upon an air pressure sensor mounted in the vehicle to 
determine the ambient air pressure. When the ambient pressure drops below 
a certain value, fueling to the engine is reduced, reducing the engine 
power or speed, and ultimately reducing the speed of the turbocharger. 
One problem with this approach is that most on-board pressure sensors are 
accurate to only .+-.5 percent. An error of this magnitude is equivalent 
to an error of .+-.1000 ft. in the altitude of the vehicle. This sensor 
error can result in premature derating of the engine performance if the 
sensor reading is less than the actual ambient pressure. On the other 
hand, if the sensor reads a pressure that is greater than the true ambient 
pressure, the risk of turbocharger overspeed arises. 
In addition to the accuracy problems associated with on-board pressure 
sensors, a further issue concerns the cost of the instrument. The typical 
pressure sensor can cost in the range of $10-20. Over an entire fleet of 
vehicles and through an expected number of sensor replacements, the 
overall cost of an on-board pressure sensor can become very high. 
Moreover, as with any engine-based sensor, ambient pressure sensors 
deteriorate and fail over time, which again yields a risk of turbocharger 
overspeed. 
What is therefore needed is a system for controlling engine fueling, which 
overcomes the drawbacks of known engine fueling control systems. Ideally, 
such a system should control engine fueling based on actual (or somewhat 
accurately estimated) vehicle location/position. Such a system could 
dramatically reduce emissions in low emissions area and more accurately 
enable an appropriate engine fueling map regardless of the states, trends 
or statuses of engine/vehicle operational parameters. Such a system should 
further make available not only fuel economic and low emissions engine 
fueling maps, but should further provide for one or more higher output 
engine fueling maps to assist vehicle operators in hilly or mountainous 
regions. 
A system is also needed that can accurately determine the ambient pressure 
for use in controlling the engine, and ultimately a turbocharger 
associated with the engine. Ideally, such a system would not require 
additional hardware or instruments. Moreover, the need extends to a system 
that is essentially immune to independent failure. 
SUMMARY OF THE INVENTION 
The foregoing shortcomings of the prior art are addressed by the present 
invention. In accordance with one aspect of the present invention, a 
system for controlling fueling of an internal combustion engine of a 
vehicle according to vehicle location comprises a receiver associated with 
a vehicle for receiving radio signals relating to vehicle location for 
determining a geographical location of the vehicle, means responsive to 
the geographical location of the vehicle for determining an engine fueling 
map corresponding to the geographical location of the vehicle, and a 
control computer providing the fueling signal to the fueling system 
according to the engine fueling map. 
In accordance with another aspect of the present invention, a system for 
controlling fueling of an internal combustion engine of a vehicle 
according to vehicle location comprises a receiver associated with a 
vehicle for receiving radio signals relating to vehicle location, a 
fueling system responsive to a fueling signal to provide fuel to an 
internal combustion engine of the vehicle, a memory unit having a number 
of different engine fueling maps stored therein, and a control computer 
connected to the receiver, the fueling system and the memory unit. The 
control computer is responsive to the radio signals relating to vehicle 
location to determine therefrom a geographical location of the vehicle, 
retrieve from the memory unit an appropriate one of the engine fueling 
maps corresponding to the geographical location of the vehicle, and 
provide the fueling signal to the fueling system according to the 
appropriate one of the number of engine fueling map. 
In a further feature of the invention, a system is provided for preventing 
turbocharger overspeed as the vehicle travels to higher altitudes. In one 
approach, the engine speed is reduced or the engine is derated to produce 
a commensurate reduction in turbocharger speed. In the preferred 
embodiment, the radio signals received by the vehicle include signals 
indicative of the altitude of the vehicle. A processor, preferably within 
the engine control computer, receives the altitude signal and accurately 
determines the ambient air pressure at that altitude. Deriving the ambient 
pressure from altitude signal produces a more accurate value to be used by 
the control computer. A more accurate air pressure value reduces the risk 
of derating the engine prematurely, or not derating the engine when the 
ambient pressure is within the range at which the turbocharger will spin 
beyond its limit rotational speed. 
This ambient air pressure value is compared to a threshold pressure value 
indicative of a condition at which the turbocharger is susceptible to 
overspeed. If the ambient pressure value falls below this threshold value, 
the engine fueling system is commanded to reduce the quantity of fuel to 
the engine, which leads to a decrease in the speed of the turbocharger. 
In another embodiment, rather than commanding a fuel reduction, the 
invention contemplates a system that commands the turbocharger wastegate 
valve. When the ambient air pressure falls below the predetermined 
threshold, the wastegate valve is opened to divert a portion of the engine 
exhaust away from the turbocharger, again reducing the speed of the 
turbocharger. 
One object of the present invention is to provide a system for providing an 
internal combustion engine with a fueling map appropriate for a current 
location of the vehicle carrying the engine. 
Another object of the present invention is to provide such a system 
including a memory unit having a number of engine fueling maps stored 
therein, wherein the system further includes a vehicle location 
determining unit and a control computer operable to retrieve an 
appropriate one of the number of engine fueling maps for the current 
geographical location of the vehicle. 
A further object of the present invention is to provide such a system 
alternatively including a communications unit operable to communicate with 
a remote communications unit to receive either an appropriate engine 
fueling map therefrom or instructions therefrom to retrieve an appropriate 
engine fueling map from the memory unit. 
Yet another object of the present invention is to provide such a system 
wherein the number of engine fueling maps includes at least a low 
emissions engine fueling map, a fuel economy engine fueling map and a high 
engine output engine fueling map. 
Still another object of the present invention is to provide such a system 
wherein the low emissions engine fueling map is selected when the vehicle 
is operating in an urban geographical area, the fuel economy engine 
fueling map is selected when the vehicle is operating in a rural 
geographical area and the high engine output engine fueling map is 
selected when the vehicle is operating in a geographical area having 
inclined road grades. 
A further object is addressed by features of the invention that control 
engine fueling as a function of altitude. A more particular object is to 
control engine power at higher altitudes to eliminate the risk of 
turbocharger overspeed. 
These and other objects of the present invention will become more apparent 
from the following description of the preferred embodiments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
For the purposes of promoting an understanding of the principles of the 
invention, reference will now be made to the embodiments illustrated in 
the drawings and specific language will be used to describe the same. It 
will nevertheless be understood that no limitation of the scope of the 
invention is thereby intended, such alternations and further modifications 
in the illustrated devices, and such further applications of the 
principles of the invention as illustrated therein being contemplated as 
would normally occur to one skilled in the art to which the invention 
relates. 
Referring to FIG. 1, a motor vehicle 10, such as a tractor truck-trailer 
combination, is shown including a vehicle position receiver 20 for 
receiving radio frequency signals indicative of vehicle position, in 
accordance with the present invention. In a preferred embodiment, vehicle 
position receiver 20 is a known Global Position Satellite (GPS) signal 
receiver operable to receive GPS signals broadcast by a number n of earth 
orbiting satellites S.sub.1 -S.sub.n. Presently, 24 such earth orbiting 
satellites S.sub.1 -S.sub.24 are in orbit above North America, wherein 
each satellite continuously broadcasts radio frequency signals, and 
wherein the satellites are arranged relative to each other such that at 
signals from at least three satellites are detectable anywhere in North 
America. In accordance with know GPS technology, the radio signals from at 
least three such satellites may be received and processed by known GPS 
receiving systems to determine the present geographical coordinates of the 
system with a high degree of accuracy. 
A similar satellite-based system, GLONAS, is also currently in place over 
Russia and much of Western Europe and operates in a substantially similar 
manner to the GPS system. Thus, while vehicle position receiver 20 is 
shown and described above as a GPS receiver, those skilled in the art will 
recognize that receiver 20 may alternatively be a known GLONAS receiver 
operable to receive GLONAS position signals broadcast by GLONAS 
satellites. In another alternative embodiment, vehicle position receiver 
20 may be a know LORAN-C receiver operable to receiver LORAN-C signals 
from a LORAN-C based position system as is known in the art. As it relates 
to the present invention, however, those skilled in the art will 
appreciate that position signal receiver 20 may be any receiver operable 
to receive broadcast signals from a suitable broadcast system and from 
which present vehicle position may be computed or estimated in accordance 
with known techniques. 
Referring now to FIG. 2, an internal combustion engine control system 15 is 
shown connected to the vehicle position signal receiver 20, and is 
operable to determine an appropriate engine fueling map corresponding to 
current vehicle location, in accordance with the present invention. As 
used herein, the term "engine fueling map" includes any mathematical 
function, table of values or the like mapping engine fueling requests to 
appropriate fuel quantities, fuel injection timing, and the like. Central 
to system 15 is a control computer 30 which has an input IN3 connected to 
vehicle position signal receiver 20 via signal path 42, and further 
interfaces with various motor vehicle components as will be described more 
fully hereinafter. Control computer 30 is preferably microprocessor-based 
and includes a memory 66, digital I/O, a number a analog-to-digital (A/D) 
inputs at least one communications port (COMM) such as a DUART. 
The microprocessor portion of control computer 30 runs software routines, 
manages the overall operation of system 15, and is, in one embodiment, a 
Motorola 68336 or equivalent microprocessor. However, the present 
invention contemplates using any one of a number of known microprocessors 
capable of managing and controlling system 15. 
The memory portion 66 of control computer 30 may include ROM, RAM, EPROM, 
EEPROM, FLASH MEMORY and/or any other reusable type of memory known to 
those skilled in the art. Memory 66 may further be supplemented by 
external memory connected thereto (not shown). 
System 15 further includes a cab-mounted accelerator pedal 32 which 
includes a sensor 34 operable to produce an accelerator signal indicative 
of accelerator pedal deflection, which signal is provided to input IN2 of 
control computer 30 via signal path 36. In one embodiment, sensor 34 is a 
potentiometer producing a dc voltage level on signal path 34 indicative of 
accelerator pedal position or deflection, although the present invention 
contemplates that other known sensors may be alternatively associated with 
accelerator pedal 32 to provide an analog or digital signal or signals on 
signal path 34 is/are processed by control computer 30, as is known in the 
art, to determine a quantity indicative of driver requested torque. 
System 15 further includes a known cruise control system 38 connected to 
input IN2 of control computer 30 via signal path 40. As is known in the 
art, control computer 30 is responsive to one or more cruise control 
signals provided on signal path 40 when cruise control system 38 is active 
to determine a quantity indicative of cruise control requested torque. As 
is known in the art, control computer 30 is responsive to the driver 
requested torque and cruise control torque quantities, as well as other 
engine and vehicle related parameters, to determine engine fueling rates 
from an engine fueling map stored in memory 66. 
System 15 further includes a known engine fueling system 44 operatively 
associated with an internal combustion engine 46 of vehicle 10, and 
connected to output OUT of control computer 30 via signal path 48. Engine 
46 includes an engine speed and/or position sensor 50 that is connected to 
input IN4 of control computer 30 via signal path 52. Engine speed sensor 
46 is preferably a Hall Effect device operable to sense speed and/or 
position of a toothed gear rotating synchronously with the engine crank 
shaft. However, the present invention contemplates that engine speed 
sensor 50 may be any other known sensor, such as a variable reluctance 
sensor for example, operable to sense engine rotational speed and provide 
an engine speed signal to control computer 30 via signal path 52 
corresponding thereto. Control computer 30 and engine speed sensor 50 
comprise a known closed-loop control system whereby control computer is 
responsive to torque request signals provided by accelerator pedal 26 
and/or cruise control system 38, the engine speed signal provided on 
signal path 52 and other known signals, to process such signals in 
accordance with an engine fueling map stored in memory 66 and provide an 
engine fueling signal corresponding thereto to fuel system 44 via signal 
path 48. Preferably, known closed-loop control techniques, such as 
proportional-integral-derivative (PID) techniques and the like, are used 
to produce the engine fueling signal provided on signal path 48. 
System 15 further includes a transmission 54 operatively connected to 
engine 46 as is known in the art, wherein transmission 54 may be a manual, 
automatic or manual/automatic transmission having a number of selectable 
gear ratios. A propeller shaft, or tailshaft, 56 extends from transmission 
54, and a vehicle speed sensor 58 is preferably connected thereto. Vehicle 
speed sensor 58 is connected to input IN5 of control computer 30 via 
signal path 60 corresponding thereto. Vehicle speed sensor 58 is 
preferably a variable reluctance sensor, although the present invention 
contemplates that sensor 58 may be any known sensor operatively associated 
with any suitable vehicle component to provide a vehicle speed signal to 
control computer 30 via signal path 60 indicative of vehicle speed. 
As is particularly well known in the tractor truck industry, transmission 
54 may typically include a separate microprocessor-based auxiliary 
computer 62 connected to a communications port JCOM of control computer 30 
via a communications bus 64. Preferably, communications bus or datalink 64 
is an SAE (Society of Automotive Engineers) J1939 two-wire bus and 
operates in accordance with the technical specifications set forth in the 
SAE J1939 bus industry standard. According to the SAE J1939 industry bus 
standard, control computer 30 and auxiliary computer 62 are operable to 
send and receive information relating to engine, vehicle and/or 
transmission operation. Thus, all information available on datalink 64 is 
available not only to control computer 12 but to auxiliary computer 62 as 
well. Those skilled in the art will therefore recogize that auxiliary 
computer 62 may alternatively be operable to compute some or all of the 
engine fueling information discussed above, and provide such information 
to control computer 30 for controlling fuel system 44. 
As shown in phantom in FIG. 2, system 15 may optionally include a two-way 
wireless communication system 68 having an antenna 70 connected thereto, 
wherein system 68 is connected to a communications port COMM of control 
computer 30 (or alternatively to auxiliary computer 62) via signal path 
72. As will be discussed in greater detail hereinafter, communications 
system 68 may be used to communicate data with another computer system. In 
one embodiment, communications system 68 is a cellular telephone 
transceiver operable to transmit/receive data from/to control computer 30 
(and/or auxiliary computer 62) to/from to remote computer. Alternatively, 
communications systems 68 may be an RF transceiver or a satellite 
communications transceiver operable as described with respect to the 
cellular telephone transceiver embodiment. 
Referring now to FIG. 3, operation of system 15, in accordance with one 
embodiment of the present invention, will be described in detail. FIG. 3 
illustrates an example geographical map having a road 80 extending through 
a city 82 and a mountain range 84, with vehicle 10 (including system 15 of 
FIG. 2) traveling there along. In the example shown, an urban geographical 
region or area 86 surrounds the city 82, a hilly geographical region or 
area 88, i.e. a geographical area in which road 80 includes inclined road 
grades, surrounds the mountain range 84, and all other geographical areas 
through which road 80 passes define rural areas. In accordance with the 
present invention, system 15 is preferably operable to fuel engine 46 
according to a low emissions engine fueling map whenever the vehicle 10 is 
operating in an urban area, to fuel engine 46 according to a fuel economy 
engine fueling map whenever the vehicle 10 is operating in a rural area, 
and to fuel engine 46 according to a high engine output engine fueling map 
whenever the vehicle 10 is operating in an area having inclined road 
grades. In the example map of FIG. 3, system 15 is thus operable to fuel 
engine 46 according to a low emissions engine fueling map as long as the 
vehicle 10 traveling within geographical area 86, to fuel engine 46 
according to high engine output engine fueling map as long as the vehicle 
10 is between points C and D of geographical area 88, and to fuel engine 
46 according to a fuel economy engine fueling map. 
In carrying out the above-described operation, system 15 preferably 
includes a number of engine fueling maps within memory 66, wherein the 
number of engine fueling maps includes at least one low emissions engine 
fueling map, at least one fuel economy engine fueling map and at least one 
high engine out put engine fueling map. Memory 66 further preferably 
includes maps, tables or mathematical functions of geographical areas or 
regions with engine fueling map indicators associated therewith. It will 
be appreciated by those skilled in the art that any known technique may be 
used to partition geographical territories into the various geographical 
regions or areas of interest for purposes of the present invention. For 
example, in accordance with one preferred embodiment of the present 
invention, geographical regions or areas corresponding to low emission 
areas and high engine output areas, such as areas 86 and 88 for FIG. 3, 
are defined as circles having predefined center point geographical 
coordinates and predefined radii, and all areas outside of such 
geographical circles correspond to fuel economy areas. Thus, geographical 
area 86 (low emissions area) has a geographical center point of (X.sub.1, 
Y.sub.1) and a radius of R.sub.1), and geographical area 88 (high engine 
output area) has a geographical center point of (X.sub.2, Y.sub.2) and a 
radius of R.sub.2. It will be understood, however, that other geometric 
shapes, as will be understood, however, that other geometric shapes, as 
well as local, national or international borders, could be used to define 
the geographical regions or areas of interest, and/or that geographical 
areas corresponding to fuel economy areas could alternatively be defined 
by area boundaries. 
A number of known techniques exist for determining whether the present 
vehicle position is located within (or outside of) the boundaries defined 
by the geographical regions or areas of interest, and any one of more of 
such known techniques may be used for purposes of the present invention. 
For example, in accordance with one embodiment of the present invention, 
memory 66 preferably includes one or more geographical engine calibration 
tables including at least the latitudinal and longitudinal coordinates and 
radii of each geographical circle of interest along with a particular one 
of the number of available engine fueling maps corresponding thereto. 
Table 1 illustrates an example of one such table for the geographical 
territory shown in FIG. 3, although it is to be understood that the 
present invention contemplates providing the information shown therein in 
other forms, such as a mathematical equation, for example. 
TABLE 1 
______________________________________ 
GEOGRAPHICAL ENGINE CALIBRATION TABLE 
Latitude 
Longitude Radius 
Engine Fueling Map 
______________________________________ 
x.sub.1 Y.sub.1 R.sub.1 Low Emissions 
x.sub.2 Y.sub.2 R.sub.2 High Engine Output 
______________________________________ 
Referring now to FIG. 4, a flowchart is shown illustrating one preferred 
embodiment of a software algorithm executable by control computer 30 (or 
auxiliary control computer 62) for selecting appropriate engine fueling 
maps based on vehicle location. The algorithm 100 begins at step 102 and 
at step 104, vehicle position signal receiver 20 receives vehicle position 
information in accordance with any of the radio signal techniques 
described hereinabove. Thereafter at step 106, control computer 30 
determines the present vehicle geographical coordinates (VGC). In 
accordance with one preferred mode of operation of system 15, vehicle 
position receiver 20 is operable to continuously receive GPS or other such 
radio signals as described hereinabove. Receiver 20 may include circuitry 
for decoding such signals, in which case receiver 20 is operable at step 
106 to periodically or continuously pass latitudinal and longitudinal (and 
optionally altitudinal and time) coordinate data to control computer 30 
corresponding to present vehicle geographic coordinates (VGC), or receiver 
20 may alternatively pass the received radio information to control 
computer 30 in which case control computer 30 is operable at step 106 to 
decode such information into the vehicle geographical coordinate (VGC) 
data. 
In either case, algorithm execution continues from step 106 at step 108 
when control computer 30 is operable to compare the present vehicle 
geographic coordinates (VGC) with the data stored in memory 66 relating to 
the geographical regions or areas (GA) of interest. As discussed 
hereinabove, many techniques are known and can be accordingly used to 
carry out such a comparison in step 108, although if a Geographical Engine 
Calibration Table such as Table 1 is used, control computer 30 preferably 
determines whether any of the distances between the present vehicle 
location coordinates and any of the geographical circle center coordinates 
are less than or equal to the corresponding circle radius value. 
Algorithm execution continues from step 108 at step 110 where control 
computer 30 tests whether the present vehicle geographic coordinates (VGC) 
fall within any of the geographic regions or areas (GA) of interest, as a 
result of the comparisons of step 108. If not, then algorithm execution 
continues at step 112 where control computer 30 retrieves a default fuel 
map from memory 66. In accordance with the partitioning of the geographic 
territory illustrated in Table 1, if the current vehicle location does not 
fall within any of the geographic circles of interest, then the vehicle is 
presumed to be operating in a rural area and the default engine fueling 
map is therefore a known fuel economy engine fueling map. Algorithm 
execution continues from step 112 at step 116. 
If, at step 110, control computer 30 determines that the vehicle 10 is 
presently located within one of the geographic regions or areas (GA) of 
interest, control computer 30 retrieves an engine fueling map from memory 
66 appropriate for the geographical region or area of interest at step 
114. For example, with reference to Table 1, if control computer 30 
determines at step 110 that the vehicle 10 is presently located within 
area 86 (FIG. 3), then control computer 30 retrieves, at step 114, a known 
low emissions engine fueling map. If, however, control computer 30 
determines at step 110 that the vehicle 10 is presently located within 
area 88 (FIG. 3), then control computer 30 retrieves, at step 114, a known 
high engine output engine fueling map. In one embodiment of the present 
invention, the high engine output engine fueling map is a high engine 
output power engine fueling map, while an alternative embodiment, the high 
engine output engine fueling map is a high engine torque engine fueling 
map. In any case, algorithm execution continues from either of steps 112 
or 114 at step 116 where control computer 30 is operable to fuel the 
engine 46, as discussed hereinabove, according to the fueling map 
retrieved in either of steps 112 or 114. Algorithm execution continues 
from step 116 at step 118 where algorithm execution returns to its calling 
routine (or alternatively routes back to step 104). 
Referring now to FIG. 5, one embodiment of a base station 150, in 
accordance with another aspect of the present invention, is shown. Base 
station 150 is preferably a fixed position station having a control 
computer 156 connected to a communication system 152 via signal path 158, 
wherein communications system 152 is also connected to an antenna 154. As 
with optional communications system 68 illustrated in FIG. 2, 
communications system 152 may be a cellular telephone transceiver, a radio 
frequency transceiver or a satellite communications transceiver, although 
it should be understood that the two communications systems 68 and 152 
must be compatible in their types of communication technology to thereby 
permit control computer 30 (or auxiliary control computer 62) to 
communicate with control computer 156 via system 68 and 152. Base station 
150 further includes a memory unit 160 connected to control computer 156 
via signal path 162, wherein memory unit may be internal to computer 156 
or may comprise a known diskette memory or CD ROM memory, for example. 
Station 150 preferably further includes a display unit 164 connected to 
computer 156 via signal path 166 and a keyboard or other known user input 
means 168 connected to computer 56 via signal path 170. 
If system 15 is equipped with optional communication system 68, system 15 
may, in an alternative embodiment of the present invention, receive some 
or all of the vehicle geographical coordinate (VGC), geographical region 
or area of interest (GA) information and/or engine fueling rate map 
information from a remote computer such as base station control computer 
156. In accordance with one alternative embodiment of the present 
invention utilizing base station 150, control computer 30 (or auxiliary 
control computer 62) is operable to determine the vehicle geographical 
coordinates (VGC) as discussed hereinabove with respect to steps 104 and 
106 of algorithm 100, and provide such data to control computer 156 of 
base station 150. In so doing, control computer 30 is operable to provide 
the vehicle geographic coordinate data to communications transceiver 68 in 
a known manner, wherein transceiver 68 is operable under the direction of 
either control computer 30 or control computer 156 to transmit such data 
to communication transceiver 152 of base station 150. The vehicle 
geographic coordinate data received by transceiver 152 is then passed to 
control computer 156, wherein control computer 156 is operable as 
discussed hereinabove to carry out either steps 108-114 or alternatively 
only steps 108-110 of algorithm 100. In either case, the geographical 
regions or areas (GA) and/or engine fueling maps in memory may be 
contained within computer memory 160 or may alternatively be contained 
within an external memory device such as a diskette or CD ROM. 
Alternatively, control computer 30 may simply pass the radio signal 
information from vehicle position receiver 20 directly to the base station 
control computer 156 so that control computer 156 is operable to 
additionally carry out step 106 of algorithm 100. 
If control computer 156 is programmed to carry out all of steps 108-114, 
control computer 156 is operable to provide data relating to an 
appropriate fueling map to communications transceiver 152. If, on the 
other hand, control computer 156 is programmed to carry out only steps 
108-110, control computer 156 is operable to provide data relating to 
which of the plurality of engine fueling maps within memory 66 to 
retrieve. In either case, transceiver 152 is operable, under the direction 
of either control computer 156 or control computer 30, to transmit the 
data provided thereto to transceiver 68 of system 15. Such data received 
by transceiver 68 is passed to control computer 30 (or auxiliary control 
computer 62) and, if such data represents an engine fueling map, control 
computer 30 (or auxiliary computer 62) is operable to carry out step 116 
of algorithm 116 by fueling the engine 46 according to the engine fueling 
map data. If, on the other hand, such data represents an engine fueling 
map indicator, control computer 30 (or auxiliary computer 156) is operable 
to carry out steps 112, or 114 and step 116 of algorithm 100 by first 
retrieving an appropriate engine fueling map from memory 66 according to 
the engine fueling map indicator provided thereto by control computer 156, 
and then fueling the engine 46 according to the selected engine fueling 
map. 
In a further aspect of the invention, a system is providing for controlling 
engine power as a function of vehicle altitude. More specifically, this 
aspect controls engine power for a turbocharged engine to prevent 
turbocharger overspeed at high altitude, low ambient air pressure 
conditions. One form of turbocharged engine is depicted in FIG. 6. This 
engine is a modification of the engine illustrated in FIG. 2, with like 
component numbers corresponding to like elements as described above. For 
example, the engine 46 is provided with fuel through a fueling system 44. 
The fueling system 44 is controlled by signals along signal path 48 
generated by the control computer 30. The control computer 30 receives 
signals on path 42 from a position signal receiver 20. As discussed in 
more detail above, the receiver 20 can accept GPS signals from a plurality 
of geosynchronous satellites. 
In addition to the elements discussed previously, the engine includes a 
turbocharger 200 that includes a compressor 202 and a turbine 204. The 
compressor 202 includes an air intake 206 that draws in ambient air, 
compresses the air, and directs the compressed air charge to discharge 
conduit 208. The discharge conduit 208 can be integrated into the engine 
air intake manifold in a known manner. 
The turbine 204 is driven by exhaust gas discharge from the engine along 
exhaust conduit 210. In one embodiment, the exhaust conduit 210 can be 
directly connected to the turbine 204. In the illustrated embodiment, the 
exhaust gas is first directed through a wastegate valve 212, and 
ultimately to the turbine through inlet nozzle 214. The flow of exhaust 
gas drives the turbine 204, which is connected to the compressor 202 by 
turbine shaft 205. The reduced energy gas is discharged from the turbine 
at exhaust 216. 
In the illustrated embodiment, the wastegate valve 212 is also connected to 
a wastegate bypass 218 that merges with the turbine exhaust 216. The 
wastegate valve 212 receives signals on signal path 220 from the control 
computer 30 that control the opening and closing of the valve. When the 
valve is closed, all of the engine exhaust is directed to the turbine. 
Conversely, when the wastegate valve 212 is open, some of the exhaust is 
directed to the bypass 218 and away from the turbocharger. Preferably, the 
wastegate valve 212 is a variable position valve capable of diverting 
controllable amounts of engine exhaust to the bypass 218 or through nozzle 
214 to drive the turbocharger. 
As is known, the speed of the turbocharger is a function of the mass flow 
rate of the engine exhaust gas impinging on the turbine 204. This exhaust 
mass flow rate is itself a function of engine power, so that as engine 
power increases, exhaust flow increases, and ultimately turbine speed 
increases. It is also known that the turbocharger rotational speed is 
inversely related to the ambient air pressure at the compressor intake 
206. For a given engine power, an increase in ambient air pressure will 
cause the turbocharger speed to decrease, while a decrease in air pressure 
has the opposite effect. 
As with any rotating machinery, the turbocharger has a rated limit speed. 
Rotation above the limit speed can result in a failure of the turbocharger 
components. Often this failure can be catastrophic. Prior control systems 
for optimizing turbocharger performance have primarily focused on engine 
intake manifold pressure and engine speed. Such known systems do not 
ensure that the turbocharger does not operate beyond its rated limit 
speed. 
In the case of a road vehicle, most of the engine operation will occur at 
lower altitudes. At elevations below 5000 ft., for instance, the risk of 
turbocharger overspeed is minimal. As the vehicle ascends to higher 
elevations, such as while driving through mountainous terrain, the ambient 
pressure can change substantially. As depicted in the graph of FIG. 7, 
ambient air pressure can change from 29.92 in.Hg at sea level, to 20.58 
in.Hg at 10,000 ft., a change of over thirty percent. Even a 2000-ft. 
change in elevation results in about a seven-percent change in ambient air 
pressure. 
Of course, an engine benefits greatly from a turbocharger when tackling a 
long uphill grade. It is under these circumstances that the turbocharger 
is most susceptible to failure--the engine is running at, or even above, 
its full rated power, and the ambient pressure is decreasing. The graph of 
FIG. 8 illustrates the relationship of turbocharger speed to engine power 
and altitude. The graph depicts a line 240 passing through data points 241 
corresponding to the limit speed for the turbocharger beyond which failure 
can occur. Vertical line 230 through points 231 corresponds to the engine 
rated power. A family of lines 250 shows the increase in turbocharger 
speed with engine power at different altitudes and ambient air pressures. 
It is understood that the graph of FIG. 8 is idealized primarily for 
illustrative purposes only. 
It is well known that most engines can operate beyond the rated power or 
speed, usually at 110 percent of that power/speed. The typical engine and 
turbocharger are sized and calibrated so that the rated engine speed will 
not cause the turbocharger to operate beyond its limit speed at a certain 
calibration altitude, usually sea level. Thus, as depicted in FIG. 8, the 
turbocharger speed corresponding to the engine rated power or speed at sea 
level falls well below the turbocharger limit. Moreover, the turbocharger 
limit speed is sufficiently high to allow the engine to run at its 110 
percent limit over a range of elevations above sea level. 
When the engine is operating at its rated power and the ambient pressure 
decreases with altitude, the turbocharger speed increases. At some point, 
this increase in turbocharger speed exceeds the limit speed, represented 
by the horizontal line 240. 
Considered from another perspective, a maximum engine power (at a rated 
speed, for example) for each elevation can be determined. Referring still 
to FIG. 8, the indicia 241 are located at the intersection of the several 
altitude lines 250 with the horizontal turbocharger limit speed line 240. 
At sea level, as represented by the rightmost indicia, the engine can be 
operated well beyond its rated power before the turbocharger reaches its 
limit speed. As the vehicle altitude increases, the maximum permissible 
engine power decreases. At 10,000 ft., the leftmost indicia points to a 
maximum engine speed significantly below the engine rated speed. 
This relationship between engine power and altitude to maintain the 
turbocharger beneath its limit speed is depicted in FIG. 9. Again, the 
maximum speed at which the engine can be safely operated decreases as 
altitude increases and ambient air pressure decreases. As indicated above, 
the graph of FIG. 9 is intended to be illustrative. Consequently, the 
point at which the altitude curve crosses the engine rated power (or 
speed) line may vary. The salient point, however, is that at some altitude 
and air pressure the engine can no longer be operated at full power or at 
its rated speed without risking a turbocharger failure, or an unacceptable 
degradation in turbocharger longevity. 
With this understanding, the present invention contemplates a system that 
first accurately determines the altitude of the vehicle. In the most 
preferred embodiment, the system receives signals at the receiver 20 from 
a GPS satellite system. The receiver can be configured to receive not only 
lat-lon data but also altitude data that is accurate to within tens of 
feet. This vehicle position data, including an altitude signal, is 
provided to the control computer 30 through signal path 42 or other 
similar connections. 
In accordance with this aspect of the invention, the control computer 30 
preferably includes an ambient pressure module 225 that generates an 
ambient pressure value from the altitude signal. The module 225 can 
include table look-up software for extracting a pressure value from a 
table stored in memory, such as memory 66. The table can include hundreds 
of discrete altitude values with corresponding ambient air pressure 
values. Alternatively, the ambient pressure module 225 can implement an 
algorithm, either electronically or using software, that converts the 
altitude signal to an ambient air pressure value usable by other routines 
of the control computer 30. 
As discussed above, the control computer 30 includes an algorithm for 
generating fueling commands provided to the fuel system 44 on signal path 
48. To accommodate the present feature of the invention, the fueling 
algorithm is modified to reduce the fueling command, and therefore the 
engine power, in relation to the ambient air pressure value generated by 
the module 225. The fueling algorithm can implement this fueling 
modification in a variety of ways. For instance, a scaling factor can be 
applied to the fueling command in which the factor is the ratio of the 
ambient pressure value to the sea level pressure value--e.g., 
P.sub.ambient /29.92, for pressure in inches of mercury. Alternatively, 
the algorithm can utilize a more sophisticated relationship between the 
ambient air pressure and the reduction of the fueling command, such as a 
non-linear equation implemented in software. 
As a further alternative, the control computer 30 can modify a maximum 
engine power, speed or torque fueling command parameter maintained in 
memory 66. The maximum fueling command parameter is preferably an existing 
value implemented by the control computer to restrict the level of the 
fueling signal provided to the fuel system 44. This maximum parameter can 
be scaled as a function of the ratio P.sub.ambient /29.92 discussed above. 
Optionally, the maximum fueling command parameter can be calculated 
directly within the ambient pressure module 225. Since the turbocharger 
operating speed has a known relationship to the ambient air pressure, the 
maximum allowable engine power also has a known relationship to 
P.sub.ambient. Likewise, since the fueling command has a known 
relationship to the engine power, as a function of speed and torque, a 
predetermined relationship can be developed between altitude or the 
ambient air pressure and a maximum fueling command parameter. This 
relationship can be embodied in a table stored in memory 66, or in an 
algorithm implemented by the module 225 or the control computer 30. Using 
either approach, the maximum fueling command parameter can be generated 
and stored in the memory 66 for use by the engine fueling algorithm 
conducted by the control computer. 
In the preferred embodiment, the ambient pressure module 225 operates 
continuously to receive altitude signal from the receiver 20 and generate 
engine derating or speed reduction/limiting signals. The invention can be 
applied in a curative or preventative mode. In the curative mode, the 
engine power is reduced from its current operating speed when a 
determination is made that the ambient pressure is low enough relative to 
the engine power to result in a turbocharger overspeed condition. 
However, most preferably the invention is a preventative measure, designed 
to prevent the turbocharger from ever being placed in conditions likely to 
produce an overspeed. Thus, the module 225 continuously monitors the 
ambient pressure and generates the appropriate parameters to limit the 
engine power according to the altitude. 
In an additional embodiment of the invention, the turbocharger speed is 
controlled using the wastegate valve 212, rather than by limiting the 
engine power or speed. Since the speed of the turbine 204 is directly 
proportional to the mass flow through nozzle 214, the speed of the 
turbocharger 200 can be controlled by limiting the exhaust mass flow 
received from the engine. In accordance with this embodiment, the 
wastegate valve is a variable position valve that can control the amount 
of gas discharged through the engine exhaust 210 that is diverted to the 
wastegate bypass 218. The wastegate valve 214 receives control signals 
from the control computer 30 along signal path 220. 
In one approach, the wastegate valve control signals are generated by a 
wastegate control module within the control computer. This module can 
operate under normal engine operating conditions to control the operation 
of the turbocharger. For instance, some engine control routines invoke the 
turbocharger only under certain engine operating conditions. Other 
wastegate control modules operate to control the turbocharger operation 
based on compressor/turbine temperature/pressure. 
The present invention can be readily integrated into known wastegate or 
turbocharger control modules to modify the turbocharger control protocol. 
Since the turbocharger speed is a function of both the ambient pressure 
and the engine power, the turbocharger or wastegate control modules must 
consider both parameters. For instance, the turbocharger can operate at 
full capacity at any altitude and ambient air pressure if the engine is 
not running at its rated power. On the other hand, the turbocharger can 
operate at full capacity with the engine at or above its rated power or 
speed, depending upon the altitude of the vehicle. 
Consequently, the turbocharger/wastegate control algorithms may be somewhat 
more involved than the engine power or speed control protocols discussed 
above. In one approach, a two-dimensional table can be stored in memory 66 
that relates current altitude/ambient air pressure and current engine 
power to a wastegate control signal. In this approach, the control signal 
determines the degree of opening of the wastegate valve 212, which in turn 
determines the proportion of engine exhaust gases discharged through the 
bypass 218. 
This table can take the form shown in FIG. 10. As can be seen in the 
figure, most of the table entries will correspond to a valve open value 
(1.0), meaning that all engine exhaust passes to the turbocharger. 
However, at the higher altitudes and lower ambient pressures, the control 
value is less than full open, being proportionately reduced with 
increasing engine power and increasing altitude. It is understood that the 
table of FIG. 10 can define its row entries as a function of engine power, 
or by the components of power, engine speed and torque. 
As with the engine fueling parameter discussed above, generation of the 
control signal for the wastegate valve 212 can be accomplished using an 
algorithm implemented by the control computer 30 or the 
wastegate/turbocharger control module. The algorithm can receive the 
ambient pressure value from the module 225 and the engine speed from the 
engine speed sensor 50. 
While the invention has been illustrated and described in detail in the 
foregoing drawings and description, the same is to be considered as 
illustrative and not restrictive in character, it being understood that 
only the preferred embodiments have been shown and described and that all 
changes and modifications that come within the spirit of the invention are 
desired to be protected. For example, if system 15 includes the optional 
communications transceiver 68, the base station computer 156 may be used 
to monitor vehicle travel and load memory 66 with a new set of 
geographical regions or areas of interest (GA's) when the vehicle enters a 
new geographical territory, such as new county, state, country or the 
like.