Patent Publication Number: US-6701897-B2

Title: Engine fuel delivery management system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation-in-part of U.S. patent application Ser. No. 09/784,336, filed Feb. 16, 2001, now U.S. Pat. No. 6,539,299 which is currently and assigned to the assignee of the present invention. The entirety of this earlier filed patent application is hereby expressly incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention is directed to an engine fuel delivery management system for an internal combustion engine. In particular, this invention is directed to a system and method that compensates for a change in engine operating state by altering an amount of an operating parameter, such as quantity of fuel to be delivered. 
     BACKGROUND OF THE INVENTION 
     It is believed that the performance of an internal combustion engine is dependent on a number of factors including the operating cycle (e.g., two-stroke having 360 degrees of crankshaft rotation per cycle, four-stroke having 720 degrees of crankshaft rotation per cycle, or Wankel), the fuel type (e.g., gasoline or diesel) the number and design of combustion chambers, the selection and control of ignition and fuel delivery systems, and the ambient conditions in which the engine operates. 
     Examples of design choices for a combustion chamber are believed to include choosing a compression ratio and choosing the numbers of intake and exhaust valves associated with each chamber. In general, it is believed that these choices cannot be changed so as to calibrate engine operation after the engine has been built. 
     With regard to ignition systems, breaker point systems and electronic ignition systems are known. It is believed that these known systems provide spark timing based on an operating characteristic of the engine, e.g., speed of rotation and load. In the case of breaker point systems, it is believed that engine speed is frequently detected mechanically using centrifugally displaced weights, and that intake manifold pressure or exhaust manifold pressure is commonly used to detect engine load. In the case of electronic ignition systems, it is believed that engine speed is generally detected with an angular motion sensor associated with rotation of the crankshaft, and that engine load is frequently detected, for example, by the output of a throttle position sensor, intake manifold pressure or mass airflow sensor. In each case, spark timing is typically fixed for a given steady operating state of the engine. 
     With regard to fuel delivery systems, carburetors and fuel injection systems are known. It is believed that those known systems supply a quantity of fuel, e.g., gasoline and air, in accordance with the position of the throttle as set by the operator. In the case of carburetors, it is believed that fuel is delivered by a system of orifices, known as “jets.” As examples of carburetor operation, it is believed that an idle jet may supply fuel downstream of a throttle valve at engine idling speeds, and that fuel delivery may be boosted by an accelerator pump to facilitate rapid increases in engine load. It is believed that most carburetors must be disassembled and different size jets or pumps installed to modify the amount of fuel delivery at a particular engine load. However, that is a laborious process that, it is believed, most often, can only be done while the engine is not running. 
     It is believed that known fuel injection systems, which can be operated electronically, spray a precisely metered amount of fuel into the intake system or directly into the combustion cylinder. The fuel quantity is believed to be determined by a controller based on the state of the engine and a data table known as a “map” or “look-up table.” It is believed that the map includes a collection of possible values or “setpoints” for each of at least one independent variable (i.e., a characteristic of the state of the engine), which can be measured by a sensor connected to the controller, and a collection of corresponding control values, for a dependent variable control function, e.g., fuel quantity. 
     Conventionally, it is believed that maps are developed by the engine manufacturer and permanently set in an engine control unit at the factory. Currently, for on-road vehicles, this is believed to be legally required in order to meet emissions regulations. However, it is believed that even when it is not legally required, the manufacturers prevent engine operators from modifying the maps for a variety of reasons, such as the manufacturers believe that their maps provide the best engine performance, the manufacturers are concerned that an engine operator might damage the engine by specifying inappropriate control values, or the manufacturers assume that an engine operator might not have sufficient skill to properly modify a map. However, it is believed that the manufacturers have “optimized” their maps to perform best under a set of conditions that they specify. In certain cases, however, it is believed that those conditions do not match the conditions in which the engine is operated. Consequently, stock maps sometimes limit, rather than optimize, an engine&#39;s performance. 
     Conventional maps, furthermore, are typically created to provide fuel delivery and ignition timing suitable for the engine when operating at a steady-state. Thus, map values may not be appropriate for an engine operating in transition such as, for example, an accelerating or decelerating engine. 
     Further, engine performance is believed to be substantially dependent on how combustion is accomplished in the ambient conditions. The stoichiometric mass fraction ratio of air to gasoline is approximately 14.7:1. However, it is believed that ratios from about 10:1 to about 20:1 will combust, and that it is often desirable to adjust the air-fuel ratio (“AFR”) to achieve specific engine performance (e.g., a certain level of power output, better fuel economy, or reduced emissions). Properly calibrating the fuel delivery system of an engine to deliver the optimum AFR under all operating conditions is one of the most important goals of a calibration effort. It is also frequently the most time consuming, difficult, and costly part of the calibration effort. Similarly, it is also believed to be desirable to adjust ignition timing, commonly measured in degrees of crank rotation before a piston reaches top-dead-center of the compression stroke, to achieve specific engine performance (e.g., lowest fuel consumption or reduced emissions). 
     It is believed to be a disadvantage of known ignition timing systems and fuel delivery systems that engine operation is constrained by the fixed controls established by the suppliers of these systems. It is also believed that a simple, effective system and method for varying fuel delivery during engine operating state transitions is needed. Thus, there is believed to be a need to overcome the disadvantages of known fuel delivery systems. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a system, method and apparatus for adjusting a quantity of fuel delivered to an engine when an engine operating state transitions. In accordance with one form of the present invention, there is provided such a method that includes determining from a data table a current steady-state quantity of fuel to be delivered to the engine under a steady-state condition and adding a transitory quantity of fuel to the current steady-state quantity of fuel. The transitory quantity of fuel is based on a difference between a previous steady-state quantity of fuel delivered and the current steady-state quantity of fuel to be delivered. The steady-state quantity of fuel is a quantity of fuel delivered or to be delivered to an engine when the engine is operating at any steady-state. The data table from which the steady-state quantity of fuel is determined may be a two-dimensional map utilizing engine load and engine speed to determine steady-state fuel quantity. The steady-state quantity determined may be the closest value on the map corresponding to an engine operating state that is retrieved and used as the required steady-state fuel mass required. Alternately, the steady-state value may be interpolated from multiple values on the map. For example, when interpolation is used the steady-state value may be interpolated from the two speed values closest to the current engine operating state and the two load values closest to the current engine operating state. A transition occurs when an engine shifts from one operating state to another. A transition may, therefore, correspond to any movement from any one position to any other position on a map. Compensation for transitions resulting in both positive and negative transitory fuel quantities may be implemented and different weights may be placed on positive and negative transitory fuel quantities. 
     The present invention is also directed to an engine transitional fuel control apparatus and method of operating that apparatus. The engine transitional fuel control apparatus includes a processor, a fuel supply device; and a fuel supply actuator. The processor has an output and a memory, whereby the memory contains a fuel delivery table and instructions. When executed by the processor, the instructions cause the processor to determine a steady-state amount of fuel to be delivered, add a transitory quantity of fuel to the steady-state amount of fuel to be delivered for a period of time following initiation of the transition, and apply a signal corresponding to that total amount of fuel to the output. The steady-state amount of fuel to be delivered is determined by reference to the fuel delivery table and the transitory quantity of fuel is based on a difference between a previously determined steady-state quantity of fuel and the current steady-state amount of fuel to be delivered. The fuel supply actuator is coupled to the output of the processor and operably coupled to the fuel supply device to control fuel flow therethrough. 
     The present invention provides a number of advantages including the ability for fuel delivery to be adjusted electronically without need for component removal or system disassembly. Another advantage is the ability of the present invention to electronically adjust fuel delivery, including specifically transitory fuel quantity, while the engine is running. Yet another advantage is that fuel supply to an engine can be controlled by way of a program that compensates for changes in engine operating state. Another advantage is that fuel supply to an engine can be controlled by way of a program that compensates for desired changes in engine operation. 
     Accordingly, the present invention provides solutions to the shortcomings of prior engine control systems and methods. Those of ordinary skill in the art will readily appreciate, therefore, that those and other details, features, and advantages of the present invention will become further apparent in the following detailed description of the preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated herein and constitute part of this specification, include one or more embodiments of the invention, and together with a general description given above and a detailed description given below, serve to disclose principles of the invention in accordance with a best mode contemplated for carrying out the invention. 
     FIG. 1 is a schematic illustration of an embodiment of a system for calibrating engine operation; 
     FIG. 2 is a schematic illustration of an embodiment of a fuel delivery system; 
     FIG. 3 is a cross-sectional view of an embodiment of a cylinder in a four-stroke engine; and 
     FIG. 4 illustrates an embodiment of a system by which a vehicle operator may trim engine operating characteristics. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. It is to be understood that the Figures and descriptions of the present invention included herein illustrate and describe elements that are of particular relevance to the present invention, while eliminating, for purposes of clarity, other elements found in typical engines and engine control systems. 
     As they are used in connection with the present invention, the expressions “trim” or “trimming,” “group,” “trim definition,” and “map set” have specific meanings. The expressions “trim” and “trimming” refer to changing the value of one or more map setpoints or transient operating parameters. The value of this change, which can be positive or negative, can be a function of the original value or a selected increment. The expression “group” refers to an aggregation or parcel of setpoints or transient operating parameters that are acted upon in unison by a trimming action. A group can be defined by a “trim definition.” For example, a trim definition can parcel out an engine control map so as to create a group of setpoints that lie within one or more selected ranges of one or more independent variables, e.g., sensed engine operating characteristics. The expression “map set” refers to a single engine control map and/or transient operating parameter or to an association of more than one related engine control map or transient operating parameter. For example, a map set can consist solely of a fuel delivery map. Alternatively, a map set might comprise an ignition timing map, a fuel delivery map, and increasing and decreasing fuel transient operating parameters. 
     It is also noted that any reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of phrases such as “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment. 
     FIG. 1 illustrates an embodiment of an engine management system  10  that includes a library of engine management files in an external computer  130 . Those engine management files can be made available to an engine control system via a processor  120 , and can be used for calibrating engine performance. The engine management system  10  includes an engine control unit  20  that is coupled (e.g., via wires, fiber, wirelessly, or other coupling device) to one or more input or output devices (e.g., sensors or actuators). The engine control unit  20  can include a processor  120  that uses coded instructions to act on one or more electrical input signals and to supply one or more electrical output signals. According to one embodiment, wires electrically connect the engine control unit  20  with various other components, which will be described in detail below. The engine control unit  20  may have a housing  20   a  mounted to a vehicle chassis through which other components can be electrically grounded with respect to the vehicle chassis (not shown), e.g., a motorcycle frame, in a known manner. 
     According to one embodiment, the engine control unit  20  can provide a single engine operating control value, i.e., for adjusting a single engine control, such as fuel quantity delivery. According to another embodiment, however, the engine control unit  20  can provide a plurality of engine operating control values, i.e., for controlling a plurality of engine controls, such as fuel quantity and ignition timing. 
     FIG. 2 illustrates an embodiment of a fuel delivery system  40  that may be utilized in connection with the present invention. The engine control unit  20  is electrically connected to the fuel delivery system  40  as illustrated in FIG.  1 . The fuel delivery system  40  depicted includes a fuel tank  302 , a coarse filter  304 , a fuel pump  306 , a pressure regulator  308 , a fine filter  310 , a fuel injector  312 , and a fuel line  314 . The fuel tank  302  contains a fuel, such as gasoline or diesel, for delivery to and consumption by the engine  100 . The fuel line  314  may be, for example, a steel or stainless steel conduit in fluid communication with the fuel tank  302  and the fuel injector  312 . 
     The coarse filter  304  may be located along the fuel line  314  to remove large contaminants from the fuel as the fuel travels from the fuel tank  302  to the fuel pump  306 . The fuel pump  306  may also be located in the fuel line  314  between the fuel tank  302  and fuel injectors  312 . The fuel pump  306  may alternately be placed elsewhere, such as in the fuel tank  302 . The fuel pump  306  typically creates a pressure differential in the fuel line  314  between a pump inlet  316  and a pump outlet  318 , thus transporting fuel from the fuel tank  302  through the fuel line  314  and in-line components and, ultimately, through the fuel injector  312 . The fuel pump  306  can be electrically interconnected with the engine control unit  20 , and may be, for example, a positive displacement type pump or a dynamic type pump. 
     The pressure regulator  308  measures differential pressure in the fuel line  314  and may be piped in fluid communication with the fuel tank  302  and the pump outlet  318 . The pressure regulator  308  may control operation of the fuel pump  306  to maintain the pressure differential at a desired level. The pressure regulator  308 , in one embodiment, relieves excess pressure by returning a portion of the high-pressure fuel stream to the fuel tank  302 . The pressure regulator  308  may alternately or in addition be interconnected with the engine control unit  20 , providing an input signal to the engine control unit  20 , such that the engine control unit  20  may control operation of the fuel pump  306  to maintain a desired fuel differential pressure. The fine filter  310  may be located in the fuel line  314  between the fuel pump  306  and the fuel injector  312  to remove small particles of contaminants remaining in the fuel which might otherwise become lodged in the fuel injector  312 . The fuel injector  312  atomizes the fuel and sprays the fuel toward one or more cylinders  362  as required. The fuel injector  312  can be oriented so as to spray a precisely metered amount of fuel toward, for example, an intake port in a two-stroke engine or an inlet tract  352  in a four-stroke engine. In the case of four-stroke engine designs having a plurality of intake valves, each of the fuel injectors  312  can be oriented so as to spray fuel into an inlet tract  352  for a single valve as illustrated in FIG. 3 or a fuel injector  312  may provide fuel to multiple intake valves. 
     FIG. 3 illustrates an embodiment of a cylinder of a four-stroke engine  350  that may be utilized in connection with the present invention. It will be recognized that other cylinder configurations may be utilized with the present invention including, for example, two-stroke engines and configurations in which a fuel injector  312  supplies fuel to either one or multiple cylinders  362 . The embodiment of FIG. 3 includes a fuel injector  312 , an inlet tract  352 , an inlet valve  354 , a spark plug  356 , an exhaust valve  358 , an exhaust tract  360 , the cylinder  362 , and a piston  364  attached to a crankshaft (not shown) via a connecting-rod  366  and a bearing  368 . 
     Pressurized fuel from the fuel line  314  illustrated in FIG. 2 is sprayed through a nozzle  370  of the fuel injector  312  when a valve, such as an electrically operated solenoid valve (not shown), is opened permitting fuel to flow through the fuel injector  312 . That valve may be an electrically operated solenoid valve that is actuated through an output of the engine control unit  20 . Control of such a solenoid valve is usually performed by pulse width modulation such that a longer opening duration will provide more fuel into the cylinder or cylinders  362  supplied by the fuel injector  312 . A butterfly valve may be positioned to permit airflow into the inlet tract  352  of one or more cylinders  362 . The butterfly valve may be pivotal about an axis between a first position preventing airflow into the inlet tract  352  and a second position permitting airflow into the inlet tract  352 . An actuator cam (not shown) may be connected to the butterfly valve for pivoting the butterfly valve against the bias of a return spring, e.g., a torsion spring, from the first position to the second position. The actuator cam can be connected, via a throttle cable (not shown), to an operator controlled throttle control element (not shown). Alternately, the actuator cam may be controlled by an output of the engine management system  10  and the throttle control element may serve only as an input to the engine management system  10 . A throttle position sensor  44 , as illustrated in FIG. 1, may, for example, be connected to the butterfly valve for measuring the angular position of the butterfly valve as it is pivoted about the axis, and/or may be connected to a throttle control element for input to the engine management system  10 . 
     Fuel is typically permitted to flow through the inlet valve  354  to the cylinder or multiple cylinders  362 . The inlet valve  354  then closes and the fuel is ignited by the spark plug  356 , thereby driving the piston  364  away from the inlet valve  354  and outlet valve  358 . The exhaust valve  358  opens as the piston  364  moves back toward the inlet valve  354  and exhaust valve  358 , thereby forcing exhaust gases out of the cylinder  362 , through the exhaust valve  358  and away through the exhaust tract  360 . 
     It should be noted that fuel delivered to the cylinder  362  often passes through an inlet tract  352  where the fuel may be mixed with an oxidant, such as air, drawn through the inlet tract  352 . Liquid fuel may thus build-up on a wall  372  of the inlet tract  352  or on the back of the inlet valve  354 . Fuel may be delivered both during the approximately one-quarter cycle of a cylinder  362  in a four-stroke engine  350  when the inlet valve  354  is in an open position and during much of the three-quarters of a cycle when the inlet valve  354  is in a closed position when the engine is under high load. Thus, substantial build-up may occur on the inlet tract walls  372  and on the intake valve  352 , and in the airstream present in the inlet tract  352 , particularly under such high load engine conditions. The present invention is directed, in part, to compensating for lean operation when fuel, intended to be delivered to the cylinder  362 , instead remains in the inlet tract  352 , or rich operation when fuel from the inlet tract  352  is provided to the engine  100  in addition to fuel provided by the fuel injector  312 . 
     The engine control unit  20  may be electrically connected to a dash panel  80  that is described in U.S. Pat. No. 6,539,299. As the engine management system  10  is shown in the figures, the engine control unit  20  supplies a signal controlling fuel quantity. It should be recognized, however, that additional control signals, for example controlling ignition timing, may also be provided by the engine control unit  20 . In general, a map set can include different numbers of maps (i.e., fuel timing, power jet applications, or power valve actuation), or different combinations of map types (e.g., ignition timing, fuel timing, and power valve actuation). 
     Table 1 shows an example of a map that includes an arbitrarily selected number of steady-state fuel quantity setpoints. Fuel quantity setpoints typically vary from one engine to any other engine, thus optimum fuel quantity setpoints are calibrated uniquely for each engine  100 . Fuel quantity setpoints also generally vary for any particular engine  100  depending on the operating characteristic to be optimized, i.e., maximum power, minimum fuel consumption, emission regulations, etc. 
     An engine state may be defined by measuring the value of one or more operating characteristics of an engine. It is common practice in engine management that engine speed and load are used to define a two-dimensional plane of engine operating states. It is also common for a controlled value such as engine fueling to be measured for a finite number of operating states. Thus, a map may include fuel values corresponding to known engine states. In a two-dimensional map having a measurable characteristic corresponding to engine load as a first axis and a measurable characteristic corresponding to engine speed as a second axis, a particular engine state may be defined as the intersection of the current engine load and current engine speed on the plane of the map. 
     Thus, the operating state of an engine  100  may be determined in many ways including measuring the speed of rotation of the engine  100  and the load on the engine  100 . Engine speed is usually expressed in units of revolutions-per-minute or rpms. Engine load may be sensed by a variety of sensors including, for example, a throttle position sensor  44 , a manifold vacuum sensor (not shown), or a mass airflow sensor (not shown) positioned to sense air flowing into one or more cylinders  362 . The present invention also contemplates utilizing air mass per cycle delivered, or to be delivered, to an engine  100  or cylinder  362  to sense engine load. Each setpoint in Table 1 corresponds to the values of two engine operating characteristics, i.e., an engine speed value and an engine load value. Thus, for a given value of engine speed (e.g., as sensed by or derived from an output signal from a crankshaft angular motion sensor  102  coupled to an engine  100 ) and for a given value of engine load (e.g., as measured by the throttle position sensor  44 ), fuel quantity setpoints are assigned in a map and may be read therefrom. For example, the map illustrated in Table 1 causes the engine control unit  20  to deliver twenty-five grams of fuel per cycle at 2000 revolutions per minute (rpm), when the throttle is opened 50%. At 5000 rpm, when the throttle is fully open, the engine control unit  20  will vary fuel delivery to provide fifty grams of fuel per cycle. Thus, when either the engine load (e.g., throttle position) or engine speed changes, the fuel delivery system  40  will determine an initial, steady-state amount of fuel that is to be delivered at the new speed and load by reference to the map. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Fuel Delivery 
                   
               
               
                 (milligrams 
                 Engine speed (revolutions per minute) 
               
            
           
           
               
               
               
               
               
            
               
                 per cycle 
                 1000 
                 2000 
                 5000 
                 7000 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Load 
                  5 
                  7 
                  5 
                  4 
                  3 
               
               
                 (Percentage 
                 25 
                 10 
                 21 
                 15 
                 10 
               
               
                 Throttle 
                 50 
                 15 
                 25 
                 37 
                 30 
               
               
                 Opening) 
                 75 
                 15 
                 25 
                 44 
                 40 
               
               
                   
                 100  
                 15 
                 25 
                 50 
                 45 
               
               
                   
               
            
           
         
       
     
     In general, a map will include a great number of setpoints that can be assigned for small increments of measured value for each engine operating characteristic utilized in the map. If the operating state of the engine falls in a gap between specified values of the characteristics (e.g., in Table 1, there are gaps of 2000 rpm or more between the specified values for engine speed and 20% or more gaps in engine load), the engine control unit  20  can interpolate the operating control values between the two closest speed columns and two closest load rows or the equivalent thereto. 
     As illustrated in FIG. 1, engine management data including one or more map sets can be downloaded to the engine control unit  20  from a processor  120 , either via a data port  110  or by “docking” the processor  120 , which may be a palm-size computer, with the fixed portion  80   a  of the dash panel  80 . Multiple maps may be downloaded to the engine control unit  20  to control different operating parameters and/or to optimize a single operating parameter for different situations or conditions. For example, a map that optimizes normal racing conditions, a map that optimizes engine operation during acceleration from a low speed, and a map that optimizes engine operation at high speed may each be loaded into the engine control unit  20 . The operator may then select any one of the three loaded maps while operating the vehicle by, for example, moving a three-position map selection switch  82  coupled to the engine control unit  20 . The operator may furthermore trim certain characteristics of each map through another interface, such as a knob or trim-up and trim-down buttons, for interfacing to the engine control unit  20 . 
     Engines  100  have two types of modes of operation, steady-state modes and unsteady-state modes, commonly called transitory or transient modes. An engine  100  operates in a steady-state mode when the engine load and speed are constant with respect to time and in a transitory mode when either the engine load or speed varies with time. In other words, an engine  100  is operating in a transitory mode anytime engine operation shifts from one state to another. A transition may, therefore, correspond to a shift from any one position on a map to any other position on a map. 
     Maps are typically optimized for steady-state engine operation. Engines  100 , however, are most often operated at varying speeds and loads. For example, the engine of a racing motorcycle may be continually changing its operating state because of changing track conditions, such as hills and turns, encountered on a typical racing track. Moreover, values such as the mass of fuel supplied to an engine, optimized for steady-state operation, are typically not optimum values for transitory operation. Thus, there is a need for a method and system that will optimize performance during transitions in engine operating states. 
     The present invention may also include an interface to the engine control unit  20  through which an operator may vary the operation of transitory fueling. For example, a three-position transitory mode selection switch  84  may be coupled to the engine control unit  20 . That switch may have, for example, an upper position, a center position, and a lower position. The upper position may be optimized for fastest engine response. The center position may be optimized for normal operation, which may, for example, be more comfortable for an operator or provide more stable operation of the vehicle. The lower position may be optimized for operation under slippery conditions. Of course, optimization for any condition and any number of transitory modes may be possible depending on the needs of an operator and/or vehicle. 
     Transitory modes may, furthermore, be tied to an individual map. Thus, different transitory control modes may operate for each map contained within the engine control unit  20 . The engine control unit  20  may contain three fueling maps having three modes of transitory compensation that are unique to each map and the transitory mode selection switch  84  may be utilized to select one of three transitory modes related to the map selected by the map selection switch  82 . 
     The coupling between the processor  120  and either the data port  110  or the fixed portion  80   a  can be via wires or wireless. In addition to the operation of the engine control unit  20  described above, the engine control unit  20  can operate smart lights and perform other functions as desired. 
     In addition to processing downloaded data, the engine control unit  20  can also be connected to any necessary on-board sensor. For example, an air-temperature sensor (not shown) and/or barometric pressure sensor (not shown) can provide sensor signals that can in turn be used to calculate the density of the air being inducted into the engine  100 . Because the displacement of an engine is typically constant and mass of combustion air is equal to the displacement times the density of the combustion air, the mass of combustion air may be calculated. Thus, inlet temperature and pressure can be used to affect global changes to all control signals based on the values in each map set that has been downloaded to the engine control unit  20 . Thus, a map may include fuel mass requirements under standard atmospheric conditions and the engine control unit  20  may compensate for various atmospheric pressures and/or temperatures, which effect air density and air mass per engine cycle. 
     In connection with this invention, the expression “global” refers to making an adjustment with respect to every setpoint in a control map, whereas “local” refers to a setpoint or a group of setpoints in a control map. The sensor signals from the engine speed sensor  102  and throttle position sensor  44 , in addition to being monitored by the engine control unit  20  for accessing setpoints, can be used to determine which setpoints are to be the basis for trimming. Using the engine management system  10  in connection with the fuel delivery system  40  including fuel injectors  312  can furthermore be considered to be analogous to carburetor jetting, i.e., below a certain throttle opening, local trimming according to the present invention corresponds to changing the slow jet, local trimming at higher throttle openings corresponds to changing the needle jet, and local trimming at still higher throttle openings corresponds to changing the main jet. 
     Additionally, a sensor (not shown) for electrical system voltage can measure variations that directly affect the reaction time and accuracy of the electromechanical movements within the fuel injectors  312 . Sensors (not shown) for gear position and side stand deployment can be used to alert a user, such as a motorcycle rider, to potentially harmful or dangerous conditions and a sensor (not shown) for detecting the initiation of a gear change can signal the engine control unit  20  to momentarily cut-off the ignition system or fuel delivery, thereby facilitating smoother shifts. Of course, the engine control unit  20  can be connected to many other sensors, e.g., sensors (not shown) for engine coolant temperature or oil pressure that can provide a warning to the engine operator or control of the engine  100 . 
     It is believed that fuel flowing into the cylinders  362  of fuel injected engines comes not only from the fuel injectors  312  but also from collateral sources including one or more walls  372  of any inlet tract  352  extending from the fuel injector  312  to the cylinder  362 , surfaces of the inlet valve  354  and the airstream in the inlet tract  352 . It is furthermore believed that when fuel delivery is not at a steady-state, for example, during acceleration or deceleration, or increasing or decreasing load, the quantity of fuel delivered by those collateral sources varies. For example, when the throttle is opened quickly, fuel delivered from the inlet tract  352  may be reduced because of greater pressure in the inlet tract  352  causing the engine  100  to run lean during that period of acceleration. Similarly, when the throttle is closed quickly, the delivery of fuel from the walls  372  of the inlet tract  352  may increase causing the engine  100  to run rich. 
     The present invention calculates necessary fuel delivery under transitory throttle conditions and compensates for changes in fuel delivered from collateral sources by varying fuel flow from the injectors during transitory engine operation. In one embodiment, the present invention senses engine speed and throttle position and reads or interpolates an associated quantity of fuel from a look-up table or map that is to be delivered to each cylinder  362  every engine cycle. 
     Quantity of fuel is expressed in the examples that follow, as a fuel mass per cycle to be delivered. It should be noted that fuel mass delivered per cycle may decrease as engine speed increases, however, the rate of fuel delivery per time unit such as per second will increase because of increased frequency of injection. The values retained within the map may, however, be expressed in terms other than fuel quantity or mass. For example, the value saved in the map may be an amount of time that an injector should be held open to deliver a desired quantity of fuel in, for example, a pulse width modulated system. The value may also correspond to fuel pressure, AFR, or a degree of injector opening, for example. 
     When an engine is operating at a steady-state, the fueling requirements are the same for each consecutive engine cycle. Engines may furthermore be operated at various steady-states in a laboratory and optimum fuel delivery may be determined by stepping the engine along its operating range. Thus, the fuel mass to be delivered for any steady-state operation may be easily determined and included in a map. Engines, however, typically transition from one operating state to another during use and the mapped steady-state fuel quantity is typically not optimized for such transitional operation. Moreover, an engine may transition in a nearly infinite number of ways. During a transition, engine speed and load may change separately or together in a wide variety of combinations. Thus, mapping transitional calibration values would be very time consuming and difficult. In contrast, the present invention provides a general purpose method to accomplish transient fueling calibration that recognizes changes in the state of operation of an engine and compensates for transitions by changing fuel delivery based on the sensitivity of the engine to changing states and the amount of change reflected in a steady-state fuel calibration map or table for the engine. 
     Thus, the present method may begin by retrieving the steady-state fuel value from a map for the current operating state. The steady-state value may then be compared to a previous steady-state value to determine an amount of change in the steady-state fueling requirements. If a change in steady-state requirement occurs, the method will adjust the fuel quantity to compensate for the transition. 
     The fuel delivery system  40  of the present invention will calculate a transient fuel differential, which is an amount of fuel that should be added to or subtracted from the current steady-state amount of fuel determined from the map. That determination may be accomplished by, for example, reading from the map or interpolating from values on the map. That transient fuel differential alters the amount of fuel that would be delivered by the map only, compensating for collateral fuel loss or gain due to the transition taking place and other transitory needs of the engine. That transient fuel differential may be expressed as a positive value where fuel is to be added and a negative value when fuel is to be subtracted from the steady-state fuel quantity determined from the map. A minimum amount of fueling change may, furthermore, be required to surpass a noise threshold before adding the transient fuel differential to the steady-state fuel requirement. Such a threshold beneficially minimizes the effect of such things as a noisy speed signal or variations in throttle position caused by unintentional variations in pressure applied to the throttle by an operator. 
     In adjusting fuel quantity to compensate for an engine transition, the present method may consider a variety of factors including the sensitivity of the engine to fueling changes, the amount of the fuel change, duration or the number of engine cycles during which compensation should persist, and a decay rate for the compensation. Engine sensitivity may be a factor related to how much compensation a particular engine requires during transitions and may be expressed as a multiplier such as the factor “ETSF” in the equation hereinbelow. The amount of change in the operating state of an engine may be expressed in terms of a change in a steady-state fueling value for an engine, engine load, engine speed or one or more other sensed or calculated values that indicate the state of the engine. The equation included hereinbelow utilizes steady-state change in fuel mass per cycle, which is equal to the steady-state mass required for the next cycle less the steady-state mass that was required for the previous cycle, or “SSCM/C.” The duration during which a transient fueling amount compensating for an engine state transition should be added may be expressed in terms of, for example, time or number of engine cycles. The duration may be as little as a single cycle such that utilizing a stack as described below is not necessary. Compensation over a duration may also be considered by use of Proportional and Integral “PI” or Proportional, Integral, and Derivative “PID” control strategies. It should be noted that in certain applications, including racing engines, transitions occur nearly every engine cycle, which may affect duration decisions. Decay is a rate of reduction of the amount of influence a single state change has as time passes. Decay may be a multiplier applied to the transitory mass of fuel each cycle or each unit of time to reduce the effect of past transitions. 
     In a certain embodiment, the transient fuel differential is equal to the sum of a stack of values stored in a data storage facility such as RAM. The values that are stored in the stack may be calculated by multiplying an engine transition sensitivity factor, which may be determined separately through experimentation for each engine to be controlled, by an engine requirement differential. The engine requirement differential may be equal to the difference between the steady-state fuel requirement to be delivered next and the steady-state fuel requirement that was to be delivered previously. For example, the engine requirement differential may be equal to a fuel mass determined from the map for the current throttle position and engine speed less the fuel mass delivered in the last cycle. That value may then be entered into a first position in the stack. Notably, the engine requirement differential may be calculated for each cycle of each cylinder  362 . Thus, the value entered into the first position of the stack may be calculated as follows: 
     
       
         TM/C=ETSF*SSCM/C  
       
     
     Where: 
     TM/C is the transient mass of fuel per cycle or transitory fuel differential; 
     ETSF is the engine transition sensitivity factor; and 
     SSCM/C is the steady-state change in fuel mass per cycle, which is equal to the steady-state mass required for the next cycle less the steady-state mass that was required for the previous cycle. 
     It will be recognized that, when the next steady-state mass of fuel requirement is less than the previous steady-state mass of fuel requirement, the transient mass of fuel per cycle will be a negative amount. Conversely, when the current steady-state mass of fuel requirement is greater than the previous steady-state mass of fuel requirement, the transient mass of fuel per cycle will be a positive amount. In that way, compensation for both increases and decreases in fuel delivered from collateral sources is provided by the calculated transient mass of fuel per cycle. 
     Furthermore, the engine transition sensitivity factor may alternately be a non-linear function rather than a linear factor. 
     The stack may be any size and may be variable in size depending, for example, on engine operating state. In the following example, the stack contains storage locations for five fuel mass values. The first value in the stack is the calculated transitory fuel amount for a current fuel quantity transition. The remainder of the stack is utilized to factor a decay rate for the transitory fuel differential over four additional cycles. Thus, for a first cycle, a first transitory fuel differential is calculated and placed in the first storage area in the stack. Prior to the second cycle, that transitory fuel amount is removed from the first storage area, multiplied by a decay rate, and placed in the second stack storage area. For the third cycle, the value in the second storage area is removed, multiplied by the decay rate, and placed in the third stack storage area. Similarly, the value is removed from the third storage area, decayed, and placed in the fourth storage area and then removed, decayed, and placed in the fifth storage area prior to the fourth and fifth cycles, respectively. That transitory fuel amount is then removed from the fifth storage area and has no further effect on fuel mass delivery after the fifth cycle. Therefore, when a single fuel quantity transition occurs at least five cycles after the last transition, and no fuel quantity transitions occur for five cycles after that transition, only one non-zero amount will reside in the stack. Thus, the sum of the stack storage areas will be equal to the decaying fuel mass calculated from the single transition. The values in the stack are then totaled and added to the steady-state fuel mass associated with the current engine state to arrive at a mass of fuel to be delivered to, for example, the engine  100  or a particular cylinder  362  for the current cycle. Where one or more additional transitions occur within five cycles, multiple values will concurrently reside in the stack. 
     The decay may also be a non-linear function rather than a linear rate of decay. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 2a 
                 2b 
                 2c 
                 2d 
                 2e 
                 2f 
                 2g 
               
               
                   
               
             
            
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                 8 
                 4 
                 −2 
                 −1 
                 −0.5 
                 −0.5 
                 −0.25 
               
               
                   
               
            
           
         
       
     
     Table 2 illustrates transitions occurring over seven cycles (a-g) of a cylinder  362 . In that example, the decay rate will reduce the transitory fuel differential to one half of its previous value. The engine transition sensitivity factor in this example is 0.5. In a first cycle, illustrated in column 2a of Table 2, a transition occurs for which the steady-state change in fuel mass is 16 mg of fuel. Thus, the transitory fuel differential is equal to 0.5 times 16 mg, or 8 mg of fuel. Thus 8 is placed in the first stack position. As illustrated in column  2   b , if no transition occurs in a second cycle, a zero is placed in the first stack position to correspond to a transitory fuel differential of zero and a four is placed in the second stack position to correspond to the  8  decayed by one-half. As illustrated in column 2c, if another transition occurs in a third cycle having a steady-state change in fuel mass of −8 mg, then the transitory fuel differetial is equal to 0.5 times −8 mg, or −4 mg of fuel. Thus, a −4 is placed in the first stack position, a 0 is placed in the second stack position, and a 2 is placed in the third stack position to correspond to the 8 that entered the stack in the first cycle decayed twice. As illustrated in column 2d, if no transition occurs in a fourth cycle, a zero is placed in the first stack position to correspond to a transitory fuel differential of zero, a −2 is placed in the second stack position to correspond to the −4 that entered the stack on the third cycle decayed by one-half, a 0 is placed in the third stack position, and a 1 is placed in the fourth stack position to correspond to the 8 that entered the stack in the first cycle decayed three times. As illustrated in column 2e, if no transition occurs in a fifth cycle, a zero is placed in the first stack position to correspond to a transitory fuel differential of zero, a zero is placed in the second position corresponding to the zero in the first position of the last cycle decayed, a −1 is placed in the third stack position to correspond to the −4 that entered the stack on the third cycle decayed twice, a 0 is placed in the fourth stack position, and a 0.5 is placed in the fifth stack position to correspond to the 8 that entered the stack in the first cycle decayed four times. After the fifth cycle, the decayed 8 mg transitory fuel differential will be removed from the stack and have no further effect on fuel mass to be delivered to the cylinder  362 . 
     As illustrated in column 2f, if no transition occurs during the sixth cycle, zeros are placed in the first through third stack positions, −0.5 is placed in the fourth position to correspond to the −4 that entered the stack on the third cycle decayed three times, and a 0 is placed in the fifth stack position. As illustrated in column 2g, if no transition occurs again during the seventh cycle, zeros are placed in the first through fourth stack positions and −0.25 is placed in the fifth position to correspond to the −4 that entered the stack on the third cycle decayed four times. Thereafter, the transitory fuel differential from the third cycle will have no further affect on the amount of fuel delivered. 
     Assuming that no transitions occurred in the 4 cycles prior to the first cycle described above, the total of the stack would be 8+0+0+0+0, or 8 mg for the first cycle and, thus, in addition to the steady-state fuel mass read from the map, an additional 8 mg of fuel would be supplied due to the transitory fuel differential. In the second cycle, 0+4+0+0+0, or 4 mg of fuel would be provided in addition to the steady-state fuel mass. In the third cycle, −4+0+2+0+0, or −2 mg of fuel would be added to compensate for transitory fuel needs. In the fourth cycle, 0+−2+0+1+0, or −1 mg of fuel would be provided in addition to the steady-state fuel mass. In the fifth cycle, 0+0+−1+0+0.5, or −0.5 mg of fuel would be added to compensate for transitory fuel needs. In the sixth cycle, 0+0+0+−0.5+0, or −0.5 mg of fuel would be added and in the seventh cycle, 0+0+0+0+−0.25, or −0.25 mg of fuel would be added to compensate for transitory fuel needs. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 3a 
                 3b 
                 3c 
                 3d 
                 3e 
                 3f 
                 3g 
               
               
                   
               
             
            
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                 8 
                 4 
                 2 
                 1 
                 0.5 
                 −0 
                 −0 
               
               
                   
               
            
           
         
       
     
     In another embodiment, positive transitory fuel differentials are utilized but negative transitory fuel differentials have no affect on the mass of fuel delivered. Applying that embodiment to the seven cycles described hereinbefore, the transient fuel differential is the same for the first two cycles. Thus, as illustrated in columns 3a and 3b of Table 3, respectively, in the first cycle the transient fuel differential is 8+0+0+0+0, or 8 mg and 0+4+0+0+0, or 4 mg of fuel in the second cycle. As illustrated in column 3c, in the third cycle, the fuel quantity transition to a reduced engine operation state is not utilized to modify the mass of fuel to be supplied and, thus, 0+0+2+0+0, or 2 mg of fuel would be added to compensate for transitory fuel needs. As illustrated in column 3d, in the fourth cycle, 0+0+0+1+0, or 1 mg of fuel would be provided in addition to the steady-state fuel mass. As illustrated in column 3e, in the fifth cycle, 0+0+0+0+0.5, or 0.5 mg of fuel would be added to compensate for transitory fuel needs, and, as illustrated in columns 3f and 3g, respectively, in the sixth and seventh cycles, 0 mg of fuel would be added to compensate for transitory fuel needs. 
     In another embodiment of the present invention, the engine transition sensitivity factor and the decay rate are separate parameters that may be set differently for transitions requiring additional fuel than are the engine transition sensitivity factor and the decay rate for transitions requiring a reduction in fuel. Moreover, when a negative transition requiring a reduction in fuel follows one or more positive transitions requiring an addition in fuel, all values remaining in the stack from positive transitions are zeroed. Similarly, when a positive transition requiring an addition in fuel follows one or more negative transitions requiring a reduction in fuel, all values remaining in the stack from negative transitions are zeroed. Thus, for example, in a deceleration, positive transients are eliminated so that the engine can decelerate as desired without earlier positive transients to reduce the degree of desired deceleration. 
     Furthermore, a range, such as a hysteresis band, may be set around a zero transitory fuel requirement. That hysteresis band might be utilized to eliminate the effect of a small transition in fuel requirement from a previous cycle which might be due, for example, to noisy signals or small variations in engine operation state or operator input that are not intended to zero transitory fuel. Transitions occurring in that range would not zero values remaining in the stack from previous cycles so that transitory fueling will remain in effect when small transitions occur in the opposite direction. Transitions occurring within the hysteresis band may, furthermore, trigger placement of a zero in the stack for the cycle during which that transition occurs. Alternately, only a transition falling within the hysteresis band that is in the same direction as the most recent transition will trigger a non-zero value to be included in the stack for the applicable cycle. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                 4a 
                 4b 
                 4c 
                 4d 
                 4e 
                 4f 
                 4g 
               
               
                   
               
             
            
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 
                   
                     
                     
                         
                         
                     
                   
                 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                 2.0 
                 1.0 
                 −2.0 
                 −1.0 
                 −0.5 
                 −0.25 
                 −0.13 
               
               
                   
               
            
           
         
       
     
     Table 4 illustrates an example of the present invention in which the engine transition sensitivity factor for positive steady-state fuel changes is 0.5 and the engine transition sensitivity factor for negative steady-state fuel changes is 0.2. In the example illustrated in Table 4, the decay rate is 0.5 for both positive and negative transitions and zeroing is implemented when alternating positive and negative steady-state transitions occur. Furthermore, a hysteresis band from −2 mg to +2 mg is applied so that any change in steady-state requirement that is greater than or equal to −2 mg and follows a positive transition that has a remnant in the stack will not zero the positive transition from the stack and any change in steady-state requirement that is less than or equal to 2 mg and follows a negative transition that has a remnant in the stack will not zero the negative transition from the stack. All transitions in the hysteresis band in this example will, furthermore, trigger placement of a zero in the stack for that cycle. The example illustrated in Table 4 permits a transitory fuel differential to decay for five cylinder cycles from the cycle at which the transition occurs and then discards any remnant of a transition after the fifth cycle. Thus, for example, when a positive transition has occurred in the last five cycles, and a negative transition of greater than or equal to −2 mg occurs, the positive transition remnant in the stack will remain in the stack and a zero value will be placed in the stack corresponding to the cycle in which the small negative transition occurred. 
     In a first cycle illustrated in column 4a of Table 4, no transition occurs, however a remnant from a positive transition that occurred in the previous cycle resides in the second stack position. In a second cycle illustrated in column 4b of Table 4, a negative transition of −1 mg occurs. That transition falls within the hysteresis band and so initiates entry of a zero in the stack for that cycle while permitting the positive remainder from the positive transition to remain in the stack. Thus, a zero is placed in the first memory area of the stack for the second cycle. The positive transition is decayed by multiplying the value in the second memory area of the stack by the decay rate of 0.5 and placing a 1.0 in the third memory area of the stack. All other memory areas of the stack are filled with zeros to correspond to the lack of transitions during those cycles. 
     In a third cycle illustrated in column 4c of Table 4, a negative steady-state transition of −10 mg occurs. Thus, −10 is multiplied by the negative transition factor of 0.2 to arrive at a value of −2 to be placed in the first stack location. The zero value from the transition that occurred in the second cycle carries into the second stack location. The third stack location is set at zero to correspond to the lack of transition during the first cycle. The fourth stack location is also zeroed because the current negative transition is outside the hysteresis band, thus causing the positive transition to be zeroed. The fifth stack location is also zeroed to correspond to no transition occurring during the corresponding cycle. In the fourth through seventh cycles, which are illustrated in columns 4d-4g of Table 4, no additional transitions occur and the values that entered during the transitions of the second and third cycles are shown decaying through the stack. 
     In the various embodiments of the present invention, the sum of the stack will appropriately account for the multiple transitions. When a decay multiplier of less than one is applied in the equation, the earliest transitions using such a decay factor will decay more than later transitions, so than more recent transitions have a greater effect on the mass of fuel delivered. Thus, the stack also appropriately accounts for the proximity in time of each transition when an appropriate decay factor is applied. 
     FIG. 4 illustrates a system by which a driver or rider of a vehicle may adjust or “trim” engine operating characteristics including transient fueling. The embodiment illustrated is a grouping of input and output devices that constitute a rider trim system  400  for attachment to one or more handlebars of a vehicle. An operator is provided with information regarding vehicle performance through indicators and is able to modify operation through input devices. The input devices may be analog devices such as potentiometers or binary devices such as switches, buttons, or general contact based devices. 
     The rider trim system illustrated in FIG. 4 includes a kill switch  402 , a map select switch  404 , a trim up switch  406 , a trim down switch  408 , a system power indicator  410 , a diagnostic indicator  412 , an engine temperature indicator  414 , a transient trim enable/disable indicator  415 , a first map indicator  416 , a second map indicator  418 , a third map indicator  420 , a display  422  and a trim defeat switch  426 . Those switches may have dual functionality such that certain switches may be selectively activated to trim map, set point, and transient operation. The switches will be described herein, however, only in connection with trimming transient fueling. 
     The kill switch  402  will stop engine operation when activated and is typically intended as an operator initiated emergency shut-down system. The map select switch  404  may be operated to alternately activate an assortment of maps to vary performance of the engine  100 . Furthermore, because each map may include transient operating parameters, only the parameters of the selected map are adjusted by the trim up and trim down switches  406  and  408 . 
     The trim up and trim down switches  406  and  408  may be assigned, by way of a trim definition setup, to trim any engine operating characteristic. Those engine operating characteristic may include transient control parameters individually or in combination. Such transient control parameters include, for example, the positive engine transition sensitivity factor, the negative engine transition sensitivity factor, the positive decay rate, the negative decay rate, the duration for which a positive transition will affect fueling and the duration for which a negative transition will affect fueling. Moreover, while engine trimming may be performed when the engine  100  is not operating, it may also be performed in a particularly beneficial manner while the engine  100  is operating. 
     In a certain embodiment, the trim up and trim down switches  406  and  408  are defined to adjust both the positive and negative engine transition sensitivity simultaneously. That approach provides a very simple yet powerful transient calibration tool. For example, where a trim factor of one is set initially, by depressing the trim up switch  406  one time, the trim factor may be increased to 1.2. Each time the trim up switch  406  is depressed thereafter, the transitory fuel differential will be increased by 0.2 up to a limit set in a transitory fuel trim definition. Likewise, each time the trim down switch  408  is depressed the transitory fuel differential will be decreased by 0.2 until a limit set in the transitory fuel trim definition or zero is reached. The calculated transitory fuel differential may also be limited to a minimum of zero. When the trim up switch  406  is depressed once, for example, and the transitory fuel differential is 2.5 mg, the amount of transitory fuel delivered to the engine would be 2.5 mg times 1.2 or 3 mg. Similarly, when the trim up switch  406  is depressed once and the transitory fuel differential is −2.5 mg, the amount of transitory fuel delivered to the engine would be −2.5 mg times 1.2 or −3 mg. When the trim down switch  408  is depressed once in that example, and the transitory fuel differential is 2.5 mg, the amount of transitory fuel delivered to the engine would be 2.5 mg times 0.8 or 2 mg. Similarly, when the trim down switch  408  is depressed once and the transitory fuel differential is −2.5 mg, the amount of transitory fuel delivered to the engine would be −2.5 mg times 0.8 or −2 mg. The trim defeat switch  426  permits an operator to alternate between one or more settings created by use of the trim switches  404 ,  406 , and  408  and one or more original untrimmed settings. The trim defeat switch may thus operate as an A-B-A switch to permits alternation between the trimmed settings and the original settings and back again with each operation of the switch. 
     The display lights  410 ,  412 ,  414 ,  415 ,  416 , and  418  illuminate to indicate certain engine conditions to the operator and the display  422  is utilized to display pertinent information to the operator. The first map indicator  416  may illuminate to indicate that a first preprogrammed steady-state map has been selected with the map select switch  404 . Similarly, the second map indicator  416  may illuminate to indicate that a second preprogrammed steady-state map has been selected with the map select switch  404  and the third map indicator  416  may illuminate to indicate that a third preprogrammed steady-state map has been selected with the map select switch  404 . The transient trim enable/disable indicator  415  may illuminate when trimming is enabled and dark when trimming is disabled by operation of the trim defeat switch  426 . 
     Thus, the engine management system  10  provides many advantages including calibrating engine performance with adjustments that can be made while the engine  100  is being operated in its intended environment, and enabling adjustments to delivered fuel quantity to compensate for transitions in state of engine  100  operation. 
     The embodiments of the engine management system  10  can be provided for internal combustion engine powered land traversing vehicles, watercraft, and flying vehicles, and thus, include automobiles, trucks, motorcycles, all-terrain vehicles, snowmobiles, boats, personal watercraft, and airplanes. 
     The embodiments described above are examples of the present apparatus and method for trimming an engine management system  10  whereby a number of advantages are achieved. 
     Those advantages include allowing engine operation to be calibrated during continuous operation in the engine&#39;s intended environment and improving operation of an engine  100  when the engine operating state changes, for example, during acceleration or deceleration of the engine  100 . For example, the performance of a race engine can be improved by preventing lean operation during acceleration. Moreover, engine performance can be modified within particular user defined ranges of engine performance. 
     While the present invention has been disclosed with reference to certain embodiments, numerous modifications, alterations, and changes to the described embodiments are possible without departing from the scope of the present invention, as defined in the appended claims. Accordingly, it is intended that the present invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims, and equivalents thereof.