Optimum shift position indication using successive two-dimensional data maps

An electronically controlled system in an internal combustion engine for indicating shift position for a manual transmission thereof so as to maintain optimum fuel consumption by the engine, comprising:

• first detecting means for detecting current engine speed;
• second detecting means for detecting current throttle position;
• third detecting means for detecting current shift position;
• first determining means for determining current engine torque based on said current engine speed and current throttle position in accordance with a first two-dimensional map of engine speed and throttle position;
• second determining means for determining current fuel consumption rate based on said current engine speed and determined current engine torque in accordance with a second two-dimensional map of engine speed and engine torque, said second map including isometric curves representing curves of equal fuel consumption rates;
• calculating means for calculating driving force of the engine in accordance with current engine speed and current engine torque, said calculating means further including:
• first comparing means for comparing said current fuel consumption rate obtained by said second determining means with an assumed one-step-transmission upshifted fuel consumption rate determined by one-step-transmission upshifted engine speed and one-step-transmission upshifted engine torque defined by said second map,
• second comparing means for comparing said current fuel consumption rate obtained by said second determining means with an assumed one-step-transmission downshifted fuel consumption rate determined by one-step-transmission downshifted engine speed and one-step-transmission downshifted engine torque defined by said second map,
• outputting means for outputting a first signal indicative of one-step upshifting, a second signal indicative of one-shift downshifting, or a third signal indicative of stopping both one-step upshifting and downshifting, respectively, whenever said first comparing means determines said assumed fuel consumption rate of one-step upshifting is less than the currently detected fuel consumption rate, said second comparing means determines said assumed fuel consumption rate of one-step downshifting is less than the currently detected fuel consumption rate, or both values of fuel consumption rate calculated in said first and second comparing means are detemined greater than the currently detected fuel consumption rate;
• and
• representing means for alternatively representing whichever of said three signals are output by said outputting means.