ABSTRACT
Torque Function and the Engine Speed-The Vehicle Dynamics The torque developed by an engine depends upon the energy released in the com bustion stroke, and the efficiency o f the energy transfer into the crankshaft-the mechanical system that converts the stroke into rotating motion. Obviously this is a function o f the mass o f fuel-air mixture in the cylinders, the air to fuel ratio (how lean or rich the mixture is), and the spark advance (the closer the spark t im ing is to the point where the engine is at top dead center, the smaller the amount o f torque that w i l l be created because o f the time it takes for the combustion wave to propagate through the fuel-air mixture). A n empirical model for this function o f three variables is used to establish the engine torque. Thus, we model the torque as:
Where m a is the mass o f the fuel-air mixture in the cylinders; A / F is the air to fuel ratio (we w i l l model the case for stochiometric mixtures only so that A /F = 14.6); a is the spark advance angle in degrees before top dead center; and the constants in the curve fit are: a = -181.3, b = 379.4, c = 21.91, d = -85 , e = 0.26 and f= -0 .0028 .
