1. A method for computing mean effective pressure in an internal combustion engine, said method comprising: determining a set of geometric parameters for the engine, including stroke, connecting rod length, piston area, and cylinder volume; defining a sampling resolution for a series of sampling events, said sampling resolution being an amount of crankshaft rotation between the sampling events; computing and storing a volume array, said volume array containing combustion chamber volume as a function of crankshaft position for each crankshaft position corresponding to the sampling resolution; computing and storing arrays of first and second derivatives of the combustion chamber volume with respect to crankshaft position, evaluated at each crankshaft position corresponding to the sampling resolution; defining a first function f, where f is a function of cylinder pressure and the first derivative of combustion chamber volume with respect to crankshaft position; defining a second function M, where M is a function of the first function f, the sampling resolution, and a previous value of M; defining a cubic spline function S, where S is a function of the first function f, current and previous values of the second function M, the sampling resolution, and a previous value of S; running the engine; initializing a cycle by evaluating the volume array, the first and second derivative of volume arrays, the first function f, the second function M, and the cubic spline function S, where all arrays and functions are evaluated at a crankshaft position of bottom dead center at the beginning of a cycle; taking a cylinder pressure measurement at each crankshaft position corresponding to the sampling resolution; storing the cylinder pressure measurement for a current sampling event for calculation purposes; calculating the first function f based on the cylinder pressure measurement for the current sampling event and the first derivative of volume array; computing the second function M and the cubic spline function S for the current sampling event; storing values of the first function f, the second function M, and the cubic spline function S for the current sampling event and a previous sampling event; continuing to measure cylinder pressure and calculate the first function f, the second function M, and the cubic spline function S, as long as the crankshaft position has not reached bottom dead center upon completion of one full crankshaft rotation from initiation of the cycle; and outputting mean effective pressure for an engine cycle as a final value of the cubic spline function, and initializing a new cycle, when the crankshaft position reaches bottom dead center upon completion of one full crankshaft rotation from initiation of the cycle.