Engine Torque Question

Computing the compression in every cylinder versus angle of crankshaft and making the vectorial sum. A safety coefficient has to be considered. The compression can be assumed adiabatic in a first approximation. In fact the wall being cold the exponent is slightly different since at start rpm are low.

One of the ways would be to measure the starting current and apply it to the performance curve for the starter motor (assuming its performance has been analysed by the motor manufacturer and a performance curve is available).

use a torque wrench on the harmonic balancer.