How do you measure torque?

Question

Do they measure torque at the piston? What about when the piston is in between top dead center and bottom dead center, how is there the most torque then? Is it the distance from the crank pin or the length of the connecting rod used in the equation to calculate torque? If it is distance from the crank pin then what about the sideways movement? Is the equation force of piston times distance from the crank pin or the length of the connnecting rod? What about when the piston is in between top dead center and bottom dead center, how is there the most torque then?

Answer 1

There may be mathematical equations to come up with a very close answer but true engine torque is generally taken off the crankshaft on an engine dynamometer. It measures engine horsepower and foot pounds of torque at various engine rpm's.

There are literally hundreds of variables: Bore, stroke, rod length, piston material, ring fit and seal, crankshaft weight and journal size ( friction in bearings), camshaft bearings (regular or roller) camshaft profile and location, oiling system (dry sump or internal oil pump) and a big one, engine oil viscosity. Lighter weights = more horsepower. High viscosity oil makes either oiling system work much harder, robbing horsepower
Lets mention an area worth 40 - 60 conservative horsepower and torque. Cylinder heads and induction system. Head port sizes and shape and combustion chamber contour and spark plug location greatly influence torque and hp.. Rocker arm geometry coupled with valve sizes and push rod length add efficiency.
Two other important areas is the intake manifold contour, and carburetor size. Both should be carefully chosen for the motor's intended rpm / torque range that the combination is going to be used.

Answer 2

Torque is a ratio of Horsepower to RPMs, so right it is the formulation Torque = (Horsepower x 5252) / RPM so shall we say your engine is making that 116 hp at 3500 RPM then the formulation might appear as if this; Torque = (116 x 5252) / 3500 which equals 174. So your torque at that RPM with 116 HP may well be 174.