Why does a diesel engine have more torque developing capacity than a gasoline engine?

We all have that some question in our mind in automobile field..May be this post will help you about the torque Producing capacity in Diesel and petrol engine

Torque = Force x Perpendicular Distance

What force we are discussing here is gas force which is produced inside the combustion chamber..

gas force = pressure x area

link 1-crankshaft bearing

link 2-crankshaft

link 3-connecting rod

link 4-piston

During the expansion process(power stroke) high amount of pressure is developed,which makes the piston to move downward at high speed..Hence force is acting through the connecting rod(gas force)..Then what is the perpendicular distance?? By this seeing the crank slider diagram we can identify perpendicular distance is crank..

Torque = Gas force ( pressure x area) x perpendicular distance (crank radius)

By above formula,If we increase the pressure area or crank radius we can increase the torque..

In diesel engine..Compression ignition is takes place..During combustion ignition peak pressure will be higher than the petrol engine due to the compression ratio is high..If peak  pressure and area (compression ratio) is higher simultaneously torque will be higher..

This is the main reason we have use diesel engine for commercial vehicle(to carry more load) which will give more torque(force required to rotate the crankshaft)..