!The negative torque in TMD (torque moment diagram) of a 4 stroke engine is due to the power stroke and compression stroke being out of phase. During the power stroke, the expanding gases push the piston down, creating positive torque. However, during the compression stroke, the piston is pushed up against resistance, creating negative torque. This results in a dip in the TMD curve.
The negative torque in TMD can affect the smoothness of the engine's operation and can lead to vibrations and noise. It can also cause a decrease in power output and fuel efficiency if not properly balanced.
While it is not possible to completely eliminate the negative torque in TMD, it can be minimized by proper engine design and balancing techniques. For example, using counterweights and balancing the reciprocating mass can help reduce the negative torque and improve engine performance.
The negative torque in TMD can actually have some benefits. It can help to dampen the peak torque produced by the power stroke, resulting in a smoother engine operation. Additionally, it can help reduce the stress on engine components and prolong their lifespan.
In 2 stroke engines, there is no negative torque in TMD because both the power and compression strokes occur simultaneously. This results in a more constant torque output. However, 4 stroke engines have a more even power output due to the negative torque being present, resulting in a smoother and more efficient operation overall.