Converting engine bmep to engine torque

[nb89]

I looked it up on wikipedia and found this:

http://en.wikipedia.org/wiki/Mean_effective_pressure

which states that 'BMEP is calculated by taking the torque exerted by the engine over a revolution for a two-stroke engine and two revolutions for a four-stroke, and dividing it by its displacement.' I am confused about what the displacement is. What is it the displacement of?

 

[brewnog]

Displacement of the engine. It's the cylinder volume displaced per cycle.

 

[Dr.D]

Be aware, however, that this is the torque integrated over the thermodynamic cycle (one crank revolutions or two), so that the torque you calculate when you multiply BMEP by displacement is only average torque. This is important because torque from an IC engine fluctuates significantly. For a single cylinder engine, the torque can completely reverse during a part of the cycle, and the maximum torque will be several times the average torque. Thus if you need a value for designing shafting, the BMEP*displacement is not of much help.