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      05-07-2013, 06:43 AM   #50

Drives: 2015 SO/CSAT F80 M3
Join Date: Jun 2006
Location: Canton, MI

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Originally Posted by CanAutM3 View Post
It is true that only one cylinder spark plug "fires" at once. However the power stroke, the time positive cylinder pressure applies force on the piston, lasts about half a revolution. So for engines with more than four cylinders, power strokes will overlap.
This is why I said "sum of all forces" in an earlier post. But the pressure is still greatest at TDC and combustion typically occurs then (or near it at least). The force diminishes over time.

The sledgehammer example is not really representative because it refers to an impact. If you have 100 fingers pushing on a object with 1lb each, it will yield the same force as a person leaning with his shoulder on the object with 100lbs.
The sledgehammer was an exaggeration to highlight the nature of the comparison, I revised it right after to tone it down. The point is that the force is applied all at once vs. over some interval of time.

Since peak torque is measured for a given RPM, I still think torque of the engine pulses need to be averaged to properly reflect an engines abilities.
It is a summation of the torque made in each cylinder. If all cylinders fired at the same time, two engines with the same stroke and differing cylinder counts (and every thing else normalized) would clearly yield the same torque curve. This would also be the case if the force acting on the piston decreased at the same rate in both cases.

We are deep into all of the complexities that led to me revising my original response. To be more precise at this point would mean applying the math to properly model the system. Il'l have to take a look at the graphs that Boss330 posted to see if they cover what I am saying.
A gen-u-ine BMW eff-eight-zero with them tandem clutches in the transmission and that dad gum sun roof on the top-a da cawr.