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      05-03-2013, 10:05 PM   #39
CanAutM3
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Quote:
Originally Posted by mkoesel View Post
That's true, but - and this gets into the complexity that I was talking about earlier - the summation of all the forces on the crankshaft at any particular instant will be limited by the maximum force applied during a single combustion event.

Even if we assume zero friction in the system (just for simplicity), the more cylinders the engine has, the smaller the maximum force available to act on the crankshaft. Consider a 100 or 1000 or 1000000 cylinder engine. One tiny piston applying force to the rotating mass at any given time. As cylinder count goes up toward infinity, there is not even enough force to turn the engine over. As it goes down toward 1, that force is maximized. It is true that more cylinders mean more chances for combustion. However, it is a bit like beating on a piece of sheet metal with a sledge hammer once every few seconds vs. tapping on it with your fingers very quickly. The former has a much more significant effect. Okay, well your fingers don't have as much mass as a sledge hammer - so lets use a rubber mallet instead, and maybe you are wearing some serious SuperBowl-ring-like bling on each of your fingers when you are doing the tapping. Still, you get further with the mallet.
I'm still not following, maybe it's just me that is thick .

Let's assume the 1000000 cylinder engine example you mention. Maybe one cylinder will not be able to turn the crank. However with that many cylinders, way more than one cylinder is pushing on the crank at any given time (250000 of them actually). The combined forces of all these cylinders should yield the same average torque than a lower cylinder count engine.

Further, to evaluate torque, I don't think it is representative to measure instantaneous torque. An average output will give better representation of an engine capabilities. If you take the other extreme of an example, a one cylinder engine. Such an engine produces torque for only about half a revolution of every two rotations. It also needs to rely on a heavy flywheel to store energy for its compression cycle. So yes, it is quite torquey on the power stroke, but the rest of the time...

Quote:
Originally Posted by mkoesel View Post
Yes, and that's a good point. However this is true only assuming a similar compression ratio since a higher compression engine will require a larger ring- to-cylinder contact area to avoid excessive blow-by.
Agreed. I assumed everything being equal except cylinder count.

Last edited by CanAutM3; 05-03-2013 at 10:45 PM..
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