Quote:
Originally Posted by lucid
I haven't studied this in detail, but the basic understanding I have suggests that what you are saying above is over-simplified since cylinder pressure varies with piston position (and cylinder geometry), and there are additional geometry-dependent variables such as piston side loading. So, I find it hard to believe that things simply cancel out and that stroke (or rod ratio although one can hold stroke constant while varying rod ratio) at fixed displacement has no effect (you say "little", but what is little in this case?) on torque at the crankshaft. If you can reference a credible source on this topic that I can read, that would be informative.
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Certainly it's oversimplified. There are books written on this topic.
Wasn't intending to imply (or allow room for the reader to infer), that it all works out exactly equal though, because it essentially never does. My bad if that's how it read. Just wanted to show how increased stroke for a given displacement doesn't intrinsically make more torque.
Your comment that "cylinder pressure varies with piston position" has no bearing, however, since all I said was that at given cylinder pressure, there will be more downward force on a larger piston mitigated by having less of that force translatable to rotational force. I personally felt that the gentleman with the question didn't need to hear about how rod length and piston pin placement might affect the outcome, or how flame front propagation vs timing vs cylinder pressure vs rod angle might affect the outcome, or how that outcome might vary depending on rpm.