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jdemaris
03-27-2006 20:12:47
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Words change over time in reply to MarkB_MI, 03-27-2006 19:09:08
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What you are saying would be fine if all words meant the same thing, all the time, regardless of context. Our language does not work that way - never has and never will. Many words and phrases used today connote a different meaning than a hundred or so years ago. I can give you hundreds of examples if desired. Decimate used to mean to destroy by ten-fold. Now, it simply means to destroy a lot of stuff. The phrase "four stroke cycle" used to mean something just by the words it contained, now the same engine type is referred to as "four cycle" which, taken at "word value", makes no sense - a so-called four cycle engine has only one cycle composed of four-srokes. How about the word "gay." It's a French word for brightly colored. 40-50 years ago, "gay" meant happy. And, what does it usually mean today? Diesel fuel used to be the fuel Rudolph Diesel ran his engine with - peanut oil. Thus the language in change. There are some places, like France, that have tried to make and enforce rules so word-meanings stay the same, forever. But, this is not France. The primary/standard defintion of a "dead language" is a language that no longer changes - and American English has not died yet. Making the argument that "what makes sense" must be correct, is not a valid way to prove something. I suspect - but cannot verify - that the term "cubic inch displacement originally evolved from exactly what you've mentioned - i.e. how much area is actually being displaced - in this case - by the travel of the piston from BTC to TDC. Perhaps a measurements for steam engines. Many older spec. sheets for engines are more specific, and will state "piston displacement" instead of a general term i.e. "cubic inch displacement" or "engine displacement." So, today, with the phrase "cubic inch displacement", the meaning depends on who is using it, and why, and where. As aforementioned, various racing organizatons absolutely DO require combustion chamber volume to be factored into cubic inch displacement. And, some don't. It appears, just as many words have multiple definitions and usages, so do many phrases. Seems "cubic inch displacement" can denote the area being displaced by a moving piston or rotor, and can also indicate the total area of combustion activity within an engine. I can cite references, and/or cut and paste here pages of rules set forth by aforementioned organizations explaining their requirements for calculating what they call "cubic inch displacment." What reference are you using that indicates I am in error? In regard to calculating compression ratio - what you stated works for the "mechancial compression ratio", but not the "effective compression ratio." A bigger chamber does not have to result in a drop in horsepower if the "effective compression ratio" is raised by alternative means, e.g. intercooling to condense air by temperature drop, or a turbocharger or supercharger by raising PSI.
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