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I need to know why centrally located spark plugs burn more efficiently than non centrally located spark plugs. Also, what are your views on harmonics?

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one way to synthesize crystal* is to hook up jumper cables to a steel screen until it is red hot. then spray Raid on it. should crystalize immediately. turn off car, allow screen to cool, scrape off crystals and find some Reynold's

*this is not actual d-methamphetamine hcl

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My speculation would be that if the plug is on one side of the combustion chamber, the fuel doesn't burn quite as evenly and the fuel at the "far" side of the combustion chamber would ingnite later. Shortest distance between all points. Also, it could have something to do with direction of explosive energy (more downward force directly over the center of the piston).

Harmonics in what context?

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Originally posted by quanto_magnus:

My speculation would be that if the plug is on one side of the combustion chamber, the fuel doesn't burn quite as evenly and the fuel at the "far" side of the combustion chamber would ingnite later. Shortest distance between all points. Also, it could have something to do with direction of explosive energy (more downward force directly over the center of the piston).

Harmonics in what context?

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True for a hemishperical combustion chamber in general. A lot depends on valve angle (e.g. chevy big block 'porcupine' heads vs. nailhead buick. vs. FE Ford), swirl rate (if any), valve location, piston shape (domed? dished? flycut? how deeply?), combustion chamber shape (hemi? semi-hemi? wedge?), injector placement (over, under, or alongside port, TBI) or if it is a carb engine (CFM of carb, large or small ports, valve size), stroke, etc...

Sometimes it IS best for center placement, sometimes not. it may be more efficient, but if the piston hits the plug, you've got a wasted engine.

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quanto is pretty much on the money. cwm40.gif

without getting overly complicated, if you set aside all other mechanical variables, and simply consider a theoretically symmetrical combustion chamber, a centrally placed spark plug would be equidistant from the surface to be acted upon, namely the circular plane of the piston top. therefore, once the ignition process begins, the flame front would spread across the cylinder volume and would reach concentric surfaces of the piston in a more even fashion, resulting in a smooth, efficient conversion of thermal to mechanical energy.

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Centrally located to the combustion chamber. I was thinking of hemispherically shaped chamber, two valves on either side of the plug. Sometimes I wonder why all cars aren't built for the most efficient/most powerful way to run an internal combustion engine. Stemming from the old "hemi's" of the 50's and 60's, todays top fuel cars are still using the same basic principles of combustion. Why then wouldn't ALL cars be built today with hemispherical combustion chambers, centrally located spark plugs, FOUR valves surrounding the plugs and aluminum blocks and heads for better dissipation of heat? With more valves and the use of aluminun, higher compression ratios can be used without resorting to racing octanes, thus resulting in more power. ANYWAY, thank you guys for answering that question. Now, as far as harmonics goes, I was asked the question "what does an harmonic balancer actually do?" Crackornian answer "stops the crank from vibrating by providing some kind of reciprocating force that cancels the vibration." How accurate is that? BUT WHY DOES THE CRANK VIBRATE? I know that when anything rotates it goes through harmonic vibrations at certain cycles. But do these points come along at set variables for every different rotating mass? (please forgive my ineptness to explain myself properly) For example- say an engine redlines at 6000rpm, and the first cycle (?) of vibrations occur at, lets say, 500rpm. Would they then occur at double that speed, then double that speed? I tried to correlate it with the opera singer who can crack a crystal glass. If they can copy the number of cycles which would be that actual "note" of the crystal, vibrations might crack it. But let's say the "note" of the glass is an "A". There are an infinite amount of "A's" from the lowest cycle to the highest, so the singer would have to hit the exact one to actually crack the glass. Yet ALL the "A's" would make the glass vibrate to a certain degree. When do these "A's" occur? Am I making sense" ARE YOU GUYS MAKING FUN OF ME????? DO I HAVE TO CALL COXWINGIN OUT FOR SOME WHOOP ASS???? Anyway, I'm babbling and not making much sense, so, WHATEVER!!!!!!!!!!!!!!!

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Too crazy for Boys Town, too much of a boy for Crazy Town.

I may not be here but I'll always be there.

AIM: crackorn71

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Originally posted by Crackorn:

Now, as far as harmonics goes, I was asked the question "what does an harmonic balancer actually do?" Crackornian answer "stops the crank from vibrating by providing some kind of reciprocating force that cancels the vibration." How accurate is that? BUT WHY DOES THE CRANK VIBRATE? I know that when anything rotates it goes through harmonic vibrations at certain cycles. But do these points come along at set variables for every different rotating mass? (please forgive my ineptness to explain myself properly) For example- say an engine redlines at 6000rpm, and the first cycle (?) of vibrations occur at, lets say, 500rpm. Would they then occur at double that speed, then double that speed? I tried to correlate it with the opera singer who can crack a crystal glass. If they can copy the number of cycles which would be that actual "note" of the crystal, vibrations might crack it. But let's say the "note" of the glass is an "A". There are an infinite amount of "A's" from the lowest cycle to the highest, so the singer would have to hit the exact one to actually crack the glass. Yet ALL the "A's" would make the glass vibrate to a certain degree. When do these "A's" occur? Am I making sense" ARE YOU GUYS MAKING FUN OF ME????? DO I HAVE TO CALL COXWINGIN OUT FOR SOME WHOOP ASS???? Anyway, I'm babbling and not making much sense, so, WHATEVER!!!!!!!!!!!!!!!

My impression was that harmonics was the other way around. You imply that the interval gets larger as vibration increases, but I thought it was the other way around.

Using a stringed instrument (guitar, violin, etc.) To produce harmonics on the strings, you might place your finger over the fifth of the string (people use this frequently in tuning). You would then get another harmonic on the octave (eigth of the string). As you move further up the scale the distance to produce another harmonic actually reduces.

Now back to the crank. Being the shape that is is for piston movement, is not inherently 100% balanced (that's why you have all of the aftermarket shops...). That is also why you have different engine configurations. "V" engines can offset some of the balance issues just by the nature of their design. A 45 degree "V" configuration is in what they call perfect primary balance because the piston opposing motions and angle to each nullify a large majority (if not all) of the imbalance of the crank. 65 - 75 degree "V"'s need counter balancers help reduced the piston/crank vibration. If this were not done, max piston speed would have to be reduced to the point of being useless otherwise the vibration would be so bad the engine would literally shake itself apart. In-line engines are also closer to primary balance. OK... Well, I could just keep babbling on, but I won't...

There's my $13.57

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email: ibhugh@yahoo.com

aolim: hugesk8r

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in theory, you're right. in practice, there are more variables.

and a 45 degree v8 is far inferior to a 90 degree v8 in terms of NVH. Umnless you meant 45 degrees from vertical for each cylinder bank? Theoretically speaking, of course.

spent too many of my 24 years around engines to close practical considerations out and think pure theory...sorry James.

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