| to sound like I was making any claims to know everything about the combustion process, although I do think I have a pretty good mental model of its workings. I know I dont know it all but hopes are through doing something different I might learn something new. I know there are sharper knives in the kitchen than I, but I dont quit trying to cut the better slice of bread. To try and elaborate on my theory of spark placement in the chamber though, it is my understanding that once the ignition of the mixture begins, there is a pressurewave that travels all through the chamber; its greatest intensity being at the core of the flame itself, which only occupies a distinctive radiating band from the point of ignition. As this 'flame front' propogates from its point of origin and strikes the components of the engine, primarily the walls of the cylinder and the crown of the piston, some energy is transferred to these parts in the form of heat. When the spark is located closer to the center of the combustion chamber, the flame-front will propogate towards the top of the combustion chamber and its angle of impact will be greater, thereby putting a little more heat energy into the head rather than keeping it within the gases of the chamber. This is the primary impact of the flame-front/pressurewave, which is also reflected or 'bounces' off the area downward towards the piston, but at this point it has lost some energy due to the initial reflection. With the plug at the very top of the chamber, the direction of the flame front/pressurewave is going to be parallel to the top of the combustion chamber at the surface of the head, but the rest of the flame front/pressurewave is directed at all angles towards the piston. By guiding, or aiming the flamefront such that it spends as much time as possible passing through the gases rather than bouncing off of internal parts, it will produce higher cylinder pressures by heating the gas rather than the solid parts of the engine. Here's a drawing I put together that might show where I am coming from.
 My thought is that this theory is right. The thing to keep in mind is that putting the shorter plug into the head was primarily done to de-shroud the valves as the shorter plug will create less obstruction for the incoming and outbound gases. The theory behind the combustion process was simply secondary, and likely has less significant effects than the deshrouding effect, but it was just a thought I was trying to share. What do you think about the theory of the reflecting waves losing energy?
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[ agpowers@bellsouth.net ] Enthusiasts soon understand each other. --W. Irving.
Are you an enthusiast? If you are out to describe the truth, leave elegance to the tailor.
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15:40:46 11/24/04
