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Dirt Bike Mods & Maintenance
why dont 2 strokes use thermostats?
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[QUOTE="yardpro, post: 233578, member: 25269"] SAGE HOPE THIS ANSWERS YOU QUESTION: the reason the hand through the flame works is because to the relative transfer times. your hand is in the cool air longer than the hot air therfore radiates the picked up heat. Yor are correct however in the fact that faster moving h20 will not gain as much heat from the engine, but you are not looking at the leat loss side. the same fast moving h20 will not loose as much heat as it passes through the radiators. it you do the math (delta t equation) the velocity is not a factor, as long as the gain/loss transfer areas remain constant, because the time spent in each area will cancel each other out. the air speed however plays a major role. the faster the heated air around the radiator fin is replaced with cooler air, the more efficently the h20 will transfer heat the the air. this is why the idling superbike overheats. Thermostats work by reducing the heat loss area ( radiators). perssure- faster moving h20 has less pressure. it is the same with fluids as air. a plane flys because the air moves faster over the top of the wing than the bottom. this creates a low pressure area above the wing, in effect sucking the plane upwards. pump pressure is controiled by dynamic head and flow rate. constricting h20 does not increase pressure past the restriction ( the h20 moves faster but with less pressure and lower flow rate ( they are inversely proportional). the water is actually slowed on the pre restriction side, decreasing flow rate, and increasing pressure. the pressurised h20 works better because the pressure raises the vapor pressure of the h20, raising its boiling point. liquid h20 transfers heat more efficently in the system design, that's why restrictors are used. this is also why when you release the pressuer ( by removing the cap for example, the h20 boils, expands, and comes spurting out of the overflow, cap etc. everybody follow? sage- the examples you give work on an open system, but colloin systems are closed, so you have to cons forgive the tyop's, this thing was too darn long to edit. if you want me to go more in depth on anything let me know [/QUOTE]
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why dont 2 strokes use thermostats?
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