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Message: <blockquote data-quote="sexycar" data-source="post: 326966" data-attributes="member: 2014">wow.. u all so happy without thermostat eh? have a read below:From: Neon John Subject: Re: Cooling system fact or fictionDate: Thu, 23 Sep 1999 06:12:19 EDTNewsgroups: alt.autos.rod-n-custom,rec.autos.rod-n-customWhat some people will say in public. This is absolutely false, ofcourse. Try to conceive of blowing on something hot, say a spoonfulof soup, first slowly and then more rapidly. Which cools faster? For extra credit, try imagining the same spoon with first slow andthen fast water moving across the bottom. Sheesh!The issue with running without a thermostat is two-fold. The firstpart is that the thermostat provides drag on the water flow. Thisdrag increases the backpressure the water pump and all of the enginesees. This additional pressure, over and above the nominal 15 psistatic pressure the radiator cap sets, raises the boiling point ofthe coolant. The reason this is important is that it suppresseslocalized film boiling at hot spots such as around the exhaustport. The transition from nucleatic boiling (bubbles of steamoriginating from irregularities on the surface) to film boiling(where the hot surface is coated with a film of steam) is calledDeparture from Nucleatic Boiling or DNB. DNB is very bad, for steamis a very good insulator compared to water. Once DNB occurs, thearea under the steam gets hotter because the steam doesn't removevery much heat, adjacent metal which is still wetted heats fromconduction. DNB happens there. The process spreads untilsubstantially all the coolant-wetted surfaces are insulated by afilm of steam. The engine overheats. In addition, the buildup insteam pressure forces the radiator cap open, bleeding coolant,therefore making the situation worse. The second issue is that of water pump cavitation and surge. If thepump is operated at high RPM with insufficient head pressure(provided by the frictional losses in the coolant passages and thethermostat), there is a great likelihood that the pump will eithercavitate (localized boiling and/or degassing on the impeller) orsurge (an unstable flow regime). Either phenomena is destructive. Cavitation's collapsing bubbles act like little sand blaster,eroding away impeller material. Surge can do the same thing and inaddition, can vibration stress the impeller enough to break it. Many times what looks like corrosion damage to the impeller,especially when the housing is damage-free, is actually cavitationdamage.The myth of velocity originated among those unschooled in physics orthermodynamics, I suppose, because a common racer "solution" is topress a fixed restriction into the thermostat housing neck when nothermostat is desired. The conventional (but wrong) wisdom is thatthe restriction "slows the water" as stated by the previous poster. In reality, all it does is provide some more dynamic pressure in theblock by restricting the flow. The exact same result could beaccomplished (assuming the water pump doesn't surge or cavitate)with a higher static pressure (cap pressure), assuming the systemcould withstand it.John-- John De Armond<a href="mailto:johngdSPAMNOT@bellsouth.net">johngdSPAMNOT@bellsouth.net</a>http://neonjohn.4mg.comNeon John's Custom NeonCleveland, TN"Bendin' Glass 'n Passin' Gas"</blockquote>

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