Guest Anonymous Posted December 2, 2001 Share Posted December 2, 2001 While I know this has been gone over in here before, I feel that previous discussions haven't been entirely conclusive. I've been doing a lot of thinking on the best water temperature to run at for a carbed non computerized SBC. According to David Vizard, the water should be at 170 and the oil should be at 210. While I can see why it is advantageous to run the oil at a high(er) temp, I'm not so certain about the water temp. Nascar/race engines run at 200-210 and those guys fight for every scrap of power they can get. So this is pretty confusing, is it better to have your water temps above 180 or below? Now the Water Temperature debate goes both ways. From what I know about thermodynamics and the Carnot cycle, which an internal combustion engine strives to approximate, engine efficiency (how much work and thus power and engine makes from a given amount of fuel) is proportional to (Tmax-Tmin)/Tmax where Tmax is the peak temperature experienced during combustion and Tmin is the temperature of the air/fuel mixture at the beginning of the compression cycle. Increasing water temperatures increases Tmax while having a slight effect on Tmin (mixture absorbs a bit more heat due to radiation, let us minimize this by assuming that we are running a COLD AIR INTAKE) Decreasing water temperatures would have the opposite effect, it reduces Tmax while increasing Tmin very slightly. However, decreasing the water temperatures has the side-effect of reducing nucleate boiling or local "hot-spots" reducing detonation and smoothing out combustion. Also I suspect that running the engine hotter reduces the cooling losses (power lost through the cooling system), thus increasing efficiency, but only up to a point. So as you can see, the matter of finding the best water temperature to run at is pretty tricky, its a matter of compromise. One can theorize and conjecture all day but it all comes to nought. What matters is real life experience. Let us set the following conditions for the engine: We've taken all the possible measures to minimize intake temperatures. Cold air intake, no exhaust or water heating the manifold, some kind of heatshield installed on the bottom of the manifold, and a phenolic spacer beneath the carb. As for the cooling system. Let us assume an efficient aluminum radiator and water pump, and a 75/25 water/coolant mixture with some Water Wetter added in. Having taken all these measures to maximize power and efficiency, what would you guys say the best water temp to run at would be? Quote Link to comment Share on other sites More sharing options...
ZROSSA Posted December 2, 2001 Share Posted December 2, 2001 howdy, I would say vizard is on track. I have seen this temperature used in other books as well that are compleatly independant. Dont forget that on pure race engines they are also looking for aerodynamic advantages as well. So with a higher temp. they can run a smaller radiator or inlet and get higher top speed. Formula 1 engine run higher temps again but, everything is designed to work at that temp. Your chevy isnt. Cheers, Douglas Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted December 3, 2001 Share Posted December 3, 2001 Very interesting, but wouldn't this happen regardless of water temperature (within limits of course)? I mean what difference would it make if the water temp is at 170 instead of 200 (assuming you don't get nucleate boiling)? The rear cylinders are always going to run hotter and thus wear more. Vizard says 170 is optimal while Smokey Yunick says 200 is what you should aim for. I find this all very confusing... Where else have you seen/read that 170 is the best temperature to run at? Quote Link to comment Share on other sites More sharing options...
ZROSSA Posted December 3, 2001 Share Posted December 3, 2001 Performance 4 stroke tuning A Graham Bell Awsume book Douglas Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted December 3, 2001 Share Posted December 3, 2001 plane and simple cooler=longerlasting all though you may get more power out of a little more heat think of the parts going out whats worth it more power arnt guna help you if it ant runing Quote Link to comment Share on other sites More sharing options...
patzky1 Posted December 3, 2001 Share Posted December 3, 2001 To chime in: If you want your car to run well for a long time a lower temperature than 200 is beneficial. Higher temperatue over a long period of time will cause the cylinders to wear unevenly (more in the front). This is solely due to the fact that the cool water coming out the radiator enters the front of the block and makes its way to the back. The water is heated right away and the rear cylinders end up being hotter longer than the front so the front cylinders contract more on the piston and cause more wear. At least, this is my simple interpretation of the complex process. For example, when I took apart my L28 after it died at about 200,000 miles the front cylinder had a "burr" or a "ledge" from the friction part to the cylinder head which was very much larger than that on the rear cylinder. By the way, the compression on the front cylinder was considerably lower than the rear. bottom line is: race engines are fine with higher heat and so would be drag engines I assume. But for a durable and dependable ride you want to keep it cool. Visard is a straight shooter. Pat P.S. Or am I wrong?? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted December 5, 2001 Share Posted December 5, 2001 Well, we didn't get much of a response here, but the guys over at Chevytalk had some pretty interesting about this, here is the link for anyone who is interested... http://forums.chevytalk.com/forums/Forum64/HTML/005526.html Anyne care to comment on the points they made? Quote Link to comment Share on other sites More sharing options...
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