What degree Thermostat?

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73AbodEE said:
a thermostat is continually opening and closing to maintain temperatures.
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If the thermostat is constantly cycling at constant engine load, the control loop is unstable. I doubt they designed it that way, but I could be wrong. Insure that your source was an automotive engineer and not an "automotive expert" or "automotive writer" (I am a mechanical engineer, not automotive but once worked at Bendix). My expectation is that it is designed to be a stable proportional control loop, and thus establishes a constant position for a given thermal load from the engine, between full-open and full-closed. That is similar to the float level control in a carburetor and different than home on-off control loops that people are familiar with (oven, water heater, etc). Otherwise, I agree with the description 73AbodEE posted.

cudamark is correct that the thermostat adjusts the water flow to meet varying engine thermal loads. It must do so to maintain its setpoint temperature (not perfectly). If it goes full open in normal operation, that means the cooling system is under-sized. However, I expect most cooling systems can't match the needs of continuous max horsepower operation on a hot day, so it probably goes wide open then and the engine temperature slowly rises. That is why you see a car pulled over every 1/2 mile with the hood up on all major roads out of the L.A. basin on >100 F summer days. Cars are barely designed for WOT uphill at 60 mph for a continuous climb from 1000 ft to 5000 ft elevation when new. Even worse in the Spring when inattentive owners let their coolant levels drop during the winter and the road discovers them.
 
StrokerScamp said:
The thermostat has basically one purpose. For quicker engine warmup. Once it's open, it's open. You think it's gonna close again with the engine running? No, because it sees coolant above the marked temperature on the engine side of the thermostat the whole time the engine is running after warmup. All the thermostat does is regulate flow to warm the engine up. Period. It's the radiator's and all accompanying accessories such as the fan, shroud and water pump that KEEP the engine cool, NOT the thermostat.
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bingo... i have a 160 in my slant right now... an when i went to MATS last yr it snowed on my way up there, as it should it only ran at 160 becasue the outside temp was so cold...

now normally im used to 80-120*F temps so i went with the 160 becasue it heats up so fast...
 
Good timing! I'm gonna put a trans cooler in, so the air passing through the radiator will se some what warmer than out side air. I figured I'd have to go to a cooler thermostat. After reading this it seems maybe I should stay at 180. Any advice?
 
Stay with the correct thermostat temperature. There is no reason or need to put in a colder one, and plenty of good reasons not to, already explained in this thread.
 
The difference is not going to be dramatic (except maybe the heater) If you put a 160 thermostat in it's not going to start smoking a week later but over the life of the engine, you'll get more miles from an engine with a 180 T-stat over a 160 and you'll usually get a little better mileage and power too.
 
cudamark said:
The difference is not going to be dramatic (except maybe the heater) If you put a 160 thermostat in it's not going to start smoking a week later but over the life of the engine, you'll get more miles from an engine with a 180 T-stat over a 160 and you'll usually get a little better mileage and power too.
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prove it
 
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A friend of mine works at GM in the emission control section where years ago they did studies of mileage, emissions, and engine wear at various engine temps. The results showed that the mid 190's were the best for all three as a whole. (some areas were better at an even higher temp but it was deemed too high for reliablity reasons with the public thrashing them) 180 was about the same except for the emissions and 160 was worse for all three. Like I said, it's not a huge difference but when they were trying to squeeze every hydrocarbon in the emission battle, they did what worked the best to meet the new requirements. I'm sure if you searched the web, you could find other studies showing something similar. I'm not trying to convince you to change, I'm just stating what I know to be true. Follow it or not.....it won't change my life any and probably won't change yours either to any great degree.
 
cudamark said:
The difference is not going to be dramatic (except maybe the heater) If you put a 160 thermostat in it's not going to start smoking a week later but over the life of the engine, you'll get more miles from an engine with a 180 T-stat over a 160 and you'll usually get a little better mileage and power too.
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that may be true when the temp is cooler, say a 65 and lower, but here in AZ were normal 75+, obviously not during a storm or something but even during the winter its still at least in the 70's...

my motor still runs at 200 weather its 75 or 120 lol... i will admit when i drove to mats last year and it snowed on me it was only at 160 but damn, talk about freak!

Motopsycho said:
prove it
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Motopsycho said:
prove it
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Did you see that graph, its all over the internet. Doesnt make it Gods truth, but it does have some references. Unless you are putting 10's of thousands of miles on your Mopar a year, Its probably not an issue. We used to take them out when I was young and dumb, heck a colder engine produces more power right?? or all out radiators were as cheap as our cars back then.
 
805moparkid said:
that may be true when the temp is cooler, say a 65 and lower, but here in AZ were normal 75+, obviously not during a storm or something but even during the winter its still at least in the 70's...

my motor still runs at 200 weather its 75 or 120 lol... i will admit when i drove to mats last year and it snowed on me it was only at 160 but damn, talk about freak!



location location location
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If your cooling system is running at 200 degrees with a 160 thermostat, you're producing too much heat and/or your cooling system is at it's capacity. You should have more cooling system than your engine requires so the thermostat can do it's job. Also, if your system is running at 200 degrees, what's the point of the 160 thermostat? Why not run a 180 or 195? Once the thermostat is wide open, it's not going to make it run any hotter.
 
cudamark said:
If your cooling system is running at 200 degrees with a 160 thermostat, you're producing too much heat and/or your cooling system is at it's capacity. You should have more cooling system than your engine requires so the thermostat can do it's job. Also, if your system is running at 200 degrees, what's the point of the 160 thermostat? Why not run a 180 or 195? Once the thermostat is wide open, it's not going to make it run any hotter.
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exactly why i said i was gonna try a 180... but with a 25" core 2 pass aluminum rad and elctric fan my only choice is a better fan set and or a clutch... i just havn't bothered to do either yet lol...
 
The 160 degree thermostat allows your engine to run cooler, making more power by increasing charge density and reducing the propensity for knock. A cooler thermostat can often allow you to run more ignition timing at the new lower coolant temperatures.

The low temperature thermostat is especially helpful at the drag strip when you are trying to cool your engine down between runs. With a stock thermostat, once your coolant reaches 192 degrees, the thermostat is closed and it takes a lot longer to cool the engine down because no coolant is circulating through your radiator. With a 160 thermostat, this doesn't happen until your coolant reaches 160 degrees.
 
Motopsycho said:
The 160 degree thermostat allows your engine to run cooler, making more power
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Sure, that's one of many interrelated factors in how the engine runs. It's not the only one, but you seem to think it's the predominant one. Can you prove it with data? Back-to-back dyno pulls changing nothing but the thermostat would be needed, do you have those? Because if not…

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Speaking from PERSONAL experience,back about 1974ish,I was the proud owner of '71 Duster 340.And as an ignorant 18yo I took the Thermostat out of the motor because I was told I didn't need it !! Well,on a trip from sunny and hot St Creaturesburg Fla. to Conn I started noticing something peculiar.The cooler it got,the colder the therm read.Seemed odd to me,as we were cruising and the motor certainly should have been warmer than what was registering.Pulled over into a service station,explained the problem,in went a 180* therm and I was on my way without any more issues !!My lesson learned,the thermostat was put there to keep the engine at its optimum performance temp,when it reached that,the water would circulate and be again held in the radiator to be allowed time to be cooled !! So there's my .02 for what it's worth !!!
 
Motopsycho said:
The 160 degree thermostat allows your engine to run cooler, making more power by increasing charge density and reducing the propensity for knock. A cooler thermostat can often allow you to run more ignition timing at the new lower coolant temperatures.

The low temperature thermostat is especially helpful at the drag strip when you are trying to cool your engine down between runs. With a stock thermostat, once your coolant reaches 192 degrees, the thermostat is closed and it takes a lot longer to cool the engine down because no coolant is circulating through your radiator. With a 160 thermostat, this doesn't happen until your coolant reaches 160 degrees.
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I think we're talking about a street car here. Most serious race engines don't use a thermostat but use a fixed diameter restrictor washer. They also use an electric motor and/or water pump for flow instead of a crank driven pump. If it's a street/strip engine, I don't think they would be using a 192 degree thermostat....and shouldn't if they do. 180 is plenty cool enough but still allowing the engine to reach operating temps for better ring sealing.
 
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