I have read some pros and cons of the 160 thermo for street driving. Any opinions would be helpfull.
Fred

 

It'll take longer for the engine to reach operating temperature. Driveability will suffer. Sludge formation in the engine. Higher emissions. Poor fuel economy. Less efficient heat rejection. Etc.

Do realize that the fans don't come on until 215F. A thermostat only sets the *minimum* engine temperature of a fully warmed up engine. It can, and will, run hotter than that depending on load and on the amount of available cooling airflow through the radiator.

 

No adverse problems here...

 

[QUOTE=shopdog]It'll take longer for the engine to reach operating temperature. Driveability will suffer. Sludge formation in the engine. Higher emissions. Poor fuel economy. Less efficient heat rejection. Etc.

Why would it take longer? Assuming you have a fan module to turn fans on properly for a 160 thermostat, wouldn't your operating temp be 160? +/- ?

 

The stock stat according to GM is 186.6 Degrees. The cars run anywhere from 192-198 on the open road. Yes the fans start cycling at about 214 Degrees,and tunners haven't found fan controls yet. I ran a 160 stat in my C5 and tore the engine down at 60,000 miles and found no sludge build up at all. I ran mobil-1 in 10-30 changed it at 2500-3000 miles. never had a problem. Now the car didn't run at 160, and I do agree that that temp would be to cold.
Although Ed at LPE told me that they make there best dyno pulls at 160 Degrees. My C5 and now my C6 both run when warmed up at between 180-185 on the road. My oil temp is at between 199-214 depending on the type of driving I'm doing. Highway driving oil temp is 199-203. So the oil is getting hot enough to clean the engine, and the proof is my tear down of my C5 LS1 engine. BTW according to my tunner Ron Zimmer and Ed at LPE If your gas milage doesn't take a dump it's not to cold. With the hotter stock stat I was getting 27mpg on the highway and now with the 160 stat running at 180, I'm getting 29.1 highway. I think you run the temp where you personaly feel comfortable with. I'm thinking when all of us see summer comming for the first time with these C6's, these cars with stock stats will see much higher temps. Not that thats bad. But remember GM had to set these cars up for the general population, not just us gear heads who want finite performance. Again According to Ron and Ed these cars are very heat sensitive and they pull timming when they get hot. Anyway you decide!

Andy G.

 

I agree. I have a fan module and 160 thermo from Cartek. I haven't installed yet, waiting for more info on where the module goes. I've always believed a cooler engine( to a point) runs better. We'll see.

 

[QUOTE=RWSjr]The primary purpose of a thermostat is to allow rapid warm up of the engine. Once water starts circulating, heat is being rejected to the atmosphere via the radiator. Engine temperature is then determined by system thermodynamic equilibrium, which is a function of the design area of the radiator, the amount of air flowing through the radiator, and of course the amount of heat being generated by the engine.

By opening at a lower temperature, the 160F thermostat allows heat to start being dumped to atmosphere before the engine reaches full design operating temperature, thus it takes longer for the engine to get up to its equilibrium 190F operating temperature. The only ways to make the equilibrium temperature lower are to reduce load on the engine, increase radiator size, or increase airflow through the radiator. Once it opens, the thermostat is completely out of the picture.

Now, if you only take short trips, air temperature is low (winter), etc then the engine may not have a chance to reach design temperature with a early opening thermostat. Then you will run into driveability problems, poor fuel economy, high emissions, and sludge formation.

 

I agree with that.

 

This is NOT how the cooling system or thermostat operates. I read a lot of posts about thermostats and there is a lot of misinformation about how the thermostat actually works and why engine temps are never what the temperature rating of the thermostat is.

This is going to be a little bit of a book, but that's what it takes to describe this operation.

The thermostat is the brain of the cooling system. Just like the computer is the brain of the engine. The thermostat is designed to regulate the flow of water in order to maintain a desired temperature depending on the temperature rating of the thermostat. When the engine is cold, the thermostat is closed and prevents the flow of coolant out of the engine in order to warm the engine up quicker. Once the engine coolant reaches the operating temperature of the thermostat, it starts to open to permit the flow of coolant through the engine and radiator. Air moves through the radiator and absorbs the heat which in turn cools the coolant. The cooler coolant now starts to leave the radiator and go back into the engine. If the coolant is colder than what the thermostat is rated for, then the thermostat moves toward the closed position in order to restrict the flow until the coolant warms up. If the engine is under load, high power, etc, then obviously it will be putting out more heat. The thermostat now opens more to increase the flow of coolant in order to cool the engine. The thermostat will continue to regulate the flow of coolant by slowly moving towards the open or closed position in order to maintain the rated temperature of the thermostat. As situations changes, primarily the outside temp, speed, and engine load, the thermostat will continue to regulate the flow of coolant accordingly in order to maintain its rated temperature.

For the below example, lets use the stock thermostat which will be 194 degrees.

Say, for example, if the outside temp suddenly goes from 100 to 50, that much cooler air will be going through the radiator. That coolant that is in the radiator will now be colder than previously. So when it leaves the radiator and goes to the engine, the thermostat will sense change in temperature. The thermostat will start to move towards the closed position in order to slow the flow down which will heat the coolant back up in order to maintain 194 degrees.

Now lets do the opposite of the above example. Say if the outside temp suddenly goes from 50 to 100. The thermostat is already more towards the closed position because of the cooler coolant entering the engine and the flow has to be slow because it has to heat it all the way back up to 194 degree. Now, as the hotter coolant enters the engine, the thermostat will sense the change in temperature and will start to move towards the open position in order to increase the flow through the radiator in order to maintain 194 degrees.

This opening and closing of the thermostat happens continuously as to maintain the temperature that its rated for as differences in outside temp, speed, and engine load change.

The vettes cooling system, (thermostat, radiator, and cooling fan), are DESIGNED to work TOGETHER as a MATCHED set. I believe the stock thermostat is 194 degrees F.

If the coolant moves too quickly through the radiator, then it will not have time to dissipate the heat into the air before going back into the engine.

Now, this is what happens when people change to lower temperature thermostats:

First of all and to make it clear again, the thermostat isnt just a simple on and off switch or is something that's just there to warm the engine up and then no longer plays any further role. Its a thermostat, and implies just what the term means. It continually moves toward the open or closed position in order to regulate the flow of coolant to maintain its designed temp rating. Just like the thermostat in your house, if you have it set to AUTO, then it will control the heater and a/c in order to maintain whatever temp you have it set at.

If you install a 160 thermostat, the engine will warm up just as quickly but only to 160 degrees initially. When the temp reaches 160, the thermostat will start to open to start the flow of coolant through the engine and radiator. As the engine continues to warm up, so does the coolant. The thermostat tries to maintain its designed temp rating by opening more to increase the flow into the engine to cool it down to 160. But the radiator wasn't designed to cool the coolant down that low. So as the coolant flows through the radiator, its not cooled enough by the time it leaves the radiator and goes back into the engine. So now the coolant in the engine continues to increase in temperature, so the thermostat senses the hotter coolant that was inadequately cooled by the radiator, it opens even more to increase the flow to cool it back down because the engine temp is increasing. But again the radiator wasn't designed to cool the coolant down that low. So now the thermostat is fully open and trying to cool the engine back down to 160 but it cant. And because of the thermostat now being fully open to allow more coolant in the engine in an attempt to cool it back down to 160, the flow through the radiator is too fast and cant dissipate the heat quick enough before entering back into the engine. This is why the engine temperature is always hotter when putting in low temp thermostats because the radiator isnt big enough to cool the coolant down that low. So most of the time youre running around with the thermostat fully open and the engine temp just varies all over the place with no consistency whatsoever because the flow of coolant is basically straight through at this point and the thermostat is unable to do its job. This is also why you read about people who put lower thermostats in and complain that it never runs at that temp and runs about 20 degrees hotter.

The cooling fans are only used when sitting still because there isnt enough airflow through the radiator. And yes the on/off settings will need to be adjusted if you insist on installing a lower temp thermostat and want to maintain the engine temp in that area.

The lower thermostat you put into your engine, the larger radiator you will need to compensate. A correctly designed and matched cooling system in a vehicle will be able to maintain the temperature of the thermostat regardless of the outside temperature, speed, or load being put on the engine. You dont want to run too cold of a thermostat because you want the oil to get to at least 190 to burn away any moisture, contaminants, etc. Me personally, I just stick with the stock thermostat (194 degree) and have the fans set to come on at 195 and I seem to make plenty of power just fine. See sig. My engine also maintains that exact 194 temp regardless of the outside temp, load on the engine etc. because its a matched setup. It will run more fuel efficient, emission efficient, and be internally cleaner.

I hope all this wasn't too confusing, I tried to make it as clear as I could.

 

I'm not sure I buy the engine gets hotter with more liquid moving through it.

Yes if you think of liquid as discrete parts then you could say part a of the liquid is not getting heated as much when it's moving faster, but your forgetting that your seeing much more part A's with a faster moving liquid also.

Let's say you double the speed, so now part A of the liquid only stays in engine half the time as before, but part A also now gets back to the engine twice as fast. So if we think of liquid as singular parts you can see that it's still going to be cooling about the same, but in actuallity faster moving liquid cools faster and here's why. Water is not in discrete parts, if you move the liquid faster through the engine you are getting more water surface area to touch more engine surface area per second. This is a good thing, because the larger the surface area of the water touching your engine the more heat it can absorb.

Now I don't disagree that your temperatures may not go down with faster moving water, but the reason is that you may already be at the limit of the cooling ability of your radiator. Radiators can only cool so much heat per airflow through them, and if you're already at that limit then moving more hot water through them will just make the radiator hotter.

If you're not at the limit of your radiator then you should get lower temperatures.

At least that's what I've seen from water cooling my computer over the years.

 

I edited that line out to make it easier to understand in the book above. I was going off on a tangent of something else but decided not to.

That is correct and why many people fail to realize why the temps never stay at the lower temp rated thermostats. The radiator cant support it.

 

I haven't noticed the fans turning on my car will usually be between 194 to 196 then afterwards can go as high as 226. This is not a Z-51 Car with all of those coolers.

 

moving more hot water through them will just make the radiator hotter..

Not to complicate the matter further but...

If the rad gets hotter, the water must get cooler.

 

You did pretty good, but you got a few things wrong. First, the marked temperature of a thermostat is the temperature at which it is fully open. You can confirm that by putting the thermostat in a pan of water with a candy thermometer and heating up the water until the thermostat fully opens, then read the candy thermometer. Once a thermostat is fully open, you get full water flow. So the thermostat doesn't regulate engine temperature once the coolant temperature reaches the thermostat's marked value. It acts only to set a lower limit or floor to engine temperature.

Second, heat rejection to the atmosphere is a function of the temperature difference between the water flowing in the radiator and the air flowing across the radiator. The greater the temperature difference, the greater the amount of heat which will be rejected to atmosphere (it is actually a 4th power function). For an efficient radiator, you want to maximize the difference between coolant temperature and air temperature so that the maximum amount of heat will be transferred from the coolant to the atmosphere. This is one of the reasons modern cars run hotter thermostats, to increase radiator efficiency.

Note that temperature and heat aren't the same thing. Temperature, measured in degrees, is a measure of random (thermal) molecular motion. Heat, measured in calories or BTU, is a measure of system energy (in this case, waste energy we're trying to remove from the engine). An electrical analogy is that temperature is voltage and heat is current. The hotter the coolant, and the cooler the air, that are in immediate contact via the radiator, the greater the heat transfer you get. (Same as the greater the voltage across a resistor, the greater the amount of current which will flow through it.)

For best heat transfer efficiency, the inlet and outlet coolant temperatures will be close to the same. The greater the inlet to outlet temperature drop, the lower the radiator's efficiency at coupling heat to the atmosphere will be (because part of the radiator will be at a lower temperature with respect to the atmosphere, and can't transfer as much heat to the air as if it were nearer inlet temperature).

Coolant flow only matters in so far as it needs to be fast enough to keep the coolant temperature in the radiator high, and air flow through the radiator needs to be fast enough to keep the air in contact with the radiator cool. In other words, increasing coolant flow in the radiator doesn't reduce heat rejection, it increases it. Same as increasing air flow increases heat rejection to the atmosphere. This is fortunate since when we floor the throttle, engine speed increases, water pump speed increases, and water flow through the radiator increases just when we need to reject more heat to the atmosphere. Vehicle speed does the same thing for us on the air side, the faster we drive, the more air flow there is, and the greater heat transfer to atmosphere we get, again just when we need it most.

The notion that increased water flow won't allow "enough time" for heat transfer is an old wive's tale. Conducted heat flows at the speed of thermal molecular motion, and that's about 1 mile a second at 200F. Radiated heat moves at the speed of light (186,000 miles a second). Even at 6000 RPM, water is flowing through the radiator at speeds *far* lower than the time required for heat transfer to occur.

The ideal in a liquid cooling system is for it to be isothermal. In other words, it should stablize to nearly the same temperature all the way around the loop. The thermostat helps to set a floor for that equilibrium temperature, and the sizing of the radiator versus the engine sets a ceiling on that equlibrium temperature, provided enough water and air flow are maintained to handle the amount of heat to be rejected.

 

Sigh. No, I didnt. I will explain a couple of things but im not going to waste too much time on this.

This is a way to check the operation of the thermostat but if you were precise enough to vary the temp in your pan of water, then you would see the thermostats valve opening varies with temperature.

That is completely wrong. Here is a little paragraph from the internet that states what I said in my previous book above.

“””Question: What does the thermostat do?

Answer: The thermostat's job is relatively simple, but extremely important. It regulates the engine's operating temperature. It does this by restricting the flow of coolant from the engine back to the radiator. The thermostat is usually located in a housing where the upper radiator hose is connected to the engine. The thermostat is a valve that is held shut by spring tension. A wax filled thermal element in the thermostat opens the valve. As the engine begins to warm up and the coolant gets hot, the wax inside the sealed element expands and pushes the thermostat valve open. This occurs at a preset temperature (typically 195 degrees F. or so), which is usually stamped on the thermostat itself. The thermostat should be fully open about 20 degrees F. above the rated temperature.
The opening of the thermostat allows coolant to circulate through the engine and cooling system. As the temperature of the coolant begins to drop, the wax element cools off and contracts allowing the thermostat to partially or fully close. Thus, by cycling open and shut a relatively constant operating temperature is maintained.”””

The thermostat MAINTAINS the temperature of the engine. PERIOD

For the most part, the above paragraph is accurate, but only with a stock cooling system and thermostat. Install a 160 thermostat and the radiator will not be able to dissipate that much heat because its simply not capable of getting rid of that much heat fast enough because its too small and the coolant doesn’t stay in the radiator long enough because the 160 thermostat is wide open and the flow is too fast.

Let me give you a little analogy. If you have a red hot frying pan (this is the coolant) and want to cool it off, putting it into a sink full of water (this is the radiator) for only a second and pulling it back out, it will still be hot as hell. Put it in the sink for a minute, and it will cool all the way down. It’s the same if the coolant is unable to stay in the radiator long enough (due to the flow being too fast because the thermostat is wide open) to dissipate its heat.

Oh yeah?? If that were the case, then people that put in 160 degree thermostats would be able to maintain that constant temperature, but they cant. Its usually 20 degrees higher, give or take, because the thermostat is wide open trying to cool the engine down to 160 but it cant because the radiator isn’t designed to, in other words large enough, to cool the coolant down that low. And like I mentioned previously, the coolant is flowing too fast through the radiator and doesn’t have enough time to dissipate the heat before going back into the engine.

There is no such thing as equilibrium, not with your analogy anyway. You are way off track. The thermostat sets a “floor” as far as a minimum temp as the engine warms up, but afterwards, it plays a vital role in engine cooling by REGULATING the flow in order to maintain its designed temp. Again, if it weren’t for the thermostat, the engine temp would be all over the place depending on outside temp, speed, and engine load. BUT because we have a THERMOSTAT, the engine temp remains constant regardless of outside temp, speed, and engine load. Now granted the fans are set to come on at a little higher temp, but if the fans were on constantly, the temp would never change regardless of outside temp, etc..

 

Wow, interesting reading! Somebody is right, and somebody is wrong. Bottom line, I'm sticking with what the engineers designed.

And for the record, I have been to the dragstrip eight or nine times in both my C5's and my C6. I have made runs with the water temp at 190 on early runs, and over 225 degrees on later runs, and have seen virtually no dropoff in performance.

 

Everything I wanted to know about thermostats, but was afraid to ask.

 

I have 200 tons of refrigeration on my boat and have many years of real world trying to make something get cold. Really thats what your talking about, refrigeration, because refrigeration is nothing more than trying to make things get colder. Imagine my case. I have 4 holds full of fish. its about a half million lbs of fish between them. They would be comparable to your engine, I pump seawater into them till they are slightly presssurized, about 4psi max. And then turn around and start recirculating that water through my flooded freon chillers and back to my tank. That seawater is my coolant and my compressors are my means of chilling the coolant comparable to wind/fans in your car. From there I need only adjust my vavles on the circulation to optimize the flow for maximum cooling. This is comparable to your thermostat and consists mainly of slowing down the flow (I have the cabability to move 6000 gns a minute which is far beyond the amount of flow required for the task) till I have achieved maximum heat transfer from the fish to the seawater. I say transfer because refridgeration does not add coldness, it removes heat. We transfer that heat from what we are cooling to a medium (freon in your fridge, seawater in my tanks, coolant in your car, etc.) which we then take someplace and in turn affect a cooling of that medium (using a radiator, refer compressor, etc) so we can circulate it back into the thing we are trying to get colder and it can pick up more heat. This is the process made simple as it must be for a lowly fisherman to understand. Now the thing is that in order to maximize cooling the cooling medium must be allowed enough time to grab as much heat as is practical in the situation. If you slow it down too much it will have largely, or completly, if given enough time, expended its ability to pick up heat (as the temp difference gets closer the energy transfer slows down) and you are better off getting it back to your compressor or radiator where it can be cooled again. The point being you reach a point where you are better off getting your cooling medium back and using your refridgeration/radiator to turn it into a more viable cooling medium rather than letting it pick up heat at a lower rate as the delta closes between the temp of what your cooling and your coolant. You can also go the other way. If I increase my flow too much I cant maximize my ability to cool the medium within which I am affecting the energy transfer. Maximum cooling is achieved when I best balance these two competing factors. I am sure that the smart folks on here can explain the science far better than I can but that is the real world of the situation.

 

Av8ter is correct. Esp. about the opening of the thermostat. The temp rating of the stat usually indicates when it starts to open. It won't be fully open until usually 15 degrees above that rating. So: a 160 stat usually will run around 175 degrees, an equillibrium between the rad's ability to cool the coolant with the stat wide open. If you drive the car is VERY cold weather, the temp will get up to 175, and then drop down to 160, the stat will slowly close, temps will rise, stat will re-open, temps will drop ......and repeat!

 

Just going to a 160 is not going to change your overall temp's in the long run. All a 160 will do for is open sooner then the stock and as a result the coolant will stay cooler for a longer period; however, the ultimate temp you will see is going to be equal to the cooling ability of your car. There are SEA studies that suggest a colder stat may not be good for the engines' life span, but I suspect that in the real world it really doesn't make a much of a difference.