Originally Posted by George V

My 160 give me 169 on the highway on a 50-degree day, oil is about 190. Is that too cold? Do I just have cold running 160?

Originally Posted by Dan_the_C5_Man

Good post Top Cat..

And thank you for clarifying this point; "Either experiment with a stock stat to get to 180 like Dan or go the simple route and put in a Hypertech 160 and get 175-180 all summer long. Note: if in cold climates, winter driving will necessitate switching back to the stock stat to maintain proper operating temps."

The stock C5 cooling system w/ a stock (or close to stock) motor has enough capacity to bring the engine coolant down to below 160. If I had to guess you could probably get it down to the 140's w/ no t-stat, depending on the out side temps. The point here is that a 170 degree stat is probably ideal (supplying us w/ 180 temps year-round), but as far as I know the only "reputable" company that makes aftermarket t-stats sell either 160 or 180. There are forum vendors that sell "170*" t-stats, but they look like modded stock stats. I figured I'd do the same thing on my own, only cost being a bit of my time.

Originally Posted by TopCat

Thanks Dan, and good additional points. Glad you brought up the inferior 170 (also 172F) stats....don't know if they're "made" the same way still (cut springs if I recall correctly).
I agree, a 170 would be perfect (business opportunity??)

Speaking of learning, you had to remove the guts of the thermostat to get to the socket in the stat housing where you inserted the shim, thereby increasing the force against the large spring, right? Allows the wax pellet to open the stat at a lower temp? Did you test in hot water to get to the right shim thickness? I might re-modify my stock stat and create a combo cut spring/shimmed stat for grins.

Originally Posted by Korreck

I woukd say that's about 10 degrees on the cool side.

Bob

Originally Posted by TopCat

Av8ter, you were a little confusing AND misleading.

Originally Posted by TopCat

Of course, I may just confuse the issue more .

Originally Posted by TopCat

Uh, yes and no. This could be misunderstood as meaning that the engine won't be able to cool the engine because you have too much coolant flowing.

Originally Posted by TopCat

Let's make it clear, if you increase flow of either component (air or coolant) you will increase cooling. It's basic thermodynamics that correlates heat transfer to mass flow. More heat is removed per unit time, e.g. BTU per minute, through the radiator at a higher flowrate through the radiator.

Originally Posted by TopCat

If you're running 194F with a stock t-stat, the 'leaving radiator temperature' may be, for example, 184F (delta T = 10F). However, the air temperature coming out of the radiator into the engine compartment approaches 194F, heating the underhood components and the firewall/floorboards of your C5.

Originally Posted by TopCat

We don't want 160F coolant, we want 175-180F coolant to minimize wear and increase performance, albeit sacrificing some in emissions (from startup to 174F temps since the cats don't work well until they heat up).

Granted, using a 160 stat is a stopgap measure and not technically correct (vs. a 180 stat with a proper sized radiator), but it works, and works well.

Originally Posted by TopCat

For clarification also to those reading this, the t-stat is on the downflow side of the engine and there is a lag between the time the coolant heats up and the time the t-stat 'sees' the hotter water and opens up further to increase flow to the radiator. It is not instantaneous.

Originally Posted by TopCat

....... you are correct in explaining why the engine operates at a temperature that's higher than the rating of the thermostat..... because the radiator doesn't have enough fin surface area to transfer the heat to the volume of air passing through it, or because there isn't enough air passing through the radiator for the number of fins.

Originally Posted by TopCat

So what? This is written up like it's a bad thing. Those of us that use the 160 don't use it to try to get 160 coolant temperatures, we use it to get close to 180 (BTW, the only way I know of to get right at 180 is like Dan_the_C5_Man did...modify an original t-stat....I did similar by cutting the coils, but didn't like the way the spring was seated in the housing afterwards).

Originally Posted by TopCat

You must not have enough experience with 160 stats because that's not true.

Originally Posted by TopCat

As a matter of fact, my temperature fluctuated WAY more with the stock stat than with the 160.

Originally Posted by TopCat

Considering how consistent my temps are, it wouldn't surprise me if the engineers designed the LS1 to run at 175-180 with a 160 stat,,,,

Originally Posted by Dan_the_C5_Man

Good post Top Cat..

And thank you for clarifying this point; "Either experiment with a stock stat to get to 180 like Dan or go the simple route and put in a Hypertech 160 and get 175-180 all summer long. Note: if in cold climates, winter driving will necessitate switching back to the stock stat to maintain proper operating temps."

Originally Posted by Dan_the_C5_Man

The stock C5 cooling system w/ a stock (or close to stock) motor has enough capacity to bring the engine coolant down to below 160. If I had to guess you could probably get it down to the 140's w/ no t-stat, depending on the out side temps. The point here is that a 170 degree stat is probably ideal (supplying us w/ 180 temps year-round), but as far as I know the only "reputable" company that makes aftermarket t-stats sell either 160 or 180. There are forum vendors that sell "170*" t-stats, but they look like modded stock stats. I figured I'd do the same thing on my own, only cost being a bit of my time.

Originally Posted by Av8ter

The engine wont be able to cool the engine?? What does that mean??

Originally Posted by Av8ter

If more heat were removed through the radiator due to a higher flow rate of coolant, then you would see temps get down to 160.

Originally Posted by Av8ter

If you modified the stock thermostat to change it to 180 AND had a larger radiator to compensate, then you could get 180 [/b]ALL YEAR LONG[/b] consistent engine operating temps and wouldn't have to change it again at all. Why create more hassle?



After the engine is warmed up with a 160 thermostat, it is already WIDE OPEN and its essentially the same as not having a thermostat at all and there is no way that with a stock radiator that it will get anywhere close to 140 or even 160 unless its very cold outside.

Originally Posted by TopCat

My only purpose was to support the use of a 160 stat and clarify your misstatement, which you repeated....

Originally Posted by TopCat

Nobody ever said a 160 stat would give you 160 coolant. Sigh..............

Originally Posted by Dan_the_C5_Man

I have a stock radiator. My engine runs at 180 w/ my modified stock t-stat, not lower, not higher, on the freeway, 365 days a year.. I live in Georgia where the temps vary from 25* to 95*.

Originally Posted by Dan_the_C5_Man

My temps dropped below 160 when I had a 160 t-stat installed. The stock cooling system is not as under-engineered as you think it is.

Originally Posted by Av8ter

Good for you if thats where you want your engine to be operating, although I dont agree with it. I could see where 180 would be much easier for the radiator to keep stabilized, especially with decent outside temperatures.



If thats true, then youre the first ive ever seen or read about that has gotten that low and I wonder if that was a stabilized temp going down the road? And how would you explain how everyone else seems to be running around 15-20 degrees higher while cruising on highway?

Originally Posted by Av8ter

Good for you if thats where you want your engine to be operating, although I dont agree with it. I could see where 180 would be much easier for the radiator to keep stabilized, especially with decent outside temperatures.



If thats true, then youre the first ive ever seen or read about that has gotten that low and I wonder if that was a stabilized temp going down the road? And how would you explain how everyone else seems to be running around 15-20 degrees higher while cruising on highway?

Originally Posted by TopCat

Uh, yes and no. This could be misunderstood as meaning that the engine won't be able to cool because you have too much coolant flowing through the radiator. Let's make it clear, if you increase flow of either component (air or coolant) you will increase cooling. It's basic thermodynamics that correlates heat transfer to mass flow. More heat is removed per unit time, e.g. BTU per minute, through the radiator at a higher flowrate through the radiator.

The difference is that the temperature leaving the radiator will be closer to the temperature leaving the engine, e.g. Temp into radiator = 174 and temp leaving is 168 (delta T = 6F). Bonus: the air temperature coming out of the radiator will be no higher than 174 F.

If you're running 194F with a stock t-stat, the 'leaving radiator temperature' may be, for example, 184F (delta T = 10F). However, the air temperature coming out of the radiator into the engine compartment approaches 194F, heating the underhood components and the firewall/floorboards of your C5.

Nevertheless, the temp out of the radiator is still 16F higher (184 vs 168) and the engine is kept hotter.

A great disadvantage for a 192F stat: if you run the car hard, the water in the engine is already at 192F and has less cooling capacity than my water at 174F (the delta T between the head temp and the cooling water temp, as well as the flow rate, dictates the cooling rate of the head under load and since flow rate is constant, my 174F will be able to draw more heat out of the head quicker). The heat soak in the head will lead to detonation and KR by the PCM, reducing performance and increasing NOx, i.e. decreasing performance and increasing emissions.



True, sorta, but that's not the point. We don't want 160F coolant, we want 175-180F coolant to minimize wear and increase performance, albeit sacrificing some in emissions (from startup to 174F temps since the cats don't work well until they heat up).

Granted, using a 160 stat is a stopgap measure and not technically correct (vs. a 180 stat with a proper sized radiator), but it works, and works well.

For clarification also to those reading this, the t-stat is on the downflow side of the engine and there is a lag between the time the coolant heats up and the time the t-stat 'sees' the hotter water and opens up further to increase flow to the radiator. It is not instantaneous. There is design work by the large car manufacturers to incorporate an electromechanical valve to work quicker and closely maintain engine temperatures to eliminate KR due to heat buildup in the engines, but the expense and reliability issues associated with the design currently preclude its use in mass produced cars.




....... you are correct in explaining why the engine operates at a temperature that's higher than the rating of the thermostat..... because the radiator doesn't have enough fin surface area to transfer the heat to the volume of air passing through it, or because there isn't enough air passing through the radiator for the number of fins.

So what? This is written up like it's a bad thing. Those of us that use the 160 don't use it to try to get 160 coolant temperatures, we use it to get close to 180 (BTW, the only way I know of to get right at 180 is like Dan_the_C5_Man did...modify an original t-stat....I did similar by cutting the coils, but didn't like the way the spring was seated in the housing afterwards).




You must not have enough experience with 160 stats because that's not true. As a matter of fact, my temperature fluctuated WAY more with the stock stat than with the 160. Considering how consistent my temps are, it wouldn't surprise me if the engineers designed the LS1 to run at 175-180 with a 160 stat, knowing that hot rodders use 160s all the time.....but maybe I'm justifying myself, or giving them too much credit, or both




They only complain if they don't do their homework and don't listen to the many members of the forum that tell them they want @ 180F for top performance, longevity, etc.

Plain and simple, heat kills and the LS1 should be run as cool as effective, and 180 pulls less KR and is hot enough to burn condensation and fuel out of the oil and hot enough to reach the clearances designed into the components made of dissimilar materials. Either experiment with a stock stat to get to 180 like Dan or go the simple route and put in a Hypertech 160 and get 175-180 all summer long. Note: if in cold climates, winter driving will necessitate switching back to the stock stat to maintain proper operating temps.

Originally Posted by TopCat

Read following link. Coolant temp is not so sensitive for engine survival. Coolant temp primarily affects emissions and performance. Oil temps affect durability and performance. If coolant is "cool" between 160 to 210, the average would be 185.

10 Tips for Engine Survival

Now, engine component clearances have been used to argue maintenance of certain chosen (favorite) temperatures. The coefficient of thermal expansion of aluminum and cast steel are 13.7 x 10e-6 in/in/degree F and 8.3x10e-6 in/in/degree F, respectively. For each linear inch of material, a ten degree difference in temperature would yield the following changes:

1" bar of Aluminum would shrink/grow .137 thousandths of an inch or 0.35 microns (a human hair is 60 microns)

1" bar of steel would shrink/grow .086 thousands of an inch or 0.22 microns

The difference, or gap, that would be created between the dissimilar metals is .14 microns per inch per 10 degree difference.

Aluminum pistons in steel sleeves. Approximate diameter of both in an LS1(for simplicity) is 3.9 inches. Assuming linear expansion, the difference in expansion between the two, at a 10 degree difference, would be 3.9 x 0.14 microns = 0.546 microns = 2 ten-thousandths of an inch (.0002 in). I believe that would fall within the blueprint tolerances for the engine component dimensions. I can't see the tolerances being in a range of 1 to 2 microns (4 to 8 ten-thousandths of an inch (.0004 to .0008). Standard oil filters pass particles that are 40 microns in size.

I prefer lower temps to give me some thermal inertia for heat when I stomp on the throttle; my coolant temps have climbed to 205-210 after a hard mile run on the interstate. However, my oil temps don't get above 200.
When running the stock stat my oil was hotter to begin with (typically @ 195F) and after a nice high speed jaunt, it easily climbed over 210....same with the tranny fluid, ended up at a higher temp.

As mentioned in the posted link, 200 is as high as you want to go with engine oil. Also, I'd run into KR and accelerated fluid oxidation and material corrosion with the higher temperatures.

This might be enough information to help those sitting on the fence decide.