Anyone run cooler T-stats in their LS?

Discussion in 'High Tech Retrofits' started by badazz81z28, Jun 14, 2019.

  1. lightly-modded

    lightly-modded Member

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    Personal experience with the engines i work on- 160 for boosted, 170 N/A. Now those are engines that see almost exclusively track time (road course), for a street engine I would bump it up 5 to 10 degrees from there, depending on use/driving style/planned track days, etc. Better question, what are your engine specs/what has been done to your engine (how much heat are you creating)? Stock/mild cam- go 180 and call it a day. Big bore/big cam/high compression/destroked 8000 RPM screamer- go 170-175. Running 15 psi through a top mount supercharger on pump gas- ~165ish.
     
  2. Goat

    Goat Veteran Member Lifetime Gold Member

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    Two things. First running the engine hotter will help remove water, volatile by -products, and many other unwanted chemicals that accumulate in the oil through air intake and combustion.

    Secondly, from a thermodynamics law, the larger the difference in temperature between a "heat engine", in our case a thermal combustion engine, and the ambient (surrounding) air, the higher the efficiently of the engine. This is not easy to explain, but we were required to prove this theory when I took thermodynamics in college. In our case we have a few limiting factors, the major one being that oil begins to break down at some point. simply put, there is a 'sweet' spot in engine temperature where the oil is happy and all moving parts mesh in harmony.

    If this does not impress you, then all you really need to know is that GM designed their engines to run at these 'higher' temperatures for a reason. My Silverado runs @ 210+ all day long...

    Contrary to what a lot of people think, GM engineers are pretty sharp - I have worked with several of them over the years. :)
     
  3. lightly-modded

    lightly-modded Member

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    Absolutely agree. But most engines that see higher than stock compression, boost levels, and/or higher or longer sustained rpms have the opposite issue. Meaning higher than stock oil temps, often to the point of needing an added cooler to keep oil temps to the mid 200s.

    True, sorta. It's not the engine's temp vs ambient so much as intake (ambient) vs exhaust. Amount of energy released in the burning of the fuel. More energy released, the larger the expansion of the gases. In a "perfect" engine all of the "explosive" force of the expanding gasses would be transferred to the piston with no heat being transferred to the piston or cylinder. All of said heat would go out the exhaust. A true "heat engine's" purpose is to create heat, in an automotive engine heat is a byproduct. Unless you are referring to the fact that higher cylinder temperature increases the rate of burn of the fuel (to which one could argue efficiency). This is true, but it's also what leads to detonation. I prefer to heat my intake charge through increased pressure (compression or boost) than through the radiant heat of the cylinder wall (much better increase in efficiency).

    Again, completely agree. Stock engine don't change a thing. On a tuned engine you have already taken those engineers out of the picture though. The purpose of a lower thermostat is lower cylinder temps, which reduces the chances of detonation in an engine running more timing, higher compression, or boost. Again, in a stock engine, engineers have figured out the safe operating parameters of the engine, and changing the thermostat will gain you little to nothing, and may even hurt you.
     
  4. lightly-modded

    lightly-modded Member

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    Just realized I need to clarify some things about the "hp increases" some report. You should see no real hp increase from a thermostat change. Slight chance of a minimal increase due to a reduction of radiant heat entering the intake charge, but we are talking so small that an average dyno isn't accurate enough to definitively prove it. Every "increase in hp from a thermostat" I've seen has been because the computer was reducing timing due to detonation (or the high possibility of detonation, LT4/LT5 corvettes seem to be overly cautious in their programming). Most often cause seems to be engines that are tuned aggressively and/or exceptionally high temps (like being at the race track when its 110* out).

    To the op:
    If you have pushed your car as hard as you plan to, in the harshest environment you plan to (or at least relatively close to it) and your engine wasn't pulling timing due to heat/detonation, there is absolutely no reason to change your thermostat.
     
  5. Lowend

    Lowend Administrator. .a car, a man, a maraca. Staff Member Lifetime Gold Member

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    I've never seen a good case for running cooler thermostats on modern engines
     
  6. badazz81z28

    badazz81z28 Veteran Member

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    My engine is cammed, heads worked over and dyno tuned. 650hp
     
  7. Goat

    Goat Veteran Member Lifetime Gold Member

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    You and I are talking apples and oranges. I was trying to explain a fundamental concept that applies to heat engines (a thermo term that includes combustion engines). Everything I said is 100% true, not "sort of". Those are not my words, but words out of a thermodynamics handbook. 'Heat' in itself is not bad. Heat is energy. Energy is a good thing. Heat does not kill your engine. Charred oil, detonation, etc is the culprit. Yes, cooler inlet temperatures are better - nothing to do though with my point.

    I am not trying to dispute anything other people are saying here. Just trying to add a little insight into a subject that goes beyond most people's experience. I pretty much agree with most of what you have said - just has nothing to do with the point I was trying to get across. :)
     
  8. lightly-modded

    lightly-modded Member

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    I understand what you are trying to say, it's just that the heat absorbed by the engine is part of the waste heat, not the work output. Heat input would be the total energy of the fuel added (btu output of completely burned fuel). As the gasses expand and push the piston down, they cool as the energy is transferred to the piston. All heat left (both what is absorbed by the cylinder walls/coolant and what goes out the exhaust) is waste heat. The larger the difference in temperature you were talking about was between the btu output of the fuel and the waste heat. So, if the intake and exhaust temperatures are the same, and no heat is absorbed by the engine/coolant, then all of the heat energy went toward work output (completely impossible, but you should understand the point). I tried to make it easier to understand and apply to our application in my previous post, and took too many liberties when talking with someone who understands this. Sorry for any confusion. (Engineering Physics major back in college, have no problem talking more in depth if you want, but this really isn't helpful to the ops original question)
     
  9. lightly-modded

    lightly-modded Member

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    For an LS7 that's nothing to crazy. Assuming that you are not pushing your engine in adverse conditions (again, 110* track days) 180 should be fine.

    For what it's worth, a stock thermostat on a stock engine keeps the coolant temps between 210-215, on average. A 160* thermostat on the same engine will be around 190. Outside of boosted apps, you want your coolant temps at least in the 200s. Otherwise you are just increasing wear without any benefits.
     
  10. Goat

    Goat Veteran Member Lifetime Gold Member

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    No, absolutely not what I am referring to - not even close.

    Nothing to be accomplished by continuing this dialogue - I'm done. Have a good one amigo.
     

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