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http://www.tuneruniversity....whats-the-advantage/

"Low Temp Thermostats: What’s the Advantage?

This week we're talking about low temperature thermostats, another item that nearly every tuning house sells and yet fail to really explain what they're for. A few months back, we talked about high pressure radiator caps and what advantage they offered, this time though we're looking at a part that is far more perplexing.

Here are a few descriptions from websites/manufacturers selling these, notice the trend of extremely vague language:

The SPOON Low Temp Thermostat S2000 Integra Civic will increase the vehicles cooling ability (false) by changing the operation temperature from 90C (stock)[194] to as low as 80C [176F]. This in turn will give your Honda a chance to be free of overheating (false). For best results, it is recommended that the Thermostat be used in conjunction with a low temperature Thermo Switch.

The SARD Low Temperature Thermostat - SST12 Mazda is a drop-in direct replacement for your OEM unit. The Sard unit will lower the temperature at which the cool water can mix with the warmer temperatures inside the engine (true). This will lead to a motor than can now run much more efficiently (false).

The FEEL'S Low Temperature Thermostat Civic FD2 will provide better, more reliable and faster cooling for your FD2 (false). By lowering the opening temperature to 68 degrees, and full open at 82 degrees there is a smooth transition in cooling (???), and you engine will be cooled optimally faster (?).

The MUGEN Low Temp Thermostat NSX S2000 will increase the vehicle cooling ability (still false) by allowing the circulation of the chilled water earlier than the OEM unit would allow it to (that part, true). Stock thermostats are intended for normal driving conditions and aren't made for those intending to give their car a work-out (false).

Reading these make you believe that a low temp thermostat are a good idea for those "pushing their car harder" and that they somehow improve cooling performance. There are other descriptions that also seem to indicate that they lower engine/intake temps to make more power. All rubbish.

The Function of the Thermostat & Cooling System Basics

The biggest misunderstanding about thermostats is that people believe they make the engine run cooler. They don't necessarily do that. The cooling system and load on the engine determines how hot the engine gets, the thermostat fully open will still be the mercy of the coolant system's ability to remove heat.

Most engines run slightly above the thermostat's minimum opening temperature under normal loads. Under high loads, they will run at or above the thermostat's fully open temperature - in other words, under hard driving, the thermostat's opening temperature is completely irrelevant.

The thermostat can only determine when the cooling system is allowed to start cooling the engine. It sets a floor, not a ceiling on engine temperatures. The thermostat basically behaves like the hot and cold knobs in your shower, if the water is too hot, it turns the cold on a little more and if the water is to cold, it turns up the hot water.By regulating the flow through the cooling system it speeds up and slows down the flow of coolant into and out of the engine block.

In liquid cooling systems, the ability to cool is determined by a number of factors, but the basic keys are the surface area of the radiator (how big/how many small fins), the air flow through the radiator (fans on/off, speed of car), and how quickly or slowly the cooling fluid goes through the radiator. If the coolant spends a small amount of time in the radiator, it loses less heat. If it spends a lot of time there, it loses far more heat. Therefore you don't want the flow to be too high as the cooling system's ability to cool the engine will be reduced, not increased.

The thermostat is there primarily to help the engine warm up in the morning. As we discussed in a previous article, the engine is designed to operate at it's operating temperature. Most engine wear occurs when the engine is cold, once it's warmed up there is very little wear in a healthy engine. Thus, we definitely want to run a thermostat to allow the engine to warm up as quickly as possible until it reaches our desired and designed operating temperature.

If the engine is below operating temperature, the bearings, rings, and other components are not yet expanded in size and therefore they "bang" against the other metals in the engine more than they would at operating temperature. No good.

So if we don't run a thermostat at all, it takes a lot of constant load to get the engine properly warmed up and to keep it up to temperature on cold days. We also in some circumstances may experience overheating if flow through the system is too high as the coolant has to spend a certain amount of time in the radiator to actually cool down.

Some race teams do choose not to run a thermostat, but they are the minority. They usually run at least a restriction plate in place of the thermostat to slow down flow and allow some warm up to occur. The reason that they may not run one at all is usually to remove a point of failure in endurance type races. In other words, if the thermostat fails and sticks closed, it could cause a pit stop or end the race. By removing it, they tolerate possible engine wear since they know they'll be at high loads throughout the race. Their cooling system is usually tuned to compensate for the lack of a thermostat as well.

Running the factory thermostat will on the other hand ensure that the engine comes up to the designed minimum temperature very quickly. Until the engine is up to temperature, there is no cooling occurring. The factory thermostat will not however change how the engine runs under load because the thermostat will be fully open when under load. It effectively isn't there under load.

What they're used for

So what then would a low temperature thermostat accomplish? Not much.

Around town and in the pits, you warm up faster than no thermostat at all, but you will take a while to warm up from 160 to 180 for example. You will get there however, especially on warm days, the only difference is you're trying to cool the car off as it's trying to warm up. As a mater of fact, if you sit there at idle, the temp will go up until the radiator fans kick on since radiators are poor cooling devices without air flow. In other words, sitting still, the thermostat opening temperature doesn't matter much at all.

Once you're moving, on the highway, with a 160 degree thermostat on a cooler day you could be cruising at 160-180 degrees (opening temp->designed operating temp). This is possible because the load on the engine is low and the outside temps are low. Therefore, the thermostat opening temp maters somewhat here. If you're coasting down a mountain, it will be a certainty that your coolant will reach the thermostat minimum if you coast long enough.

The problem with a low temp thermostat then for regular driving is that there are times when the car will be running at a temperature lower than it's design intended. The result is increased wear on the engine's internals. It's essentially the same as if you assembled the engine with clearances tighter than designed for because you didn't follow the directions or your tools were not calibrated properly.

As for the intake temperature argument, while cooling the intake manifold down could be useful, there are a few problems with the argument. The first is that very little heat is transferred from the intake manifold to the intake charge, period. The intake charge is moving very fast and there is a LOT of air flowing through. The surface area of the intake system is very small and the temperature differential in real terms is not that high. There is already very little heat being added to the intake charge by the intake system regardless of what some ads claim. If the new thermostat DID bring the temps of the intake manifold down 20 degrees, the actual change in intake temps would be negligible to 0 on the road.

Regardless, it would take literally a second or two before temps would be regulated by the cooling system, not the thermostat anyway since under load the engine is going to run well above the thermostat fully open mark anyway.

Remember that the thermostat is fully open pretty much any time the engine is under full load because the coolant temperatures spike pretty quickly.

In a race car, the floor (opening temp) of the thermostat is completely irrelevant unless you are running a very efficient and large radiator. Once you're out on the track for half a lap or so, your coolant temps are going to be in the 200 range anyway so the thermostat is fully open regardless.

You can use a low temp as a "band-aid" at the track sometimes. For example, if you know that your coolant temps are hitting the opening temp of your current thermostat at points the track and you're experiencing mild overheating, you might be able to patch this up by using a lower temp thermostat, especially if you're willing to run your radiator fans manually to help.

Why? Because during low load parts of the track you allow the coolant system to cool off more which means it will cope with higher load sections a bit better and may chase of mild overheating problems. This is acceptable on a race track as a temporary solution as wear is usually an acceptable compromise to get through the race. However, the right solution is to upgrade the radiator or check for possible malfunctioning sections of the cooling system. It is also more acceptable here because load is high during a race. On the street, even on hard drives, it's usually reasonably low.

Conclusion

So if you want to test this, the best thing to do is get an OBDII scanner and go out in an OBDII car and monitor the ECT sensor and watch how coolant temps regulate and spike as load changes.

The bottom line however is that in a street car, you're increasing wear and getting no benefit. In a race car, it's a band-aid but not one that you should plan to rely on.

If you're having overheating problems, check the cooling system thoroughly and if all is well, upgrade the radiator, fans or even the water pump -- not the thermostat. If your coolant gauge never goes above normal then your cooling system is adequate for your use of the car.

If you're chasing more power, this isn't a place to look. Any power gain would be circumstantial (ie, only under certain conditions), incredibly negligible, and at the risk of accelerated wear on your expensive engine internals (especially in street cars)."

While can agree use correct Tstat the article is awful. You copy/past the rag doesn't help because looses formatting.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

I run a 180*F thermostat and coolant temperatures never rise above that. This is done to try and hold KR's down, to help maximize power and to keep transmission temps at a safe level. There is a school of thought that says that the low temperature stat will move the coolant too fast not allowing sufficient time in the radiator to cool but have not experienced this phenomenon.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

quote Originally posted by theogre: While can agree use correct Tstat the article is awful. You copy/past the rag doesn't help because looses formatting.

Wow

Thanks 2.5 for posting the article 👍

quote Originally posted by theogre: While can agree use correct Tstat the article is awful. You copy/past the rag doesn't help because looses formatting.

Not sure whats wrong with the format.

But more importantly anything wrong with what they said?

Good article full of useful, pertinent and correct information.

I'm not a professional journalist or editor, so I won't offer an opinion on the formatting.....

[This message has been edited by olejoedad (edited 05-21-2018).]

quote Originally posted by 2.5:But more importantly anything wrong with what they said?

There is one thing I would take slight issue with, and that is the comment about the "speed" of the coolant. While in an absolute sense it's possible for the rate of flow in a cooling system to be too fast or too slow to be effective, within anything approaching reason that would never come into play on an automotive cooling system. There is an old hotrodder's myth that "removing the thermostat causes the coolant to move too quickly" and that's been proven false over and over again. Similarly, there are some vendors out there selling "high flow" cooling systems, and for a while (maybe still?) there were vendors selling "load-based controllers" for electric water pumps. They don't do much, if anything.

A couple things to remember is that water is a very good conductor of heat, so within a reasonable degree water moving faster or slower won't have a big effect on the radiator's ability to shed heat. Somewhat related, it's worth noting that one of the main functions of a water pump is to introduce turbulence into the cooling system - a good water pump will essentially turn the water inside out and that helps even out the water's temperature and thus helps it move heat. If you think about it it's a bit obvious: If the point was just to move water quickly, there are a lot of superior pump configurations to get that done. Automotive water pumps are specifically designed to stir the water up to make the entire system more effective.

To add onto the article, I think it's important to note that while hotter is generally better for wear, performance, and emissions that engine design will factor into what the "perfect temperature" actually is. An all-iron naturally aspirated engine like a 60*V6 can run very, very hot. 220 degrees ain't no thing. On the other hand, an all aluminum boosted motor like an LNF will want to run much cooler - say, 190 degrees. Part of that is the metallurgy but also forced induction adds a whole new dimension of heat management, with different overhead and safety margin concerns. Point being, there is no "one size fits all" perfect temperature, but somewhere between 190 and 220 degrees is going to describe virtually every fuel injected engine's ideal operating temperature. It's a remarkably narrow range.

On that note, I think it might be worth a mention that a lot of the mythology surrounding cooling systems originates from a long time ago. Carb'd cars have some seriously different considerations than injected motors - since the fueling point is much earlier than injected cars, and not only are you balancing proper combustion but you also need to get the gas into the cylinders safely! Related, carb'd cars have essentially one dimensional fueling - more air flow = more fuel. They can't account for engine temps or air density or anything else whereas an injected car can account for all of that, plus a bunch of other variables. The safety margin for a carb'd car is necessarily much bigger than the one for an injected car. In that situation, you might need to exchange some performance & economy & emissions for safe combustion, so lower temps could be desirable. In the opposite way, direct-injected cars can generally be run hotter than port injected cars because there is little risk of pre-ignition.

Overall, it's a solid article. I wish more people would take the time to understand this stuff. Running around with a 190 degree 2.8l is just wasting gas.

I think, like anything else, this 'Racer's Trick' is overused by people with stock engines and cooling systems. Systems. The entire system was designed from materials to ECM programming to operate within certain parameters, and going outside of them won't magically give you an HP boost. Cooler =/= Better just because. Some people aren't comfortable with the 2.8 running at 235, but that is what it was designed to do. Probably with a focus on emissions first and economy second. That's for road use, of course. Street cars were not made to be raced primarily, and the heat loads and conditions are different. Engine swaps are another story entirely, since those components were not designed to use a Fiero radiator, length of coolant pipe, or engine placement. As a part of actual tuning, like to reduce KR, there are obviously some possible benefits.

Throwing a 180 in the ol' hoopty and thinking it's 'better' is about as useful as a CAI. You might get a horsepower or 2 from fooling the ECM, but you may fail emissions and mileage will tank. IMO, not worth the trade.

I would bet that most people do it to mask other problems in a 30+ year old system, like the wrong radiator cap or a partially plugged radiator. People want to sell stuff, and to sell a solution you need to create a problem. Get the waterless coolant, too.

Lower temp thermostats are great for 1/4 mile racing. You can program the fans to keep the temp lower so that you are at as reasonably low a temperature as possible when you stage. Reduce KR and keep your power up for the big end.

[/strike]Water sucks as a heat transfer medium.

That's only one reason we run additives in the cooling system....

Edited for stupidity.....

WTF was I thinking....

[This message has been edited by olejoedad (edited 05-21-2018).]

I think that's a bit misleading. Per unit, water carries more heat than any conventional coolant chemistry. Glycol has a specific heat capacity that's about 1/3rd that of water - but a boiling point that's about 50% greater. Water is the superior heat conductor by far, but once it turns to steam all that capability evaporates (HA!). So, we mix coolant with water to get a hybrid function - the temperature carrying capacity of water with the high boiling point of coolant. We then pressurize the whole thing to further increase resistance to boiling.

Conventional coolant serves three purposes:

1. Lower the freezing point of water. Although raw coolant will freeze at about 10F, when mixed with water that improves to about -70F.
2. Raise the boiling point of water from about 212F to about 240F (the system pressure pushes that further to about 260F)
3. Prevent electrolysis/corrosion in the system. Without coolant heat and water would quickly eat away at the engine. Coolant stops that behavior.

Other factors notwithstanding, an engine running just water would run cooler. So much so that the entire system could be downsized by a substantial amount. Since we need coolant to perform the above three functions, we increase the size of the system by 30-50% to account for the loss of heat carrying capacity of pure water.

A quick Google would net this same answer in no time.

Here's a good read:

http://www.veoliawatertech....s/2/21823,Glycol.pdf

Here is the first sentence:

quote Water is probably the most efficent heat-transfer fluid known. If it did not freeze, water would be the ideal heat-transfer fluid for cooling applications.

[This message has been edited by thesameguy (edited 05-21-2018).]

quote Originally posted by olejoedad: [/strike]Water sucks as a heat transfer medium. That's only one reason we run additives in the cooling system.... Edited for stupidity..... WTF was I thinking....

Meh... it happens.

Just to add my two pence worth. I thought the original article was excellent. Clear explanation, well set out, easy to follow, and comprehensible even to non-experts like me. Thanks, 2.5, much appreciated.

One thing the article didn't mention was the temperature range of the cooling system. If the thermostat is set for a low temperature and the radiator fan is set for a much higher one, the engine will experience large temperature swings during operation. That's not good for the engine parts. IMO, the operating temperature range should be about 15-20*F. So for example, if the thermostat is set for 195*F, then ideally the radiator fan would be set for 210-215*F.

Don't know what I was thinking, and I spent my career in Chem E. (Of course, we used chems to make the water better for it's intended use.)

quote Originally posted by Blacktree: One thing the article didn't mention was the temperature range of the cooling system. If the thermostat is set for a low temperature and the radiator fan is set for a much higher one, the engine will experience large temperature swings during operation. That's not good for the engine parts. IMO, the operating temperature range should be about 15-20*F. So for example, if the thermostat is set for 195*F, then ideally the radiator fan would be set for 210-215*F.

Solid point. Somewhere I read that exact thing as well - 15-20 degree spread between thermostat and fan switch. In practice, it means the engine will actually stay in a ~10 degree range most of the time, which is desirable. The article I read addressed specifically fan switch (or sensor) placement to best achieve that result. I employed some of that when redoing the cooling system on my XR4Ti, and the end result has been fantastic. It stays between 210 and 215 degrees pretty much all the time - although I have found I can easily overwhelm the radiator when pushing it... 22psi, 6000' climb, summer heat. I need a bigger one.

A lot of people put low temp thermostats in and leave original fan switches resulting in a wide operating range, or vice versa put a low temp fan switch in without similarly adjusting the thermostat, resulting in an uselessly small range (*personally* guilty of that back in the day). Keep the engine at the highest reasonable temp in the narrowest possible range for best results.

[This message has been edited by thesameguy (edited 05-22-2018).]