Cadillac CTS-V - 160 T-stat




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bbrown7888
03-05-2011, 07:15 AM
I am seeing A-LOT of you guys running 160 degree thermostats in your cars and was wondering what the gains of it are? I know you get to run your engine cooler and keep the under hood temps down a little bit however by keeping the engine a little cooler your oil will be a little cooler, thus a little thicker than if you were to run a 180 degree t stat. So although your fighting heat your also creating a little bit more drag in the crankcase VS. using a 180 deg. and running a little hotter for thinner oil. As long as your using an oil with a decent operating temp that will not break down at high RPM's I do not see a plus side to running a 160 t stat to get your engine to run 20 degrees cooler... just because it's 20 degrees cooler.

I'm sure there is a good reason since 90% of the people on here go to tuning shops, talk to professionals and do their homework, I'm just looking for an explanation of why this is such a big trend.


itsslow98
03-05-2011, 07:20 AM
160 thermostat usually runs the engine at about 180 degrees. At least it did in my SS.

good2go
03-05-2011, 07:53 AM
Running a cooler thermostat keeps the ECM from pulling timing, which it does based on AIT AND ECT.


JNR_Design
03-05-2011, 01:46 PM
You need to 'program' your ECU for such a low thermostat, or else the car will probably be in closed loop mode, or always thinking it's not warmed up and thus running rich and sucking up gas needlessly.

All a 160 degree thermostat does is open at 160 degrees +/- [think of it as a valve that opens at a given temp], to allow the coolant to circulate thru the radiator; it does not necessarily 'cool' the engine, but in some cases, it will allow it to run cooler, since it is not holding in the coolant in the engine (thermostat closed) until 195-205 degrees (I'm not sure what the caddy oem thermo rating is, but these are typical temp ratings for cars from factory). The engine is designed to operate most efficiently at a higher temp, but not overly so; especially from the factory, where they have to deal with smog and such.

The better thing to focus on would be a cooler, or denser, air mixture into the combustion chamber, but that can be tough; especially if it's 90 F outside and you're sitting in traffic, lol.

IMO, a good compromise would be a 180 F thermostat, if they make them and you could probably almost get away with that still stock, as far as engine tuning goes, but best best even there is to have your program reflect that...

serik21
03-05-2011, 02:56 PM
Our cars heat soak so fast you would not believe it. I got stock t-stat during tune after about 5 pulls I was always 361. Tuner let the car cool down for 30 min noting on the tune was touched first 3 pulls it was at 365 rwhp

good2go
03-05-2011, 05:07 PM
You need to 'program' your ECU for such a low thermostat, or else the car will probably be in closed loop mode, or always thinking it's not warmed up and thus running rich and sucking up gas needlessly.

All a 160 degree thermostat does is open at 160 degrees +/- [think of it as a valve that opens at a given temp], to allow the coolant to circulate thru the radiator; it does not necessarily 'cool' the engine, but in some cases, it will allow it to run cooler, since it is not holding in the coolant in the engine (thermostat closed) until 195-205 degrees (I'm not sure what the caddy oem thermo rating is, but these are typical temp ratings for cars from factory). The engine is designed to operate most efficiently at a higher temp, but not overly so; especially from the factory, where they have to deal with smog and such.

The better thing to focus on would be a cooler, or denser, air mixture into the combustion chamber, but that can be tough; especially if it's 90 F outside and you're sitting in traffic, lol.

IMO, a good compromise would be a 180 F thermostat, if they make them and you could probably almost get away with that still stock, as far as engine tuning goes, but best best even there is to have your program reflect that...

Actually when a car is in warmup mode it is in open loop mode and these cars go into closed loop at MUCH lower temps than that, usually at about 120-130, so a lower temp thermostat, even a 160 will never cause it to stay in open loop mode.
Also, the high operating temp from the factory is for emissions, not for performance. It will make more horsepower when run a little cooler. It is best to tune to have the fan come on at a lower temp and at a higher percentage than stock settings for better performance in stop and go driving. Running cooler AIT and ECT will help during warm weather.

JNR_Design
03-05-2011, 06:07 PM
Yeah, I may be mistaken on the closed loop mode, although when the engine runs too cool for its parameters, it will not run to its full potential and waste gas by trying to compensate with a richer mixture...I do agree about the emissions part and why I mentioned the smog, but will say by simply swapping the t-stat and leaving the ECU as is, you will not make more power and it will not even run as good. But, by tuning the ECU's parameters for a cooler operating temp, yeah you could potentially increase power, to a certain extent. Running the engine too cool is not always good, either, obviously, but not sure what temp these cars would run with constant coolant flow, as it would naturally run above 160 unless it was like 0 degrees ambient temp, or something. Personally, to reiterate, I think 160 t-stat is too low and a 180 would be better, but with the proper tune to go with it. Remember that the pistons (esp with an alum. block) and other components have a certain expansion rate they are designed for, so another thing to take into consideration, but a relatively neglible point in reality, I bet.

I have run 160's in the past though, in my Syclone (but with a chip designed for it) and my chevelle, but that was carb'd and no sensors, so I was able to compensate. I do remember the thing would hardly warm up and I want to say I ended up changing to a 180 later on.

Turning the fan(s) on more often may not a bad idea and doubt these fans draw too much amperage; the electic fan I was gonna run in my chevelle has a 40A draw (but 5,000+ cfm), so not sure I'd want that on all the time, more than necessary.

good2go
03-06-2011, 08:43 AM
There's a difference between "too cool" and "a little cooler". I'm speaking from many years of experience with tuned and modded LS1'S, LS3's, and LS7's, with a 160 stat and a reprogrammed fan you will run about 180 ECT. Not too cool. If you look at the ECM tune you will see it starts to pull timing at 196 to 202 degrees (depending on engine/year) and performance drops. That's why drag racers cool down their cars between runs. Now you could just change the tune to not pull timing until higher temps, but that timing reduction is there to keep your engine from knocking and the knock sensors would pull it anyway (and pull more, and for a longer time) so it's just best to not get into those temps anyway. Also, if you look at the tune once you get into closed loop mode (at WAY cooler ECT's than you'll see with a 160) it runs the same A/F, not richer at slightly lower temps.

The change in expansion for an aluminum block and aluminum pistons is negligible between 180 and 200 degrees, no worry there. And no, the oil is not too thick at those temps and causing any more wear, it's 10W (or winter) 30, and flows just fine at a little cooler temps.

Any time someone mentions a 160 you get the same concerns mentioned: too cold, open loop, not proper operating temp, oil too thick, wear out engine too soon, etc.

The sky is not falling, and a 160 stat is a good mod, even in modern engines.:cheers:

JNR_Design
03-06-2011, 02:06 PM
I've been doing this for 22+ years and also speak from experience :) I'm glad this has worked for you, but saying most people operate their cars under 'normal' conditions 98% of the time and the loss in mileage and drivability is not worth it to me and again if you keep the ECU parameters stock (designed for the hotter temps), it's not going to work optimally, but if somebody wants to try it, then do a real world day-to-day operation and see what you really gain...Drag racers cool their engine between rounds after a hard run, but the real benefit is icing down the intake, which keeps the air mixture cooler on a successive run; certainly don't want the engine itself to get too cool.

So, why even run a thermostat then if a 160 works so well? I mean, other than taking longer to warm up, the engine will almost always be over 160 degrees, so what would be the harm then (using it as analogy)...You need some control to keep the engine from going too cool. I do agree though a few degrees cooler temp will help, but there is a point that is too much and what's the point then...

And drag racing is a lot like 4x4'ers (yeah, did that for many years too and I don't mean the fire roads, lol)...things that work there may not give you good results on the street, where you do most of your operation (unless it's a dedicated rig)...Anyway, not here to argue it, but many folks only go by what they read on forums, hear what others say, or magazines, etc. and that information is not always geared to all around, if that makes sense.

ColeGraham
03-06-2011, 04:04 PM
i like my 160 t-stat. my car, on average, will run between 172 and 176. it was really nice having that driving from LA to Phoenix. i was stuck in traffic in LA and my coolant never got about 200 (engine not above 205). and then blasting along I10 at 85 to 90 mph, with outside temp (on the DIC) at 110F and my A/C never off (set at 72F). that little run my temps never got 195 for coolant and engine. now, my tranny on the other hand hit 235 or 240 at one point, but that was after 18 hours of straight driving from Abliene, TX to Barstow, CA (about 1200 miles) with minimal stop times.

good2go
03-07-2011, 08:49 AM
I've been doing this for 22+ years and also speak from experience :) I'm glad this has worked for you, but saying most people operate their cars under 'normal' conditions 98% of the time and the loss in mileage and drivability is not worth it to me and again if you keep the ECU parameters stock (designed for the hotter temps), it's not going to work optimally, but if somebody wants to try it, then do a real world day-to-day operation and see what you really gain...Drag racers cool their engine between rounds after a hard run, but the real benefit is icing down the intake, which keeps the air mixture cooler on a successive run; certainly don't want the engine itself to get too cool.

So, why even run a thermostat then if a 160 works so well? I mean, other than taking longer to warm up, the engine will almost always be over 160 degrees, so what would be the harm then (using it as analogy)...You need some control to keep the engine from going too cool. I do agree though a few degrees cooler temp will help, but there is a point that is too much and what's the point then...

And drag racing is a lot like 4x4'ers (yeah, did that for many years too and I don't mean the fire roads, lol)...things that work there may not give you good results on the street, where you do most of your operation (unless it's a dedicated rig)...Anyway, not here to argue it, but many folks only go by what they read on forums, hear what others say, or magazines, etc. and that information is not always geared to all around, if that makes sense.

There is no loss in mileage.

There is no change in the drive-ability.

A 160 works best with resetting the fan parameters but is fine with a stock tune, it just won't run much cooler in stop and go driving.

No thermostat? Please. :jest:
You need to control the flow of coolant through the radiator to keep the ECT in it's optimal range. The factory range is designed for 100,000+ miles of lowest emissions. If you want a little better performance you can reset that range a little lower with a lower temp thermostat.

ecotec88fiero
03-07-2011, 08:12 PM
I have heard of only good things from a 160 degree thermostat from the V's and Vettes around here.
No mileage loss or drivability problems. Keeps things a bit cooler for less heat soak after a lot of hard pulls.
Would reprogram the fan though as this helps take full advantage of a lowered operating temperature.

kenp
03-09-2011, 08:39 AM
This debate about thermostats has been going on for years. If you're running a dedicated track car and changing the oil after every event it's fine. For a daily driver, not such a good idea. Here's a tech tip from Vinci High Performance I think hits the nail on the head.


Proper Coolant Temperature and Camshaft Life!
Have you ever tried to find what proper coolant temperature is for most automotive engines? There are a lot of people who think they know, but it is difficult to find specifics, even in textbooks. We know we want the intake air to be as cold as possible (for best power) because cold air is denser (there are more oxygen atoms per cubic foot). The coolant temperature, however, is a different matter. The internal combustion engine changes chemical energy stored in gasoline into heat energy that is focused on the piston tops. If the cylinder heads and engine block are too cold, they will absorb much of the combustion heat before it can be used to push the piston down the cylinder. If the engine gets too hot, engine lubricants can break down, as well as overheating of the intake charge can lead to detonation, etc.
It turns out that coolant (usually a 50/50 mixture of coolant and water) has some fantastic properties that are ideal for use in engines. With a properly pressurized cooling system, coolant will not freeze until –30F, and it won’t boil until +270F (new oils don’t start to break down until well over 270F). With these characteristics, engine designers have decided that engines should operate at approximately 210-215F. Why, you ask? Well, it has to do with operating the engine at a high enough temperature to boil water out of the oil after the engine is cold started. If you have dew on the grass, it is certain that you have water in your oil, as the crankcase is open to atmospheric pressure! You can either remove the water by draining it out the bottom of the oil pan (remember the oil floats on water) or run the engine long enough and hot enough to boil the water out of the lubrication system. Years ago, coolants weren’t as sophisticated and engines were run at 165-180F, but the oil was changed every 1000 miles or so. That’s why many old timers think engines should run at 165-180F. Have you ever noticed that Ford doesn’t put temperature marks on their gauges? They just mark C for cold and H for hot and write “normal” through the center. If you hook up a scan tool to a GM, you will often find that the gauge reads much lower than the coolant temp sensor. That is because they know most drivers don’t understand how hot an engine should run.
So what does this have to do with camshafts? Many enthusiasts erroneously think that the colder their engine runs the better! If they are not running the engine hot enough to boil the water out of the oil, the oil becomes contaminated and the lifter/cam lobe interface is the highest load point in the engine. Engines running too cool can contribute significantly to camshaft and lifter failure. Think about it: What good does it do to use the most expensive synthetic oil and then run the engine so cold that it is contaminated by water vapor??!! Another point, piston manufacturers’ piston-to-wall clearance recommendations assume you will be running the fully warmed engine at 200+F. Run the engine too cold, and you could see some scuffed pistons because the cylinders had not expanded enough to provide clearance.
If your engine will only run its best at the drag strip with the engine at 165F, you probably have too cold of a spark plug heat range and you are probably jetted way too rich! If you keep the engine hot (not the intake charge), you will be using more of the heat energy in the gasoline to make power instead of just heating up your block. It does take “tuning know-how” to run an engine at 200-210F, but you might be surprised how well and how long it runs when you do!! One final point - running a computer managed engine at 165F compared to the factory 210F will often cost you as much as 4 MPG. The reason for this is that the computer thinks that the engine is not off the “choke cycle” and it is still putting out a rich mixture! Check the science on this and don’t pay attention to the “old wives tales” of the past. Materials and lubricants are much better and different today than they were in the past!!

DMM
03-09-2011, 01:26 PM
This is something that started long ago. Hell, the TPI and TBI motors would go into open loop while idling at a stop light no matter how long you had been driving. The lost MPG claims from a t-stat has been a thing of the past for a long time now thanks to heated O2 sensors.

I wouldn't worry about it.

shadyLS6
03-09-2011, 02:08 PM
i run a 160 w/ tune and my car running op is a solid 195.. and never goes above 201 even after a 3hr 70mph highway ride and then 5mph stop and go traffic. but i live in FL soo that was one of the reasons i switched but i ran this in jersey too

i havent lost any mph either..

safemode
03-09-2011, 02:09 PM
KenP has it. or rather the guy he quoted does. It's a balance between physical limitations and ideal physics. You want the engine block hot so most of the energy in combustion is used to push the cylinder. You have fuels and lubricants that can't take heat over a certain level, so the best temp is one that is just low enough to not hurt lubricants and not predetonate your fuel. Any lower than that and you start to lose efficiency and _usually_ performance. That's not really something that can be argued. What can be debated is application dependent, since people's fuel mixture may require different temps to detonate (due to turbos, E85, nitrous, etc), this will change how hot you can let the engine get before predetonation.

The oil part is new to me. That's interesting and makes sense.

LS6BlackCTS-V
03-09-2011, 02:21 PM
Have the 160 t-stat in the V and seems to work fine and keep the engine at about 171, I don't know about any large power gains, but that seems to be the sweet spot for when the car runs it's best as far as temp..

good2go
03-09-2011, 04:20 PM
This debate about thermostats has been going on for years. If you're running a dedicated track car and changing the oil after every event it's fine. For a daily driver, not such a good idea. Here's a tech tip from Vinci High Performance I think hits the nail on the head.


Proper Coolant Temperature and Camshaft Life!
Have you ever tried to find what proper coolant temperature is for most automotive engines? There are a lot of people who think they know, but it is difficult to find specifics, even in textbooks. We know we want the intake air to be as cold as possible (for best power) because cold air is denser (there are more oxygen atoms per cubic foot). The coolant temperature, however, is a different matter. The internal combustion engine changes chemical energy stored in gasoline into heat energy that is focused on the piston tops. If the cylinder heads and engine block are too cold, they will absorb much of the combustion heat before it can be used to push the piston down the cylinder. If the engine gets too hot, engine lubricants can break down, as well as overheating of the intake charge can lead to detonation, etc.
It turns out that coolant (usually a 50/50 mixture of coolant and water) has some fantastic properties that are ideal for use in engines. With a properly pressurized cooling system, coolant will not freeze until –30F, and it won’t boil until +270F (new oils don’t start to break down until well over 270F). With these characteristics, engine designers have decided that engines should operate at approximately 210-215F. Why, you ask? Well, it has to do with operating the engine at a high enough temperature to boil water out of the oil after the engine is cold started. If you have dew on the grass, it is certain that you have water in your oil, as the crankcase is open to atmospheric pressure! You can either remove the water by draining it out the bottom of the oil pan (remember the oil floats on water) or run the engine long enough and hot enough to boil the water out of the lubrication system. Years ago, coolants weren’t as sophisticated and engines were run at 165-180F, but the oil was changed every 1000 miles or so. That’s why many old timers think engines should run at 165-180F. Have you ever noticed that Ford doesn’t put temperature marks on their gauges? They just mark C for cold and H for hot and write “normal” through the center. If you hook up a scan tool to a GM, you will often find that the gauge reads much lower than the coolant temp sensor. That is because they know most drivers don’t understand how hot an engine should run.
So what does this have to do with camshafts? Many enthusiasts erroneously think that the colder their engine runs the better! If they are not running the engine hot enough to boil the water out of the oil, the oil becomes contaminated and the lifter/cam lobe interface is the highest load point in the engine. Engines running too cool can contribute significantly to camshaft and lifter failure. Think about it: What good does it do to use the most expensive synthetic oil and then run the engine so cold that it is contaminated by water vapor??!! Another point, piston manufacturers’ piston-to-wall clearance recommendations assume you will be running the fully warmed engine at 200+F. Run the engine too cold, and you could see some scuffed pistons because the cylinders had not expanded enough to provide clearance.
If your engine will only run its best at the drag strip with the engine at 165F, you probably have too cold of a spark plug heat range and you are probably jetted way too rich! If you keep the engine hot (not the intake charge), you will be using more of the heat energy in the gasoline to make power instead of just heating up your block. It does take “tuning know-how” to run an engine at 200-210F, but you might be surprised how well and how long it runs when you do!! One final point - running a computer managed engine at 165F compared to the factory 210F will often cost you as much as 4 MPG. The reason for this is that the computer thinks that the engine is not off the “choke cycle” and it is still putting out a rich mixture! Check the science on this and don’t pay attention to the “old wives tales” of the past. Materials and lubricants are much better and different today than they were in the past!!

He's got it wrong on a couple of points.

First, the crankcase is not open to the atmosphere, it's a closed system.
Second, you don't have to reach boiling temps to run off the contaminants, watch a hot tub at 105 and you'll see.
Third, we aren't dealing with quadrajets with sticky chokes. The ECM goes into closed loop operation based on a few parameters, one of which is ECT. The point at which it goes out of warmup is in the 120-130 range. So running a 160 will ABSOLUTELY NOT COST ANY GAS MILEAGE.
Fourth, his point about running the engine as hot as you can for thermal efficiency is correct BUT only up till the point you lose control of the burn. On the modern LS series engines that point is below or right at 200 degrees. That's when you start pulling timing or getting knock. So you want to keep your engine below that point. To do that over a full 1/4 mile pass you gotta start at/about 180. Same on the street, or worse due to stop and go driving not getting full cooling.
Also, who's talking about running an engine at 165? At least in the Corvettes, running a 160 thermostat will keep your operating temp at least 10 degrees above that.
How old is this article? Jets and choke cycle:confused:
Has anybody seen a piston maker specifying 200+ degrees for proper temp? I'd like to see that.

greddy91
03-09-2011, 04:55 PM
160 makes 170's in temp. The norse gods that originally created the first LS based motors suggested that this was an optimal horsepower making temperature.

kenp
03-10-2011, 12:19 AM
The crankcase in the engine certainly is open to the atmosphere. Metered air is pulled into the crankcase past the MAF. That's the line that goes to the valve cover. It's called Positive Crankcase VENTILATION.

What you see at a hot tub is not water vapor boiling off. What you are seeing is air heated by the water colliding with cooler air and reaching a dew point. Water vaporizes at 212*.

As for pulling timing at higher temps, you've got to see 110*C to have 1* pulled.

good2go
03-10-2011, 07:53 AM
The crankcase in the engine certainly is open to the atmosphere. Metered air is pulled into the crankcase past the MAF. That's the line that goes to the valve cover. It's called Positive Crankcase VENTILATION.

What you see at a hot tub is not water vapor boiling off. What you are seeing is air heated by the water colliding with cooler air and reaching a dew point. Water vaporizes at 212*.

As for pulling timing at higher temps, you've got to see 110*C to have 1* pulled.

The PCV system is not open to the atmosphere for emissions reasons. Open would be air flowing in and out, it doesn't. It is metered and fed to the intake, not out to the atmosphere. Open would be like in the 60's, with a valve cover breather.

You don't need to reach boiling point to remove contaminants from the oil.

Different LS engines pull timing at different points. The LS7 starts to pull timing at 196. Pull the timing table and see. I would like to see the LS-A table, I'd bet it's similar.

JimmiB
03-10-2011, 08:40 AM
See what you started?

I have been told that it is a trade off, Lower emmisions higher temps, little shorter engine life and a little less performance.

good2go
03-10-2011, 10:07 AM
See what you started?

I have been told that it is a trade off, Lower emmisions higher temps, little shorter engine life and a little less performance.

You're right. There's a chart floating around that isn't very specific but shows performance best in the 180-200 range, and engine life best in the 200-220 range. Above or below that and wear increases and performance decreases.

kenp
03-14-2011, 05:17 AM
The PCV system is not open to the atmosphere for emissions reasons. Open would be air flowing in and out, it doesn't. It is metered and fed to the intake, not out to the atmosphere. Open would be like in the 60's, with a valve cover breather.

You don't need to reach boiling point to remove contaminants from the oil.

Different LS engines pull timing at different points. The LS7 starts to pull timing at 196. Pull the timing table and see. I would like to see the LS-A table, I'd bet it's similar.

Well, the PCV system pulls air in from the intake track and it is OPEN to the atmosphere PERIOD. Vacuum from the engine pulls vapors from the crankcase and the air that replaces those vapors comes from the intake tract , that, once again, is open to the atmosphere. THE INTAKE TRACT IS OPEN TO THE ATMOSPHERE.

System components and operation details
http://upload.wikimedia.org/wikipedia/commons/thumb/8/80/Pcv-valve.jpg/200px-Pcv-valve.jpg (http://www.ls1tech.com/wiki/File:Pcv-valve.jpg) http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png (http://www.ls1tech.com/wiki/File:Pcv-valve.jpg)
PCV valve on Ford Taunus V4 engine (http://www.ls1tech.com/wiki/Ford_Taunus_V4_engine) in a Saab 96 (http://www.ls1tech.com/wiki/Saab_96), between left valve cover and intermediate flange on intake manifold


The PCV valve is only one part of the PCV system, which is essentially a variable and calibrated air leak, whereby the engine returns its crankcase combustion gases. Instead of the gases being vented to the atmosphere, gases are fed back into the intake manifold (http://www.ls1tech.com/wiki/Intake_manifold), to re-enter the combustion chamber as part of a fresh charge of air and fuel. The PCV system is not a classical "vacuum leak". All the air collected by the air cleaner (and metered by the mass air flow sensor, on a fuel injected engine) goes through the intake manifold. The PCV system just diverts a small percentage of this air via the breather to the crankcase before allowing it to be drawn back in to the intake tract again. It is an "open system" in that fresh exterior air is continuously used to flush contaminants from the crankcase and into the combustion chamber.
The system relies on the fact that, while the engine is running under light load and moderate throttle opening, the intake manifold's air pressure is always less than crankcase air pressure. The lower pressure of the intake manifold draws air towards it, pulling air from the breather through the crankcase (where it dilutes and mixes with combustion gases), through the PCV valve, and into the intake manifold.
The PCV system usually consists of the breather tube and the PCV valve. The breather tube connects the crankcase to a clean source of fresh air—the air cleaner body. Usually, clean air from the air cleaner flows into this tube and into the engine after passing through a screen, baffle, or other simple system to arrest a flame front, to prevent a potentially explosive atmosphere within the engine crank case from being ignited from a back-fire (http://www.ls1tech.com/wiki/Back-fire) in to the intake manifold. The baffle, filter, or screen also traps oil mist, and keeps it inside the engine.
Once inside the engine, the air circulates around the interior of the engine, picking up and clearing away combustion byproduct gases, including a large amount of water vapor which includes dissolved chemical combustion byproducts, then exits through another simple baffle, screen, or mesh to trap oil droplets before being drawn out through the PCV valve, and into the intake manifold. On some PCV systems, this oil baffling takes place in a discrete replaceable part called the oil separator......

No, you don't have to get water in the crankcase to 212* to remove it from the oil, but a higher temperature is clearly more effective. This is probably the best analysis of removing water from the crankcase from a post @ BITOG: Any fluid, water included, will maintain an equilibrium of liquid and gas in an enclosed and only partially filled space. The pressure of the vapour over the liquid is determined by the temperature of the system, and it's a constant at a constant temperature. If you remove vapour from the system, liquid will evaporate to compensate for the loss until the previous pressure is restored. That's how the PCV system gets water out of your motor oil without boiling it out.

Of course, when such a closed system is raised to the "boiling point" of the liquid, the liquid absorbs heat and converts to vapour until all the liquid is gone. This is "boiling off" the liquid.

To clean the water out of your engine oil without boiling, you just have to keep removing the water vapour from the space above the liquid (ie - the enclosed crankcase volume), and the water in the oil will continue to evaporate in an effort to re-establish it's equilibrium vapour pressure.

If your oil is at 200 degrees (F), the vapour pressure of water is relatively high, and your PCV system will draw the vapour out of the engine very efficiently until all that's left is a tiny amount of water vapour inside the crancase. That moisture will condense into the oil as the engine cools, but it will be a negligible amount.

There are two reasons you get creamy oil when running a cold engine:

1 - more water vapour condenses inside the cylinders in the first place (instead of being expelled) because the mass of the engine itself is cold. This means there is more input of water to the oil.

2 - the whole system is cool, so the vapour pressure of the water in the crankcase is quite low, so the PCV system can't extract it. The water's happy being a liquid and riding around in the oil, and until it feels the call of warmer temperatures, it has no inclination to try to support a higher vapour pressure.

Here's info from an oil cooler company - They don't open until oil is 180* for a reason:

THERMOSTATS

http://www.batinc.net/images/header.gif http://www.batinc.net/images/Ot1.GIF http://www.batinc.net/images/thermo3.gifMOXXX thermostats are designed to prevent engine oil from flowing through the oil cooler until the desired temperature is reached. Prolonged use of engines in conditions that oil cannot reach optimum working temperatures will cause sludge formation and crankcase oil dilution, leading to excessive wear especially in the cylinder bores. Thermostats combat this by regulating oil flow to accelerate warm up. This in turn reduces drag, helping to yield optimum engine efficiency and performance. The proven design and reliability of the MOXXX thermostat make them the choice of automotive and marine racing teams world wide. They are also well suited for aviation applications.
MOXXX thermostats are available two styles. The OTI version utilizes push-on hose barbs and is available for either 3/8" or 112" i.d. hose. 0T2 type thermostat is designed with thread-on male fittings available in all popular JIC/-AN sizes (-8AN, -lOAN, -12N, -I6AN) and BSP sizes (1/2", 5/8"). For additional plumbing versatility a 1/2" female thread OT2 version is available which will allow any male/male union to be installed.
http://www.batinc.net/images/Thermo2.GIF
0T1 Specifications

0T2 Specifications


All Aluminum CNC machined housing
Push-on hose barb 3/8", 1/2" O.D.
Lightweight (8oz)
Factory set 180 degree operation
Includes mounting bracket


All aluminum CNC machined housing
Aeroquip compatible male fittings AN-8, AN-10, AN-l2and AN-16
Lightweight (16 Oz.)
Factory set 180 degree operation
(optional temperatures ranges available)
Includes mounting bracket
So, run the 160* thermostat in your daily driver with the knowledge that you are not optimising the combustion characteristics of the fuel or the capability of your PCV system to remove water from your oil. ;)

safemode
03-14-2011, 07:53 AM
I think people are confusing metered air with not being open to the atmosphere. It definitely is, it's just measured. So when the car is off, this air is moving back and forth and the fact that it's measured doesn't matter cuz the car is off.

Metered doesn't mean there is some magical one way valve that blocks the air now. Even the TB can't stop air from freely moving around the oil because the PCV is in front of the TB. (not that the TB is air tight either.)

good2go
03-14-2011, 08:50 AM
Hey Ken: I agree with you completely on how a modern PCV system works, I just don't want it confused with the old open systems of decades ago. If people think that they can just put a breather on the valve cover with or without rerouting the PCV lines they will be disabling the system and without the vacuum pulling air through the crankcase their oil will stay contaminated and need to be changed very often, or they are causing a vacuum leak to affect their A/F.

As for the oil thermostats, they are a bad idea for LS engines. They are a restriction to oil flow and can cause our bypass valves to open, meaning no oil flow to the filter. Not good.

As for the 160, it's still a good mod. My oil and coolant get up to temps high enough for proper operation and not hot enough to cause knock. :usa: