If "ignorance is bliss".... you must be the happiest man on earth.

You are correct.... the hotter the coolant temperature, and the lower the air temperature, the more heat will be removed in the radiator. But.... and the part you don't seem to be looking at..... the warmer the coolant, the LESS heat it can remove from the combustion chamber. The driving force at the combustion chamber is still "delta T"... but now its the higher temperature of the combustion chamber driving the heat into the coolant... soooo... and think about it.... the lower the coolant temperature, the MORE heat it removes from the combustion chamber.... the less heat that is left to drive the piston down, and the less power you make. The object is not "to get heat from one point to another. " The object is to keep as much heat in the combustion chamber as you can, without getting into trouble with detonation.

I agree with you completely... NASCAR runs their engines hotter than most of us. But its NOT because its removing more heat.... its because its removing less heat from the combustion chamber, and leaving more heat in the combustion chamber to make MORE power.

This isn't some hairbrain theory.... its fundamental thermodynamics. Not easy for a 10-year old to understand. Spend 6 years in engineeering school, get a BS in mechanical engineering, and an MS, get yourself licensed to practice mechanical engineering and provide expert testimony in court, spend 40 years designing process facilities, including sophisitcated heat transfer systems.... and it all becomes a lot easier to understand.

 

Let's take the ASE L1 test to educate some people. Has anyone taken the L1 test? It was specifically designed for the California BAR97 smog check program. With the introduction of NOX testing under loaded mode, the state wanted to know the smog techs would be able to properly diagnose and repair NOX failures.
For example has anyone seen a question like this on the ASE test?

The vehicle failed for high NOX emissions. What could be the cause?
a. fowled spark plug
b. clogged fuel injector
c. burned exhaust valve
d. stuck open thermostat

NOX emissions are created when cylinder temps exceed 2500 degrees F. A fowled spark plug wouldn't ignite the air/fuel so no temp increase. a clogged fuel injector wouldn't put fuel into the cylinder which, in turn, wouldn't ignite. A burned exhaust valve would cause low compression, without compression no fire. A stuck open thermostat...??.....??.......HUMMMM, why would that cause high NOX? But, by replacing with a 195 stat, the NOX emissions are reduced. That can't be. Because we all know a lower coolant temp is more efficient, right? By replacing the thermostat and running the coolant temp at 200 degrees, the state of California and ASE says it will reduce NOX. How can that be? The only way to reduce NOX is to lower the cylinder temp. Just by installing the correct stat can reduce NOX? So what California and ASE are saying is that by running at a higher coolant temp you are lowering the cylinder temp? They must be mistaken or haven't read this post. They need to go back to school!

 

After reading all of this then researching everything Fred is 100% right as I suspected. The only this is that there must be some fine line in there because I know for a fact my car runs better hovering around 190-200 degrees with the fans on than it does with them off running at 215-225 degrees. So now I am scared to add the 160 thermostat on top of the fan because I do not want to run "too cold" which is pretty much the point of this thread. That being said, I think Fred runs the 160 in NJ in winter which is where I live....so maybe I should do it?

 

That's what the EGR valve is for under those driving conditions.

http://www.autoshop101.com/forms/h61.pdf

 

Vehicle is a Chrysler Town and Country 3.3L, No EGR, DIS system

 

Trying to teach injuneer thermodynamics is like trying to teach a doc about medicine.

 

It "fouled" plug.... "fowled" relates to chickens. Appears maybe you made the question up.

Higher temperature coolant does not remove more heat from the cylinder - plain and simple. Heat transfer is governed by the heat transfer coefficient of the combustion chamber wall, in (BTU/HR)/(SQ FT-degF). Actual heat flow is delta T X HT coefficient. Since you can't change the heat transfer coefficient (assuming velocity, turbulence and film coefficients are held constant), you can only change the delta T, and you do that by reducing the coolant temp. What part of this do you not understand?

So... your theory is, because NOx formation is increased by higher combustion chamber temperatures, it is evidence that this confirms a warmer engine runs more efficiently. And this somehow supports your theory that hot coolant is removing more heat. In fact, its doing just the opposite. Can't change the laws of thermodynamics.

While I don't agree that NOx formation has anything to do with engine efficiency (it is a measure of the propensity of oxygen to combine chemically with the seemingly "inert" nitrogen at elevated temperatures - nothing more), no one is arguing that a cooler engine runs more efficiently. The point of my posts has been that "cooler is not always better".... you apparently missed that, along with most of the other points. My argument is with your uninformed statements regarding heat transfer.... i.e. hot coolant removes more heat than cold coolant.

If you can't understand it after all this, I'm not going to waste my time trying to explain it to you. Everyone else seems to understand.

 

OK this will be my last post. I was hoping someone would see the similarity
in of theses posts, at least one, but I guess I'll have to just see if I can get a hold of this.
Now, Injuneer has stated that higher cyl temps = better efficiency. So let's
see what else everyone has said. Most seem to think that a lower temp
thermostat gives them better performance. OK, with better performance that should mean more power. So........

lower coolant temp = better performance
better performance = more power
more power = higher cyl temp
higher cyl temp = more efficiency

So, with everything equal, it seems that.......

lower coolant temp = higher cylinder temp

I think that's what I've been trying to say all along. Of course, the other thing
is that with just changing your thermostat you need to look at the other things that will change. Since heat flows from high temp to low temp, and the cylinders are creating more heat, then the other parts of the engine will also be getting hotter. Take into consideration other changes before you decide what it is you want to get out of your car. Just because someone does some kind of mod, doesn't mean you have to. All cars are different, like people. Just because they use the same parts, doesn't mean all the parts are the same. Anytime you enhance your performance, you also increase wear
and tear. Especially if you have a heavy foot. In my experience with the public, I have found they generally know very little about their cars. Putting things in technical terms usually will confuse them and make it harder to sell a repair. I have learned to try to explain in terms they can understand. Once they get the idea they usually calm down and are a little more open to repair suggestions. That's why I used the different analagies to make it easier to uderstand by someone a litte less knowledgable. What it all comes down to, is by making a "MOD," is it that important that you get to the next light a tenth of a second sooner? My 245 HP L98 TPI must be a boat achor. When I first bought it my buddy wanted to see what it would do. From a dead stop it hit 140mph at 4500 rpm is about 30 seconds. It still wanted to go but I let off because the stop sign was coming up pretty quick. I'd say that's plenty fast enough. Getting on the freeway is no poblem. If I wanted to I could hit 90mph by the time I merge. Do I need to, NO. Do I need to prove it to any one else, No. I know what it will do. There's only one person that matters, yourself.
Bye

 

wow this is still going?!

 

No.

lower coolant temp=lower cylinder temp

To answer the poster's question, in my experience my car runs similar temps while crusing at highway speeds with the 180/160- but the new stat and fan programming keeps my idle/traffic temps hovering in the bottom quarter rather than creeping up above the 200's. It comforts me for some reason to see those low temps, and it's also a benefit for stop-light drags!

Higher temps are theoretically better, but on pump gas you can only run so high without detonating. Heat soak is also a major issue that the lower temp stat helps prevent- any of us that have been to a drag strip can surely vouch that lower engine temps=faster times... (I'm talking fairly stock cars on pump gas, in case one of you 900hp nitro-methane nuts decides to chime in

 

I wonder what the original question was?

Hey Eric85, just replacing the thermostat without changing the fan turn on point, does very little. I have run a stock 94 for years with this fan switch from JET and a stock thermostat.
http://store.summitracing.com/defaul...-60602&x=0&y=0

Keeps the engine cool and never gets hot as when I first bought it.

If we knew you were using OBDI controls, I would highly recommend the switch.

Oh yeah, the block sensor looks like the picture, but the wiring is totally different. There is a threaded block plug on the passenger side below the Ex manifold where the sensor goes in. The harness plugs in line with PCM. So don't go by the picture, it's not correct.

 

theory can be debated forever. dyno a car with both thermostats (fans adjusted) and see which temp the car produced more power at. Im sure its been done.