I'm trying to decide whether or not to put a 160 deg T-stat in my car, so I've been reading stuff written by folk that aren't selling T-stats. This excerpt suggests that it isn't a great idea to change it.

I got this from a website called mgcarz.com

Myth 3: "A cool engine is a happy engine"

Actually, the hotter an engine is, the more efficient it is. It makes more power, lasts longer, and uses less fuel. Remember I said that energy can either be used to turn the wheels or dumped as waste heat? Energy will tend to "follow the path of least resistance." If there is a large temperature differential between the combustion gases and the cylinder walls and head, the thermal energy in the gases will flow readily into the cool engine parts. If you reduce that temperature differential by making the engine parts hotter, less energy will flow. A hot cup of coffee in a refrigerator will cool down quickly and will cool to the temperature of the 'fridge -- a big temperature drop. On the kitchen counter, it will cool more slowly and will fall less (only to room temp). In a 200 degree oven, it won't cool at all. Same thing in your engine -- make the cylinder walls hotter and the thermal energy won't flow into them as readily. But that energy still has to go somewhere. Some will stay in the combustion gases and go out the tailpipe, but some will go into turning the wheels. So by trying to keep the engine temp low, you're throwing away perfectly good energy (and money)!

Here's what Peter Burgess, well-known MG tuning guru, says in his book "How to Power-Tune MGB 4 Cylinder Engines": "The ideal 'stat is 88 degrees Celcius (190F)." Here's what the late, great Smokey Yunick, a god of internal combustion, said in his book "Power Secrets": "It is easy to see how overheating can be a problem, but I think some racers overlook the fact that it is possible to 'overcool' the engine. Some guys go to great lengths to keep the engine temperature down to 180 degrees. And, though the engine doesn't overheat, they don't realize that they're putting energy (heat) into the cooling system that could be used to produce power at the crankshaft. Running the engine at 180 degrees will drop the overall horsepower by 2%-3%. For max power the cooling temp should be at least 200 degrees...."


Another site talked about the cooling fan on/off timing issues, and also mentioned that the modern car's computer will run A/F and spark timing values off of warm-up tables up to a certain temp (likely higher than 160 F), then will actually change to other tables when the car is at the expected operating temp, using data from O2 sensors, etc. Someone on the forum had a CEL for failing to warm up while using a cooler T-stat. Obviously, most people aren't having that problem, but it still gives me pause.

What do you guys think? Is it worth it, and what would the benefits really be anyway (less chance for predetonation, get to advance the timing a tad)?

Too much over thinking for such a simple mod. What you have to remember is the ECU will start to retard timing based on coolant temps when they reach a certain level. So, the cooler engine will allow for the most timing advance. Putting in a 160 t-stat is good and no ill effects.

Mark

Keep in mind that the thermostat-rated temperature is the temperature at which a thermostat BEGINS to open. In my case with a Gen I CTS-V the addition of a 160 T reduced operating temperature from about 190 to about 180. My CTS-V operates continusly in closed loop with no hassles at 180 or so. As for performance gains, I think they are marginal with a 160.
I also researched the subject of the ideal coolant temp, and found similar information you found. As for running a motor as hot as possible, check out writings of Smokey Yunick who advocates this - but with an entirely different type of motor.
In general I did not find a consensus as to an "ideal coolant temp". Traditionally back to the flathead Ford days tuners seemed to like 180. Seems to me that the main benefit of lower coolant temp is lower engine compartment heat, which in turn lowers intake air temp, which in turn benefits performance, particularly with a blown motor.
There seems to be no doubt that a motor likes cooler head temps, particularly around the exhaust valves. GM reversed coolant flow with the LT1 motor running coolant first to cylinder heads. With the LS motor they went back to conventional coolant routing. My understanding is that this reverse course was caused by patent infringement litigation against GM, but I cannot verify this. Whatever, the current coolant flow pattern originated many years ago with Model T ear autos which did not have water pumps at all relying on heat to flow coolant.

I have a 160* stat on my GN and a 178* stat on my C5. The C5 coolant runs at 180 to 190 in the summer. Never checked oil temps, probably should have to see if there was any effect. Not sure about the GN (poor, rudimnetary gauges). My concern with the cooler stats was that the cooler temps would not let the oil temp get hot enough to burn off contamintants and could comprimise the oil sooner

Is sludge an issue? :tisk:

I have a 160* stat on my GN and a 178* stat on my C5. The C5 coolant runs at 180 to 190 in the summer. Never checked oil temps, probably should have to see if there was any effect. Not sure about the GN (poor, rudimnetary gauges). My concern with the cooler stats was that the cooler temps would not let the oil temp get hot enough to burn off contamintants and could comprimise the oil sooner
Not to change the subject at hand, or derail the thread, but you should be running at least a "Scanmaster II" in any well heeled turbo Buick. With a 160˚ thermostat you should be running about 165˚ or so at freeway speeds and about 175˚-185˚ at slow speeds, slight hills, so forth. HTH. Look into a "Scanmaster II and at least a "Turbotweak" chip for safe tuning. Now back to our normal scheduled programming.

One other opinion...there is a huge difference between forced induction engines and normally aspirated engines as pointed out above.

When you move into the boosted arena you add lots of parameters that normally aspirated engines do not usually face. The added pressures and temperatures are a major factor. In engines that have the electronic capability to pull timing as temperatures rise (to avoid detonation) intake temperatures are critical...but usually only in extreme performance situations. If you are hot lapping without 20 or 30 minutes of cooling time at the strip, you will see ever decreasing performance due to the computer pulling timing to avoid problems. If you are cooling the engine between runs and not in high ambient temperature environments you will probably never notice the difference.

Another factor that some ignore is changing the temperature at which the fans come on. That is done in the cpm...and if you are going to use a lower thermostat, to not change the point at which the fans start, is just a half way modification.

I have mentioned this before but there are a lot of us old timers that fool the cpm by putting a resistor in the intake temperature sensor to fool the cpm into thinking the air is cooler than it actually is...this keeps the cpm from pulling timing. But the engine I do this in is a fully built (bottom up) forged engine that can withstand very high temps and extreme pressures...

Just my opinion...I am frequently wrong...as my students love to point out!:(

Back to my own experiences with a NA '05 CTS-V with a 160: My coolant temp has been reduced from around 190 to around 180. I did not alter the fan initiation settings, and see no advantage to doing so. I have run the car on highway from high 20s to high 90s outside temp; and it consistently remains around 5 degrees of 180. Before, it was consistently within 5 degrees of 190.
As for oil temperatures, they seem unchanged. My usual operating temp is around 190-195, sometimes going as high as 210. Note, I don't live in Phoenix and do not track the car, so this is just normal geezer driving.
I run a scan gauge continuously and monitor the difference between outside air temp and intake air temp. I have a cold air intake also. My results with the intake and thermostat is usually about an eleven degree temp. rise from amibient to intake at normal highway speeds. On a hot day it may go as high as 13 degrees difference. In town with stop and go the difference is considerably higher particularly on a hot day.
Seems to me that whether blown or NA intake temperature is a critical issue and anything done to reduce that temp betters performance.

At highwat speeds, fans don't matter because the ecu will turnthem off above a certain mph as the fans will actually block air instead of pulling more in. Fans are only needed for stop and go traffice and that is where you will notice a difference in turning them on sooner.

Mark

the bigger question is why mess with it.

won't improve performance, won't improve durability, won't improve mileage, won't improve service

will void some parts of warranty, may interfere with ECU calibration...

the best you can say for it - is most people seem to get away with it with no ill effects. woopee.