Motor Thermostat question

[winmag4582001]

I have a 2010 E350, 5.4L
Temp gauge seems to always run a hair below TDC.
Could I put in a 185 degree thermostat to lower the running temp a bit?
Or will that mess with the computer?
Thanks

[86Scotty]

I wouldn't think it would matter to the computer but why bother? Do you have any other symptoms like slow heat?

I would plug in a Scangauge or other OBDII reader or just buy a digital temp gauge and see where you really are first. If you're hovering around 190 to 200 with normal driving you're just fine. Those dummy gauges really don't tell you anything.

[boywonder]

Originally Posted by winmag4582001

I have a 2010 E350, 5.4L
Temp gauge seems to always run a hair below TDC.
Could I put in a 185 degree thermostat to lower the running temp a bit?
Or will that mess with the computer?
Thanks

Putting a lower temp thermostat won't reduce the running temp...it will just open sooner if the stock thermostat is set higher. The engine still makes the same amount of heat when running; the total volume of coolant and size of the radiator determines the running temp.

On a slightly other note.............there are several measures of efficiency for an internal combustion engine..volumetric efficiency, thermal efficiency, etc.

From a thermodynamic standpoint, internal combustion engines are heat engines (gasoline engines follow the otto cycle and diesel engines follow the diesel cycle).

That being said the higher the temperature difference between the engine and ambient the higher the thermal efficiency, which means more power output. Today's engine's are limited in max temp by the materials they are made of, properties of motor oil, etc. Some day we may have ceramic engines that can run way hotter.

...so that's one reason why radiator caps pressurize the coolant above ambient....to allow the coolant to stay liquid (for heat transfer) and allow the engine to run hotter for a given amount of coolant....same way pressure cookers work on the stove.

These engines are great heat engines; most of the 115,000 BTU's in a gallon of gas (139,000 BTUs in a gallon of diesel) ends up going out the radiator, a small percentage of the heat energy in a gallon of fuel actually spins the wheels.


In case anyone is interested.....

Otto cycle

https://en.wikipedia.org/wiki/Otto_cycle


Diesel cycle

https://en.wikipedia.org/wiki/Diesel_cycle

[ShuttlePilot]

Boywonder, nice explanation there. If I may add to your post. Most engines gas or diesel today under a certain temperature are in a very different "run mode" than when up to temperature. Things like spark timing, fuel injector pulse, boost pressure, etc are configured in a way that generate a lot of heat at the expense of power to the wheels to get the engine up to temperature as fast a possible. Depending on engine type, this warm up algorithm isn't the most healthy to be in for an extended period of time. So, if someone was to say have a large/efficient radiator, chose a thermostat that was to close to that set temp or even had a stuck on fan in the winter you could be in that warm up mode a lot. Not only would you probably lose a lot of fuel mileage and power but could set up a cascade of part failures. And that would be the worst part, potentially a lot of part failures. When I first got my 6.0 PSD it was unnerving to see how warm it's normal range was until I learned that is what it's designed to be. I had to let go of my old gas V8 idea of 190 degrees is normal no mater what. My recommendation is have a big efficient radiator, preferably all aluminum, clean and specified coolant, a radiator cap that you know is working at the specified pressure, and a thermostat at the factory temperature. You wont go wrong.

-Eric

[winmag4582001]

Thank you for the replies. All your responses make sense. All my vehicles have been either way old or under warranty. This is the first vehicle I've had that is in that "mid" age range.

On a side note: Factory trans cooler vs. after market. Is my factory 11 row trans cooler sufficient or should I upgrade to a Tru-Cool Transmission Cooler 24,000 GVW 20,500 BTU?

[boywonder]

Originally Posted by winmag4582001

Is my factory 11 row trans cooler sufficient or should I upgrade to a Tru-Cool Transmission Cooler 24,000 GVW 20,500 BTU?

I'm asking myself that question a lot lately....seems like you are aware of the recent trans cooler thread...do you tow anything?

Folks here have typically updated to the 40,000 BTU Tru-cool cooler.....

I'm considering that or perhaps the 13 row HD factory cooler (on ebay new for around $60-$70).....I have a 5.4L and only tow a tiny open motorcycle trailer....

Do you have a means of knowing what your trans temp is?

[boywonder]

Here is some very relevant thermal efficiency info from a wiki:


The second paragraph touches on the efficiency differences between gas and diesel engines......gasoline (otto cycle) engines suffer large frictional losses (throttling losses) at less than wide open throttle (WOT). Since diesels don't have throttles, they don't have these losses.

The frictional and pumping losses are losses in volumetric efficiency....


Modern gasoline engines have a maximum thermal efficiency of about 25% to 30% when used to power a car. In other words, even when the engine is operating at its point of maximum thermal efficiency, of the total heat energy released by the gasoline consumed, about 70-75% is rejected as heat without being turned into useful work, i.e. turning the crankshaft.[1] Approximately half of this rejected heat is carried away by the exhaust gases, and half passes through the cylinder walls or cylinder head into the engine cooling system, and is passed to the atmosphere via the cooling system radiator.[2] Some of the work generated is also lost as friction, noise, air turbulence, and work used to turn engine equipment and appliances such as water and oil pumps and the electrical generator, leaving only about 25-30% of the energy released by the fuel consumed available to move the vehicle.




At idle, the thermal efficiency is zero, since no usable work is being drawn from the engine. At low speeds, gasoline engines suffer efficiency losses at small throttle openings from the high turbulence and frictional (head) loss when the incoming air must fight its way around the nearly closed throttle; diesel engines do not suffer this loss because the incoming air is not throttled. At high speeds, efficiency in both types of engine is reduced by pumping and mechanical frictional losses, and the shorter period within which combustion has to take place. Engine efficiency peaks in most applications at around 75% of rated engine power, which is also the range of greatest engine torque (e.g. in most modern passenger automobile engines with a redline of about 6,000 RPM, maximum torque is obtained at about 4,500 RPM, and maximum engine power is obtained at about 6,000 RPM). At all other combinations of engine speed and torque, the thermal efficiency is less than this maximum.

[winmag4582001]

I'll be occationally towing a 2500lb enclosed trailer. I do live in Colorado and I70 through the mountains eats thousands of trannys a year.
I'm curious to know how warm other peoples trans get with the factory cooler.
My 95 Bronco's factory cooler was way too small, even for normal driving. Just a simple drive from Denver to Leadville would get the trans hot enough to boil your soda if you left it in the cup holder. Installed the biggest cooler NAPA had and it helped. Some.

I should also note that I'm a van virgin.

[ShuttlePilot]

Originally Posted by winmag4582001

I should also note that I'm a van virgin.

We all were at some point. Don't worry about it.

Yes, having a larger transmission cooler can be the answer to keeping trans temps lower. But I wanted to mention about locking torque converters. I'm going to take a leap in assuming gas vans have locking torque converters like the diesels do. Torque converters by nature can produce a lot of heat in the trans fluid when under a heavy load. Like climbing Vail Pass. Put simply vehicle manufacturers have added a clutch or lock in the torque converter to hard couple the engine and trans thus eliminating any slip in the torque converter. This helps get more energy (think horse power) to the drive wheels which increases economy and performance. On many, not sure all, a computer is controlling when this clutch/lock locks or uncouples based on driving conditions. A slipping torque converter (which is desirable in certain conditions) is putting a lot of energy(heat) into to the trans fluid which has to be removed by the trans cooler to the air. So a way to reduce the amount of heat that is put into the fluid in the first place is to drive as much as possible with the converter locked. I have an engine monitor (Edge Insight but there are many others) that shows when the torque converter is locked or not. Watching that I can change throttle position or turn off over drive a tad early on a climb to keep the converter locked. Which is getting the power down to the ground and keeping my fluid temp from rising as much. I'm not sure if this was the best explanation but I hope it helps.

-Eric

[Bbasso]

Informative guys!
As for trans cooler, I run a smallish one just to remove excess heat for those rare occasions and add some longevity to the trans fluid. ( ie. Service intervals)
I've yet to see a problem from a cool trans VS overheated.