Paradigm Shift: Run A/C to keep your engine cool!
#1
09-10-2009, 09:49 AM
Join Date: Mar 2005
Location: All over the Central U.S.
Posts: 3,616
Paradigm Shift: Run A/C to keep your engine cool!
Driving through the mountains of Nevada and California, you may have seen the signs on the mountain grades that say: "Avoid Overheat - Turn off A/C".
Presumably, and based on conventional wisdom, running the A/C puts more load on the engine, an engine that may be near capacity already to maintain highway speeds on a steep grade, in the desert, in summer.
THE REVERSE IS TRUE FOR THE FEH!
RUN THE A/C to keep your FEH engine cooler! Why?
The FEH has electric radiator fans, not engine driven.
The FEH has variable speed fans ( well, I think 3 speed fans, low, med, high )
Below 198 degrees inferred water temp. the fans DO NOT RUN!
Then, presumably, they come on at preset intervals for low, med, high but I've not found those intervals in my own FEH.
However, running the A/C will force the fans on to HIGH speed at any water temperature. Thus, you can "pre cool" and give your radiator water a "head start" before you get on a hill and exceed 198 degrees.
I discovered this while towing over the long weekend, which required A/C during the daylight hours, and not at night.
My water temp while towing during the day ( 85'F OAT ) was about 188 to 190'F while the A/C was on. At night ( 65'F OAT ) my water temp was 198 to 204'F while the A/C was off.
So the conclusion I draw is: A/C cools the engine, too!
Presumably, and based on conventional wisdom, running the A/C puts more load on the engine, an engine that may be near capacity already to maintain highway speeds on a steep grade, in the desert, in summer.
THE REVERSE IS TRUE FOR THE FEH!
RUN THE A/C to keep your FEH engine cooler! Why?
The FEH has electric radiator fans, not engine driven.
The FEH has variable speed fans ( well, I think 3 speed fans, low, med, high )
Below 198 degrees inferred water temp. the fans DO NOT RUN!
Then, presumably, they come on at preset intervals for low, med, high but I've not found those intervals in my own FEH.
However, running the A/C will force the fans on to HIGH speed at any water temperature. Thus, you can "pre cool" and give your radiator water a "head start" before you get on a hill and exceed 198 degrees.
I discovered this while towing over the long weekend, which required A/C during the daylight hours, and not at night.
My water temp while towing during the day ( 85'F OAT ) was about 188 to 190'F while the A/C was on. At night ( 65'F OAT ) my water temp was 198 to 204'F while the A/C was off.
So the conclusion I draw is: A/C cools the engine, too!
#2
09-10-2009, 12:10 PM
Re: Paradigm Shift: Run A/C to keep your engine cool!
How can you turn a engine sideways and have a engine driven fan? I'd guess that most all FWD have electric fans. That's why you can walk by a parked car and hear the fan still running!
#3
09-10-2009, 07:15 PM
Ridiculously Active Enthusiast
Join Date: Sep 2006
Location: Beautiful Pacific NW
Posts: 1,678
Re: Paradigm Shift: Run A/C to keep your engine cool!
Driving through the mountains of Nevada and California, you may have seen the signs on the mountain grades that say: "Avoid Overheat - Turn off A/C".
Presumably, and based on conventional wisdom, running the A/C puts more load on the engine, an engine that may be near capacity already to maintain highway speeds on a steep grade, in the desert, in summer.
You have this just a teeny bit wrong.
Running the A/C results in the A/C condensor PRE-HEATING the already HOT airflow that's needed to cool the engine coolant in the "downstream" radiator, and therefore increases the risk of engine coolant overheating.
THE REVERSE IS TRUE FOR THE FEH!
RUN THE A/C to keep your FEH engine cooler! Why?
The FEH has electric radiator fans, not engine driven.
The FEH has variable speed fans ( well, I think 3 speed fans, low, med, high )
Below 198 degrees inferred water temp. the fans DO NOT RUN!
Then, presumably, they come on at preset intervals for low, med, high but I've not found those intervals in my own FEH.
However, running the A/C will force the fans on to HIGH speed at any water temperature. Thus, you can "pre cool" and give your radiator water a "head start" before you get on a hill and exceed 198 degrees.
I discovered this while towing over the long weekend, which required A/C during the daylight hours, and not at night.
My water temp while towing during the day ( 85'F OAT ) was about 188 to 190'F while the A/C was on. At night ( 65'F OAT ) my water temp was 198 to 204'F while the A/C was off.
So the conclusion I draw is: A/C cools the engine, too!
Presumably, and based on conventional wisdom, running the A/C puts more load on the engine, an engine that may be near capacity already to maintain highway speeds on a steep grade, in the desert, in summer.
You have this just a teeny bit wrong.
Running the A/C results in the A/C condensor PRE-HEATING the already HOT airflow that's needed to cool the engine coolant in the "downstream" radiator, and therefore increases the risk of engine coolant overheating.
THE REVERSE IS TRUE FOR THE FEH!
RUN THE A/C to keep your FEH engine cooler! Why?
The FEH has electric radiator fans, not engine driven.
The FEH has variable speed fans ( well, I think 3 speed fans, low, med, high )
Below 198 degrees inferred water temp. the fans DO NOT RUN!
Then, presumably, they come on at preset intervals for low, med, high but I've not found those intervals in my own FEH.
However, running the A/C will force the fans on to HIGH speed at any water temperature. Thus, you can "pre cool" and give your radiator water a "head start" before you get on a hill and exceed 198 degrees.
I discovered this while towing over the long weekend, which required A/C during the daylight hours, and not at night.
My water temp while towing during the day ( 85'F OAT ) was about 188 to 190'F while the A/C was on. At night ( 65'F OAT ) my water temp was 198 to 204'F while the A/C was off.
So the conclusion I draw is: A/C cools the engine, too!
#4
09-10-2009, 07:46 PM
Re: Paradigm Shift: Run A/C to keep your engine cool!
Can't say this holds true for "all" Ford engines but I've read, maybe in the Ford WorkShop Manual if the PCM detects excessive engine heat it will shut down some cylinders till the temperature drops. Just wonder how'd that would work while going up some mountains or other loads like towing and it overheats a bit. Will it cut engine power???? Nice time for that to happen!!
#5
09-11-2009, 06:52 AM
Join Date: Mar 2005
Location: All over the Central U.S.
Posts: 3,616
Re: Paradigm Shift: Run A/C to keep your engine cool!
My Grandfather had a 1985 Dodge car with electric fans.
So they've been used a long time.
FWIW, I've tried my HARDEST to get the FEH to overheat and no matter how hard I try, it won't go past 20x degrees.
Only way to overheat, I suspect, is to lose fluid. Or have some catastrophic failure.
To a point, a warmer engine is better though.
#6
09-11-2009, 08:56 AM
Re: Paradigm Shift: Run A/C to keep your engine cool!
I didn't mean to imply the FEH was unique in having electric fans. Sorry.
My Grandfather had a 1985 Dodge car with electric fans.
So they've been used a long time.
FWIW, I've tried my HARDEST to get the FEH to overheat and no matter how hard I try, it won't go past 20x degrees.
Only way to overheat, I suspect, is to lose fluid. Or have some catastrophic failure.
To a point, a warmer engine is better though.
My Grandfather had a 1985 Dodge car with electric fans.
So they've been used a long time.
FWIW, I've tried my HARDEST to get the FEH to overheat and no matter how hard I try, it won't go past 20x degrees.
Only way to overheat, I suspect, is to lose fluid. Or have some catastrophic failure.
To a point, a warmer engine is better though.
WWest is correct, that's why a ICE's temperature was raised from 180F to 210F max, to improve combustion.
#7
09-11-2009, 10:10 AM
Ridiculously Active Enthusiast
Join Date: Sep 2006
Location: Beautiful Pacific NW
Posts: 1,678
Re: Paradigm Shift: Run A/C to keep your engine cool!
Can't say this holds true for "all" Ford engines but I've read, maybe in the Ford WorkShop Manual if the PCM detects excessive engine heat it will shut down some cylinders till the temperature drops. Just wonder how'd that would work while going up some mountains or other loads like towing and it overheats a bit. Will it cut engine power???? Nice time for that to happen!!
#8
09-11-2009, 02:59 PM
Join Date: Mar 2005
Location: All over the Central U.S.
Posts: 3,616
Re: Paradigm Shift: Run A/C to keep your engine cool!
If the car was severely hot, then I would hope the electric fans would be on "high" speed already, so the A/C would not be needed as a trigger to get the fans on "high".
One thing I am quite positive of is, the A/C does NOT go off if the car is at WOT. I've confirmed this in my 2005 at least. *exception
*If A/C is on to the cabin, WOT will not turn it off. If however, A/C is on just for the battery pack ( in the 75-95'F range ) then WOT will turn off the A/C.
You think it would be the reverse, but nope. You would think the battery would have priority over the humans, but nope. Or it was a program error only for 2005, so I'd be curious to hear from owners of later models.
One thing I am quite positive of is, the A/C does NOT go off if the car is at WOT. I've confirmed this in my 2005 at least. *exception
*If A/C is on to the cabin, WOT will not turn it off. If however, A/C is on just for the battery pack ( in the 75-95'F range ) then WOT will turn off the A/C.
You think it would be the reverse, but nope. You would think the battery would have priority over the humans, but nope. Or it was a program error only for 2005, so I'd be curious to hear from owners of later models.
#9
09-11-2009, 06:22 PM
Re: Paradigm Shift: Run A/C to keep your engine cool!
Having watched this one for a few days I have some thoughts.
Given that increased air flow through the radiator produced by running an electric fan or two will produce a lower coolant temperature, there are some errors in the thinking.
1st - The idea that an electric fan, of the same flow capability as a belt driven one, doesn't use as much or more engine power than a belt driven fan is wrong. It has to use more engine power because of the additional energy conversions involved and the power comes from the engine.
2nd - Some how the laws of thermodynamics seem to be repealed in at least one FEH. If the A/C is producing any cooling at all it will raise the engine coolant temperature proportionately because the A/C condenser is first and its output air is the input air to the engine radiator.
So if the A/C is running the engine is producing more power so its internal temps are higher. Thermodynamics is like that.
I believe that the only basis for the temps reported is the fact that the fans come on increasing air flow. Not a bad trick to have in your bag of tricks... but keep in mind that in most cases you are increasing engine power to do that.
The real issue is where is the thermostat set? The thermostat is set to produce efficient combustion by regulating the coolant temperature to a desired point.
Given that increased air flow through the radiator produced by running an electric fan or two will produce a lower coolant temperature, there are some errors in the thinking.
1st - The idea that an electric fan, of the same flow capability as a belt driven one, doesn't use as much or more engine power than a belt driven fan is wrong. It has to use more engine power because of the additional energy conversions involved and the power comes from the engine.
2nd - Some how the laws of thermodynamics seem to be repealed in at least one FEH. If the A/C is producing any cooling at all it will raise the engine coolant temperature proportionately because the A/C condenser is first and its output air is the input air to the engine radiator.
So if the A/C is running the engine is producing more power so its internal temps are higher. Thermodynamics is like that.
I believe that the only basis for the temps reported is the fact that the fans come on increasing air flow. Not a bad trick to have in your bag of tricks... but keep in mind that in most cases you are increasing engine power to do that.
The real issue is where is the thermostat set? The thermostat is set to produce efficient combustion by regulating the coolant temperature to a desired point.
#10
09-11-2009, 07:08 PM
Join Date: Mar 2005
Location: All over the Central U.S.
Posts: 3,616
Re: Paradigm Shift: Run A/C to keep your engine cool!
FYI What I stated ( using the A/C to keep the engine cooler ) will obviously lower your MPG. It is obvious, so obvious, I'm surprised Bill Whiney felt he needed to point this out. Did someone suggest an electric fan uses less gas?
I don't see it on here. Bill???
I have always said ( and 5 years of posts prove this ) that laws of physics do apply to the FEH. I'm usually one of the first to point that out. Sorry Bill, I didn't think you needed a reminder.
Second, I never stated this is recommended to do. It is just information I'm making available. If you were about to climb a long hill, perhaps while towing, it might be advantagous to start at the bottom of the hill at 188'F vs. 206'F.
You can do that by "pre cooling" before getting to the hill.
Third, this "trick" might be helpful in unusual circumstances, like if you are having car trouble, or, if by chance your coolent level is low, and you are not in a position to add more, this might just "get you by".
Fourth, the FEH has very good self preservation modes.
If the engine did get too hot, it would, if all is well, turn the fans on itself.
It is up to each individual to decide the usefullness, if any of this particular effect. I just thought it was nice to point it out to others.
I don't see it on here. Bill???
I have always said ( and 5 years of posts prove this ) that laws of physics do apply to the FEH. I'm usually one of the first to point that out. Sorry Bill, I didn't think you needed a reminder.
Second, I never stated this is recommended to do. It is just information I'm making available. If you were about to climb a long hill, perhaps while towing, it might be advantagous to start at the bottom of the hill at 188'F vs. 206'F.
You can do that by "pre cooling" before getting to the hill.
Third, this "trick" might be helpful in unusual circumstances, like if you are having car trouble, or, if by chance your coolent level is low, and you are not in a position to add more, this might just "get you by".
Fourth, the FEH has very good self preservation modes.
If the engine did get too hot, it would, if all is well, turn the fans on itself.
It is up to each individual to decide the usefullness, if any of this particular effect. I just thought it was nice to point it out to others.
