OVERHEATING
"Ok, one more time. I use the term YOU in the general sense, not as in YOU personally.
You have a fixed cooling medium temperature to work with. That’s ambient temperature. So for ***** and giggles we’ll say that’s from about 20-110 degrees Fahrenheit.
That’s ALL you get.
Again, for ***** and giggles we’ll say you love to run your engine at 195 degrees.
Now we have the temperatures we are working with.
So, let’s say that it’s a 60 degree day and you are rolling down the road at 195 degrees. You have a 135 degree temperature difference between ambient and coolant temperature. Assuming you have a 195 degree thermostat it is partially closing at some points to maintain your 195 degree temperature.
On a 100 degree day, you now only have a 95 degree temperature difference. You have less ability to remove heat from the coolant. Now the thermostat is wide open all the time and the coolant temp climbs to 205 degrees because the ONLY thing the thermostat does is set the MINIMUM coolant temperature.
Now you come on here and say my engine overheats at 205 on hot days. One response is it’s not overheating. And that’s true. It’s isn‘t OVER heating but it’s too hot. IMO 195 is too hot for a performance engine but that’s another topic for another post. And you just don’t want the engine at 205 degrees.
The other stock in trade answer is what you gave. Slow the coolant down so it stays in the radiator longer. Obviously at first blush that makes perfect sense. But it’s DEAD wrong.
Since (in this example) we are dealing with a 95 degree temperature difference (I should be saying delta but you get the point) the longer the coolant stays in the radiator, the longer the coolant stays in the engine. And when the coolant stays in the engine longer, it picks up more heat. Since you only have a 95 degree temperature difference, the coolant staying in the radiator doesn‘t do a pinch of **** of good. In fact, it’s *** backwards.
Think it through. The coolant is in the block longer, so it picks up more heat. The radiator just can’t shed any more heat no matter how much longer the coolant stays in it because the difference in temperature between ambient and what is coming out of the engine isn’t enough to effect a coolant temperature change.
That’s exactly what happens and it shows up in the difference in coolant temperature at the gauge and the temperature rating of the thermostat.
If your cooling system is running at peak performance your temperature should be at or within 5 or no more than 10 degrees of what the thermostat rating.
How many times do we see guys running a 180 thermostat but the gauge (assuming the gauge is accurate) says 200??? All the time.
Thats an example of what happens when you don’t have enough air flow, coolant flow or both.
Again, thinking it through and now understanding that keeping the coolant in the radiator longer also means the coolant stays in the engine longer, collecting more heat we can now look at the other side of the equation.
We speed up the coolant (and if you are running a mechanical fan you are speeding up the fan too which is a GOOD thing most of the time) so that the coolant isn’t in the engine as long, and since it’s not in the engine as long the coolant has a lower temperature going to the radiator.
Now we give the radiator a better temperature difference (lower coolant temperature out of the block requires LESS heat to be removed by the radiator and ambient temperature) to allow the system to shed heat.
I can’t make it any more plain than that. Leaving the coolant in the radiator longer means that same coolant stays in the engine longer and therefore is picking up more heat that the radiator and ambient temperatures have to deal with.
If you are constantly running at ambient temperatures of say 80 degrees or lower then you can have more errors in the system and not pay for it.
But, if you don’t want 190 plus degree coolant temperatures (I don’t, it’s too hot for performance) then it’s even more critical to get the coolant out of the engine sooner to the temperature difference is as great as it can be.
We can’t control ambient temperatures but we can control how long the coolant stays in the engine, how big and how many (or how few) cores the radiator has and how fast we turn the water pump (which controls along with the thermostat how long the coolant stays in the engine and radiator) and all that controls the operating temperature of the engine.
So the TL;DR is speed up the coolant and let the thermostat set the minimum operating temperature and the radiator and ambient temperature control maximum operating temperature."
Uhhh.......
************************************************************************************************************************
"Never. like in Never never never...
Ok, made up example time bear with me... this is a long one :)
- you have a supply of water at 80*C , you have at your disposal a beer can and a themomenter and a watch. ambient temperaure is 20*C and stays at that throughout.
- you have a requirment for a beer cans worth of water at 40*C so you fill your beer can, put in the thermometer and you wait. it takes 1/2 an hour to cool to 40*C
- you do it again, takes half an hour
- you do it agian takes half an hour
water it seems takes a while to cool... a measureable time... quite a long time
-some kinda constant is at play here 80* water in a beer can takes 1/2 an hour to cool to 40...
- if you need a beer can quantity of 40* water every half an hour...all is well.. life is good
your requrements for 40* water change suddenly you decide you need it more often...
- so you fill your can
- you wait 15 minutes
- and you know what? when you empty it at 15 minutes the water that comes out is at 60*C
- you fill the can and wait 15 minutes and the water after 15 minutes is 60*C
- 60*C water is NOT your requirment, you appear to want a beer cans worth of water at 40*C every 15 minutes.
- changeing the speed at which the can is filled and which it is emptied has done you no good what so ever. the water is still at 60*
What can we do... well i could give you another beer can, you can offset the filling by 15 minutes and have 40* water every 15 min, because you now have the luxury of 2 cans and can have them both cooling for 30 minutes... when one is at 40 you empty and refill while the other still has 15 minutes to get from 60 down to 40, but that involves an increase in capacity because an increase in flow didn't help.
increase the no. of cans and you get what you want, is the gist
take it further
the water is supplied to you at 80* by a bizzare little combustion engine with a magic pump that spits the full motor content when it reaches 80* and then every 1/2 hour. The motor has an 80* themostat that snaps open at 80* and shut again at 79*.
-It runs at constant load
- it has 1 beer cans worth of water in it as coolant
- it dumps this water when it reaches 80* into a beer can
- we fill up motor with water at 40*
- you have 2 cans one emptied into the motor and one cooling
- the motor produces enough heat energy in 1/2 an hour to take 40* water to 80* water in the motor. but as luck would have it it also takes 1/2 an hour for the 80* water that it spits out to cool in a beer can to 40*.
basicaly every 1/2 hour i catch a can full of 80* water as the thermostat opens and i put it asside and let it cool
and ive emptied in, my previous can full, that is now at 40* to cool the motor
My motor temperature varies from somwhere over 40* up to 80* over a half hour period
and the process repeats every half hour for ever.
-Mr Rat Basid comes over to give some advice.
-he tells me ive done it all wrong
-so we give him an identical motor, 2 cans and let him do his thing
-he set his motor up so that it pumps the water out by force every 15 minutes
- once it gets up to 80*c his dumpes water out at 15 minute intervals
- he is of course constrained by his Can/radiator so the water he puts back in is at 60*
- but its only in there 15 minutes NOT 30
- to all intents and purposes all is good... the motor produces enough heat energy to take a can full of water from 40-80 in 1/2 an hour BUT
- we move the water every 15 minutes, a time in which the motor produces 1/2 the heat energy that it can, and a time in which it takes our Can/radiator to lose half the heat energy in the water
Motor runs great.
Mr Bastid suggests a dyno comp
-my motor and his motor under exactly the same load as they are now
-My motor shows some variance it doesn't produce as much power when in the 40-60*range but matches Mr Bastids for output when in the 60* to 80* range
- Mr Basid is quite rightly pleased and says "I sure whupped Yer *** boy..." "I am RIGHT" Etc etc
- and its true this type of motor produces best power when running in the 60* to 80* range
- he pumped faster and got more consistent power than i did ..
So if swapping out the cans at 15 miutes gets us more power lets get silly
lets swap em out every minute i.e dramaticlaly increase the pumping speed into and out of our Can/Radiator
- under same load
- at water reaching 80* it pukes into a can
- we leave the can to cool and refill motor with contents of last can
-we have to do this every minute
- its a bit of a chore
-Can cools for 1 minute
-we loose 1 1/3rd of a degree while it cools in its can
-water going back in is at 78 2/3 *
-its in there for 1 minute and it gains 1 and 1/3 degree
well blow me motor still runs nice, Mr Basid is well chuffed, he's doing a lttle dance...."smug bastid" says me.
we could do the other extream and never change the water. motor runs for a hour and reaches 160*c before seizing not good...
but woithout being too silly everything is fine, until we increase the load on the engines.
as we increase the load, kinda like drving up a hill, i have to swap my cans on my 1/2 hour engine a little more often, but still have time to stand back and observe Mr bastid who granted has his two "pump Faster" motors to look after
on the 15 minute motor he's swapping cans more regularly but as his motor swings only from 60 to 80 rather than 40 to 80 hes doing it every 7minutes and the water going back in is at 70* not 60
On the 1 minute motor disaster has alredy struck themal melt down due to constantly feeding it 80* water
speeding up pumping removed flexibity it removed the margin that allows the heat output of the motor to vary with load..
in the extream case we had no tollernace for load variation at all...I hope Mr Bastid didn't scald his fingers.. i'm sure i can find a cold beer can to help if he did
some benefit is seen from a performance point of view but assumes contstant load (stationary engine like a generator) or short term use, maybe applicable in some drag race categories..
The OP is trying to drive on the street with a Hotted Up combination and drag race gears
in my opinion 2 choices
slow down the pump... results in a higher average running temperaure but less chance of overheat
or get a bigger can/radiator
(but actually my view in his case is that his cooling system is ok and its igntion or fueling related )
speeding up the pump reduces flexibility and moves you closer to the type of thermal run away he already sees, Unless you massivly increase the number of cans i.e double the radiator capcity....
Mr Bastid maintains that cooler motors make more power...
No.... cooler motors wear out faster and suffer from bore wash
on a basic level to make a chemical reaction faster you add heat
this is applicable to burning fuel in oxygen as well as most other reactions
as such in an ideal world you need a cool dense charge with good fuel atomisation, no clods and hevay droplets... and a hot motor
the charge, as much as possible needs to be as dense and cool as possible to get in as much as possible, then heat it so it properly vapourises under the red hot exhaust valve so it is at the highest temperature and pressure it can be, without pre igntion, before the spark lights it off... running the motor cooler reduces this effect and you make less power.
Modern ECU controlled motors run hotter due to superlative intake charge control. running hotter increases efficiency and emissions due to the additional expansion of the charge before igntion due to heat absorbtion and keeping the CAT at appropriate temp.
slapping the lowest value thermosstat in your motor hurts output...sort your problem with changes to mixtre or timeing curve
exmaple
you take a standard iron motor
dyno it.. get a base line
you make an identical set of heads from aluminium
you swap rockers and plugs across, strap on your aluminium cloned heads
dyno it
the coolant heats up quicker
the plugs foul up
torque and max BHP are lower
The combustion chambers, the valves, the plugs run measurably cooler
aluminium is a much better conductor of heat energy that cast iron so it sucks the heat out of the exhaust valve out of the body of the plug and out of the chamber faster
it dumps the heat into the coolant faster
the radiator might run hotter but the engine is running cooler and the only way to get your power back is to increase cylinder pressure
and the only way to do that is take increase the static CR
the heat you had in the iron motor played a part in its output that was lost when the aluminium heads were bolted on
Its not real world becsue Aluminium heads rarely if ever clone an iron design in all dimensions.
Basically if you are going to drive on the street with a standard pump and a mopar like standard radiator you need to run that pump at the speed it was built for
if the motor now spends its life running on average at a higher RPM than it was ever designed for, gear the pump to run at its designed for, speed
if you have radiator the size of texas and the motor just needs to stay cool for 10 seconds and 1/4 of a mile you can do what ya like but why are you carrying around so much coolant when every lb of weight in the car hurts your ET....
This is why i think i'm right.... i could still be wrong and i can't say Mr bastid is wrong becasue he's got dyno slips for this that and the other coming out of his *** and i don't....
but his assertion that water staying in the block longer is bad and water staying in the radiator longer is bad makes no sense to me, there is a balance to be found based on radiator size, pump capcity, pump speed and the amount of heat energy produce by the motor.
the standard set up was designed to work in alaska and canada and in the desert if you overheat, look elsewhere first.
in cases where that motor is winding faster and its being used on the street the pump running too fast is a more likley candidate for causing an issue than it running too slow
too fast just speeds up a poistive feedback loop of "too hot" coolant back into the block."
What?
"Ok, one more time. I use the term YOU in the general sense, not as in YOU personally.
You have a fixed cooling medium temperature to work with. That’s ambient temperature. So for ***** and giggles we’ll say that’s from about 20-110 degrees Fahrenheit.
That’s ALL you get.
Again, for ***** and giggles we’ll say you love to run your engine at 195 degrees.
Now we have the temperatures we are working with.
So, let’s say that it’s a 60 degree day and you are rolling down the road at 195 degrees. You have a 135 degree temperature difference between ambient and coolant temperature. Assuming you have a 195 degree thermostat it is partially closing at some points to maintain your 195 degree temperature.
On a 100 degree day, you now only have a 95 degree temperature difference. You have less ability to remove heat from the coolant. Now the thermostat is wide open all the time and the coolant temp climbs to 205 degrees because the ONLY thing the thermostat does is set the MINIMUM coolant temperature.
Now you come on here and say my engine overheats at 205 on hot days. One response is it’s not overheating. And that’s true. It’s isn‘t OVER heating but it’s too hot. IMO 195 is too hot for a performance engine but that’s another topic for another post. And you just don’t want the engine at 205 degrees.
The other stock in trade answer is what you gave. Slow the coolant down so it stays in the radiator longer. Obviously at first blush that makes perfect sense. But it’s DEAD wrong.
Since (in this example) we are dealing with a 95 degree temperature difference (I should be saying delta but you get the point) the longer the coolant stays in the radiator, the longer the coolant stays in the engine. And when the coolant stays in the engine longer, it picks up more heat. Since you only have a 95 degree temperature difference, the coolant staying in the radiator doesn‘t do a pinch of **** of good. In fact, it’s *** backwards.
Think it through. The coolant is in the block longer, so it picks up more heat. The radiator just can’t shed any more heat no matter how much longer the coolant stays in it because the difference in temperature between ambient and what is coming out of the engine isn’t enough to effect a coolant temperature change.
That’s exactly what happens and it shows up in the difference in coolant temperature at the gauge and the temperature rating of the thermostat.
If your cooling system is running at peak performance your temperature should be at or within 5 or no more than 10 degrees of what the thermostat rating.
How many times do we see guys running a 180 thermostat but the gauge (assuming the gauge is accurate) says 200??? All the time.
Thats an example of what happens when you don’t have enough air flow, coolant flow or both.
Again, thinking it through and now understanding that keeping the coolant in the radiator longer also means the coolant stays in the engine longer, collecting more heat we can now look at the other side of the equation.
We speed up the coolant (and if you are running a mechanical fan you are speeding up the fan too which is a GOOD thing most of the time) so that the coolant isn’t in the engine as long, and since it’s not in the engine as long the coolant has a lower temperature going to the radiator.
Now we give the radiator a better temperature difference (lower coolant temperature out of the block requires LESS heat to be removed by the radiator and ambient temperature) to allow the system to shed heat.
I can’t make it any more plain than that. Leaving the coolant in the radiator longer means that same coolant stays in the engine longer and therefore is picking up more heat that the radiator and ambient temperatures have to deal with.
If you are constantly running at ambient temperatures of say 80 degrees or lower then you can have more errors in the system and not pay for it.
But, if you don’t want 190 plus degree coolant temperatures (I don’t, it’s too hot for performance) then it’s even more critical to get the coolant out of the engine sooner to the temperature difference is as great as it can be.
We can’t control ambient temperatures but we can control how long the coolant stays in the engine, how big and how many (or how few) cores the radiator has and how fast we turn the water pump (which controls along with the thermostat how long the coolant stays in the engine and radiator) and all that controls the operating temperature of the engine.
So the TL;DR is speed up the coolant and let the thermostat set the minimum operating temperature and the radiator and ambient temperature control maximum operating temperature."
Uhhh.......
************************************************************************************************************************
"Never. like in Never never never...
Ok, made up example time bear with me... this is a long one :)
- you have a supply of water at 80*C , you have at your disposal a beer can and a themomenter and a watch. ambient temperaure is 20*C and stays at that throughout.
- you have a requirment for a beer cans worth of water at 40*C so you fill your beer can, put in the thermometer and you wait. it takes 1/2 an hour to cool to 40*C
- you do it again, takes half an hour
- you do it agian takes half an hour
water it seems takes a while to cool... a measureable time... quite a long time
-some kinda constant is at play here 80* water in a beer can takes 1/2 an hour to cool to 40...
- if you need a beer can quantity of 40* water every half an hour...all is well.. life is good
your requrements for 40* water change suddenly you decide you need it more often...
- so you fill your can
- you wait 15 minutes
- and you know what? when you empty it at 15 minutes the water that comes out is at 60*C
- you fill the can and wait 15 minutes and the water after 15 minutes is 60*C
- 60*C water is NOT your requirment, you appear to want a beer cans worth of water at 40*C every 15 minutes.
- changeing the speed at which the can is filled and which it is emptied has done you no good what so ever. the water is still at 60*
What can we do... well i could give you another beer can, you can offset the filling by 15 minutes and have 40* water every 15 min, because you now have the luxury of 2 cans and can have them both cooling for 30 minutes... when one is at 40 you empty and refill while the other still has 15 minutes to get from 60 down to 40, but that involves an increase in capacity because an increase in flow didn't help.
increase the no. of cans and you get what you want, is the gist
take it further
the water is supplied to you at 80* by a bizzare little combustion engine with a magic pump that spits the full motor content when it reaches 80* and then every 1/2 hour. The motor has an 80* themostat that snaps open at 80* and shut again at 79*.
-It runs at constant load
- it has 1 beer cans worth of water in it as coolant
- it dumps this water when it reaches 80* into a beer can
- we fill up motor with water at 40*
- you have 2 cans one emptied into the motor and one cooling
- the motor produces enough heat energy in 1/2 an hour to take 40* water to 80* water in the motor. but as luck would have it it also takes 1/2 an hour for the 80* water that it spits out to cool in a beer can to 40*.
basicaly every 1/2 hour i catch a can full of 80* water as the thermostat opens and i put it asside and let it cool
and ive emptied in, my previous can full, that is now at 40* to cool the motor
My motor temperature varies from somwhere over 40* up to 80* over a half hour period
and the process repeats every half hour for ever.
-Mr Rat Basid comes over to give some advice.
-he tells me ive done it all wrong
-so we give him an identical motor, 2 cans and let him do his thing
-he set his motor up so that it pumps the water out by force every 15 minutes
- once it gets up to 80*c his dumpes water out at 15 minute intervals
- he is of course constrained by his Can/radiator so the water he puts back in is at 60*
- but its only in there 15 minutes NOT 30
- to all intents and purposes all is good... the motor produces enough heat energy to take a can full of water from 40-80 in 1/2 an hour BUT
- we move the water every 15 minutes, a time in which the motor produces 1/2 the heat energy that it can, and a time in which it takes our Can/radiator to lose half the heat energy in the water
Motor runs great.
Mr Bastid suggests a dyno comp
-my motor and his motor under exactly the same load as they are now
-My motor shows some variance it doesn't produce as much power when in the 40-60*range but matches Mr Bastids for output when in the 60* to 80* range
- Mr Basid is quite rightly pleased and says "I sure whupped Yer *** boy..." "I am RIGHT" Etc etc
- and its true this type of motor produces best power when running in the 60* to 80* range
- he pumped faster and got more consistent power than i did ..
So if swapping out the cans at 15 miutes gets us more power lets get silly
lets swap em out every minute i.e dramaticlaly increase the pumping speed into and out of our Can/Radiator
- under same load
- at water reaching 80* it pukes into a can
- we leave the can to cool and refill motor with contents of last can
-we have to do this every minute
- its a bit of a chore
-Can cools for 1 minute
-we loose 1 1/3rd of a degree while it cools in its can
-water going back in is at 78 2/3 *
-its in there for 1 minute and it gains 1 and 1/3 degree
well blow me motor still runs nice, Mr Basid is well chuffed, he's doing a lttle dance...."smug bastid" says me.
we could do the other extream and never change the water. motor runs for a hour and reaches 160*c before seizing not good...
but woithout being too silly everything is fine, until we increase the load on the engines.
as we increase the load, kinda like drving up a hill, i have to swap my cans on my 1/2 hour engine a little more often, but still have time to stand back and observe Mr bastid who granted has his two "pump Faster" motors to look after
on the 15 minute motor he's swapping cans more regularly but as his motor swings only from 60 to 80 rather than 40 to 80 hes doing it every 7minutes and the water going back in is at 70* not 60
On the 1 minute motor disaster has alredy struck themal melt down due to constantly feeding it 80* water
speeding up pumping removed flexibity it removed the margin that allows the heat output of the motor to vary with load..
in the extream case we had no tollernace for load variation at all...I hope Mr Bastid didn't scald his fingers.. i'm sure i can find a cold beer can to help if he did
some benefit is seen from a performance point of view but assumes contstant load (stationary engine like a generator) or short term use, maybe applicable in some drag race categories..
The OP is trying to drive on the street with a Hotted Up combination and drag race gears
in my opinion 2 choices
slow down the pump... results in a higher average running temperaure but less chance of overheat
or get a bigger can/radiator
(but actually my view in his case is that his cooling system is ok and its igntion or fueling related )
speeding up the pump reduces flexibility and moves you closer to the type of thermal run away he already sees, Unless you massivly increase the number of cans i.e double the radiator capcity....
Mr Bastid maintains that cooler motors make more power...
No.... cooler motors wear out faster and suffer from bore wash
on a basic level to make a chemical reaction faster you add heat
this is applicable to burning fuel in oxygen as well as most other reactions
as such in an ideal world you need a cool dense charge with good fuel atomisation, no clods and hevay droplets... and a hot motor
the charge, as much as possible needs to be as dense and cool as possible to get in as much as possible, then heat it so it properly vapourises under the red hot exhaust valve so it is at the highest temperature and pressure it can be, without pre igntion, before the spark lights it off... running the motor cooler reduces this effect and you make less power.
Modern ECU controlled motors run hotter due to superlative intake charge control. running hotter increases efficiency and emissions due to the additional expansion of the charge before igntion due to heat absorbtion and keeping the CAT at appropriate temp.
slapping the lowest value thermosstat in your motor hurts output...sort your problem with changes to mixtre or timeing curve
exmaple
you take a standard iron motor
dyno it.. get a base line
you make an identical set of heads from aluminium
you swap rockers and plugs across, strap on your aluminium cloned heads
dyno it
the coolant heats up quicker
the plugs foul up
torque and max BHP are lower
The combustion chambers, the valves, the plugs run measurably cooler
aluminium is a much better conductor of heat energy that cast iron so it sucks the heat out of the exhaust valve out of the body of the plug and out of the chamber faster
it dumps the heat into the coolant faster
the radiator might run hotter but the engine is running cooler and the only way to get your power back is to increase cylinder pressure
and the only way to do that is take increase the static CR
the heat you had in the iron motor played a part in its output that was lost when the aluminium heads were bolted on
Its not real world becsue Aluminium heads rarely if ever clone an iron design in all dimensions.
Basically if you are going to drive on the street with a standard pump and a mopar like standard radiator you need to run that pump at the speed it was built for
if the motor now spends its life running on average at a higher RPM than it was ever designed for, gear the pump to run at its designed for, speed
if you have radiator the size of texas and the motor just needs to stay cool for 10 seconds and 1/4 of a mile you can do what ya like but why are you carrying around so much coolant when every lb of weight in the car hurts your ET....
This is why i think i'm right.... i could still be wrong and i can't say Mr bastid is wrong becasue he's got dyno slips for this that and the other coming out of his *** and i don't....
but his assertion that water staying in the block longer is bad and water staying in the radiator longer is bad makes no sense to me, there is a balance to be found based on radiator size, pump capcity, pump speed and the amount of heat energy produce by the motor.
the standard set up was designed to work in alaska and canada and in the desert if you overheat, look elsewhere first.
in cases where that motor is winding faster and its being used on the street the pump running too fast is a more likley candidate for causing an issue than it running too slow
too fast just speeds up a poistive feedback loop of "too hot" coolant back into the block."
What?