My Cooling Improvement Project (hopefully)
- Thread starter "Dart67"
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67dartgtgo
Well-Known Member
Fantastic shroud work. Going to try to fab one too.
BillGrissom
Well-Known Member
I'll consider that explanation more if anyone can reference an engineering text or technical paper that states it, and I don't mean rodder sites. Until then, I'll continue to understand that higher fluid velocity increases the convective heat transfer rate. Most hot rodders have only a vague understanding of the difference between temperature and heat flow, similar to how people unschooled in electronics can't distinguish current flow and voltage drop.
Charrlie_S
Well-Known Member
Not an engineer or anything close. I think it has more to do with "flow channels" through the radiator, and engine, when the coolent flow is too fast. Therefore effectivly, losing surface area. I do know in the "old" days we used to put a large "washers" in the upper hose outlet on the engine, and adjust the size of the hole to get the water flow for best cooling. In general The higher rpm the motor ran the smaller the hole needed to be. This was on circle track cars.
Another thought: Possible water pump cavation? Another thing we used to do was remove some blades from the water pump, and or drill holes in the blades.
Dorian
dorian
Sorry Bill, no engineers degree, just experience from owning a radiator shop and having that explained to me by my partner who was in the industry for 20 years and since then getting my journeyman's sheetmetal ticket and quoting my instructors who were very knowledgeable.
The "hot travels to cold" part is common knowledge in the industry.
Most people say "close that door its cold outside do you want to let winter in?" When actually you are letting the heat out. Something to do with faster moving molecules travel easier to an area with slower moving molecules.
That is how an A/C condenser works outside your house. It is just like the radiator in your car.
The "hot travels to cold" part is common knowledge in the industry.
Most people say "close that door its cold outside do you want to let winter in?" When actually you are letting the heat out. Something to do with faster moving molecules travel easier to an area with slower moving molecules.
That is how an A/C condenser works outside your house. It is just like the radiator in your car.
BillGrissom
Well-Known Member
Charrlie_S explanation makes sense. If the water pump cavitates, you will have less water flow rate, which would decrease heat transfer in the block and radiator. One would need more instrumentation, like flowmeters in the plumbing to know what is really going on. If restrictors work, by all means use them. I doubt that water flow would channel differently in the radiator at higher flows. For that to happen, the water would have to enter in a narrow, high-velocity jet. You would need a pump from a fire engine to do that in a 1.5"D hose.
AC theory is less abstract than Dorian's explanation. It cools by boiling off the refrigerant, the same as how any can pressurized with liquid (hair spray, propane) cools as you use it. Since we don't want to keep throwing refrigerant away, we condense it outside (re-compress & reject heat) and re-use in a closed cycle.
AC theory is less abstract than Dorian's explanation. It cools by boiling off the refrigerant, the same as how any can pressurized with liquid (hair spray, propane) cools as you use it. Since we don't want to keep throwing refrigerant away, we condense it outside (re-compress & reject heat) and re-use in a closed cycle.
383Duster
Well-Known Member
Guess all of the cars that run cooler after installing a restrictor when they didn't have a thermostat in them didn't go to school................
67Dart273
Well-Known Member
This doesn't prove that the coolant slowed down through the radiator---it still could have been a pump cavitation problem.
So if that really cures a problem, it may actually be for "the wrong reasoning."
All this talk about "too fast through a radiator" does indeed pretty much go against conventional heat exhanger theory.
FISHBREATH
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Interesting subject. Four factors affect conduction of heat from one area to another are:
1) The difference of temperature (delta-T) between the warmer and colder areas;
2) The length of time (t) over which the transfer occurs;
3) The area (A) in common between the warmer and colder areas; and
4) The resistance (R) to heat flow and conduction (U) between the warmer and colder areas.
Heat flows from warmer to colder areas. The greater the delta-T, the greater the rate of heat transfer; the rate is directly proportional. The amount of heat (BTU) is directly proportional to the time span of heat transfer (t). BTU/H is the amount of heat transferred in one hour. The larger the area common to the warmer and colder areas through which heat flows, the greater the rate of heat conduction. [For the same material, the same length of time, the same delta-T, the amount of heat (BTU) transferred is directly proportional to the area (A).
The rate that heat flows through a material is a function of the material's resistance to heat flow (R) or conductivity (U). Conductivity (thermal transmittance) is used in calculations.
R=1/U; U=1/R
Conductivity of a material is determined by laboratory testing; it is the amount of heat (BTU) passing through 1 square foot of a material in 1 hour with a 1 degree F temperature differential on one side of the material compared to the other.
The steady state calculation of this would be:
U=BTU/sq.ft. hour degree F
We then determine the amount of heat transferred (Q):
Q = U x A x delta-T x t
Thermodynamic engineers are also concerned about the boundary layer of air against the material because air is an insulator. You will actually see a temperature gradient on both sides of the material in a steady state condition, but it reduces dramatically with air flow across the surface of the material.
Consider a car radiator. The calculations become more involved because the condition is no longer a steady state situation, but rather one with constantly changing variables, such as water temperature, air temperature, and the rate of water and air flow.
The engineer must also be concerned about the water pump and the fan. The fan must be able to move enough air across the radiator at engine idle, but also not restrict air flow at higher miles per hour speed. The concern at higher speeds is that the fan begins to act like an aircraft propeller on a dead engine; it acts almost like a solid disc, inducing tremendous drag. This has been addressed with flexible fan blades, clutch fans, and electric fans. Most aircraft propellers can be feathered, that is turning the blades into the wind; that has not yet been accomplished on cars.
Also consider the operating range of an engine. An engine produces a specific amount of waste heat at a 500 RPM idle over time, but produces a huge amount more at 5,000 RPM per the same time. It is a simple function of physics. The cooling system must be designed to operate efficiently from one end of the range to the other.
As to the question of the necessary speed of cooling water flow through an engine, the answer can surely be calculated by a thermodynamic engineer with the necessary parameters, such as combustion chamber heat, materials, surface areas, etc. Theoretically, over a given period of time, the higher the cylinder head temperature, the more coolant is required to flow. [Aircraft with radial engines have cowl flaps to regulate cylinder head temperatures.] Also, it is not so much the rate of coolant flow through the radiator in controlling the amount of heat exchange as is the temperature differential between the coolant and the cooling air at any given time, the greatest factor being the speed of air through the radiator. Remember, it is air that must carry away the heat from the radiator.
The ideal world would be a variable speed water pump combined with a variable speed fan along with a computer, thus keeping cylinder head temperatures within a specific design range for optimum efficiency.
1) The difference of temperature (delta-T) between the warmer and colder areas;
2) The length of time (t) over which the transfer occurs;
3) The area (A) in common between the warmer and colder areas; and
4) The resistance (R) to heat flow and conduction (U) between the warmer and colder areas.
Heat flows from warmer to colder areas. The greater the delta-T, the greater the rate of heat transfer; the rate is directly proportional. The amount of heat (BTU) is directly proportional to the time span of heat transfer (t). BTU/H is the amount of heat transferred in one hour. The larger the area common to the warmer and colder areas through which heat flows, the greater the rate of heat conduction. [For the same material, the same length of time, the same delta-T, the amount of heat (BTU) transferred is directly proportional to the area (A).
The rate that heat flows through a material is a function of the material's resistance to heat flow (R) or conductivity (U). Conductivity (thermal transmittance) is used in calculations.
R=1/U; U=1/R
Conductivity of a material is determined by laboratory testing; it is the amount of heat (BTU) passing through 1 square foot of a material in 1 hour with a 1 degree F temperature differential on one side of the material compared to the other.
The steady state calculation of this would be:
U=BTU/sq.ft. hour degree F
We then determine the amount of heat transferred (Q):
Q = U x A x delta-T x t
Thermodynamic engineers are also concerned about the boundary layer of air against the material because air is an insulator. You will actually see a temperature gradient on both sides of the material in a steady state condition, but it reduces dramatically with air flow across the surface of the material.
Consider a car radiator. The calculations become more involved because the condition is no longer a steady state situation, but rather one with constantly changing variables, such as water temperature, air temperature, and the rate of water and air flow.
The engineer must also be concerned about the water pump and the fan. The fan must be able to move enough air across the radiator at engine idle, but also not restrict air flow at higher miles per hour speed. The concern at higher speeds is that the fan begins to act like an aircraft propeller on a dead engine; it acts almost like a solid disc, inducing tremendous drag. This has been addressed with flexible fan blades, clutch fans, and electric fans. Most aircraft propellers can be feathered, that is turning the blades into the wind; that has not yet been accomplished on cars.
Also consider the operating range of an engine. An engine produces a specific amount of waste heat at a 500 RPM idle over time, but produces a huge amount more at 5,000 RPM per the same time. It is a simple function of physics. The cooling system must be designed to operate efficiently from one end of the range to the other.
As to the question of the necessary speed of cooling water flow through an engine, the answer can surely be calculated by a thermodynamic engineer with the necessary parameters, such as combustion chamber heat, materials, surface areas, etc. Theoretically, over a given period of time, the higher the cylinder head temperature, the more coolant is required to flow. [Aircraft with radial engines have cowl flaps to regulate cylinder head temperatures.] Also, it is not so much the rate of coolant flow through the radiator in controlling the amount of heat exchange as is the temperature differential between the coolant and the cooling air at any given time, the greatest factor being the speed of air through the radiator. Remember, it is air that must carry away the heat from the radiator.
The ideal world would be a variable speed water pump combined with a variable speed fan along with a computer, thus keeping cylinder head temperatures within a specific design range for optimum efficiency.
"Dart67"
Well-Known Member
Well, I finally got a chance today to take the Vert for a drive to test my cooling mods.
The temps were not as warm as I would have liked for a really good test.
It was around 75* to 78* and the air was pretty damp, we had rain moving in.
We drove the car at varying speeds and loads so that the F.A.S.T. XFI 2.0 would learn. The roads here are very curvy and hilly.
The first leg of the trip was 10 miles. The car held a steady 192*. We stopped and let the car idle while we saved the log and started a new log for the trip home. While stopped the car climbed to 198* then up to 203*.
The return trip was the same 10 miles back home and same type of driving. The last mile to the house is a narrow , curvy, hilly blacktop road so that part of the trip is not much over idle.
When we turned off the road for the last 1000 feet to the shop, the temp was still 203*. By the time we got to the shop the temp had climbed to 206* and on shut down heat soaked to 210*.
All in all much better then the 240*,250* and at times 260* temps I was seeing before the mods.
I think some if not a lot of the temps being a little high at the end of the trip are due to the F.A.S.T. XFI 2.0 not being tuned properly, but at least now I can drive the car and let it tune where I could not before.
I need to learn how to tune the system beyond the self tune on the fuel tables.
I may try to build another shroud from aluminum and mount and install the duel 11" Spall fans and see what happens.
Herb
The temps were not as warm as I would have liked for a really good test.
It was around 75* to 78* and the air was pretty damp, we had rain moving in.
We drove the car at varying speeds and loads so that the F.A.S.T. XFI 2.0 would learn. The roads here are very curvy and hilly.
The first leg of the trip was 10 miles. The car held a steady 192*. We stopped and let the car idle while we saved the log and started a new log for the trip home. While stopped the car climbed to 198* then up to 203*.
The return trip was the same 10 miles back home and same type of driving. The last mile to the house is a narrow , curvy, hilly blacktop road so that part of the trip is not much over idle.
When we turned off the road for the last 1000 feet to the shop, the temp was still 203*. By the time we got to the shop the temp had climbed to 206* and on shut down heat soaked to 210*.
All in all much better then the 240*,250* and at times 260* temps I was seeing before the mods.
I think some if not a lot of the temps being a little high at the end of the trip are due to the F.A.S.T. XFI 2.0 not being tuned properly, but at least now I can drive the car and let it tune where I could not before.
I need to learn how to tune the system beyond the self tune on the fuel tables.
I may try to build another shroud from aluminum and mount and install the duel 11" Spall fans and see what happens.
Herb
I remember the big block Chrysler station wagons with a/c had a smaller water pump pulley than cars without a/c....and reading a circle track article one evening, it was discussing adding (3) 3/16 hole around the edge of the thermostat to increase the flow of water back to the radiator for additional cooling...might be worth a try...
"Dart67"
Well-Known Member
abody, Tech857, Thanks for the input.
The thermostat has bleed holes drilled and is a high flow 160*.
The thermostat is not the problem.
Herb
The thermostat has bleed holes drilled and is a high flow 160*.
The thermostat is not the problem.
Herb
/6 Matt
30 Degrees Crooked
I think you're 160 thermostat is the problem. It opens too soon and the water just keeps flowing throughoutt the radiator not giving the water time to cool. Hence the high idle temps. Try a 180 for ***** and giggles.
I was using a high flow tstat and found that in cooler weather it was never really closed. Engine took too long to warm up. But any way Dart67 when trying to figure out cooling issues I like to see what the temp of the lower hose is like. This time of year around here the lower hose on my dart stays pretty cool as the radiator is able to get rid of mostly all of the heat. If your lower hose is as hot as the upper then you need more radiator or more air flow to get rid of the heat. Or tune till your putting out less heat if your running too lean or what not. Ive read throught this whole thread and it seems you've done everything right. Fans shroud ect. I've got a large 19" flex fan with 6 or 7 huge blades on it. Its off of some other old mopar. It moves a ton of air at idle with no shroud. It does a lot better than the smaller 18" clutch fan with shroud that was stock on my car.
67Dart273
Well-Known Member
Sorry, these "theories" about water through the rad too fast are just ....not.....
bremereric
Well-Known Member
[quote="Dart67";1969969068]Well, I finally got a chance today to take the Vert for a drive to test my cooling mods.
The temps were not as warm as I would have liked for a really good test.
It was around 75* to 78* and the air was pretty damp, we had rain moving in.
We drove the car at varying speeds and loads so that the F.A.S.T. XFI 2.0 would learn. The roads here are very curvy and hilly.
The first leg of the trip was 10 miles. The car held a steady 192*. We stopped and let the car idle while we saved the log and started a new log for the trip home. While stopped the car climbed to 198* then up to 203*.
The return trip was the same 10 miles back home and same type of driving. The last mile to the house is a narrow , curvy, hilly blacktop road so that part of the trip is not much over idle.
When we turned off the road for the last 1000 feet to the shop, the temp was still 203*. By the time we got to the shop the temp had climbed to 206* and on shut down heat soaked to 210*.
All in all much better then the 240*,250* and at times 260* temps I was seeing before the mods.
I think some if not a lot of the temps being a little high at the end of the trip are due to the F.A.S.T. XFI 2.0 not being tuned properly, but at least now I can drive the car and let it tune where I could not before.
I need to learn how to tune the system beyond the self tune on the fuel tables.
I may try to build another shroud from aluminum and mount and install the duel 11" Spall fans and see what happens.
Herb[/quote]Baby steps Herb. Before you pay out big cash for the Spall fans check out a $116.00 Ford Contour SVT factory fan.
The temps were not as warm as I would have liked for a really good test.
It was around 75* to 78* and the air was pretty damp, we had rain moving in.
We drove the car at varying speeds and loads so that the F.A.S.T. XFI 2.0 would learn. The roads here are very curvy and hilly.
The first leg of the trip was 10 miles. The car held a steady 192*. We stopped and let the car idle while we saved the log and started a new log for the trip home. While stopped the car climbed to 198* then up to 203*.
The return trip was the same 10 miles back home and same type of driving. The last mile to the house is a narrow , curvy, hilly blacktop road so that part of the trip is not much over idle.
When we turned off the road for the last 1000 feet to the shop, the temp was still 203*. By the time we got to the shop the temp had climbed to 206* and on shut down heat soaked to 210*.
All in all much better then the 240*,250* and at times 260* temps I was seeing before the mods.
I think some if not a lot of the temps being a little high at the end of the trip are due to the F.A.S.T. XFI 2.0 not being tuned properly, but at least now I can drive the car and let it tune where I could not before.
I need to learn how to tune the system beyond the self tune on the fuel tables.
I may try to build another shroud from aluminum and mount and install the duel 11" Spall fans and see what happens.
Herb[/quote]Baby steps Herb. Before you pay out big cash for the Spall fans check out a $116.00 Ford Contour SVT factory fan.
"Dart67"
Well-Known Member
Eric,
I already have the fans. I had them on the old crossflow radiator.
I just need to fab a new shroud/mount for them.
Herb
I already have the fans. I had them on the old crossflow radiator.
I just need to fab a new shroud/mount for them.
Herb
I also think installing a 180 or even a 190 will help. It might be the best $10 you ever spent.
72BBSwinger
Well-Known Member
I went from a 160 to a 180 and it is staying that way. Thinking you will keep any BB mopar at 160 degrees on the street is stupid. So why have a stat that opens before 180-190 when those are realistic operating temps?
furyus2
Well-Known Member
I didn't see anything about the radiator cap pressure rating. may want to try a cap with a higher rating.
"Dart67"
Well-Known Member
I just got back from a 26 mile round trip to the gas station and back.
The temp is 91* and high humidity.
On the way to the station the car held 206* when we stopped fro fuel and shut down it went to 226*.
I blocked the hood scoop intakes for the trip home temp only dropped to 221*.
I stopped about 3miles down the road and removed the scoop blocks and the temp dropped to 216* for the rest of the trip home.
Considering the FAST XFI is not tuned well and the IAC is not working, I am sure that the radiator is working.
I think I now need to work on air flow and the tuning issues.
I will have to send my XFI ECU back to FAST to have the IAC drivers repaired.
For now I am going to go back to a carb temporarily.
Herb
The temp is 91* and high humidity.
On the way to the station the car held 206* when we stopped fro fuel and shut down it went to 226*.
I blocked the hood scoop intakes for the trip home temp only dropped to 221*.
I stopped about 3miles down the road and removed the scoop blocks and the temp dropped to 216* for the rest of the trip home.
Considering the FAST XFI is not tuned well and the IAC is not working, I am sure that the radiator is working.
I think I now need to work on air flow and the tuning issues.
I will have to send my XFI ECU back to FAST to have the IAC drivers repaired.
For now I am going to go back to a carb temporarily.
Herb
BillGrissom
Well-Known Member
[quote="Dart67";1969981904]
...
I will have to send my XFI ECU back to FAST to have the IAC drivers repaired.
For now I am going to go back to a carb temporarily.
Herb[/quote]
You should run this by FAST before returning the system. I don't see how the IAC could cause it to overheat. The IAC controls air flow to the motor. The computer will sense that (via MAP, then O2 sensor) and add the appropriate fuel to keep the mixture proper. The result is that your idle speed will be too high, but it will not run lean.
If you don't believe this, try a simple test on any of your modern cars. Pull the vacuum hose off the brake booster, which simulates a stuck-open IAC valve. The engine will speed up, but will still run smooth, without the shaking of a lean condition.
...
I will have to send my XFI ECU back to FAST to have the IAC drivers repaired.
For now I am going to go back to a carb temporarily.
Herb[/quote]
You should run this by FAST before returning the system. I don't see how the IAC could cause it to overheat. The IAC controls air flow to the motor. The computer will sense that (via MAP, then O2 sensor) and add the appropriate fuel to keep the mixture proper. The result is that your idle speed will be too high, but it will not run lean.
If you don't believe this, try a simple test on any of your modern cars. Pull the vacuum hose off the brake booster, which simulates a stuck-open IAC valve. The engine will speed up, but will still run smooth, without the shaking of a lean condition.
This goes along with the air dam, but did you close off the under side of the car from the rear of the radiator support all the way to the front of the K member? Believe it or not, this will help direct even more air through the radiator. Look at any new car with a small grill. There are no openings in that area. All kinda little plactic shields and such. Just an idea.
"Dart67"
Well-Known Member
Bill,
I did not say that the IAC was causing the higher temps.
I was trying to say that due to the poor state of my incomplete tune that the engine is still running on the lean side contributing to the higher temps.
There is a problem with the FAST XFI box.
It is throwing a Stayus 12 code which is "Thermal Overload".
According to the FAST Tech Forum, that means the IAC driver curcuit in the box is bad and needs repair.
With the IAC not functioning the car is very hard to drive due to idle problems caused by having no throttle follower.
When coming off a crusie condition on slow down or at a stop light. The throttle close to quick and the engine will die.
Herb
I did not say that the IAC was causing the higher temps.
I was trying to say that due to the poor state of my incomplete tune that the engine is still running on the lean side contributing to the higher temps.
There is a problem with the FAST XFI box.
It is throwing a Stayus 12 code which is "Thermal Overload".
According to the FAST Tech Forum, that means the IAC driver curcuit in the box is bad and needs repair.
With the IAC not functioning the car is very hard to drive due to idle problems caused by having no throttle follower.
When coming off a crusie condition on slow down or at a stop light. The throttle close to quick and the engine will die.
Herb
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