Electric Water Pumps & Rear Mounted Radiators

[Jimbo]

Part of my job is understanding fluid dynamics and cooling isn't about flow rates it's about temperature differentials. Everytime i've taken the thermostat out it's run wayyyy colder due to the increased flow without the annular restriction of a thermostat. I've NEVER had it run hotter without a thermostat. We have to consider drill bit cooling when we design a drill string and pump rates. And every calculator i've ever used assumes higher rates of flow increase cooling.

First you say it has nothing to do with flow (all about temp differentials) and then you say increasing flow makes it cooler!!!

[rockcrawler31]

Part of my job is understanding fluid dynamics and cooling isn't about flow rates it's about temperature differentials. Everytime i've taken the thermostat out it's run wayyyy colder due to the increased flow without the annular restriction of a thermostat. I've NEVER had it run hotter without a thermostat. We have to consider drill bit cooling when we design a drill string and pump rates. And every calculator i've ever used assumes higher rates of flow increase cooling.

First you say it has nothing to do with flow (all about temp differentials) and then you say increasing flow makes it cooler!!!

You're right, i'm not a wordsmith and i didn't articulate very well. I don't really know the best way to describe how it was taught to me, but if you take the analogy of the coolant just being a method of picking up and moving the heat, and then go to extremes then it makes more sense.

zero flow = zero transfer eventually the water in the block will have picked up all the heat it can before it boils and there is no differential between the block and the coolant hence no more cooling

motza flow = as soon as the coolant has picked up a little bit of temperature there is a brand new bit of coolant in its place that has a higher differential (i.e. it's cooler straight from the radiator)

fark me. i'm glad i decided to be a driller and not an english teacher. Besides, shouldn't you be talking to lawyers instead of browsing gen tech??

[ludacris]

If you are in the left side of the graphs, you need to look at your water pump. If you are in the right hand side (but still having overheating issues) then your blue line is too close to your green line (or is above it) and you need to look at air flow, rad size, etc.

This is what led me to think about the rad. All the water is doing is moving the heat to another spot, flow rates or otherwise.

If the engine produces more heat than the radiator can cope with it will over heat.
If the rad is larger than the heat produced it will cope with the heat load until something else reduces efficiency. Blocked rads, airflow, sticking thermostats reducing flow, positive air pressure pockets limiting flow and so on

As an aside, is the temp guage working properly? i recently thought the motor was running hot but the VDO guage or sender wasn't working properly (so much for VDO being the ducks guts.) It was reading 104 and when i put a laser temp reader on the rad it was reading 75 degrees and at the back of the block (traditionally the hottest part of the 1HZ and where the sender is) was reading 84 degrees.

We are using the factory temp sender and haltec computer for temp.

Cris

[Jimbo]

I have been to lawyer and at $260/hr i dont want to ring her and have a chat about the weather!

I cant be bothered explaining but chimps last post does a good job of it.

[its aford not a nissan]

Itsaford... on reflection I am not sure whether what you think I'm saying, and what I'm actually saying, are the same thing. If you look at the original post, Ludacris got advice that the "the water maybe flowing too fast", causing his engine to get too hot. I am saying this advice is wrong and suggested he should be looking at his airflow.

If you think that Ludacris's engine may be getting too hot because his water pump(s) are flowing too much coolant, please say so as otherwise I am not sure what the discussion is.

.

there is 2 possibilities that i can see
1st
, if everything else is fine with his engine ie: no leaky head gaskets , blockages any where , and has sufficient air flow through his radiator ,then what im trying to say is that his thermostat is opening too early , and as the motor is working hard it is producing more and more heat thus it is opening the thermostat more and more to try and get more cooled coolant in to maintain the opening temp of the thermostat , so basicly the hotter the engine , the more open the thermostat is ,the more open the thermostat the faster the coolant flows through the radiator , pretty much what it all is suposed to do . now the thermostat has an opening temp , lets say 82 deg , and a fully open temp which is around 10 to 15 deg higher , say 95 deg , if the coolant temp gets too close to 95 deg or above then the thermostat isnt controling the coolant temp any more and the coolant is soley relying on air flow to take the heat out , now his air flow is fixed and doesnt vary , this fixed airflow can only remove a set amount of heat and seeing as the coolant is flowing very quickly through the radiator , the airflow cant remove enough heat fast enough as the coolant is being replaced too fast

now as to Why the coolant got too hot in the first place ? this is harder for me to put into words describing how , the easiest way to describe it is it wants to run hotter , or by the time the coolant circulates through the motor it is already hotter than the opening temp of the thermostat ( increased flow inside the motor may help here , remember that the coolant is always recirculating inside the motor )

the other possibility or a combination of both
2nd
considering his radiators are rear mounted and his thermofans are automaticly switched to come on a a set temp say 84 deg then he has roughly 10 odd liters of coolant that is already at around 80 deg that has to pass through the motor that is already probly at 86 /88 deg and rising , this happening will only make the thermostat open faster , leaving the thermo fans on or setting them to come on at a much lower temp may stop this cycle before it is out of control,

what i would do is fit the highest cfm thermofan to a shrowd so they suck the air through the entire radiator , have the thermofans switch on at around 50 deg or always on , and see how that goes , if it still heats up too much ( over 100 deg then i would fit a hotter thermostat , if yours is 82 deg try one at 90 deg , the hotter thermostat basicly increases the temperature difference between ambient air and the coolant , the bigger the difference the easier it is for the air to remove a higher percentage of heat


if you want i can come down to your place and give you a hand ( ludacris ) and report the findings ( good or bad ) here

[ludacris]

Itsaford... on reflection I am not sure whether what you think I'm saying, and what I'm actually saying, are the same thing. If you look at the original post, Ludacris got advice that the "the water maybe flowing too fast", causing his engine to get too hot. I am saying this advice is wrong and suggested he should be looking at his airflow.

If you think that Ludacris's engine may be getting too hot because his water pump(s) are flowing too much coolant, please say so as otherwise I am not sure what the discussion is.

.

there is 2 possibilities that i can see
1st
, if everything else is fine with his engine ie: no leaky head gaskets , blockages any where , and has sufficient air flow through his radiator ,then what im trying to say is that his thermostat is opening too early , and as the motor is working hard it is producing more and more heat thus it is opening the thermostat more and more to try and get more cooled coolant in to maintain the opening temp of the thermostat , so basicly the hotter the engine , the more open the thermostat is ,the more open the thermostat the faster the coolant flows through the radiator , pretty much what it all is suposed to do . now the thermostat has an opening temp , lets say 82 deg , and a fully open temp which is around 10 to 15 deg higher , say 95 deg , if the coolant temp gets too close to 95 deg or above then the thermostat isnt controling the coolant temp any more and the coolant is soley relying on air flow to take the heat out , now his air flow is fixed and doesnt vary , this fixed airflow can only remove a set amount of heat and seeing as the coolant is flowing very quickly through the radiator , the airflow cant remove enough heat fast enough as the coolant is being replaced too fast

now as to Why the coolant got too hot in the first place ? this is harder for me to put into words describing how , the easiest way to describe it is it wants to run hotter , or by the time the coolant circulates through the motor it is already hotter than the opening temp of the thermostat ( increased flow inside the motor may help here , remember that the coolant is always recirculating inside the motor )

the other possibility or a combination of both
2nd
considering his radiators are rear mounted and his thermofans are automaticly switched to come on a a set temp say 84 deg then he has roughly 10 odd liters of coolant that is already at around 80 deg that has to pass through the motor that is already probly at 86 /88 deg and rising , this happening will only make the thermostat open faster , leaving the thermo fans on or setting them to come on at a much lower temp may stop this cycle before it is out of control,

what i would do is fit the highest cfm thermofan to a shrowd so they suck the air through the entire radiator , have the thermofans switch on at around 50 deg or always on , and see how that goes , if it still heats up too much ( over 100 deg then i would fit a hotter thermostat , if yours is 82 deg try one at 90 deg , the hotter thermostat basicly increases the temperature difference between ambient air and the coolant , the bigger the difference the easier it is for the air to remove a higher percentage of heat


if you want i can come down to your place and give you a hand ( ludacris ) and report the findings ( good or bad ) here

I might take you up on this but first I will do some testing on Saturdays run and see how we go. I like the idea of turning the fans on a lot earlier and upgrading to a higher temp thermostate.

Cris

[chimpboy]

Itsaford - I don't want to shock you but I agree with most of what you wrote.

what i would do is fit the highest cfm thermofan to a shrowd so they suck the air through the entire radiator , have the thermofans switch on at around 50 deg or always on , and see how that goes

Good call, but since...

Is the puller in a cowl or is it hard up against the rad? Just personally I would try leaving off the two smaller fans and mounting the larger fan in a cowl such that it is pulling air through the entire radiator. It would be a bit of work though if you currently have it hard against the rad.

I would also try ditching the electric pump and just running the mechanical one.

And then I would kind of take it from there, but I would probably not have fans both in front of and behind the rad.

Just some thoughts.

... which is almost the same fricking thing, wasn't it a bit harsh to say I was giving bad advice and posting "dribble"?

BTW the other good thing about a hotter thermostat is that it will probably improve fuel economy a little.

[its aford not a nissan]

sorry but the " dribble " i was refering to was

" the faster the coolant flows through the total circuit the more efficient the cooling system will be."

this part i dont agree with , i wasnt dissagreeing with the other advise , just this bit as i believe the opposite , atleast through the radiator


sorry if i came across as attacking you whole heartedly

[PGS 4WD]

Couple of things I've noticed over the years of performance cars and in particular my 5.7 LS1 Turbo Patrol that has nproven itself i n long and short course events.

Firstly don't rely only on the fans, I had a roof scoop that pushed air through the radoator at speed, unlkie most rear mounted fans, mine didn't need to run at cruise.
If you remove the thermostat the likely hood of boiling is greater as the pump generates pressure against the thermostat, even when open the thermostat is open it poses enough restriction for the pump to produce 3-4 psi pressure in the block and heads reducing the likelyhood of spontaneous boiling in dirty little hot spots.
Electric pumps are great because, if air gets into your system and you go up a big hill, the mechanical pump will quite likely cavitate and you will loose cooling as it is the high point, a rear electric pupm will still be immersed and continue to pump. Also if you loose a drive belt and the belt driven pump stops you can still complete a stage without killing and engine.

I have witnessed many occasions where removal of the thermostat reduced cooling, particularly on the Cleveland V8, where fitment of a high flow thermostat cooled the engine better than no thermostat.

Avoid setting the fans at 50 degrees if you can, look at where the air is coming from and make sure you are not negating fan air flow with the normal eddy current at the back of the cab.

Joel

[chimpboy]

sorry but the " dribble " i was refering to was

" the faster the coolant flows through the total circuit the more efficient the cooling system will be."

this part i dont agree with , i wasnt dissagreeing with the other advise , just this bit as i believe the opposite , atleast through the radiator


sorry if i came across as attacking you whole heartedly

No problem. I can't work out why it frustrates me so much that you won't agree with something so basic and obvious, but I am slowly getting over it

[its aford not a nissan]

sorry but the " dribble " i was refering to was

" the faster the coolant flows through the total circuit the more efficient the cooling system will be."

this part i dont agree with , i wasnt dissagreeing with the other advise , just this bit as i believe the opposite , atleast through the radiator


sorry if i came across as attacking you whole heartedly

No problem. I can't work out why it frustrates me so much that you won't agree with something so basic and obvious, but I am slowly getting over it

dont worry i used to think exactly the same way as you do now and for the most part it worked ,but it did cost some power some times with increased fan speeds when needed , but there was a few cars where i couldnt solve the issue no matter what i did , then i had my own issues with running hot and i was stumped again and everything i did made it worse , colder thermostat , holes in thermostat , no thermostat , locked up fan etc , none helped and just made it run hot faster , this is when i realised that the colder i tried to make it run the hotter it would get , so by reasoning if i made it run hotter maybe it will run cooler or stop over heating , i got the thermostat that had no holes in it , pulled the little pin out that opens it and ground a couple of mm off it basicly makeing it a 90 deg thermostat , sure it ran hotter on the guage ( 1/2 way instead of 1/4 ) but that is where it stayed , i know the coolant had slowed down in the radiator because the fan hardly ever locked up anymore ( fitted my good fan back in ) where previously it was always locked up , this has worked every time so far that i have tried it , but i always get met with hesitation as no one believes me that running the car hotter will stop it overheating , but thats my aim " to stop it OVERheating " and i believe a motor running 10 degress hotter constantly is better for it that having the temp fluctuate 20 plus deg

so thats my reasoning " if you were interested "

[chimpboy]

I don't see any issues with running a hotter thermostat to keep temps stable (within reason) but I don't see what it has to do with the fact that more coolant flow gets you a more efficient cooling system.

[its aford not a nissan]

I don't see any issues with running a hotter thermostat to keep temps stable (within reason) but I don't see what it has to do with the fact that more coolant flow gets you a more efficient cooling system.

how i see it

given a set volume of water that is constantly being heated , you pump that water through a radiator which has air flowing through it at say 3000cfm the air has a limit of how much heat it can remove , lets say 50 percent of heat is removed , coolant enters at 80 deg and exits the radiator at 40 deg and say we draw a line down the center of the radiator and the temp would be 60 deg , now we increase the coolant flow, the line down the center of the radiator isnt at 60 deg any more, the 60 deg line is moving towards the radiator outlet and the temp at the outlet is rising , increasing the fan speed normally compensates for this but air isnt as good of a conductor of heat as water is , if you work it out roughly it takes 3000cfm of air to cool 30 cfm of coolant at a set temp ( figures are an approximate ) , now speed up the coolant flow by 10% to 33 cfm the fan would roughly have to draw 3300 cfm of air but im sure if i get the thermal transfer rates and work it out it would require more air flow ,

now slow down the coolant in the radiator and the 60 deg line is moving closer to the inlet side of the radiator and the temp at the outlet is closer to ambient air temp thus removing a higher percentage of heat from the coolant , slow down the coolant even more then it requires less airflow to remove the heat , the temp at the outlet of the radiator is much cooler and the motor requires less cooled coolant to maintain temps due to the greater difference in temp

different radiators may be more efficient at removing heat ( bigger surface area , larger capacity etc) but increasing coolant flow without increasing airflow subsantially more wont make it more efficient, increasing air flow would use more power generating more heat ( beit not that much but still does)

and if we are talking thermo fans where the air flow is fixed then slowing down the coolant is more important

[Ruffy]

Two major issues which need to be addressed here..
The first is an understanding of latent heat.
Chimpboy i am only going to have one attempt at this and i don't expect a reply if you still fail to understand.
Coolant CAN flow too fast through a cooling system. There IS an optimal speed for the coolant to travel. The optimal speed for the coolant to travel is at the point when the ENTIRITY of the coolant in the engine is at approx 85% saturation of heat. This means that all the coolant has absorbed heat and will be cooled as it passes through the radiator.
If the coolant flows too slow it will saturate and therefore before the heated water exits the engine it has absorbed too much heat and is struggling to take on more causing overheating issues.
If the coolant flows too fast then the coolant that doesn't come incontact with the engine block/head hasn't absorbered anywhere near enough heat and continues to absorb heat from the hotter water which is obviously inefficient as the water entering the radiator has already cooled since leaving the engine.
To try and give an example would be to say if you flow water through a 50mm pipe at high speed with a flame around the pipe obviously the water contacting the pipe absorbs the heat first and then the central of the water absorbs heat from the hotter water around the outside of the pipe. If you slowed the flow then the water would have a greater amount of time to absorb the heat. This is not a theory, it's a fact.
Secondly.. Having fans that push and pull can be detrimental to the flow of air rather than aid it. If the air being pushed is getting pushed it at a greater rate than the air being drawn through the you actually create a pressure difference between the two fans and that acts as a restriction slowing the air flow. If the push fan is pushing less than the pull fan then the pull fan has to work harder to draw the air through the slower spinning fan...

[Wendle]

My buggy might be a good example for you Ludacris. I have a Commodore V6 that used to overheat occasionally in my old buggy with the radiator in the front and the mechanical pump only.
In my current buggy I have the radiator in the rear with an electric pump and the mechanical pump still running. With the same radiator and fan I was running before the engine runs probably a little too cold.
I pulled the guts out of the thermostat so it just has the outer cage type section installed.
The electric and mechanical pumps can definitely work well together.


EDIT: Just noticed this is in "Trips and Tracks" WTF?

[chimpboy]

given a set volume of water that is constantly being heated , you pump that water through a radiator which has air flowing through it at say 3000cfm the air has a limit of how much heat it can remove , lets say 50 percent of heat is removed , coolant enters at 80 deg and exits the radiator at 40 deg and say we draw a line down the center of the radiator and the temp would be 60 deg , now we increase the coolant flow, the line down the center of the radiator isnt at 60 deg any more, the 60 deg line is moving towards the radiator outlet and the temp at the outlet is rising

The hotter the radiator is the more heat the air can remove, so 3000cfm doesn't have a limit of how much heat it can remove as such. If the radiator is cold then the air removes little heat, if the rad is at 10 degrees hotter than the air it removes a bit of heat, if the rad is 20 degrees hotter the air removes twice as much heat, and so on. If you don't believe me think of it as the air getting colder, rather than the radiator getting hotter - obviously colder air does a better job of cooling than hotter air, it works the other way too (when it's the radiator that gets hotter instead of the air getting colder). In other words just as "cold air removes heat better", "a hot radiator sheds heat better" because it's the temp difference that matters (airflow matters because it indirectly affects the temp difference, it is removing hot air and replacing it with cold air).

To try and give an example would be to say if you flow water through a 50mm pipe at high speed with a flame around the pipe obviously the water contacting the pipe absorbs the heat first and then the central of the water absorbs heat from the hotter water around the outside of the pipe. If you slowed the flow then the water would have a greater amount of time to absorb the heat. This is not a theory, it's a fact.

That is a good analogy. It's true that if you flow the water faster then the water will remove less heat per litre (or cc or whatever you like) of water. But it will remove more heat per second. Focus on the pipe for a second: if you flow the water faster, the pipe will be cooler.

lol welcome to Trips and Tracks!

[ludacris]

How did this end up in trips and tracks. I am sure I started this thread in General Chit Chat.

Any how took the truck for a good run today and temp sat on 85 and crepped up to 98 on a long uphill drive and held itself at 98 then once at the top brought it self back down to 85. I am still going to remove the 3 thermos and replace them with au twins which will make the system more efficient. Thanks for your advise peoples. I think we have all learnt something from this thread. Especially me.

Cris

[Struth]

Yes why is this in trips and tracks.

It is good tech once you can work out who is right and who is wrong (I haven't worked that out yet).

But my theories on cooling engines have been challenged, my thoughts were always that the water should remain in the radiator and subject to heat exchange as long as possible, likewise in the block and exchanging heat form engine to coolant. But there is, no doubt, a linear equation that applies to this somewhere that could well blow my theory to bits and pieces.


Now I just don't know , but I recently placed a 71 degree thermostat in my engine as opposed to the 82 degree unit I was running (purely because the engine performs better when 10 degrees cooler). It remains to be seen what happens on an extended highway run, will the engine run hotter than normal?

This will at least tell me something over time