Uprated Aluminium Radiator
Discussion
It seems that there are two camps, one that suggest that the std setup with copper rad works as expected, and obviously the factory support this stance, and another where owner/ builders have run into problems, in particular when standing still in traffic, or maybe on the track, and are either thinking about of have made changes to try to combat this problem.
Many start with changing the copper rad for a thinner ally one + uprated fans, although there seems to be some disagreement and debate on whether the std rad is as good as or worse than ally.
Some that have changed to ally still experience problems in extreme situations when the ambient temperature is unusually high (for the UK anyway), and have hit a traffic jam.
Most, it seems, do not suffer problems when on the move with either configuration.
So, I guess idling + restricted airflow is an issue for some in these conditions even with the mods mentioned, so the next step seems to be suggested as trying to improve water flow during idle (electronic water-pumps), or water wetters, or more extreme methods of trying to get more of the radiator cooler.
I know some that have gone down the water pump replacement route, and it is suggested that this fixes the problem. Is that true?
Many start with changing the copper rad for a thinner ally one + uprated fans, although there seems to be some disagreement and debate on whether the std rad is as good as or worse than ally.
Some that have changed to ally still experience problems in extreme situations when the ambient temperature is unusually high (for the UK anyway), and have hit a traffic jam.
Most, it seems, do not suffer problems when on the move with either configuration.
So, I guess idling + restricted airflow is an issue for some in these conditions even with the mods mentioned, so the next step seems to be suggested as trying to improve water flow during idle (electronic water-pumps), or water wetters, or more extreme methods of trying to get more of the radiator cooler.
I know some that have gone down the water pump replacement route, and it is suggested that this fixes the problem. Is that true?
Edited by 3Dee on Thursday 28th August 12:39
3Dee said:
so the next step seems to be suggested as trying to improve water flow during idle (electronic water-pumps)
I know some that have gone down the water pump replacement route, and it is suggested that this fixes the problem. Is that true?
Despite what you may read on the internet, changing your water pump will not help you cool your engine at idle/low speed/in traffic........I know some that have gone down the water pump replacement route, and it is suggested that this fixes the problem. Is that true?
Despite what I have read. Changing the water pump on my SBC to an electric one from CSR immediately dropped my engine temp reading from 110 at idle to 98. I can only put this down to increased flow which allows the radiator to shed the heat at a lower circulating temperature. The engine never boiled but just settled at the higher temp so the heat was manageable but a larger temp gradient was required. Just didn't like to see temps that high and higher in v hot weather. The fact that the pump runs on after shut down was also a factor in my decision. I did remove the clam grill before making the upgrade and also uprated the fans (and wiring to them) massively. Made a difference but not enough.
Your engine is always generating the same amount of heat at idle.
If you increase water flow, the temperature of the water leaving the engine will be lower
(heat flux = Mdot.Cp.DeltaT so if Mdot increases, deltaT MUST fall)
So, you radiator, which takes the top hose outlet water temp in, now has a LOWER mean temperature difference between itself and the ambient environment, and due to the higher water flow rate, has less time in which to cool the water flowing through it, which means it cannot reject as much heat as before to the environment, and as such, the bottom hose temp will increase.
That higher radiator outlet temp now makes it back round to the engine water intake (bottom hose) and the effect is to push the "average" engine water temp back up to where it was before.
ie:
at say 20l/min flow, bottom hose = 85 degC, top hose = 95degC, average engine = 90degC
at say 40l/minflow, bottom hose = 87.5degC, top hose = 92.5degC, average engine = 90degC
You dash gauge says your engine is 2.5degC colder, but in reality, the metal temps in the engine (which is what we care about, but don't directly measure) haven't changed.
This is because the average water temp in the system is set by the radiators heat rejection capability and not the heat flux of the coolant flow (which doesn't change). In effect what you do by increasing the massflow at idle is to reduce the temperature difference between the top and bottom hose.
Because we typically measure water temperature at the top hose, there are situation where you could measure a slightly lower temperature, but as a side effect, the bottom hose temp (which we don't usually measure) would be slightly higher. The bit we really care about (but generally don't measure at all) the metal temps in the engine are effectively unchanged.
If you increase water flow, the temperature of the water leaving the engine will be lower
(heat flux = Mdot.Cp.DeltaT so if Mdot increases, deltaT MUST fall)
So, you radiator, which takes the top hose outlet water temp in, now has a LOWER mean temperature difference between itself and the ambient environment, and due to the higher water flow rate, has less time in which to cool the water flowing through it, which means it cannot reject as much heat as before to the environment, and as such, the bottom hose temp will increase.
That higher radiator outlet temp now makes it back round to the engine water intake (bottom hose) and the effect is to push the "average" engine water temp back up to where it was before.
ie:
at say 20l/min flow, bottom hose = 85 degC, top hose = 95degC, average engine = 90degC
at say 40l/minflow, bottom hose = 87.5degC, top hose = 92.5degC, average engine = 90degC
You dash gauge says your engine is 2.5degC colder, but in reality, the metal temps in the engine (which is what we care about, but don't directly measure) haven't changed.
This is because the average water temp in the system is set by the radiators heat rejection capability and not the heat flux of the coolant flow (which doesn't change). In effect what you do by increasing the massflow at idle is to reduce the temperature difference between the top and bottom hose.
Because we typically measure water temperature at the top hose, there are situation where you could measure a slightly lower temperature, but as a side effect, the bottom hose temp (which we don't usually measure) would be slightly higher. The bit we really care about (but generally don't measure at all) the metal temps in the engine are effectively unchanged.
Edited by anonymous-user on Thursday 28th August 23:55
Max_Torque said:
Your engine is always generating the same amount of heat at idle.
If you increase water flow, the temperature of the water leaving the engine will be lower
(heat flux = Mdot.Cp.DeltaT so if Mdot increases, deltaT MUST fall)
So, you radiator, which takes the top hose outlet water temp in, now has a LOWER mean temperature difference between itself and the ambient environment, and due to the higher water flow rate, has less time in which to cool the water flowing through it, which means it cannot reject as much heat as before to the environment, and as such, the bottom hose temp will increase.
That higher radiator outlet temp now makes it back round to the engine water intake (bottom hose) and the effect is to push the "average" engine water temp back up to where it was before.
ie:
at say 20l/min flow, bottom hose = 85 degC, top hose = 95degC, average engine = 90degC
at say 40l/minflow, bottom hose = 87.5degC, top hose = 92.5degC, average engine = 90degC
You dash gauge says your engine is 2.5degC colder, but in reality, the metal temps in the engine (which is what we care about, but don't directly measure) haven't changed.
This is because the average water temp in the system is set by the radiators heat rejection capability and not the heat flux of the coolant flow (which doesn't change). In effect what you do by increasing the massflow at idle is to reduce the temperature difference between the top and bottom hose.
Because we typically measure water temperature at the top hose, there are situation where you could measure a slightly lower temperature, but as a side effect, the bottom hose temp (which we don't usually measure) would be slightly higher. The bit we really care about (but generally don't measure at all) the metal temps in the engine are effectively unchanged.
What about the effect of increased pressure due to the pump running at a higher RPM - this will increase heat transfer.If you increase water flow, the temperature of the water leaving the engine will be lower
(heat flux = Mdot.Cp.DeltaT so if Mdot increases, deltaT MUST fall)
So, you radiator, which takes the top hose outlet water temp in, now has a LOWER mean temperature difference between itself and the ambient environment, and due to the higher water flow rate, has less time in which to cool the water flowing through it, which means it cannot reject as much heat as before to the environment, and as such, the bottom hose temp will increase.
That higher radiator outlet temp now makes it back round to the engine water intake (bottom hose) and the effect is to push the "average" engine water temp back up to where it was before.
ie:
at say 20l/min flow, bottom hose = 85 degC, top hose = 95degC, average engine = 90degC
at say 40l/minflow, bottom hose = 87.5degC, top hose = 92.5degC, average engine = 90degC
You dash gauge says your engine is 2.5degC colder, but in reality, the metal temps in the engine (which is what we care about, but don't directly measure) haven't changed.
This is because the average water temp in the system is set by the radiators heat rejection capability and not the heat flux of the coolant flow (which doesn't change). In effect what you do by increasing the massflow at idle is to reduce the temperature difference between the top and bottom hose.
Because we typically measure water temperature at the top hose, there are situation where you could measure a slightly lower temperature, but as a side effect, the bottom hose temp (which we don't usually measure) would be slightly higher. The bit we really care about (but generally don't measure at all) the metal temps in the engine are effectively unchanged.
Edited by Max_Torque on Thursday 28th August 23:55
You also forget about the ability to run your battery flat by leaving the pump running with the engine off. This helps to keep the temps down too.
macgtech said:
What about the effect of increased pressure due to the pump running at a higher RPM - this will increase heat transfer.
No it won't. Heat flux is driven by temperature difference and velocity when it comes to fluids (the extra velocity would increase heat flux, but because the total heat flux is determined by the radiator and not the engine, this is cancelled by the lower fluid outlet temp) macgtech said:
You also forget about the ability to run your battery flat by leaving the pump running with the engine off. This helps to keep the temps down too.
indeed ;-) but unless you have a race car, and even then, there are literally millions of cars that are driven every day, even in 50degC ambients that manage just fine with conventional crank driven water pumps! No, i'm not saying run on water pumps are a bad idea, they have there place, but they will not improve the "cooling" of your engine when you are sat idling in traffic!I confess that I am not clued up on flux capacitors or dilithium crystal management, but since most find perfectly adequate cooling when moving at normal road speeds, but when stationary the temps start to rise, and rise, and rise.. then in my mind there are only two elements of the cooling that must be directly exacerbating the problem.
One is the speed that the coolant is being transferred twix the engine and radiator, and the other is the cooling airflow effect through the radiator itself.
To my stupid mind, this suggests that at idle, if the radiator/ fan configuration IS doing its job, then not enough of that cooling effect is getting where it is needed....thus finding a way to get that cooler coolant to the engine when idling..
or that rad/fan configuration is NOT passing enough airflow through to promote the drop in temperature needed.
The problem with the latter is that since cooling IS sufficient at speed, how can one emulate that at standstill, especially if you have already invested in the most powerful fans available today. Pacet, when they were alive, now Kenlow but they don't meet the best of Pacet... nothing else seems to come close that I have found.
So we are stuck with a twin-fan configuration that appear not to be able to promote sufficient airflow through the whole surface area of the radiator.
Maybe in an ideal world, one could make up some sort of cowl that will achieve such full use of the rad area and fan pull effect, thus an effective way of fixing the problem, however there doesn't appear to be enough depth left behind the radiator to achieve, but could it be done?
With the cowl on, this would restrict airflow at speed naturally, but for me anyway, I see the temp drop quite substantially on runs thus an increase would not be a problem..
One is the speed that the coolant is being transferred twix the engine and radiator, and the other is the cooling airflow effect through the radiator itself.
To my stupid mind, this suggests that at idle, if the radiator/ fan configuration IS doing its job, then not enough of that cooling effect is getting where it is needed....thus finding a way to get that cooler coolant to the engine when idling..
or that rad/fan configuration is NOT passing enough airflow through to promote the drop in temperature needed.
The problem with the latter is that since cooling IS sufficient at speed, how can one emulate that at standstill, especially if you have already invested in the most powerful fans available today. Pacet, when they were alive, now Kenlow but they don't meet the best of Pacet... nothing else seems to come close that I have found.
So we are stuck with a twin-fan configuration that appear not to be able to promote sufficient airflow through the whole surface area of the radiator.
Maybe in an ideal world, one could make up some sort of cowl that will achieve such full use of the rad area and fan pull effect, thus an effective way of fixing the problem, however there doesn't appear to be enough depth left behind the radiator to achieve, but could it be done?
With the cowl on, this would restrict airflow at speed naturally, but for me anyway, I see the temp drop quite substantially on runs thus an increase would not be a problem..
I run a cowl with twin fans, I can run the car at 900rpm or 1400rpm on idle (been running 1400rpm for a while for various unrelated to heat reasons) and my car never overheats in traffic despite the fact that I have glowing headers at the higher idle speed with egt over 600deg c and thus engine compartment temps a lot higher than my canal ever had (that was marginal in traffic and overheated if the idle crept up over 900rpm)
Standard noble without the cowl but with the same rad and half the power and idling at 750rpm overheat in traffic!
The noble cowl is a simple alloy panel with a 1-2inch gap to the rad and the fans attached, similar lack of space as an ultima.... Id say you need a cowl to maximise the rads cooling when stationary.
Standard noble without the cowl but with the same rad and half the power and idling at 750rpm overheat in traffic!
The noble cowl is a simple alloy panel with a 1-2inch gap to the rad and the fans attached, similar lack of space as an ultima.... Id say you need a cowl to maximise the rads cooling when stationary.
As i have demonstrated, it's all about the rad and fans and NOT about the water flow rate!
As the coolant system is circular, increasing the flow rate of the system just changes the deltaT and not the average temp. That can only be affected by the heat source(engine) and the heat sink (environment via radiator).
If you look at modern high performance vehicles, they a have both a massive radiator and massive fans. Typical modern OEM fans are now >750watts, that's over 1 horsepower, and the ducting and airflow from those fans is very very carefully managed, both in and out.
As the coolant system is circular, increasing the flow rate of the system just changes the deltaT and not the average temp. That can only be affected by the heat source(engine) and the heat sink (environment via radiator).
If you look at modern high performance vehicles, they a have both a massive radiator and massive fans. Typical modern OEM fans are now >750watts, that's over 1 horsepower, and the ducting and airflow from those fans is very very carefully managed, both in and out.
It's also worth noting that people seem think that and engine being "Hot" is an issue. The engine doesn't really care these days. As long as it doesn't actually boil and vent it's coolant, your all good. 110degc Top hose in a traffic jam is fine, no worries. OEM vehicles usually are rated to around 120degC top hose max after a fully loaded "Hill climb" (Großglockner pass etc) in a high ambient (>40degC)
Not disagreeing with the obvious mechanics of the cooling process. The system stabilises which means that heat produced = heat rejected by the radiator. The water temp at the outlet of the engine is higher. The flow is less but the quantity of water flowing is able to absorb the heat produced and the rad is able to reject it. I run a highly tuned SBC and prefer less of a temp gradient through the engine as well as the 2 min run on. Also in my case the extra space and removal of a belt at the front of the engine was helpful and aesthetically pleasing.
Andygtt (defo not teaching you to suck eggs) but glowing headers at idle is usually a sign of not enough ignition advance leaving the fuel still burning as it exits the exhaust ports or in rarer cases too weaker mixture which in turn needs more advance to burn in the cylinder.
Andygtt (defo not teaching you to suck eggs) but glowing headers at idle is usually a sign of not enough ignition advance leaving the fuel still burning as it exits the exhaust ports or in rarer cases too weaker mixture which in turn needs more advance to burn in the cylinder.
Edited by MarkWebb on Friday 29th August 18:26
Edited by MarkWebb on Friday 29th August 18:27
My car has quite a few non-standard Factory parts and my engine is only 580hp but cooling of the engine has never been a problem even with an oil-over-water oil cooler (all heat removed by the front rad).
Even sat in 30+ deg C in France for over an hour at tick over the engine temp never went over 95 deg.
The fuel temp was another matter..... Not Factory standard system though.
If you fit 1000hp then I think it is reasonable to expect cooling issues. Bugatti fit 10 radiators to the Veyron for a reason!!!
Paul
Even sat in 30+ deg C in France for over an hour at tick over the engine temp never went over 95 deg.
The fuel temp was another matter..... Not Factory standard system though.
If you fit 1000hp then I think it is reasonable to expect cooling issues. Bugatti fit 10 radiators to the Veyron for a reason!!!
Paul
mine used to boil sometimes in traffic.
A few things to bear in mind,
a cooling system requires water to be circulated and turning off an engine in traffic actually causes the temp to raise as the engine is still cooking under the clam and the coolant in the engine being heated.
also check your rad caps... make sure they are both sealed properly... ive just returned from Wilton house and saw a little weap of coolant over 500 miles. the cap was sealing at idle and some rpm but at higher pressure slight leak. i thought all was ok until i put a coolant tester on each cap. the cooling system needs a pressurized system
Also the biggest advantage of an electric water pump, is higher circulation at low rpm.... at idle the coolant isnt circulating that fast while the engine at idle generates less raising temperature. so to increase flow and cooling effect at the rad you will see a lower idle temp. at higher rpm the coolant circulates quicker and the engine generates more heat under load, but as the car goes along this heat arround the engine is reduced due to air movement in and out of the clam area... one thing i have done in the ownership of mine is remove the wire mess behing the gear box,,, if heat can escape it will cool the engine faster.
ive played with different tick over rpms due to the aircon needing a higher rpm when not in use...no aircon and tickover set at 1000 rpm. the temp normal, but set the idle to 1300 rpme(aircon off) the temp raises.i need 1300 rpm because when aircon turned on tickover is back to 1000 rpm.... Charles Dunn has now fitted a very clever switch on the throttle and i can now have 1000 rpm idle both aircon and non aircon and temp now normal. aircon on also increases idle temps alot.
dom
A few things to bear in mind,
a cooling system requires water to be circulated and turning off an engine in traffic actually causes the temp to raise as the engine is still cooking under the clam and the coolant in the engine being heated.
also check your rad caps... make sure they are both sealed properly... ive just returned from Wilton house and saw a little weap of coolant over 500 miles. the cap was sealing at idle and some rpm but at higher pressure slight leak. i thought all was ok until i put a coolant tester on each cap. the cooling system needs a pressurized system
Also the biggest advantage of an electric water pump, is higher circulation at low rpm.... at idle the coolant isnt circulating that fast while the engine at idle generates less raising temperature. so to increase flow and cooling effect at the rad you will see a lower idle temp. at higher rpm the coolant circulates quicker and the engine generates more heat under load, but as the car goes along this heat arround the engine is reduced due to air movement in and out of the clam area... one thing i have done in the ownership of mine is remove the wire mess behing the gear box,,, if heat can escape it will cool the engine faster.
ive played with different tick over rpms due to the aircon needing a higher rpm when not in use...no aircon and tickover set at 1000 rpm. the temp normal, but set the idle to 1300 rpme(aircon off) the temp raises.i need 1300 rpm because when aircon turned on tickover is back to 1000 rpm.... Charles Dunn has now fitted a very clever switch on the throttle and i can now have 1000 rpm idle both aircon and non aircon and temp now normal. aircon on also increases idle temps alot.
dom
I am a bit surprised at the relatively high tick over rpm some of you are running.
Mine ticks over at about 1100rpm on start up but once warm it drops to 900. You can feel the aircon compressor kick in and it might knock 100rpm off for a second or two but then it's back to 900.
How do you manage in stop-start traffic? I must play hell with your clutch when you have to slip it.
I can trickle along at tick over in the first 3 gears without touching the throttle.
Paul
Mine ticks over at about 1100rpm on start up but once warm it drops to 900. You can feel the aircon compressor kick in and it might knock 100rpm off for a second or two but then it's back to 900.
How do you manage in stop-start traffic? I must play hell with your clutch when you have to slip it.
I can trickle along at tick over in the first 3 gears without touching the throttle.
Paul
V8Dom said:
Charles Dunn has now fitted a very clever switch on the throttle and i can now have 1000 rpm idle both aircon and non aircon and temp now normal. aircon on also increases idle temps alot.
dom
Your engine management should take care of any parasitic loads, air con, rad fans running etc. You shouldn't need an extra switch to sort engine idle. dom
First of all Mag tech and Steve always add something to the conversation. Do you guys work together or is this two separate folks? But his point about removing the Screen behind the radiator is spot on. The screen WILL impede the flow of air through the radiator at standstill when its only the fan generating flow. The idle thing is worth pursuing idling at elevated RPM 1100+ is going to add heat to the process that has to be disposed. These engines should idle comfortably at 900. Look at the efficiency charts and you will see that antifreeze lowers the efficiency of the medium water/antifreeze to eliminate heat. Yes it will raise the boiling temp but I don't want to get that hot in the first place. Also I believe that ceramic coated headers would be a factor in putting more heat out the tail instead of into the engine bay. All that said if you have not incorporated a proper shroud to use all of the radiator when at a stand still then I think your missing one of the big items to try first. Obviously for a track only car no shroud is required because moving the car is doing the work not the fan if they even have one. lEE
.... After looking at the profiles I realize that I actually met Steve a couple of years ago at his shop, Furthermore I see that there is not an obvious connection between Steve and the racing team. My bad
.... After looking at the profiles I realize that I actually met Steve a couple of years ago at his shop, Furthermore I see that there is not an obvious connection between Steve and the racing team. My bad
Edited by ROWDYRENAULT on Sunday 31st August 17:30
ROWDYRENAULT said:
.... After looking at the profiles I realize that I actually met Steve a couple of years ago at his shop, Furthermore I see that there is not an obvious connection between Steve and the racing team. My bad
No connection at all. Its a case of 'great minds think alike and fools seldom differ'.Edited by ROWDYRENAULT on Sunday 31st August 17:30
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