
Radiator change results
#1
Posted 29 March 2006 - 01:05 PM
I decided to see whether this was my imagination or whether the myth that larger radiators can run hotter is true or not so I bought a stock 3 core VK radiator to compare.
The stats of both radiators are as follows
Custom 4 core $500, 12.5kg, 45 tubes top to bottom, 67mm thick, fins tightly packed
Stock 3 core $200,8kg, 35 tubes top to bottom, 52mm thick, fins not tightly packed
Verdict. The custom $500 radiator was a waste of money. The temps as per readout on the laptop (EMS) measuring from one point, and the dash gauge measuring from another point on the engine both indicate at cruise a 3 to 4 degree reduction in temp and basically back to where it used to be when I remember it. Basically I think the airflow thru the radiator is reduced once everthing is so tightly packed.
I know that this may sound like only a small temp drop but it definately demonstrates that big is not always better with radiators.
#2
_Dirty Deeds_
Posted 29 March 2006 - 01:18 PM
I think a lot of it has to do with the efficiency of the radiator and how blocked it is. For the sake of $70, its worth getting your radiator cleaned at least every 5000 k's.
#3
_devilsadvocate_
Posted 29 March 2006 - 01:31 PM
Im sure youve approached your test scientifically, but its a little uncertain as to the conditions during your comparison.
Was the temp measured at the bottom radiator hose outlet, top hose outlet, cylinder head, temp sensor? ambient temperature on both occasions was, was same? Actual coolant temp was? Thermostat temp is?
Were you running an engine fan or just using ram air?
Choice of crossflow radiator, why? would reduce available area of fins exposed to air in the torrie and be less effective than a vertical flow rad. Regardless, using cross flow both times makes comparing the cores valid.
#4
_Herne_
Posted 29 March 2006 - 01:41 PM
I can only agree with turbotorana's and Dirty Deeds practical experience in this matter!
Cheers
Herne
#5
Posted 29 March 2006 - 02:13 PM

RACV MAN
#6
_devilsadvocate_
Posted 30 March 2006 - 08:24 AM
Maybe more flow in larger core rad(or perhaps there are issues with turbulence), however, more flow always enhances heat transfer, not restrict it.........seePerhaps the 4/5 cores flow quicker and don't allow "time" to tranfer heat?
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RACV MAN
cooling
cooling1
Edited by devilsadvocate, 30 March 2006 - 08:26 AM.
#7
_TORANR AMORE_
Posted 30 March 2006 - 09:33 AM
The 4 core was HEAPs better than the 3 core that the motor originally had, but when changing the radiators I also change thermostats and fans etc.
Bigger radiators eliminate heat better than smaller ones, they would have to. The rest is up to design and materials used and fans used etc. I mean, when you think about it in terms of volume difference, there is a big difference for (an arbitrary) example if you add 2 litres of boiling water to 3 litres of cold water OR add 2 litres of boiling water to 2 litres of cold water in a container with less outer surface area to dissipate heat.
Heat energy is ultimately transferred from the steel to the air and like devil said the better the flow the better the transfer just like the better the flow of air through the radiator (stronger fan) the more air that is available in a shorter time to transfer the heat.
The design of he radiator is a combination of it acting merely as a big heatsink as well as allowing the water within it to travel as much as possible inside it exposing itself to as much of the metal surface area as possible within a certian timeframe (which you can control by using various thermostats on your engine with different opening temperatures.
However, when the thermostat is closed, this is supposed to allow time for the hot water in the radiator to cool down (end of flow arguement and relies on volume + surface area + air speed velocity through the radiator). I don't think it is actually flowing at this time, but only when the thermostat has opened again and pushes it back into the engine.
I have taken thermostats completely out of engines that were real bad cookers and it 'seemed' to have worked but I'm not sure if it made any real difference. It certianly gave me third degree burns though forgetting about it and opening the cap.


#8
Posted 30 March 2006 - 10:10 AM
Thats why when i had the choice, i went for a PWR alloy. 2 core only, the tubes are ovalised, theyre 1" along the length of the oval, and they also have dimples on them to help turbulate the water so it tumbles and touches more of the tube.
All i can say is... it works a damn treat! Standard HQ size and layout and has the trans cooler in the bottom too.(never used)
Lots of good theories, and thanks for keeping it civil! and thanks turbotorana for telling us about your experiences mate!
#9
_MYLJ_
Posted 30 March 2006 - 11:35 AM
originally the car had a worked small block with a Factory 4 core with a medium/fine set of fins (as in not the finest but not the standard course core)
this system with two thermo fans (front mounted push type fans) seemed to work fine and it was only at the end of a 3 minute burnout that it was getting real hot (240+) cruising etc it would sit around 200.
When the big block went in (with the same cooling system) it cooked all the time

cooked the headgaskets and made a general mess of itself !!!
once the motor was fixed I looked for something else (couldn't afford an alloy one at the time)
so I tried a fine finned 5 core (brand new) useless,

so back to plan "A", had the 4core re-cleaned. bought a set of AU Falcon thermofans, mounted them up (even sealed the edges with silicon) now with these fans it tried to suck the plastic sheet through the grill, Much better amount of air flowing through the raidiator core

Sollution------- fitted a "Milidon" high flow thermostat (its rated to open at 160 degrees) no more spikes in temp

One thing I have not covered is the changes to the "Tuning set-up" of the engine that we have made as well that have also helped reduce temp
It use to have a 1050 dominator carby on it (too big) too much fuel = more temp
fitted my trusty old 750 double pumper

only other thing was a new ignition system (with an advance curve much more suited to the engines caracteristics)
So for me the best set up I've used so far is the 4 core with the AU fans and the high flow thermostat , but the one thing I cannot stress enough is the state of tune of the motor , a motor that is too lean (or too rich) or has over advanced (or exsessively retarded) timing , will run hot . Period !
only other thing is fuel, only ever run premium or better!!!!!!! standard unleaded is a no no , particularly if temp is an issue
#10
Posted 30 March 2006 - 11:41 AM
The high flow thermostat is one thing that i didnt think of.. I must admit though, ive put 2 into the monaro and theyre the ONLY thermostat's i'll use! I just use normal Tridon ones, they make high flow Chev thermostats and most places have them on the shelf!
Cheers mate!
#11
_devilsadvocate_
Posted 30 March 2006 - 11:52 AM
#12
_MYLJ_
Posted 30 March 2006 - 12:06 PM
do you mean a mechanical original style fan or electric fans?Burn outs, wouldnt heavy duty engine fans(dare I suggest) be your best option for keeping things cool when youve really got the motor working hard and no ram air?
I run AU falcon electric thermofans.
I don't run a stock type mechanical fan for several reasons..........
1. at high rpm the fan blades distort and do not flow properly IMPO
2. I run without a bonnet during competions (helps reduce engine bay temp) and they dont let you run a stock fan and no bonnet (I think you can if its got a metal shroud)
3. they break at high rpm (I've seen it happen)
4. there is no room to fit it with the big block and the big raidiator
5. they rob horse power and add extra load to the fan belts (and I dont know if they fit with gilmer drives)
6. there bloody ugly

#13
_devilsadvocate_
Posted 30 March 2006 - 12:45 PM
#14
_TORANR AMORE_
Posted 30 March 2006 - 12:47 PM
AU Falcon twin fans or equivalent are the best and I've heard good things about them. I bought a set for the TORRY. I should've installed them prior to the drag day at heathcote, the car wouldn't have overheated so much after that burnout. It had a single large davies craig electric fan on it which is only fine for any other circumstances. The cooling system also is using a 160 degree thermostat (From memory I think).
I'm gonna try a couple of different radiators on the Hatch, but when that motor ran, I'm told it ran cool with a standard 5 core.
What is the best radiator that people here can reccomend for a worked 5litre that is not over-expensive? Brand? Type?
#15
Posted 30 March 2006 - 03:52 PM
Cooling and
Cooling 2
Points to ponder:
Cooling 1 made no mention of the molecule being reheated on lap 2 of the cooling system or does he mean it did 2 laps of the radiator before it exited?
Cooling 2 made no mention of replacing heat exchangers with bigger capacity ones rather than altering flow speed through existing exchangers.
RACV MAN
#16
_Torana482HP_
Posted 30 March 2006 - 04:15 PM
i hope it dosent cook or else ill be pissed.
#17
Posted 30 March 2006 - 06:58 PM
Cheers!
#18
Posted 30 March 2006 - 10:38 PM
In response to the QsInteresting stuff.
Im sure youve approached your test scientifically, but its a little uncertain as to the conditions during your comparison.
Was the temp measured at the bottom radiator hose outlet, top hose outlet, cylinder head, temp sensor? ambient temperature on both occasions was, was same? Actual coolant temp was? Thermostat temp is?
Were you running an engine fan or just using ram air?
Choice of crossflow radiator, why? would reduce available area of fins exposed to air in the torrie and be less effective than a vertical flow rad. Regardless, using cross flow both times makes comparing the cores valid.
I dont run a thermostat, I cut the thermostat head off so I just have the thermostat base which gives a smaller hole to slow the water down.
The temp differences were measured while cruising, so no thermo fan was on.
There is a reason why crossflow radiators are meant to be better than downflow. Its got something to do with pressures in the system and location of radiator cap. I am no expert on this, just following something I read on years ago and mostly forgotten.
I also put in REDLINE water wetter in after the first testing of temps to see if its any good. I think this stuff is only really of benefit when the system is really hot and starting to boil. Then it may help, but at cruise It may??? have helped 1 deg but not certain.
Please note that all these results are not scientifically done, but just good old observation and changing one thing at a time.
#19
_devilsadvocate_
Posted 31 March 2006 - 12:40 PM
Thanks for all of the ^. So take it no engine fan. So with lots of ram air(at cruise) the 5core ran hotter. Ive got a theory, which Ill keep to myself for the moment.....In response to the Qs
I dont run a thermostat, I cut the thermostat head off so I just have the thermostat base which gives a smaller hole to slow the water down.
The temp differences were measured while cruising, so no thermo fan was on.
There is a reason why crossflow radiators are meant to be better than downflow. Its got something to do with pressures in the system and location of radiator cap.
I also put in REDLINE water wetter in after the first testing of temps to see if its any good. I think this stuff is only really of benefit when the system is really hot and starting to boil.
Please note that all these results are not scientifically done, but just good old observation and changing one thing at a time.
Re crossflow, the only advantage I know of, is that the rad cap can be placed on the opposite side of the rad to the water pump, and this stops the rad cap popping the cap at high revs, not something ive noticed in a conventional system. Other than that, radiators are generally constructed to fill the hole, using minimum sized top and bottom tanks for the sake of economy of manufacture, and/or to max the exposed fins to the hole, which will typically see a crossflow installed if the car is low and wide.
Redline water wetter, Ive posted heaps about that b4, but basically agree with ^
Not scientifically done? changing one variable at a time......thats part of good scientific method.
#20
Posted 31 March 2006 - 01:48 PM
#21
Posted 31 March 2006 - 03:03 PM
#22
_devilsadvocate_
Posted 31 March 2006 - 07:43 PM
Good that you read those links, but I take it by your quest you're still sceptical?I have read and understand:
Cooling and
Cooling 2
Points to ponder:
Cooling 1 made no mention of the molecule being reheated on lap 2 of the cooling system or does he mean it did 2 laps of the radiator before it exited?
Cooling 2 made no mention of replacing heat exchangers with bigger capacity ones rather than altering flow speed through existing exchangers.
RACV MAN
I �think� what he alluded to was that if the molecule did two laps of the radiator and engine, in the same time as it took to do one lap, then the molecule would have been in contact with both rad and engine for the same time in both scenarios.
This explanation isn�t complete, it really only shows that speeding it up wont have any effect on contact time with the rad or engine. It doesn�t explain why speeding it up actually �increases� cooling.
This is much harder to explain, I�ll have a go:
If the flow of coolant through the radiator is slow then yes, it comes out of the bottom of the radiator a lot cooler than if the coolant was moving fast.
The coolant has time to cool, perhaps entering the top at 90C and cooling to 80C by the time its half way down the radiator. (Unfortunately this rate of cooling wont be maintained due to �Newton�s law of cooling�, rate of cooling is proportional to the temp above the surroundings) and not as much temp drop would occur in the coolant traveling through the bottom half of the rad, perhaps only losing a further 5C.
The amount of cooling occurring in the bottom half of the radiator can be seen to be far less than than in the top half, the bottom half isn�t working so well because it is closer to the temp of the surroundings.
By making the water flow through the rad as fast as possible, ensures that the all rad stays significantly higher than the surroundings and is therefore able to transfer more heat as per Newton�s law.
I know it sounds contradictory, the slow moving example we have a temp diff of 15C, however, the prob is in the time its taken to do that, the water inside the engine would have heated up a lot more than that 15C as the surface temps of the motor are considerable hotter.
The second case, fast flowing water may enter the rad at 90 and exit at 88C. Only a 2C drop, not much? Because it is hot all the way along the rad, more heat is removed(the air coming off the radiator will be hotter), and correspondingly the water hasn�t had as much time to heat up while going through the engine.
That�s as good as I can do�., it�s a difficult concept.
#23
Posted 31 March 2006 - 11:48 PM
I am sceptical and believe that there is a threshold where flow and heat tranfer is preportional too cooling.
I do not believe that more flow increases cooling in all cases. (Original topic)
I know that I would rather have a standard radiator, than the equivilant radiator capacity in the form of a tube between the top and bottom hose with the equivilant area of fins and air flow (lets take it to its extreem) as I believe it would be more efficient.
I base my theory on experience rather than science, and things I read off the net posted by other "scientists". Lets face it, one bloke was arguing with engineers that "should know better"

I agree it is a difficult concept and that is why I believe there is a threshold.
RACV MAN
Edited by rodomo, 01 April 2006 - 12:01 AM.
#24
_devilsadvocate_
Posted 01 April 2006 - 12:49 AM
We all live by Newton's laws of physics and so far (provided we keep things at less than light speeds) no one person has found fault in any of them, so Ill be sticking with him on this one, I have gathered some "data" from real cooling situations that go with the flow too.
Edited by devilsadvocate, 01 April 2006 - 01:01 AM.
#25
Posted 01 April 2006 - 05:22 PM
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