radiator sizes and capacity

[zefarelly]

Is there a simple way of calculating radiator size and capacity, I started with a std rad, upgraded to a high efficiency double core, this struggle in the high summer, and at Spa (was running around 90-95 degrees)

I've now just bought an alloy rad designed for running BDA / vauxhaul twinks, this will fit as OE, but its extra afficiency and capacity will hopefully keep my new engine cool running up to 8500 RPM. fingers crossed it does anyway !

[Red Dog]

Good question! I have found that the rad needs to be located at the right angle to the airflow and most importantly, be very carefully ducted in and out.

[greenamex2]

You could do the maths but some of the variables would be so difficult to ascertain that the figures would be meaningless.

As Red Dog said, location and installation are more important than size anyway.

My two examples are -

- My kit car kept overheating on the road so I fitted a triple core rad. It overheated less on the road but was still hopeless on the track. The real cure was to get the radiator upright and give the air somewhere to go once it had gone through it. Now the thermosat barely opens.

- The race car had oil heat problems. I initially tried ducting and twin coolers which helped a lot. The ultimate cure was a deeper sump so the crank didn't run in oil all the time. I am now back to a single oil cooler.

[zefarelly]

hmm, interesting, as I'm a saloon I can't relocate anything, the rad is vertical and the oil cooler is right next to it, If the new rad doesnt do the trick then I'll try some ducting to assist, I've never had a problem on the road, only racing

I think I should fabricate some ducting to divert cold air into the carbs and deflect hot away from the inlet (precrossflow engine) hopefully that may help some

[Anuauto]

The alloy rads that are now readily available certainly solved the problem on the hillclimb Escort/Pinto engines of a couple of friends of mine. I actually never had a problem on mine, once there was some airflow, using a standard type but large core "Group 1" rad in either rallying or speed events.

[Tim Falce]

I was told (by a very large ally fabrication company) that an ally rad is no more efficient than a copper one, when new. The difference is when they have been used a while. Not sure how true it is but we all get fed BS now and again don't we.
One thing you may want to look at is the airflow through the rad and where it escapes behind it. If you have a very tight engine bay with not much room for the air to escape you may be getting a dam affect. Perhaps you could do with some louvres in the bonnet if you don't already have them.
I have had problems with overheating for about 18 months. I tried lots of different things such as altering the angle of the rad, bigger oil cooler more ventilation etc, nothing worked. The thing that cured it was getting the engine re-tuned and fitting larger jets and different plugs, I also got an extra 15 bhp as well.

[1200Datto27]

Falcemob,

I would say that if this mob are saying that alloy is no better than copper for a radiator, and they make alloy ones, then they are most likely telling the truth.

IIRC, copper has a slightly better heat transfer ratio than aluminium, but it is more at risk of corrosion and is heavier.

[graham bahr]

i found an electric water pump improved the cooling on my car, the temp was far more stable and less prone to getting too hot.
some times drilling 4 or 5 8th inch holes around the outer edge of the thermostat can do a lot to help the cooling, the stat will flow a little more water and also has the benifit that when the stat does actually open for the first time your nice hot cylinder bores aren't suddenly hit with cold water, as the holes in the stat will alow a little water circulation through the rad pre warming the contents of it.

[graham bahr]

re alloy rads, i talked to my radiator man, and he said they are a little better, but the better head transfer of the alloy is offset by the fact that the material is weaker so needs to be thicker than a copper version, copper also has a big advanage in that it can be soldered up easily ( like in the paddock with a small soldering iron and electrical solder) if nec oh and its much cheaper

[graham bahr]

Originally Posted by zefarelly

hmm, interesting, as I'm a saloon I can't relocate anything, the rad is vertical and the oil cooler is right next to it, If the new rad doesnt do the trick then I'll try some ducting to assist, I've never had a problem on the road, only racing

I think I should fabricate some ducting to divert cold air into the carbs and deflect hot away from the inlet (precrossflow engine) hopefully that may help some

i dont think that will help with the cooling, however many years ago i used to drag race a Volve 144 which had a volvo pre cross flow ohv engine on sidedrafts very similar to your engine, when i shelded my carbs from the exhaust heat rising from the exhaust, we gained a fair chunk of power after going up a couple of sizes on the main jets

[listernoble]

1-The oil cooler plays a major part in controlling engine temperature,is there room to fit a larger one or duct more cold air to it?
2-Are you allowed to fit extraction ducts to the bonnet to improve airflow?
3-Have you tried one of the "water wetter" products?
Lister

[zefarelly]

hopefully the ally rad will make the necessary difference, shielding the carbs is a good idea, basically to get cool air in them, and bloww hot away from the exhaust, theres a reasonable amount of space under the bonnet so it shouldnt be a problem, I don't think I'll get away with a louvred bonnet, although I could always 'adjust it' to let air out onto thwe windscreen, the Lotus cortina race cars don't seem to suffer so I shouldnt . . .although I'm learning myself, not remortgaging the house for someone else to do it for me !

[greenamex2]

Can't remember the last time I ran a thermostat on my race car. If my current engine builder finds one on my engine he throws it away!!!

Have you tried any exhaust manifold shielding products such as cool it etc. If nothing they reduce the amount of skin you lose during course of a season working in a hot engine bay.

[zefarelly]

I gutted my thermostat ages ago, I just run the mounting plate which acts as a restrictor, seems to be fine, the only trouble Ive had really is in hot weather, I have wrapped the exhaust in itchy stuff, can't remember what its called but it seems to work

[StephenRae]

Originally Posted by Denis Bassom

Can't remember the last time I ran a thermostat on my race car. If my current engine builder finds one on my engine he throws it away!!!

I fitted 2 aluminium Corsa radiators (£35 each) to my FF1600 and much to my engine mans dissaproval run a thermostat with an extra 5mm hole in it.
I think it ensures a good water flow around the head, I don't have to blank the rads off in cold weather and the engine warms up quicker.

[dtype38]

Zef... Sorry if this is a bit too obvious, but if you are running with anti-freeze then change to just water (or maybe just down to a trace of antifreeze). You'll get less corrosion protection, but it will reduce your running temp noticably. I can also vouch for water-wetter which also improves things.

[zefarelly]

I have always run with antifreeze, last time I put water wetter in as well . . . .this time I'll just try water wetter, thanks for the tip.

[1200Datto27]

I would also suggest the use of some corrosion inhibitor in the mix as well, especially if you have different types of metal in contact with the coolant.

[Chris Y]

I actually thought that antifreeze could help with cooling as well - I thought it made the water better able to transfer heat away? Is this wrong?

[dtype38]

Originally Posted by Chris Y

I actually thought that antifreeze could help with cooling as well - I thought it made the water better able to transfer heat away? Is this wrong?

'fraid its not that simple... but here goes:

If the engine is running too hot and boiling over because the radiator is limited by poor airflow, then adding antifreeze will allow the coolant to run hotter before boiling. That allows a bigger temperature difference to air and hence more heat to be rejected. In actual fact, antifreeze doesn't conduct heat as well as water but in the case above, that's not the problem so doesn't have any noticable effect (as long as the engine doesn't mind running a bit hotter).

On the other hand, if the engine is running too hot because the coolant flow is poor, or the water ways in the rad are furred up, then getting rid of the antifreeze improves the heat transfer on the coolant side and allows more heat to be rejected.

[zefarelly]

hmmm . . .interesting, my engine ust ran hot (around 95 deg C) at Spa and the rad was new, hopefully it was just not up to the job, the ally one I now have seems to have bigger cores (visible through the filler cap) and is a bit deeper,

I think I'll run water wetter and a little corrosion inhibitor or antifreeze and see how it behaves

[1200Datto27]

Also, if you have the water flowing to quickly it can lead to overheating issues. Most car water pumps are designed to have an optimum water flow around the lower middle of the normal rev range, where the engine designers expect that the engine will spend most of its time, so they tailor the flow/heat exchange charateristics to suit, now, if you go and use the same pump in a race engine, that spends most of its time in the upper rev range, and then combine it with a radiator that has a lower flow restriction, you could find that the coolant is not spending enough time in the radiator to allow for adequate heat transfer.

[zefarelly]

that makes sense Datto but if its moving that fast you could argue it won't have time to get hot !

on a more serious notm what can you do about it? . .under FiA regs I'm not sure I'd be allowed any alternative like an electric pump , I suppose I could do a degree in fluid dynamics and redesign the impelleor on the pump.

I have considered fitting an auxilliary electric pump which could be triggered by the thermostat so when I park up it circulated the water to stop the head boiling

[1200Datto27]

I asked the same question, it comes down to relevent temps, coolant traveling through a heat with hotspots of 800+ degrees, is going to pick up heat, no matter what speed it goes. Also, as the heads have a more convoluted path for the coolant to flow through, there are more slow points for the fluid to be warmed up at, and transfer the tempreture.

If you want to try and slow down the fluid flow, you can remove some of the blades from the water pump impeller, but this only works if you have and even number of blades, and more than 6, due to balance issues.

[dtype38]

Zef... the speed of the fulid flow through the rad isn't so much an issue as the impeller efficiency. Datto is correct that impellers are designed for optimum performance at mid revs. At higher revs the impeller can often work poorly or even cavitate causing significant loss of flow. This isn't a problem on the road because those sort of revs aren't usually held for very long. A common attempt to cure this problem is to remove the thermostat. This sometimes works, but often as not can make things even worse depending on the particular engine and impeller. This is because the impeller efficiency depends on the pressure it has to work against as much as it does on the flow that is required. (On my own car, taking the thermostat out makes it run hotter !! I think it might also be the cause of the popular myth that the coolant can run too fast to get rid of the heat). Anyway, what I'm trying to say is that there isn't a simple answer that works on every car. If you are limited by the rules to the pump and rad you have, then it may sound completely silly, but you could try putting a smaller pulley on the pump. This will slow the pump down so that it runs at optimum speed higher up the engine rev range.