Jon White Posted January 30, 2006 Share Posted January 30, 2006 Yes - coolant capacity does have an effect on cooling. For a V8 you need a coolant capacity of around 20 pints, ideally a bit more. Electric fans will help but at the end of the day if theres not enough coolant it'll overheat no matter what fans you put on it. A large coolant header tank might help, but ideally if you're not getting enough capacity I'd be more inclined to add an auxilliary radiator somewhere to increase capacity. Above all remember that if its on its limit with nice clean, new components on a cool day, then on a hot day with the radiator half blocked with mud it'll overheat! HTH Jon Quote Link to comment Share on other sites More sharing options...
Mark90 Posted January 30, 2006 Share Posted January 30, 2006 Update: I've just bought a pair of mundano fans (like Bish's) in shroud for a fiver off eblag, local too so i didn't have to pay the £12 postage. Cowling exactly the same height as the 90 rad (40cm) and is 4cm narrower than the rad which is 65cm. The nose of the water pump looks like it will sit between the two fans with about an inch of clearance. Quote Link to comment Share on other sites More sharing options...
MogLite Posted January 31, 2006 Author Share Posted January 31, 2006 Yes - coolant capacity does have an effect on cooling.For a V8 you need a coolant capacity of around 20 pints, Hmm measured the rad last night, and its got a capacity of less then 3 pints - didn't have a bare LR rad to hand to compare. The rad on our 4.6 P38a is similar construction to the Transit rad, I'll have to seen how that compares. Quote Link to comment Share on other sites More sharing options...
will_warne Posted January 31, 2006 Share Posted January 31, 2006 Andy, the other thing exta water does is it gives you a bigger buffer against short bursts of high temperatures (ie when you start throwing N20 into the engine). If your a bit down on capacity I'd get a nice, big, alloy header tank made up. Quote Link to comment Share on other sites More sharing options...
02GF74 Posted January 31, 2006 Share Posted January 31, 2006 Andy, the other thing exta water does is it gives you a bigger buffer against short bursts of high temperatures Yes - coolant capacity does have an effect on cooling. I have to go against the flow, as it were. Whilst the above statements are true, it is not the be all and end all. I'm no expert <-- my disclaimer; but isn't it about moving heat from the engine into the water and then into the air and finally getting rid of the hot air? The main factors that effect the efficiency is: 1. the surface area of the water to air intereface (read large finned radiator;), 2. the amount of air reaching the radiator (fans, grill opening; reisistance to air flow of radiator) 3. water flow in the radiator (water pump) (this is not full list as it depends on conductivity of raditator metal, the thermal conductivity of the fliud etc). Now would increasing the water flow rate make up for lower coolant volume? Until cavitation occurs, I reckon it can up to some point. For an extreme example: you can have a large capacity cooling system by fitting a hot water tank instead of a car radiator, you meet the criteria stated by the above 2 posters yet I think you would agree with me that is is not going to be anywhere near as effecient as having a car radiator which has a fraction of the coolant capacity. Unfortunately I don't have the asnwers to a problem that may not even exist; but once you are up and running, you can then start tweaking the cooling system by fitting larger radiator perhaps, a second radiator; more fans, vents, electric water pump, oil cooler, water butt in the back etc: What you are doing is correct IMO and it is good that you are antcipating any possible problems. Some mechanism to ensure the radiator remains clear off mud would be extemely beneficial. Quote Link to comment Share on other sites More sharing options...
bishbosh Posted January 31, 2006 Share Posted January 31, 2006 Surely the flow rate is a double edged sword....? Faster and heat is removed from the engine quicker, but it has less time to loose it as it passes throught the radiator so re-enters the engine hotter. Slower results in the heat not being removed from the engine as fast, but the input water temperature is lower as it has had more time to cool in the rad? There must be an optimum flow rate for a given cooling system, or am I missing something Quote Link to comment Share on other sites More sharing options...
MogLite Posted January 31, 2006 Author Share Posted January 31, 2006 <SNIP>Unfortunately I don't have the asnwers to a problem that may not even exist; but once you are up and running, you can then start tweaking the cooling system by fitting larger radiator perhaps, a second radiator; more fans, vents, electric water pump, oil cooler, water butt in the back etc: What you are doing is correct IMO and it is good that you are antcipating any possible problems. Some mechanism to ensure the radiator remains clear off mud would be extemely beneficial. I've got a large oil cooler ready to go on, I'm going to put a motorcycle radiator fan on that I reckon Electric water pump and gearing the mechanical water pump are both possibilities - if I need them I've got a 12L fire stainless fire-extinguisher kicking around at home. It would be easy to use that more coolant capacity, but I'll have to find space for it I'll post some pictures soon of the mounts and shrouding. The rad is very well protected from mud, being at the back, and 1m+ off the ground A very useful debate Quote Link to comment Share on other sites More sharing options...
Astro_Al Posted January 31, 2006 Share Posted January 31, 2006 For what it's worth I agree with BishBosh's statement - I've certainly haerd of cases where REDUCING the coolant flow rate has solved overheating problems - you've got to give the water time to cool down as it passes through the rad. Of course you can go too slow... Al. Quote Link to comment Share on other sites More sharing options...
Jon White Posted January 31, 2006 Share Posted January 31, 2006 Of course the other thing you've got to think about is you've got to allow time for the heat to transfer from the block to the coolant! Jon Quote Link to comment Share on other sites More sharing options...
MogLite Posted January 31, 2006 Author Share Posted January 31, 2006 Okay - some piccies The shroud With the rad just resting in place, closed cell foam will seal it to the shroud The rear is mesh to let the air out Our 38a has the transit style more modern style radiator, and is a 4.6 V8 so is in the same ball-park The 38a rads core is approx 58cm x 48cm - divide by engine size = 605 Moglites rad is 60cm x 32cm - divide by engine size = 492 So its about 20% smaller, but with good fans and decent air-flow.....fingers crossed Quote Link to comment Share on other sites More sharing options...
simon_s Posted January 31, 2006 Share Posted January 31, 2006 More pictures....! Looking really good, can't wait to see it going! Quote Link to comment Share on other sites More sharing options...
will_warne Posted January 31, 2006 Share Posted January 31, 2006 Andy, how about having the header tank at the front of the vehicle? Run water to and from it with copper pipe so you get even more capacity plus apprecable cooling. I also guess you'll be running an air to oil cooler for the autobox? If your not cooling any of the lubricants with the radiator you won't be needing to get rid of quite so much thermal energy. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 31, 2006 Share Posted January 31, 2006 I may be missing the point, but surely a header tank is used to take up the expansion/contraction of the contents of the cooling system, not provide extra capacity? Quote Link to comment Share on other sites More sharing options...
will_warne Posted January 31, 2006 Share Posted January 31, 2006 I may be missing the point, but surely a header tank is used to take up the expansion/contraction of the contents of the cooling system, not provide extra capacity? True, but its a useful bonus. Quote Link to comment Share on other sites More sharing options...
MogLite Posted January 31, 2006 Author Share Posted January 31, 2006 Andy, how about having the header tank at the front of the vehicle? Run water to and from it with copper pipe so you get even more capacity plus apprecable cooling.I also guess you'll be running an air to oil cooler for the autobox? If your not cooling any of the lubricants with the radiator you won't be needing to get rid of quite so much thermal energy. Will I've got enough hoses and pipes and wires running front <-> back, I don't need to add water to that list Yeah I've got a massive autobox cooler, and a large oil cooler with the engine, so they'll both help against heat soak. Quote Link to comment Share on other sites More sharing options...
02GF74 Posted February 1, 2006 Share Posted February 1, 2006 For what it's worth I agree with BishBosh's statement - I've certainly haerd of cases where REDUCING the coolant flow rate has solved overheating problems - you've got to give the water time to cool down as it passes through the rad.Of course you can go too slow... Al. yes. that may well be the case at high engine revs but the moglite cooling problems (and most off-roading problems) are most likely to occur at low speed and probably low rpm where naturally forced air cooling is at a minimum as indeed is water flow. It would be interesting to get some data of heat trasfer vs flow rate in the engine block and radiator. I did work out the flow rate for v8 a little while back so we have a starting ball park figure. Also there is Newtons law of cooling - heat is lost faster when there is a bigger temperature; hence you want the water entering the radiator to be as hot as possible - probably can rule this one out of the equation as the thermostat takes care of this. If going by the time between placing your hand on a hot item and going "ouch" is anything to go by, heat is transferred pretty quickly between objects; I'd be surprised water flow is flowing that fast as to be a severe detriment to the heat transfer. Where is TC with the data when you need him!!! Quote Link to comment Share on other sites More sharing options...
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