landroversforever Posted May 21, 2013 Share Posted May 21, 2013 Is it possible to have too large a radiator? Assuming that the thermostat is functioning correctly, is there a problem in having a larger and more efficient radiator than standard? Will it overcool the engine? Can't make my mind up . For arguement's sake, lets say a small watercooled bike engine hooked upto a rad for a 1500Bhp V8 Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted May 22, 2013 Share Posted May 22, 2013 Assuming the thermostat is functioning correctly, no - there is no problem in having a more efficient radiator than standard. Quote Link to comment Share on other sites More sharing options...
ejparrott Posted May 22, 2013 Share Posted May 22, 2013 No, if it gets too cold, the stat shuts it off. Quote Link to comment Share on other sites More sharing options...
landroversforever Posted May 22, 2013 Author Share Posted May 22, 2013 Cool, that's what I was thinking initially . Quote Link to comment Share on other sites More sharing options...
TSD Posted May 22, 2013 Share Posted May 22, 2013 I wonder if it might be possible to create system that's never stable, that cycles between two temperature extremes, maybe a few degrees apart, maybe more. Imagine the rad is so overspec that the 'stat can't control the temperature, because any significant opening of the thermostat causes the system temperature to drop rapidly (faster than the 'stat can move). If the stat is typically close to fully closed, then the rad will contain a mass of water that's abnormally cold, which is released into the system when the stat starts to flow coolant. This is why on some cars you see a temperature drop as the stat opens, so the needle rises from cold to just above normal, then drops back. Ideally the rad should be sized such that the stat is operating close to the middle of it's operating flow range. Don't know if such temperature cycling would cause any issues, but steady temperatures 'seem' nicer, same reason I prefer mechanical cooling fans to electric ones. Quote Link to comment Share on other sites More sharing options...
landroversforever Posted May 22, 2013 Author Share Posted May 22, 2013 I wonder if it might be possible to create system that's never stable, that cycles between two temperature extremes, maybe a few degrees apart, maybe more.Imagine the rad is so overspec that the 'stat can't control the temperature, because any significant opening of the thermostat causes the system temperature to drop rapidly (faster than the 'stat can move). If the stat is typically close to fully closed, then the rad will contain a mass of water that's abnormally cold, which is released into the system when the stat starts to flow coolant. This is why on some cars you see a temperature drop as the stat opens, so the needle rises from cold to just above normal, then drops back. Ideally the rad should be sized such that the stat is operating close to the middle of it's operating flow range. Don't know if such temperature cycling would cause any issues, but steady temperatures 'seem' nicer, same reason I prefer mechanical cooling fans to electric ones. TheWrecklessEngineer should know more about this.... How would it then work with a raw sea water cooled marine engine? That's the biggest rad in the world!! Quote Link to comment Share on other sites More sharing options...
zim Posted May 22, 2013 Share Posted May 22, 2013 TheWrecklessEngineer should know more about this.... How would it then work with a raw sea water cooled marine engine? That's the biggest rad in the world!! Offshore we just use heat exchangers (and i assume thermostats within pipework). Sea water in one end and out the other. Coolant running through plates within / next to the sea water plates. Engines warm up quickly if you loose sea water though ! G Quote Link to comment Share on other sites More sharing options...
miketomcat Posted May 22, 2013 Share Posted May 22, 2013 Offshore we just use heat exchangers (and i assume thermostats within pipework). Sea water in one end and out the other. Coolant running through plates within / next to the sea water plates. Engines warm up quickly if you loose sea water though ! G The sea in a marine set up is basically the same as the air in a car set up a heat exchanger is just a radiator inside a tube you still have a sealed system with antifreeze in it. I think tsd has a point if the rad is way over spec you shorly risk cracking something due to massive temperature change. I know the thermostat rarely opened on the tomcat unless you took it for a blast. Mike Quote Link to comment Share on other sites More sharing options...
Retroanaconda Posted May 22, 2013 Share Posted May 22, 2013 Easiest to just have a radiator that's spec'd for the engine, as you don't gain anything from going bigger than required. Certainly for the 200Tdi Land Rover built in plenty of leeway with the standard radiator based upon possible operating conditions, so I'd just stick with a standard 200Tdi radiator (or if you fancy an earth-mover core then one of those but to the same cooling spec). Quote Link to comment Share on other sites More sharing options...
Team Idris Posted May 22, 2013 Share Posted May 22, 2013 Small petrols arn't so bothered, but big diesels will not like it if they are not working hard. Normally flow is in one end of the engine block and out of the other, so if you reduce flow by shutting the thermostat, the water temperature difference goes up, which will leave one end colder. That will help bore glazing which with the big fellas' will mean engine oil coming out of the exhaust pipe! (black rain) I think a better set up was in the old days when the water flow was constant, but vents closed off the cooling air supply. Same sort of thermostat technology, but with a lever instead of a valve. Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted May 22, 2013 Share Posted May 22, 2013 TheWrecklessEngineer should know more about this.... How would it then work with a raw sea water cooled marine engine? That's the biggest rad in the world!! Yes, it is possible, but only normally seen if you have an electric controller rather than a wax type thermostat. Electric types have parameters that can be changed that dictate the system response - meaning they can be much more responsive than a simple thermostat. The simple thermostats open/close too slowly to cause system instability. It all falls under the hat of 'control theory', which is a subject that you can get a phd in should you so choose. It does however, model a surprisingly large number of systems, from cooling systems/cruise control/whether a ship will fall over/the stock market/weather. Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted May 22, 2013 Share Posted May 22, 2013 Offshore we just use heat exchangers (and i assume thermostats within pipework). Sea water in one end and out the other. Coolant running through plates within / next to the sea water plates. Engines warm up quickly if you loose sea water though !G Same here. Wax type stats on the water jacket side of the cooling system, but electric controllers for charge air coolers, lube coolers and for some bearings and other assorted machinery! Quote Link to comment Share on other sites More sharing options...
TSD Posted May 22, 2013 Share Posted May 22, 2013 It all falls under the hat of 'control theory', which is a subject that you can get a phd in should you so choose. Didn't get the Ph.D, but have been a specialist in control loop design (PLLs specifically) for 20+ years Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted May 23, 2013 Share Posted May 23, 2013 Didn't get the Ph.D, but have been a specialist in control loop design (PLLs specifically) for 20+ years I have a friend who got the Ph.D. He showed me what he was working on once. My brain promptly melted. Quote Link to comment Share on other sites More sharing options...
landroversforever Posted May 23, 2013 Author Share Posted May 23, 2013 I'll explain some the thoughts behind my ramblings 200tdi disco engine in my 90. My rad has failed so I'm replacing it. I want to go for the full size Allisport intercooler at the same time. So I'm looking at the larger replacement rad they make so future trips to hot places are not compromised by the FMIC. (I'm sure someone mentioned to me that some of the companies don't like full size ICs as they compromise the engine cooling). Quote Link to comment Share on other sites More sharing options...
Team Idris Posted May 23, 2013 Share Posted May 23, 2013 The math on this is a pig. But essentially the turbo air is really hot, (250 deg.c) but doesn't have huge amounts of energy. (An 11 litre diesel is only doing about 50-60 kW of intercooler heat). So you could say an intercooler adds five degrees to the ambient in a good air flow? So intercooler heat coming off makes the rad less efficient - Bad! But the engine rad is now full width, so with the same core thickness as OE it has more surface area - Good! But it has the air back pressure of the intercooler fins and rad fins combined - Bad! But air entering the head is cooler - Good! The engine will get less air flow so it does less block cooling - Bad! (but not very) And you can baffle a big rad, but not obtain more power from a small one. So a big rad and a big intercooler should be okay as Andy knows what he is on with and has already looked at all of above But ask him about how to get the best from your fan for the hot times. Forcing air though the rad without re-circulation is the key in a 45 deg.c ambient. Quote Link to comment Share on other sites More sharing options...
Team Idris Posted May 23, 2013 Share Posted May 23, 2013 Just as a daft aside; you could cool turbo air with the cooling air leaving the rad, but only down to a point. But a lot of heat would be removed from 250 deg.c turbo air charge even with 80 deg.c cooling air. What would work well is a cooling-pack sandwich, with two intercoolers and an engine rad as filling. Put the engine rad between the two intercoolers and pipe the intercooler nearest the engine to the turbo. Then connect the hot-intercooler exit to the intercooler at the front of the landy. This front intercooler gets fresh virgin ambient-air so it finishes off the turbo air cooling, down to say 5 deg.c above ambient. As this front-intercooler does less work than a normal one, the air leaving it is only heated a little, making the engine rads job easier. Simples But a tad expensive............. Quote Link to comment Share on other sites More sharing options...
tacr2man Posted May 23, 2013 Share Posted May 23, 2013 In Australia it wasnt the intercoolers that were causing the problems in high load /high ambient operation (climbing sand dunes) with the popular make 4x4's it was the aircon condensors stuck in front of the rads, so they had to turn them off , and sweat instead .. I was able to be smug and cool as my a/c was a roof mount Quote Link to comment Share on other sites More sharing options...
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