Cool MG
By: Boytjie
Overheating is an ongoing (and expensive) problem for our cars …. The original cooling system simply cannot cope in modern day traffic and with modern fuels which burn hotter. …. They were not designed to run in ambient temperatures that we experienced in S.A. ...(especially in summer)
I thought there may be some member’s interest in the modifications I have done to my MGA, E-Type and Healey. …Adopting these modifications, one can be assured that driving your car hard on a warm summer's day, or sitting in traffic, will never be a problem again.
Please accept that the views expressed here are my personal opinions.
For the analytically minded who need to question the technical reasons why all these mods are necessary… the major factors that influence the temperature of the engine are:
The ambient temperature ... | |
The capacity of the radiator ... (too often the standard engine is modified by increasing capacity or "breathing mods" which all means burning more fuel, but the radiator capacity is not increased) | |
The air flow through the radiator. | |
The rate of water flow through the radiator. | |
The water pressure in the radiator. | |
The air fuel ratio (rich or lean) | |
The spark advance (timing) | |
And often overlooked .... The air flow through the engine compartment. |
Some other hidden facts that affect the engine temperature may be of interest, this is especially so when trying to understand the reason why it is so important to control engine temperature and avoid overheating "at all costs" .
Firstly, the engine relies on the conversion of fuel into heat, and then into mechanical energy to produce power. Only about one third of this heat is converted into power; another third is eliminated through the cooling system... Therefore it is essential to ensure that the cooling system is operating efficiently
If the engine temp is allowed to go to too high (around 80 deg. C is ideal) it will follow that the oil temp will increase which could lead to excessive oxidation, excessive wear and possible permanent damage (ever heard of cracked or warped cylinder heads?) .... Conversely, excessive engine wear occurs if the engine is run below 70 deg C for long periods, and calls for more frequent oil changes... So about that thermostat ? ... More later.
It seems obvious that the elementary basics must be dealt with before going to all the trouble of carrying out, and modifying the cooling system ...
As a priority, ensure that the cylinder head and block have been chemically cleaned to remove 50 years of iron oxide-rust (a deposit of twelve thousands of an inch thick will cut heat transfer up to 40 % | |
The timing is set correctly. | |
The air / fuel ratio is set correctly |
Many of our old gauges do not tell the whole truth, (check em) also remember no matter what the gauge tells you, the actual temp around the combustion chamber is far higher. It is also true that after switching off the temp will increase dramatically due to loss of water circulation, hence the reason why we have to pressurize the system .... to avoid water loss, due to internal temperatures going well above 100 deg C which is inevitable after switching off. (heat soak)
There is a good argument as to where the sender unit for the temp gauge should be fitted,... in the cylinder head or on the top of the radiator ?
There is a good argument as to where the sender unit for the temp gauge should be fitted,... in the cylinder head or on the top of the radiator ?
Now to the modifications :
I am not going to get into trouble or into an argument about changing the originality of our classics. ... Fact is, I like to use my cars at any time and not limited by fear of overheating....... If necessary one can always take off the "workable mods" and put on the original parts before the meetings, the mods can always be refitted (ASAP) after the critics have left.
Taking the basics into consideration;
I am not going to get into trouble or into an argument about changing the originality of our classics. ... Fact is, I like to use my cars at any time and not limited by fear of overheating....... If necessary one can always take off the "workable mods" and put on the original parts before the meetings, the mods can always be refitted (ASAP) after the critics have left.
Taking the basics into consideration;
The ambient temp... Not much to do | |
The capacity of the radiator ..... The MGA is fitted with a 3 row copper core, I fitted a 5 row "new generation" core to the original radiator bracket/frame (Silverton) ... Only change required is to cut approx 50 mm out of the bottom shroud , (the new rad. is slightly tilted) | |
The air flow through the radiator ....... I fitted a ‘flat motor’ Ford fan on the inside (pulling) ... I personally do not like those "Twisted blade cheapies".... The fan is controlled by a relay fed via a thermo switch (fitted in the cylinder head) which comes on at 85 deg. C and off at 75 deg.(Also remember to seal the area behind the grill to ensure that ALL the air coming in, flows through the radiator). | |
The water flow through the radiator .... I fitted a Davies Craig electrical water pump, which means the mechanical pump is machined off, the impeller shaft and fan removed … Only the housing is retained .. (This gives you space for the electric fan). The electric pump is fed via a relay which is switched on from the ignition switch... giving the option to switch the pump on again after shut down, (to avoid the inevitable overheating, caused by “heat soak” Davies Craig also supply a controller that will allow run on for 2 minutes after switch off)... the fan will come on automatically if the temp is over 85 deg. C.... And yes, keep the thermostat if you are not disciplined to warm the engine by prolonged idle after first start-up. | |
Pressure in the radiator .... I fitted a "outer sealing" radiator cap (the one without the spring) on the radiator and a 6 mm hose (inner diameter) is connected from the overflow outlet on the radiator to a small header tank (taken from the older Range Rover/ 110 Landy and fitted higher than the cylinder block, against the bulkhead with pressure cap..... No more water loss! | |
Consider directing the air entering via the inlet scoop (next to the radiator) towards the exhaust manifold, which will encourage taking the hot air, in the engine compartment, down and out . ... (Hence the reason why the E - type has those sexy louvers on the bonnet) | |
I fitted a suitable alternator to cope with the additional power requirements .... V belt run directly off the crank pulley, (no more mechanical water pump). |
A lot of the above is fairly elementary and nothing new, but it might just help members to "Use their cars without fear of overheating"
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