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Without doubt I would say the that the most common concern TR owners have regarding the performance of there cars is that of engine cooling, or rather the lack of it. This has led to this outpouring but it should be emphasised that it is composed with the operating conditions found in Australia in mind. Cold climates cause other problems that we fortunately do not experience.
This is the first of three articles. The second covers the operation of the system and some common problems. The last will look at some practical improvements.
Before we look at the system itself, we should get some understanding why we need it at all. After all, if we could retain all the heat energy released during combustion the engine would be much more efficient than it is. The problem is that the materials available to be used in the construction of the engine would not stand the heat. Materials are available and engines have been built that do not use any coolant at all…. I know….. we have all had one of them at some stage but these were designed to run without coolant. The cost of these is prohibitive and life expectancy low but more importantly they are diesel.
When combustion takes place, the heat generated is quite high. High enough to destroy pistons valves etc very quickly. The temperature of all these components must be controlled. Internal components such as pistons, rings, etc are cooled primarily by the engine oil and contact with the components that are fluid cooled (block and head). The temperature of the fuel air mixture in the combustion chamber is also a very important factor in the engines operation. It must be kept at a temperature that will not allow it to self ignite before the spark is introduced or explode once the spark is introduced. If this happens we get the ‘pinging' sound we hear (pre-ignition and detonation).
The mixture is heated by a combination of,
It can be seen then, that the engines coolant temperature not only effects the physical components of the engine but also the combustion process and hence performance. Whilst the prime source of heat is the combustion process, heat is also generated by the friction of the moving parts in the engine. The oil primarily carries this heat caused by friction away.
So we have the heat generated by both combustion and friction to control. Of the heat generated by combustion approximately 1/3 is lost out the exhaust, 1/3 lost through the cooling system, and 1/3 is converted to power (HP). Of this last 1/3 some is then lost to friction in the form of heat. It is important to note that if you increase the HP output of the engine you also increase the load on the cooling system and exhaust by the same amount. This increase will of course only be felt when you use the additional power. Our concern here is with the 1/3 lost to the coolant system. This system not only consists of the one, as we commonly know it, (radiator pump, etc) but also the surfaces of the engine exposed to the air stream (block, sump, cylinder head, rocker cover, etc) and an oil cooler if fitted.
Lets look at what we term the cooling system. On the TR this is as stated previously, a fairly basic one. It consist of,
See Part 2