Internal combustion engines contain explosions, and explosions create heat—lots of it. This heat is kept in check by a cooling system that circulates fluid (except in older air-cooled vehicles) around the hottest parts. This cyclical system pushes the fluid past the hot metal components and out into the radiator, where it dissipates the collected heat into the cooler atmosphere.
Although engines are designed to deal with a certain amount of the generated heat, an inefficient or malfunctioning cooling system will allow too much to build up. If your motor is tuned to the knife-edge and the heat isn’t controlled you can end up with detonation, the engine oil will break down as it overheats, leading to lubrication issues, and all manner of other horrors could spell a noisy, smelly expensive death to your motor. Increasing the power of your engine requires upgrading of many of the car’s other components. And while it is obvious that a quicker ride requires better brakes, tires and suspension, the cooling system is often overlooked—many a massive workshop bill can testify to this sad fact.
To use a basic comparison, accepted wisdom says that in everyday life the human body requires around two liters of water per day. If you live in a particularly hot climate (say Arizona) you would want to add 25% (or half a liter) to that, or, if you partake in strenuous exercise you would also want to add half to three-quarters of a liter. Your engine is basically the same. In everyday use and in a moderate climate, as long as the fluid levels are well maintained your car’s OEM cooling system will be fine. If you live in Phoenix it will probably need topping up more often and if you drive ‘enthusiastically’ on a stock engine you’ll want to do the same. If you add some serious cash into the motor, you’ll need to seriously think about upgrading some parts.
It makes sense if you think about it. If you’re expecting 25% more power out of your engine, you can expect a similar increase in the heat load generated by the engine that is passed into the cooling system. But where do you start? Well, let’s look at the individual components. You get a radiator, a fan, a water pump, a thermostat, a few sensors, an overflow tank, coolant and a selection of hoses, belts and clamps to connect it all together. If you’ve got a turbocharged or supercharged engine you’ll likely have an intercooler as well. It’s a fairly simple setup, but let’s take them one at a time…
The most obvious cooling system constituent is the radiator—you know, that giant slab of metal that sits behind your car’s front grille. It consists of an outer frame that is bolted to the car’s chassis and rows and rows of tubes (the core) through which the coolant flows. Attached to the tubes are thousands of fins; these effectively increase the surface area. One way to upgrade the radiator is to get a larger one, but due to space constraints and the reluctance to add weight to the front of the car, this isn’t necessarily the solution. But don’t fear, there are ways of getting a more efficient radiator by increasing the surface area without greatly increasing its physical size—and also reducing weight into the bargain (a direct replacement alloy rad can save 5-8kg for most models).
Firstly, moving anything that sits between the radiator and the cooling airflow is a good move. So creating more space between the radiator and ancillaries like air conditioning condensers will expose more of its face to the cooling airflow, hence making it more efficient. More tubes and fins also increase the surface area that can transfer the heat to the surrounding air, so this is the way to go—with a word or two of caution attached. However, due to the law of diminishing returns, you can over-egg the addition of rows and fins to a radiator to the point where it becomes counter-productive and actually reduces your radiator’s performance. Any racing engineer will tell you that three or four rows of tubes in a core is probably optimum; any more and you risk slowing the coolant’s flow. This can result in laminar flow—slower moving fluids passing over each other like cards being shuffled in a deck—creating an insulating layer of coolant that actually retards the heat transfer.
In addition to this concern, adding fins is a good idea and the optimum for performance radiators is around 12-16 fins per inch; any more can place them too closely together, restricting the cooling airflow, making it less efficient and reducing heat transfer. Generally the most effective type of radiator fin is a louvered one, this turbulates the airflow and increases the cooling action. The downside is that louvered fins can become more easily clogged with dirt or debris that passes through the front grille, so they should be checked and carefully cleaned more often. Saying this, the benefits far outweigh the added hassle of occasionally having to clear the clogged debris.
To maximize the amount of cooling air fed to the radiator, cooling plates can channel this air directly to the rad. Not only do they increase the efficiency of the radiator by anywhere between 10-15%, they also look very cool in any engine bay. There are many top radiator manufacturers, including Koyorad, Mishimoto and Fluidyne, and any of their upgraded radiators, either OEM replacements or performance models, make up the first step to improving the cooling system for any performance machine.