Engine Cooling System - Keeping Your Cool

There are things in racing that are easy and things that are hard. The easy parts comprise a fairly short list, but things that are hard in racing, well, that list could go on for pages.

One thing that should be easy is keeping our race cars cool during competition. However, this is a difficult task for a stock car racing on a short track. The car is not moving particularly fast, but the engine is wide open and under full load. It is very much like going down the freeway at 65 mph with the engine doing the same amount of work it would at 150 mph. There is a heavy load being placed on the engine, and with that load comes heat. It is even tougher because you have other cars blocking the air to the front of your car and keeping needed cool air from going through the radiator. What is a racer to do?

First, we need to look at cooling the race car from a systemic perspective:

* What are the various component parts?
* Have we picked the right parts to do the job?
* Is the OEM radiator really up to the job?
* Do we really need an aluminum radiator?
* Why is an aluminum radiator a better choice?
* Is the whole system up to the task?
* Do we need a fan?
* Are we performing the correct maintenance on a weekly basis?

Within the cooling system, we have the major components: the radiator, water pump, hoses, fan, drivebelts, fan shroud, thermostat, coolant, and a pressure cap. From an integration perspective, we have to make sure all of these parts are in top operating condition and working together, or we will have some issues while on the track.

Simple things, such as a radiator hose, can cause the system to work poorly or completely fail. Leaking is a failure that is easy to understand, and the failure mode is easy to define. But the same hose that may be collapsing at high engine speeds when the water pump is really pulling can cause a system failure that is very difficult to diagnose. If the hose came with a spring in it, do not remove it simply because it is difficult to install with the spring in the hose. If that is a problem, get a different hose.

We need to remember that every race car is a custom application. This applies even to a Bomber class. If your race car has its roots as a passenger car, we need to remember that the car was not designed for the kind of heat loads it is going to experience in a race car. We are using the car for an application it was not designed for, and we are asking a cooling system to cool at a level of heat input that it was never designed to accomplish. The cooling system was designed to keep the engine cool within normal driving conditions on the street, not the racetrack. As we develop more horsepower from passenger car engines, the cooling systems that came with the car as a stock component become more marginal.

Copper has a better heat coefficient than aluminum, so you may ask why racing radiators are made from aluminum. It is about more than just the weight. Logic would dictate that you could make a radiator out of copper and it would be smaller, and consequently lighter, than an aluminum radiator due to the better heat coefficient. The real reason is that copper radiators are not all copper. They have a good percentage of lead in the copper that makes up the radiator core. This lead acts like an insulator and impedes the radiator's ability to reject heat. Another reason is that the braze material covering the copper as part of the core manufacturing process also impedes the heat transfer process.

Aluminum radiators do not have the same issues because the braze material used in the core manufacturing process is aluminum based. Plus, aluminum radiators are lighter. These are the two main reasons that aluminum is a better selection for racing radiators. Still, though, you need to be careful with aluminum radiators. Many OEM radiators are aluminum, but they are not suitable for racing applications. This is due to the fact that the tanks are not welded onto the core, and the pressures spikes that can develop in racing radiators can blow the tanks of an OEM radiator. The issue outweighs any of the potential upsides to using an OEM radiator versus a fabricated racing radiator.