How hot does your engine run? Is it on the cool side? The hot side? Where should it be? How big of a radiator should you run? Antifreeze or water? Tap or distilled? Do you need a pressurized cooling system? What is a pressurized cooling system?
The answer is yes—you need to know more about the cooling system in your race car.
Granted, a book could be (and probably has been) written about each aspect of the cooling system of a race car (and you should go find them and read them). Though we don't have the room to cover everything, we'll hit as much as possible, starting with the basics.
What is the purpose of the cooling system? An internal combustion engine is simply a self-driven air pump. Fuel and air are ignited, blah, blah, blah—you know all that. A huge byproduct of making power is heat, and that heat needs to be removed from the engine. Water is a clean and efficient way to do just that.
In a cooling system, fluid is pumped through the engine (through the cylinder heads and around the cylinders). As fluid passes through, it absorbs heat from the combustion process, but the heat needs to be removed from the fluid. Enter the radiator. Radiators are a combination of tanks, tubing, and fins that work together as a heat sink, removing the heat from the fluid as air passes though. You knew all that, so you must be a cooling expert, right? Wrong!
That is as basic as it gets. When it comes to racing, everything is a science, and the level of technology is simply astonishing. From the materials, to the design, to the speed of the fluid passing through the engine and radiator, an effective, efficient cooling system is a highly calculated orchestra where every part of the system works together.
Closed Coolant System
The closed coolant system has been the norm for street and race cars for some time. The system is fairly simple. Fluid is pumped through the engine and cylinder heads by the water pump. The coolant absorbs heat from the engine and the coolant is cooled in the radiator. Though the closed system is efficient enough for most short track racing, as races get longer and cars race closer (nose to tail) for longer periods, the closed system needs more air than the radiator gets in many cases. The byproduct is higher coolant temperatures, often resulting in the engine overheating, which can lead to engine damage.
If you run in the lower levels of short track racing where you races don't normally exceed 50 laps, this is all you need. In most cases, depending on where you live and the climate you race in, a stock or stock-style radiator is all you need to efficiently keep the engine cool enough for Saturday night.
If you run a Super Late Model, or compete in races of 100 laps or more, you may want to look at a pressurized coolant system.
1. The heart of any cooling system is the radiator. It plays an integral part of the system by removing heat from the coolant as it passes through the core. Air moving through the radiator cools the coolant.
2. The radiator cap helps control the pressure in a traditional closed coolant system.
Pressurized Coolant System
Pressurized water systems are relatively new to the short track and stock car world. This technology has been around in F-1 and Indy Cars for many years. It's more efficient and more failsafe than the customary closed cooling system that has been around for the last 80 years. This is the future for cooling systems that will make it's way into the stock car and short track arenas over the next few years.
Pressure in a cooling system is vital for keeping water in contact with the metal surfaces of the cylinder heads and block. Pressure keeps the air compressed and maintains the water-to-metal contact that is vital to prevent localized boiling or steam pockets in the combustion chamber areas of the cylinder heads. When a situation occurs that causes temperatures to rise such as lean fuel mixture, too much ignition advance, or a clogged radiator, the air in the water will expand and form small steam pockets. This will start in the combustion chamber area (hottest spot) and the steam pocket will be attached to the metal surface. These spots get very hot and since it's in the combustion chamber area, it will create a detonation problem. This is why engines lose power when overheating occurs. Once steam starts in the cooling system, the problem will magnify and continue to get worse.