While automotive cooling systems are complex in their design, it’s a simple two-step plan that will help you increase the performance of your racecar’s cooling system - maximize both the water and air flow.
According to EMP Stewart Components, a leader in automotive high-performance cooling technology, following a few simple rules will help you get the most out of your race vehicle's cooling system.
First, always consider the cooling components as a system, not as individual pieces. Adding a high performance cooling component here or there might seem like a good way to increase performance, but mismatched components usually will do more harm than good to your racing engine.
That said, a racing cooling system upgrade starts by choosing a water pump that exceeds the performance and reliability parameters of the standard factory issue water pump. High performance water pumps with features such as special high-strength castings, larger flow passages, more efficient impellers, and stronger bearings will be indicators of superior water pump design and performance.
Also, look for a pump that will give you high performance at increased RPM. Most original manufacturer pumps are designed to meet performance standards at relatively low RPM. Adding a water pump that can withstand high performance RPM situations, while drawing less horsepower than it’s more inefficient OEM counterpart, is one of the easiest and least expensive ways to add a couple of horsepower to your engine’s output.
Should you add a high performance water pump to your engine’s mix, make sure you have the appropriate pulley and drive system to match.
The optimum flow and efficiency of any water pump is based on a specific speed. A mismatched pulley or drive system will not only defeat the performance of the water pump and overall cooling system, but could also cause significant damage to your expensive racing engine.
Radiators play a big part in any cooling system – performance or otherwise. Whatever size radiator you use, remember coolant must flow through the radiator at a speed (velocity) fast enough to create turbulence.
That turbulence allows heat transfer to occur not only from the coolant to the heat exchanger by conduction but also by the random mixing of the coolant. Newer, high performance radiators with wider tubes and less cross section areas, require less velocity to achieve optimum thermal transfer.
The best radiators for racing application are made out of aluminum. They are superior to copper or brass because they dissipate heat more efficiently in addition to decreasing weight.
Radiators with a higher number of fins will cool better than a comparable radiator with fewer fins. Double-pass radiators require 16 times more pressure to flow the same volume of coolant than a single-pass radiator. Meanwhile, a triple-pass radiator requires 64 times more pressure than its single pass counterpart.
Because automotive water pumps are centrifugal in design – not positive displacement – the increased restriction of a double-pass radiator will cause a decrease in flow . This decrease in flow usually offsets any advantages gained by using a high-flow water pump, so like the pulley system, make sure your radiator is appropriately matched to your high performance water pump.
Also remember that gross flow radiators – not upright- are superior because the radiator cap is located on the low pressure (suction) side of the system. This configuration prevents the system from forcing coolant past the cap in high RPM situations.
While we’re on the topic of radiator caps, it’s always best to match the cap to the highest pressure the radiator is rated for. In most racing applications, that’s 29-32 PSI. The cap should always be mounted at the highest point of the cooling system. This allows air to migrate to just below the cap. If the cap vents any pressure from the system, it will vent the air first.
On the topic of thermostats, any thermostat used in a high performance situation should not restrict flow when open. Some thermostats, like the EMP Stewart Components/Robert Shaw Thermostat, also feature 3/16th inch holes in the poppet valve that allows coolant to bypass the thermostat even when closed. This modification allows the thermostat to function properly when used in conjunction with a high-flow water pump at high engine RPM.
A common misconception about cooling systems is that if the coolant flows too quickly through the system, it will not have time to cool properly.
Because automotive cooling systems are a closed loop, coolant allowed to stay in the radiator longer will also stay in the engine block longer producing increased coolant temperatures. This can easily lead to ‘hot spots’ and ultimately, engine failure.
It is for this reason EMP Stewart Components suggests you never use a restrictor in your racer’s cooling system.
While there are many types of coolant on the market today, water is still the best coolant available. EMP Stewart Components has tested most of the ‘miracle coolants’ on the market and has concluded that water still works the best – especially when used with a corrosion inhibitor such as Prestone Super Anti-Rust or any other such product.
While electric fans are often used to replace mechanical fans in many applications , these should not be used in dirt track racing applications.
When using a mechanical fan, always use a fan shroud. Most mechanical fans are not designed for high RPM use and will create serious vibration problems due to turbulence when run at 6,500 RPM or higher. This is not a balance problem, but a turbulence problem and will eventually destroy the water pump and other related components.
Also – remember that large fans can drain you engine of horsepower, so never use a fan larger than necessary for your particular racing application.
Finally, make sure the hoses on your cooling system maximize coolant flow. Smaller ‘AN’ style hoses decrease flow and inhibit your cooling system, so they should be avoided in oval track racing situations where the events are longer in nature.
AN lines (size 10) are best used in racing situations when they connect aluminum cylinder heads to the thermostat housing crossover. Aluminum heads usually have smaller water jackets than cast iron heads. The installation of these lines will offset the smaller water jackets and provide additional coolant flow .
A second set of 10 AN lines – from the center of the cylinder head (just below the exhaust port) to the pressure side of the water pump will offset the lack of area in the smaller water jackets due to the extra cylinder head material.
Remember, keeping your cooling system clean and functioning properly is one of the easiest ways to keep your racecar performing at peak level – especially in extended lap events.
Also, any upgrades to your car’s cooling system should first consider the effect of the new part on the entire system. Mismatched parts – whatever the area of your racecar – won’t give you the performance you are looking for and can lead to bigger problems such as mechanical failures.
By sizing up your racecar’s cooling needs and acting accordingly, you can improve performance and ultimately save money by optimizing your engine’s performance and longevity.
In the end, it’s all about staying cool.
