How Important is Oil Temperature?
Oil is the life-blood of your engine, and maintaining your oil within safe operating temperature is extremely important.
Internal combustion engines are only around 33 per cent efficient, the other 67 per cent is wasted through bi products such as heat energy and noise, which has to be managed and dissipated in one way or another.
Oil is without doubt the most important fluid contained within a car, and the only fluid in a Formula Vee motor. The amount of moving parts in the Formula Vee motor inevitably transfers into friction, and when this is metal-on-metal contact it can be extremely wearing on the components. Engine and gear oil is used to lubricate these moving parts and in turn picks up a lot of heat.
The normal operating oil temperature for a Formula Vee is in the range of 100*C. When running at Sydney Motorsport Park in the recent day night meeting the LBR Formula Vee was struggling with oil temperature issues, with oil temperatures reaching 130*C and sometimes higher. For Formula Vee’s this is the danger zone where you risk doing serious damage to your engine.
When the engine creates excessive heat, it generally needs to be released to the surroundings through some form of heat exchanger. Most people would be familiar with water cooled engines that use a radiator as a heat exchanger and engine oil systems are no different, you use oil coolers.
Oil coolers resemble miniature cross-flow heat exchangers, they can be placed in any position within a car’s body to maximise their cooling efficiency. With oil coursing predominantly through the engine block, it very quickly gains heat, especially during vigorous driving like racing.
So, before the oil enters the sump or oil reservoir to be recycled through the system, it needs to be cooled so that the oil doesn’t reach an unusable viscosity. Viscosity is a measure of how easily a fluid flows, and as oil loses and gains heat, its viscosity changes. A thick, lumpy oil has a high viscosity – meaning it has more resistance and flows slower, while a smooth, thin oil flows more easily and therefore has a lower viscosity.
Automotive oils are specially designed to sit within certain ranges of viscosity, Formula Vee generally use a 15W-40 oil which is a thick and highly viscose oil, however if too much heat is transferred to the oil, its viscosity decreases to a point where it will struggle to lubricate engine parts. So it becomes a balancing act - you want oil to be viscous enough to cling to certain gears and other moving parts to keep them lubricated but you also want them to easily flow throughout the oil system to make it around the car’s mechanical parts. With oil temperature being an important factor in the change in viscosity of oil, cooling becomes an extremely important element in Formula Vee racing.
Oil cooling works just like water cooling systems on a car, with the heat energy required to be displaced to the surroundings. The oil enters the oil cooler at a high temperature, circulates through tubes that are lined with heat-releasing fins and then exits the cooler at a lower temperature, ready to start the process again. Based on thermodynamics, the size of the oil cooler needed can be calculated and can be plumbed into a car using extended oil lines to divert the fluid through the heat exchanger.
In race cars, oil cooling is extremely important due to the amount of heat transferring into the oil from the constant flat-out driving. Therefore, oil coolers need to be placed in areas of high air flow for maximum cooling to wick temperature away.
Placement of the oil cooler is important as you want to reduce the heat transfer and build up from surrounding parts be it the engine block, gear box, heads or even poor ambient airflow. Some Formula Vee designs will incorporate scoops into the body work to direct ambient air to the cooling fan and oil cooler in order to maximise efficiency of the cooling systems.
Oil cooling forms an important part of a race car’s design due to the highly tuned nature of the engine and the need to maintain safe operating temperatures. As an engine produces more power, it naturally creates more heat energy, this heat will then transfer to the oil. If the level of heat transfer is above what the original engineering was designed to cope with, which is the case with Formula Vee using the air cooled VW Beetle engine, then measures need to be taken to reduce and remove any additional heat from the oil system.
In terms of positioning, the rear mounted engine found in Formula Vee presents its own challenges and can often require air intakes and associated ducting to direct cool air to the cooling systems. On top of this many Formula Vee’s are designed with partitions separating coolers from the engine and gear box as an added measure to reduce heat transfer.
Oil and engine cooling are an aspect of motorsport that should be taken extremely seriously. Not enough cooling and the resulting over heating can lead to catastrophic failure of the main internals of an engine. As oil is the life-blood of an engine, keeping it within its safe operating temperature range is vitally important and something that may need to be addressed if you experience high temperatures.