Reducing Friction in Car Engine Moving Parts: Techniques and Insights
Engine performance and efficiency are largely determined by the amount of friction between its moving parts. In this article, we explore the innovative methods used to reduce friction in car engines. From hydrodynamic wedging to optimized component design, we delve into the technical details and practical implications.
Understanding Hydrodynamic Wedging
One of the key strategic techniques employed in modern engine design is hydrodynamic wedging. This term describes the phenomenon where a fluid is trapped between moving parts, allowing them to glide on a film of fluid, significantly reducing friction. The best illustration of this is the hydroplaning effect observed in a car driving over a water puddle, where minimal contact with the road reduces friction almost to zero.
In the context of car engines, hydrodynamic wedging is achieved by fitting engine parts to precise tolerances and pressurizing a lubricating fluid (usually oil) to ensure a consistent film between the moving components. This method is particularly effective in the crank bearings and around the cylinder walls, where piston rings and bore walls interact.
Comprehensive Friction Reduction Study
To gain a comprehensive understanding of the sources of friction and parasitic losses in engines, a detailed friction breakdown study was conducted over several months. The investigation involved measuring the engine's rotating torque on a DC electric dynamometer, systematically removing or modifying components to attribute the friction losses to specific parts.
Our primary focus was on reducing the sliding friction between the piston and the bore wall. Low-tension piston rings played a crucial role in this. By achieving precise control over bore cylindricity, taper, surface finish, and other quality factors, we significantly reduced this type of friction. Importantly, we also monitored and confirmed blow-by and oil consumption before implementing this change.
Case Studies and Component Optimization
Several components were optimized to reduce friction and improve overall engine efficiency. One notable change was the water pump impeller design. We transitioned from a stamped steel straight vane type to a shrouded plastic swept vane type, cutting water pump torque by nearly 50% and reducing cavitation at the impeller inlet.
We also expanded the oil pump bypass orifice size, which reduced oil pressure at low temperatures and higher RPMs. The combined effects of these changes led to a 10% reduction in friction torque, with a corresponding improvements in fuel consumption of 2% on average across three different speed and load points.
Other less obvious areas were also scrutinized for improvement. For example, crankcase pumping work, which involves pushing gases from one cylinder to the next, requires careful design to minimize friction. Main bearing bulkhead flow paths and sufficient crankcase volume contribute to reducing this work. This is why many racers opt for dry sump systems under vacuum.
To further enhance aerodynamics, the crankshaft counterweights were reprofiled with a more aerodynamic “bullet nose” design. This not only improved air flow around the counterweights but also allowed for a slight reduction in the counterweight fan angle, making it easier to balance the engine.
Factors Influencing Friction Reduction
The choice of oil is another critical factor in reducing friction. The trend towards using lighter oils, such as 0W20, has seen a rise in modern engine specifications. These lighter oils provide superior flow properties at low temperatures, allowing them to effectively lubricate and cool engine components with minimal friction.
By combining these techniques, engineers can significantly reduce the friction and parasitic losses in car engines, leading to improved performance and reduced fuel consumption. The end goal is to create more efficient, durable, and reliable engines that provide a smoother and more enjoyable driving experience.
Conclusion
Through targeted modifications and optimization, the friction between the moving parts of a car engine can be substantially reduced. Hydrodynamic wedging, precise component designs, and the use of lighter oils are just some of the methods employed in this process. As technology advances, ongoing research and development will continue to push the boundaries of engine efficiency.
Marketers and automotive enthusiasts alike can benefit from a deeper understanding of these engineering principles, as it enables them to make informed choices about how to maintain and optimize their vehicles for better performance and longevity.