High-performance automobiles require seals that must face even more rigorous constraints and provide reliable performance in operating environments where standard seal designs would fail. In this blog post, we’ll review the various categories of seals used in automotive applications, discuss how high-performance automotive seals differ, and what sealing solutions are currently being used.
Automotive Seal Categories
Seals can be used for multiple purposes with the primary ones being the exclusion of contaminants, reduction of friction, leak prevention, and the containment of pressure. That said, there are several different categories of general automotive seals that also apply to high-performance automobiles.
Driveline seals are key to a smooth, reliable transmission and not only aid in reducing power losses but help to better optimize fuel consumption. In addition, driveline seals are critical to the overall performance of the transmission system. As a category of seals, they include axial seals, transmission seals, and bonded pistons.
While comfort is not typically a major concern for high-performance automobile drivers, braking capacity and the ability for the vehicle to hold the road certainly are–making high quality, reliable suspension seals essential to both safety and control in racing environments.
Keeping the oil or grease lubricant contained and uncontaminated in wheel bearings reduces friction and power losses. That happens to be the job of wheel-end seals, which must be able to withstand a wide range of temperatures and exposure to some extreme conditions, whether on a paved race track or in off-road competition.
Engines seals include those for camshafts, crankshafts, valve stems, and auxiliary shafts. There are also seals required for spark plugs, valve stems, and injector tubes are well. Engine seals need to be extremely low friction to minimize power loss and provide the ability to integrate with sensors to track engine performance. Needless to say, the materials need to be rugged enough to withstand the heat and be compatible with all media involved, including fuel additives that can damage materials.
The purpose of bearing seals is to keep the lubrication in and contaminants out of the critical bearings in a vehicle. Because the bearing seals contribute to reducing friction, they also reduce power losses. If a bearing seal gives out during a race, it will result in serious power loss and one failure after another as related systems are impacted.
Sealing Challenges in Performance Motorsports
While there are challenges in the specification of seals for any automobile, the challenges are more complex and constraints far more stringent in the design of high-performance automobiles. When the ability to shave off a fraction of a second could make or break a successfully competitive design, weight becomes a major factor: every ounce counts when trying to maximize speed and minimize losses for Indy Car, Formula 1, NASCAR, Rally, and CART vehicles.
Reliability is extremely critical for racing: when a car is moving at extreme speeds, small problems can lead to massive disasters and potential death. And reliability is just as vital for endurance and off-road races where the ability to survive in rough conditions is part of the competition.
When vehicles are moving at the extremely high speeds involved in racing, everything becomes more intense and that includes vibrations and shock loadings. And for off-road competitions, the impact loadings are even more intense. Racing seals must be able to also retain their ability to exclude contaminants and retain media (whether its fuel or lubricant) even in the presence of these extreme loads.
Dynamic seals must also be able to handle continuously higher speeds than an average automotive seal, which can make the choice of materials even more challenging. The coefficient of friction and ability to dry lubricate (as is seen with materials such as PEEK and PTFE) becomes even more important. There are also extremes in both pressures in temperature that require seals with dimensional stability, often requiring spring-energized or labyrinth seals.
Chemical inertness is also vital, especially as some newer fuel additives for racing cars have proven incompatible with rubber hoses. Materials like PTFE and PEEK are chemically inert, but it is very important to check material compatibility before moving forward with a seal design.
Another challenge faced when designing seals for high-performance automobiles lies in available space: to keep weight down and ensure that the vehicle is aerodynamic, compact sealing solutions that take up a minimal amount of space are required.
Solutions for High-Performance Automotive Seals
When designing seals for high-performance automotive applications, advanced polymer seals should be seriously considered. Polymer seals weigh a fraction of their metal counterparts and less than elastomeric seals. They involve far less friction and can be just as rugged and durable as well. Because materials such as PEEK and PTFE are dry-running and self-lubricating, they can sometimes eliminate the need for a bearing. Performance polymers also include additives that enhance the properties of a polymer, increasing its stiffness, impact resistance, and dimensional stability as well as reducing friction.
Polymers are far less susceptible to corrosion than their metal counterparts and, when the right polymer is chosen, are less susceptible to chemical attack than elastomers. Polymers also lend themselves more readily to manufacturing with complex geometries than metals and offer more freedom as far as manufacturing methods than elastomeric materials.
Engineering polymers also provide the resistance to wear, strength, and stiffness needed in the rugged environments and demanding operating conditions of racing. And the use of polymer seals as opposed to metal seals reduces problems with metal-to-metal contact such as galling and abrasion. Note, however, that in many instances, the seals required for high-performance automobiles must be custom-made to achieve the necessary level of performance while staying within design constraints.
Conclusion
The design of high-performance automotive seals can be extremely challenging and many engineers are turning to polymer seals to effectively meet those challenges. Engineering polymers such as PEEK and PTFE, including the variety of grades and fill options available, are an excellent solution to many seal designs.