Nothing puts a coating through the paces better than a good long dyno session.
Editor's Note: In this second and concluding part of our investigation into coatings for circle track applications, we'll review a couple of pertinent points and then wrap our thoughts around some of the more grassroots applications we find today-along with some observations from an engine builder well known to this magazine's readership.
Recall we previously noted that early coating techniques and materials were actually a carry-over from research conducted in the aerospace industry, most significantly throughout the 1980s. Even though there are obviously conditions in outer space that dictate a different environment than earth-bound race cars, some similarities did exist, particularly with respect to temperature control and friction. From this beginning and because of the many perceived benefits from the coatings technology community, once the motorsports sector realized the potential of the process, coating materials and services directed to this opportunity rapidly evolved. Today, as mentioned in Part 1 of this story, the flow of technological advances began to move from racing back toward aerospace, quite the opposite from how it all began.
Both these valves have been coated with the Diamond-Like Coating (DLC) and have seen servi
Tracy Trotter, president of Calico Coatings recalls, "My first exposure to coatings was in my go-kart racing days as a kid when we kept my car at A.J. Foyt's shop. He was exploring coatings back then and that's actually when I first started using them, mainly on the pistons in my kart engines. It may have been illegal to do at the time, but we did it anyway and it seemed to help. In fact, we had our best luck with coating bearings and pistons, not unlike today."
Actually, opinions can vary among engine builders about coating or not coating, particularly with regard to piston crowns and skirts. Early on, some of the plasma-applied materials (including aluminum and zirconium oxide) displayed an adhesion problem, sometimes losing the proper bond and causing related damage. And even today, opinions seem to vary. However, over time and with improved materials and applications processes, previously experienced problems are largely eliminated. But overall, requirements differ as do engine programs and parts combinations, where problems exist that could benefit from coatings and the extent to which cost becomes a deciding factor.
In fact, according to Trotter, "One of the biggest changes we've seen in recent years is that not every coating works in every program. Even the Cup teams have individual ways of doing things and it has become necessary to evaluate each situation and decide which coating best suits their needs. Of course, you need to consider that the design of certain parts and parent materials being used undergo constant change.
Note the condition of seats...
"For example, 15 or 20 years ago, we were coating valvesprings and it really helped. But today, we're finding that valvespring technology that includes spring material has improved to a point that coating doesn't seem to help. We still coat some of the older springs but seldom the high-end newer ones. It may be necessary to do in the future, but right now we're pretty much just working on improving the surface finish of the spring."
Another decision-making factor that comes into play is whether the objective to coating a part is to address durability or horsepower. With regard to increasing horsepower, opinions also seem diverse in terms of how much can be gained by the use of coatings. The reality of this seems linked to how an engine is built and, certainly, how it is used. Quantifying gains is also a function of test method and accuracy. But the consensus opinion is that there are multiple areas on and in a race car where some form of coating will be beneficial, including power and parts longevity.