In my role as a racing coach, I’ve had the opportunity to analyze the videos of many different drivers, but I’m also often asked for my take on other notable driving videos as well. Of all the famous driving videos out there, I have probably been asked about the Senna at Suzuka video more than any other. You know, the one where he’s casually wringing the neck of an Acura NSX while sporting white socks and loafers. Even if you aren’t a driving enthusiast, it’s definitely worth a look for nostalgic fashion purposes alone.
Other than the footwear, this video is noteworthy because it shows Senna demonstrating a throttle technique that is often described as if he’s “stabbing at the throttle.” I’ve heard many theories about this, with some saying it’s a habit he picked up in karting or the turbo F1 era and only his amazing driving abilities allowed him to get away with such a seemingly poor and “bizarre” technique. The truth is that Senna’s throttle technique is not something he was simply able to get away with because of his remarkable skill; it is actually a reflection of his remarkable skill.
To understand why, we’ll need to dig a little deeper into the science of car control to learn what it takes to drive a car at the very limits of traction.
To understand why, we’ll need to dig a little deeper into the science of car control to learn what it takes to drive a car at the very limits of traction.
The Limit Defined
“The limit” can be defined as when no change in driver input will cause an increase in tire force. This may sound a bit technical, but it highlights the important role driver inputs play when searching for the limits of traction. A simple example would be a driver traveling at a constant speed and then progressively tightening the steering. There would be a certain point when turning the steering wheel more would not make the car turn any tighter. The tires have reached the maximum force they can generate. In this example, it would most likely be the front tires that reached their limit first and many drivers understand this is called understeer. If the rear tires are what is limiting how fast a car can turn, then you have oversteer.
The key takeaway here is that for ultimate speed through a corner, a car should always either be at the understeer or oversteer limit so that you’ve maximized the force the tires can produce. So if we know we want to always be at the limit in a corner, how can we ensure we are actually accomplishing that? It turns out the answer is actually quite simple, although often not very intuitive.
The key takeaway here is that for ultimate speed through a corner, a car should always either be at the understeer or oversteer limit so that you’ve maximized the force the tires can produce. So if we know we want to always be at the limit in a corner, how can we ensure we are actually accomplishing that? It turns out the answer is actually quite simple, although often not very intuitive.
Time for a Test
Remember our definition of the limit? The only way to truly know if you are at the limit of traction is to change a driver input and see what happens. Try turning the steering wheel more. Did the car's path tighten? If so, then you weren’t at the limit. Did the car stay on the same path? Then you were either at the limit or over it, possibly way over it. Being over the limit is typically bad, but the only way to find out how far over the limit you are is to unwind the steering until the car lessens its rate of turning. In other words, you have to make a driver input change and see what happens. We call this process testing.
To drive at the limit, you have to constantly be testing to see if you can generate any more force from the tires. This is why you see top drivers making constant, small motions with the steering wheel during a corner. They are trying to keep the car right at the peak of grip. Testing can also be done with the pedals as well though. During corner entry, you can use the steering and brakes to test for the limit. During corner exit, you would use the steering and throttle. Some drivers will tend to use the steering wheel more, whereas some might use the pedals more. As we’ve seen, Ayrton Senna was certainly not timid about testing with the throttle to find the limit during corner exit.
To drive at the limit, you have to constantly be testing to see if you can generate any more force from the tires. This is why you see top drivers making constant, small motions with the steering wheel during a corner. They are trying to keep the car right at the peak of grip. Testing can also be done with the pedals as well though. During corner entry, you can use the steering and brakes to test for the limit. During corner exit, you would use the steering and throttle. Some drivers will tend to use the steering wheel more, whereas some might use the pedals more. As we’ve seen, Ayrton Senna was certainly not timid about testing with the throttle to find the limit during corner exit.
The reason a driver must test for the limit is that tire grip is a dynamic target. Unfortunately, there isn’t a driving cue that can accurately tell you if you are currently at the exact peak of grip. The only way to know is to change an input and see how the car responds. Even a highly accurate tire-testing machine that was programmed to maximize the force a tire produced would need at least some movement back and forth across the peak to do this.
Understand though, testing for the limit is not “I think I might be at the limit, I’ll do a test now to see.” Instead, it must be trained to the point that it is automatic and a driver will naturally try to stay at the limit by constantly modulating their inputs. These movements shouldn’t be faked however, they must be developed. Realize that each change of Senna’s throttle position was done as a response. If a novice driver attempted to simply replicate Senna by “stabbing at the throttle,” they would certainly not get his results.
It’s also important however, to understand that different cars will likewise respond differently, so a driver’s input modulations will need to adapt as well. Although the Acura NSX was a superb sports car, it was still a street car and would need relatively larger driver inputs to elicit a response. A tightly sprung formula car with immediate throttle response would need smaller, faster inputs. Unfortunately, I don’t have any pedal cam video of Senna in a formula car to compare, but I do have access to telemetry from many other skilled drivers. Below is a throttle trace from a high-powered formula car being driven well through corner exit. In this tightly wound racing machine, the driver’s throttle modulation rate reaches around five inputs per second which is around the limit of human reaction time. These small, super-fast movements are hard to even see on video, and we have to look at telemetry for the whole story.
Understand though, testing for the limit is not “I think I might be at the limit, I’ll do a test now to see.” Instead, it must be trained to the point that it is automatic and a driver will naturally try to stay at the limit by constantly modulating their inputs. These movements shouldn’t be faked however, they must be developed. Realize that each change of Senna’s throttle position was done as a response. If a novice driver attempted to simply replicate Senna by “stabbing at the throttle,” they would certainly not get his results.
It’s also important however, to understand that different cars will likewise respond differently, so a driver’s input modulations will need to adapt as well. Although the Acura NSX was a superb sports car, it was still a street car and would need relatively larger driver inputs to elicit a response. A tightly sprung formula car with immediate throttle response would need smaller, faster inputs. Unfortunately, I don’t have any pedal cam video of Senna in a formula car to compare, but I do have access to telemetry from many other skilled drivers. Below is a throttle trace from a high-powered formula car being driven well through corner exit. In this tightly wound racing machine, the driver’s throttle modulation rate reaches around five inputs per second which is around the limit of human reaction time. These small, super-fast movements are hard to even see on video, and we have to look at telemetry for the whole story.
Climbing to the Peak
It’s also been said that Senna’s throttle technique might work for cars of his era, but not in modern F1 where his throttle stabs would induce load transfers upsetting the finely tuned aerodynamics of the car. While it’s true that you typically don’t want sudden load transfers in a modern F1 car, it’s also true that if your goal is ultimate speed, you don’t want them in any racecar, from any era. Sudden load transfers not only degrade aerodynamic grip, but mechanical grip as well.
Senna’s throttle technique would not cause sudden load transfer, however. It’s important to understand that the throttle, brakes, or steering wheel do not directly cause load transfer. Only changes in acceleration cause changes in load transfer. This is an important distinction. For example, if Senna were driving along at normal road speeds and then worked the throttle as seen in the video, he would most certainly get large changes in acceleration and therefore load, but once a car reaches the limits of traction, things begin to change.
Take a look at this tire force graph to the right. While a tire does experience rapid changes in force production well below the peak in the linear area, as we enter the transitional area, the force starts to taper and then levels off. In other words, the same throttle input that would cause a large acceleration and therefore load transfer below the limit would create a much smaller response when the tire was near the peak. If we keep going and push the tire past the limit, force and therefore acceleration actually begin to drop. Detecting the very beginning of this drop is what Senna is cueing off of to keep the rear tires right at the peak of grip. As Senna increases throttle, he’s looking for the point that the rear tires begin to lose traction and the car starts to oversteer. This tells him he needs to reduce throttle and begin the process over again. For a novice first learning to drive at the limit, this most likely will cause large changes in acceleration and therefore load, and you can see this when watching their car move around as they work their way through a corner. When watching a master like Senna however, you might not realize the sometimes violent driver inputs required to keep the car flying smoothly through the corner at the limits of traction.
Senna’s throttle technique would not cause sudden load transfer, however. It’s important to understand that the throttle, brakes, or steering wheel do not directly cause load transfer. Only changes in acceleration cause changes in load transfer. This is an important distinction. For example, if Senna were driving along at normal road speeds and then worked the throttle as seen in the video, he would most certainly get large changes in acceleration and therefore load, but once a car reaches the limits of traction, things begin to change.
Take a look at this tire force graph to the right. While a tire does experience rapid changes in force production well below the peak in the linear area, as we enter the transitional area, the force starts to taper and then levels off. In other words, the same throttle input that would cause a large acceleration and therefore load transfer below the limit would create a much smaller response when the tire was near the peak. If we keep going and push the tire past the limit, force and therefore acceleration actually begin to drop. Detecting the very beginning of this drop is what Senna is cueing off of to keep the rear tires right at the peak of grip. As Senna increases throttle, he’s looking for the point that the rear tires begin to lose traction and the car starts to oversteer. This tells him he needs to reduce throttle and begin the process over again. For a novice first learning to drive at the limit, this most likely will cause large changes in acceleration and therefore load, and you can see this when watching their car move around as they work their way through a corner. When watching a master like Senna however, you might not realize the sometimes violent driver inputs required to keep the car flying smoothly through the corner at the limits of traction.
Was Ayrton Senna the Best?
I’m also often asked who I think is the best. Was it Senna? Unfortunately, this is something I can’t answer. There is some really stiff competition out there and it could even be argued that it’s impossible to determine who is truly the best among F1 drivers on the very same grid. Much less, across generations. What I can tell from watching videos is that Ayrton Senna was an absolute monster on corner exit. If you have any questions or wish to suggest the next F1 great to be analyzed, please leave a comment.
I hope you enjoyed this article. If you are interested in a complete guide to the physics of racing, we also offer The Science of Speed book series, available through our bookstore or at popular retailers such as Amazon.
by Adam Brouillard
by Adam Brouillard
