Finding the perfect gear change
What’s the most optimal shift point? What would the time difference be between an optimal shift point and a little before or a little after?
The difference between a good shift and a great shift is measured in quarters of a second.
The ultimate goal in motor sports is to go faster than everybody else, which we can achieve by either upgrading our car or improving our driving skills. We can improve many aspects in both situations, however, it’s better to work on our skills. This will give us more personal satisfaction, because in the end anyone can modify their car, but few people can really take advantage of these upgrades.
Taking complete advantage of the transmission:
When competing, one strives to go as fast as possible. Using a car with manual transmission, this is not as simple as pushing the pedal to the medal throughout the whole competition, since one must shift gears, and that’s where the human factor comes into play.
In order to understand the basic theory behind a perfect gear shift, we must know the motor’s power curve. Let’s imagine a parable, which begins from the bottom, then rises until it reaches a maximum level and finally begins to wane. The idea is to apply the maximum amount of power available and the transmission’s job is to multiply that power. This way when the car is in first gear, the power that reaches the wheels is about 4 times greater in the motor’s output shaft. In the following gears this ratio begins to diminish, in the fourth gear the ratio is approximately 1:1 in most cars.
Therefore, the front wheels will always receive more power in first gear. Unfortunately, we can’t always be in first gear since it won’t allow us to go faster than a certain speed. When shifting from one gear to another, the applied force varies according to the gear ratio, so in order to know if we should shift gears, we need to know the amount of power the wheels will receive in the next shift. If it’s less than the current amount we should wait until the RMP limit, and if it’s more we should make the shift.
Therefore, the optimal point at which we should shift is right where the power curves cross each other between the current gear and the next gear. However, this is not completely true, since during the shifting process there is a dead zone, during which one isn’t accelerating, and there will be an inevitable drop in revolutions.
Lastly, the perfect gear switch occurs when the power that will reach the wheels in the next gear is the same as the power that is currently reaching the wheels, taking into consideration the drop in revolutions during the shifting process. However, it is very difficult to know the most optimal point to shift gears without knowing the car’s power curve and the gear ratio, which of course varies from vehicle to vehicle.
In ¼ of a mile, the time difference implied in a gear shift “close” to the most optimal point, but not at the optimal point, can be around 1 second.
DataCar is very useful, it calculates the vehicle’s power curve, and analyzes it along with the gear ratio, in order to determine the most optimal point to shift gears. Once the OBD2 dongle is pluggued in, the way this information is presented to the driver is through shifting lights, widely used in motor sports. These lights are an essential piece of gear; which I will talk about in another post.