The Push-to-Pass System in IndyCar: Operation, Strategy and Impact on Racing

The push-to-pass, popularly known as the “overtake button”, is one of the most distinctive technical features of the NTT IndyCar Series. Unlike passive aerodynamic systems such as Formula 1’s DRS, push-to-pass acts directly on the car’s engine and power delivery. To understand what push-to-pass is in IndyCar and how drivers use this extra power, it is necessary to analyze turbocharger management and, more recently, integration with hybrid units. It is a finite resource, managed by the driver, that adds a layer of complex strategy to racing on mixed and street circuits, allowing for both aggressive attacks and tactical defenses based on resource management.

History and origin of the system

The implementation of extra power on demand systems has roots in the need to increase entertainment and overtaking opportunities in open-wheel categories, where aerodynamic turbulence often makes close pursuit difficult. The direct origin of the concept in IndyCar dates back to the now defunct Champ Car World Series (CCWS).

• A era Champ Car: In 2004, Champ Car introduced the “Power-to-Pass” system. It allowed drivers to increase turbo pressure for a limited time (usually 60 seconds total per race), offering around 50 additional horsepower.
• Adoption in IndyCar: After the unification of the categories in 2008, IndyCar introduced its version of the system in 2009. Initially, the focus was only on non-oval circuits, a rule that predominantly remains today.
• Evolution of the rules: Over the years, IndyCar has experimented with different formats. In some seasons, the limit was defined by “number of pulls” (e.g. 15 or 20 pulls per test). Later, the system migrated to a total “time bank” (e.g. 150 or 200 seconds), giving the pilot the freedom to use power for as long as he desired on each actuation.

Rules and technical operation

The operation of push-to-pass is a combination of mechanical engineering and engine management software (ECU). When the driver presses the button on the steering wheel, a series of commands are sent to the engine and, from 2024, to the hybrid system.

• Increased turbo pressure: Traditionally, the system operates by allowing a temporary increase in turbocharger inlet pressure. Under normal racing conditions, the turbo operates at a base pressure (e.g. 150 kPa or 1.5 bar). When pressing the button, the pressure increases (e.g. to 165 kPa or 1.65 bar).
• Hybrid Integration (ERS): With the introduction of the hybrid drive in mid-2024, push-to-pass has evolved. Now, in addition to the turbo, the system uses energy stored in the Energy Recovery System (ERS) supercapacitor. This provides a more immediate torque response, eliminating “turbo lag”.
• Power generated: The combined drive can generate an increase of approximately 60 to 100 extra horsepower, depending on the specific engine configuration for that track and the state of charge of the hybrid system.
• Usage restrictions:
• The system is deactivated at the start and restarts (generally released after the second green flag lap).
• If the driver takes his foot off the accelerator or applies the brake, the system stops immediately to save the remaining time.
• Use is restricted to street and mixed circuits (road courses). On ovals, racing dynamics and high average speeds make sudden increases in power a matter of safety and different mechanical balance.

Strategic impact and usage statistics

While there are no “titles” specifically assigned to the button, efficient management of this resource is often the deciding factor in championship victories and flagship races. Push-to-pass time management separates the strategists from the purely fast drivers.

• Attack vs. Defense: Unlike DRS, push-to-pass can be used for defense. A lead pilot can activate the system to neutralize a pursuer’s attack. This creates a “chess game” where spending seconds to defend early in the race can leave the driver vulnerable in the final laps.
• O “Overcut” e “Undercut”: Drivers often use the extra power before entering the pits (in-lap) or immediately after exiting (out-lap) to gain crucial time and gain positions during stops.
• End of test management: Statistics show that race winners on mixed circuits often reach the last 10 laps with at least 30 to 50 seconds of push-to-pass remaining. Being “zeroed” before the end of the race is statistically fatal for the chances of winning in races with late yellow flags.

System curiosities

Push-to-pass generates unique situations that are not seen in other high-level categories, influencing interactivity with the public and the dynamics of the cars.

• Visual identification: IndyCar uses LED panels on the sides of the cars (near the seat). When a driver engages push-to-pass, green lights flash on the dashboard, letting fans in the stands and viewers know exactly who is using the extra power in real time.
• No delay: In previous years, IndyCar has experimented with introducing a 5-second delay between pressing the button and activating power to prevent reactionary defensive use. However, this rule was removed to simplify the dispute and allow for instant responses, especially with the arrival of the hybrid.
• Fatal forgetfulness: There have been notorious cases where drivers lost podium positions simply because they forgot to press the button on the final straight, or thought they had run out of time when there were still a few seconds left.
• The “Panic Button”: In qualifying situations or isolated fast laps, use of the system is prohibited. The car’s ECU is programmed to block the request, ensuring that pole position is decided by the pure speed of the mechanical set-up and the driver’s skill, without the aid of extra boost.

Push-to-pass has established itself as a vital tool in IndyCar sports engineering. It not only serves as a device for artificial overtaking, but as a management feature that rewards the driver’s intelligence as much as his bravery. By integrating fuel management, tires and now hybrid power with the limited time of extra power, the category ensures that the winner is not just the fastest car, but the most efficient and strategic driver-machine combination over the race distance.