HOW LONG DOES IT TAKE TO CHARGE THE ESS TO FULL OR EMPTY THE ESS?
According to Honda/HRC US, 4.5 seconds is the magic number in both directions — to fully charge and to fully deploy.
Circling back to the “can it be charged in one brake zone” topic, there are no tracks I can think of where IndyCar drivers would brake hard for 4.5s in any single situation. One or two seconds, and maybe a tiny bit more, but not 4.5. That’s why multiple braking zones would be needed to get the ESS to 100-percent charge.
DOES INDYCAR’S ERS GIVE THAT 60HP THE ENTIRE TIME DURING DEPLOYMENT?
It does not. At a full 60-volt charge, the ESS does give 60hp to start, but as the voltage drops, the horsepower drops. So if a driver wants to put their 100-percent charge to use for that approximate 4.5 seconds in one burst at Mid-Ohio, they’d get 60hp for an early portion of that 4.5s and have it taper off to 50hp, and 40hp, and so on, on the way to 0.0s.
HMMMMM
I don’t want to beat this to death, but Chevy and Honda have done an amazing job in coming up with an ERS solution for IndyCar within the massive constraints they had to accept with creating and fitting a relatively tiny ERS package into the only place it would fit within the Dallara DW12 chassis.
But those constraints also meant the ERS units would not produce awe-inspiring power and torque, which is why some drivers have been critical of going hybrid due to the absence of big increases in performance. Hitting the deployment button does not deliver the feeling of going warp speed, nor does it set blinding lap times or lap speeds.
BUT THAT COULD CHANGE, RIGHT?
Yes, somewhat. The series says today’s cautious setting of 60hp could be turned up to 150hp at some point, which is good. And I wouldn’t expect that leap to happen at once. There would be a step or two in horsepower on the way to hitting 150hp.
The real issue right now is the lack of torque. That’s what electric motors like the MGU should do best. Turn the MGU on to deploy, and boom, instant torque is fed to the rear tires to help a hybrid race car launch off a slow- or medium-speed corner.
But that’s not what IndyCar drivers have at the moment. They have a maximum of 33.2 lb-ft of torque to assist off the corners, and that just isn’t much, and it just doesn’t give that kick in the driver’s back.
Where the ICEs from Chevy and Honda can make upwards of 750hp with raging turbo boost, they also make up to 350-375 lb-ft of torque, so while getting an extra 33.2 lb-ft from the ERS is welcome, it isn’t a game-changing number.
IMSA’s hybrid GTP ERS package is completely different than the new one devised in IndyCar, but it does help to portray the basic power and torque differences in what the drivers receive. In IndyCar, it’s the 60hp/33.2 lb-ft, and in GTP, the power is almost the same, with 67hp on tap, but it’s the torque where the GTPs get real corner-exit help with nearly 4X the number at 125.4 lb-ft.
If there’s one thing IndyCar can do in 2025 and beyond to make its hybrid package pack a bigger punch, dialing up the torque is where its greatest weakness could be turned into a big asset.
LET’S TALK MORE ABOUT THE DRIVING SIDE. IS THE ERS A MANUAL OR AUTOMATED THING?
It’s both, but in unique ways.
On the harvesting side, drivers can capture energy manually by pressing a button, or squeezing one of the clutch paddles on the back of the steering wheel — which are only activated to behave as a regeneration tool above 50mph or so — when they want. And the ERS can also be instructed to harvest automatically once the ECU sees braking pressure being applied, or if it sees partial throttle being used, or to automatically regenerate when it sees braking pressure and partial throttle.
The decision on how many of those options will be used is up to the driver, team, and their ICE manufacturer.
When it’s time to deploy, IndyCar does not allow automation in any way. For the ERS power and torque to be unleashed, the driver must choose to do so and press the deployment button on the steering wheel.
SINCE THE ERS UNITS PRIMARILY WORK UNDER BRAKING, ARE THERE ANY CHANGES TO THE BRAKING SYSTEM?
Yes on the mechanical side.
Since the cars were getting heavier with the ERS at some point in 2024, a slightly larger braking package was implemented — bigger brake discs, for example, to help slow the beefier cars — as part of the hybrid changeover. That happened at the start of the season, and now the bigger brakes will have the bigger weight they were designed to manage.
ARE THE BRAKING CHANGES LIMITED TO THE BRAKING PACKAGE ITSELF?
Correct. There are no new electronic braking aids like anti-lock braking for IndyCar drivers, nor did IndyCar adopt a brake-by-wire system like some other series use. It’s 100-percent analog and under the control of the driver’s foot and the brake bias adjuster knob like it was at the last pre-hybrid IndyCar race.
In IMSA, the hybrid GTP cars use an Electronic Braking System (EBS) control module from Bosch that intervenes when the GTPs are harvesting energy under braking and reduces brake pressure to the rear axles. Since the MGU is like a big extra brake when it’s spinning and harvesting, which would make it easy to lock the rear tires under braking when a driver is smashing the brake pedal, the EBS takes the IMSA MGU’s braking effect into account and manages the hydraulic pressure the driver applies to keep the rears from locking.
As the IMSA MGU decreases its harvesting, or the driver decreases brake pressure as they approach the corner, the EBS is constantly adjusting — simulating the effects of anti-lock braking at the rear axles — until braking is finished.
That’s IMSA’s electronic braking assistance system. IndyCar has none of this within its hybrid package.
THAT DOESN’T SOUND OPTIMAL
It isn’t.
Of everything that’s happening with IndyCar and hybridization, the changes to the behavior of the cars under braking has probably consumed more time and effort to tune and adjust in testing than any other function from the teams’ perspective.
Picture this: The pole-winning driver rockets into Mid-Ohio’s corners in the opening laps and has fresh tires and a full tank of fuel. If the car’s balance is good and the tires aren’t wearing at a rapid rate, they should be fine under braking when they harvest and the MGU fires up and acts like a fifth brake while regenerating energy. When the balance is strong, the MGU helps to slow the car, which improves performance.
But what if the balance starts to go, or the rear tires get torched halfway through the stint? Houston (and Mid-Ohio, and Toronto, and so on), we have a problem.
Thanks to the MGU behaving like an extra brake, harvesting while the car is a handful could easily lead to lockups, at best, or spins, at worst. Minus an EBS system to manage such things, the concerns over stability in the brake zones could become very real.
Enough so that, as some IndyCar race engineers have shared, they won’t be surprised if their drivers decide to abandon using the ERS altogether later in their stints if the tires are tired and braking becomes too unstable.