This story first appeared in the Winter 2021/2022 issue of RACER magazine. Click here to get your copy, or set yourself up for a full year of stellar motorsport writing and photography with a print or digital subscription.
It took the better part of two years to chase down some of the answers surrounding the NTT IndyCar Series’ most secretive project.
Announced on May 19, 2018, IndyCar declared its intent to move forward with a new 2.4-liter, V6 formula in 2022, up from the 2.2-liter motors in service since 2012. But an addendum on Aug. 1, 2019, pushed the larger internal combustion engine’s arrival to 2023. And for good reason, as the series put out a call for vendors to submit their ideas for a spec energy-recovery system to complement the robust twin-turbo motors. With a change of electronic heart, IndyCar would introduce its first hybrid powertrain.
And while Chevrolet and Honda have been beavering away on fashioning their new mills to make 800-plus horsepower, the identity of IndyCar’s chosen ERS provider, along with every other aspect of the system, has been kept under lock and key. But thanks to a growing number of hints and innuendo, RACER has put the clues together and followed the trail to Stuttgart, Germany, home of renowned racing piston manufacturer MAHLE.
Unbeknownst to most of the racing world, MAHLE does more than make precision engine componentry. Separate from its racing heritage, MAHLE’s vast e-mobility division is more than capable of supplying IndyCar with an ERS solution. And with its recent signing to supply the DTM series’ upcoming electric championship with all manner of technology, MAHLE will be busy on two fronts with its homegrown e-touring car series and an American open-wheel championship to support.
Although IndyCar is not prepared to discuss its ERS solution in any detail just yet, we’ve learned enough about the impending system to warrant a proper download of our findings, all with the proviso that everything you’ll read from hereon is subject to change and final confirmation.
Rather than accept a proposal for a more common battery-based ERS unit, or the formerly-fashionable flywheel style of storing energy, multiple sources say IndyCar has accepted MAHLE’s proposal to use a somewhat rare supercapacitor-based ERS solution.
The highest-profile use of supercapacitors in racing was from 2014-’15 in the FIA World Endurance Championship, when Toyota’s first iterations of its TS040 LMP1 HYBRID made use of an in-house system developed by DENSO and Nisshinbo. Later, the manufacturer also publicized its switch to a battery-based ERS unit to store and deploy energy, which continues in its latest GR010 Hypercar.
Of the benefits associated with a supercapacitor, its ability for rapid charging stands well above the other ERS options. In an IndyCar application, that swift recharging would be the main reason to choose a supercapacitor to handle the energy being harvested through the rear wheels under braking. How much energy will be stored, and the duration and profile of its release, are yet to be confirmed, but peak boost is set to be around 100hp.
THE OVAL CONUNDRUM
If finding out the ERS supplier’s identity was our first priority, the second was determining how IndyCar plans to recharge its ERS units at the Indianapolis 500 and on other ovals, where traditional harvesting under hard braking isn’t an option.
Assumptions that a second ERS unit would be required for the ovals – using similar or identical technology to the MGU-H systems found in Formula 1, in which exhaust energy that spins turbocharger turbines is converted into electricity – appear to be misplaced.
Provided the current plans hold, IndyCar intends to rely on a single MAHLE supercapacitor ERS unit to serve all of its track types. For road and street courses, regeneration would occur under braking – so far, so familiar. On the ovals, that same rear-braking system would be triggered through a harvesting paddle attached to the steering wheel. Drivers would squeeze the paddle to apply light rear braking with their fingertips. And while the paddle would be new to IndyCar, it’s far from uncommon.
Look on the backside of the steering wheel in a Chevy Bolt EV road car, and a similar charging paddle can be found; it serves as a useful, finger-operated tool to brush the brakes when traffic briefly slows on the highway, or in other scenarios when a full stab at the brake pedal isn’t required. But this isn’t a totally new concept to motorsports: Some of the former LMP1 Hybrid prototypes had a similar steering wheel-mounted device, while Formula E makes significant use of a regeneration paddle, where its drivers squeeze the lever and activate braking and charging of their batteries, often while coasting.
Where a harvesting paddle makes particular sense at the Indy 500 is in the routine situations when drivers are clustered together in the draft and lifting off the throttle to maintain a safe distance to the car ahead. Just as a Bolt owner would use the paddle to scrub a few miles per hour off on the highway, it’s easy to imagine IndyCar drivers doing the same entering Turns 1 and 3 throughout the 200-lap race, trading throttle lifts for short charging bursts from light plucks of the harvesting paddle.
Thanks to the quick charging attributes of the supercapacitor, it shouldn’t take an excessive number of pulls to give the drivers a significant stash of electronic ponies to unleash for their next passing attempt.
CAN THE DRIVER MAKE A DIFFERENCE?
A question posed to IndyCar by one or more drivers is how the series should write its rules for energy harvesting. In most road racing-based championships, automatic ERS charging takes place under braking. But with the inclusion of a regeneration paddle for the drivers to strum, there’s a debate as to whether MAHLE’s system should be programmed to take the supercapacitors to a full charge, or if the peak charging threshold should be set lower – somewhere in the 50- to 75-percent range – so drivers are responsible for getting the rest of the charging done on their own.
Some drivers want the freedom to distinguish themselves – to find an advantage with how and when they brake and recharge the ERS unit, and how artfully they deploy the harvesting paddle – just as they do with saving fuel and conserving tires. If a Scott Dixon or a Josef Newgarden can develop a technique to reach 100-percent charge faster or more efficiently than their rivals, why not give IndyCar’s best that opportunity to find an edge?
COST AND WEIGHT
The mechanical elements of MAHLE’s supercapacitor system account for the massive changes coming to Dallara’s long-serving DW12 chassis. With no plans to commission a new car to accommodate the hybrid package’s introduction in 2023, teams will instead need to make wholesale changes to their fleets of DW12s, at a cost estimated to be between $250,000-$500,000 apiece.
The raw weight of the ERS unit, with the motor-generator unit and supercapacitor both positioned within the bellhousing that connects an IndyCar’s transmission and rear suspension to the back of the engine, is thought to be 120lbs.
IndyCar’s current minimum weight for road and street courses is 1,700lbs for a driver who weighs 185lbs. Strap in the pilot, and you’re at 1,885lbs, and with 18 gallons of E-85 ethanol fuel added, we arrive at a ready-to-race weight of 2,010lbs.
With the ERS unit factored in, that climbs to 2,130lbs, which brings the number precariously close to IMSA’s current DPi prototypes. Fully dressed with fuel and driver, the hybrid DW12s could be among the heaviest Indy cars in almost a century.
If the sheer heft of the hybrid IndyCar isn’t enough of a mind-boggling adjustment, the added weight’s location toward the back of the car is yet another issue to mitigate. The estimated shift in rearward weight distribution is believed to be between 1 and 1.5 percent, with 1.2 percent having been mentioned as the closest approximation.
Knowing how the DW12 was rear-heavy upon arrival in 2012, the installation of IndyCar’s mandatory aeroscreen driver safety device offered some assistance in that regard in 2020 as the 60lb assembly of titanium, polycarbonate, and carbon fiber shifted the weight distribution forward. In recent offseason testing with 120lbs of ballast affixed within the bellhousing, the simulated ERS weight is understood to have brought the DW12 back to somewhere close to its pre-aeroscreen weight distribution numbers.
One negative of having the DW12 go up a few pants sizes could be rear tire longevity. With a hike in combined turbo V6 and ERS output to 900hp or so, punishing power will be sent through the rear tires. Harder compounds could be created to deal with the elevated level of torture, but that would bring less grip, which would create problems while accelerating, turning and braking.
To address some of the rearward weight issues, IndyCar has been forced to go down a route that will costs its teams a fair amount as the existing Dallara bellhousing and Xtrac transmission case, currently made from aluminum, will be replaced by new and lighter magnesium units. The hope is to carve out 35lbs with those changes, resulting in a net gain of 85lbs with the MAHLE ERS unit installed.
Providing consistent, adequate cooling for the ERS units will be another challenge for IndyCar and MAHLE to overcome. Along with the installation of larger radiators to cool the angrier twin-turbo V6s, modifications are set to take place within the right sidepod. New ducting is coming to feed the bellhousing and keep the motor-generator unit and supercapacitor within their operating temperature range. The need for secondary, liquid-based cooling for the ERS units is also said to be a possibility, with water or Fluorinert mentioned as options.
Early suggestions of a move to brake-by-wire have been nixed; the DW12’s hydraulic, dual-circuit braking system will be retained, but with help from a new and active brake-bias controller for the rear PFC calipers. A compensation valve is likely to be inserted for the rear brakes, ensuring equal pressure is maintained across left and right wheels.
Saddled with 120lbs of ballast in testing at Mid-Ohio, PFC’s brakes were reported to be more than sufficient, but as most IndyCar teams will attest, the 2.2-mile road course is among the friendliest on the calendar when it comes to brake consumption. Concerns that an upsized braking package might be needed to handle the higher weight and power at other tracks were shared by drivers and engineers after the test.
Citing ongoing manufacturing delays due to COVID-19, IndyCar, engine manufacturers Chevy and Honda, and their chosen test teams entered the new year awaiting the first ERS components from MAHLE. First track test with the system is penciled in for March, but with the sliding delivery timeline, April could be a more realistic window. Depending on the date and weather forecast, the Indianapolis Motor Speedway’s road course or Sebring’s short course in Florida are believed to be the two top destinations for the ERS shakedown.
IndyCar will look to Chevy and Honda to handle the testing using a model it refined in developing the Universal Aero Kit 18. Chevy has Arrow McLaren SP and Team Penske on deck to kick off its ERS tests, and Honda has tapped defending champs Chip Ganassi Racing to be at the ready. Following the UAK18 model, once laps are turned and data generated, information will flow upward to the series and outward to the other teams affiliated with both brands.
Throw in the upcoming track tests with the new 2.4-liter, twin-turbo V6s, and IndyCar’s path to a hybrid future is ramping up.