IndyCarTechnology

IndyCar in 2028 is bigger, badder and better! The IR-28 uncovered

Craig Scarborough
2 months ago
12 min read

IndyCar finally released details of its new IR-28 ahead of its first track tests.

This has been a long time in coming not least due to various delays in the project, but the core of the current IndyCar dates back to 2012!

It’s clear when seeing the new IR-28 that’s it’s a thoroughly modern international racecar, featuring overtaking friendly aero, more powerful hybrid, increased safety and lower costs.

Background

Motorsport.tech has covered IndyCar’s technical evolution with great interest. 

While the sport started out as a prototype (special) format series, by the 70s teams were increasingly buying customer cars from specialist companies.

With the Indy Racing League (IRL) splintering off to race a spec chassis, the series unified and similarly adopted a spec chassis, with a choice in engine manufactures.

Italy’s Dallara became the incumbent chassis supplier and raced a relatively conventional ‘IndyCar’ style chassis from 2007.

During this era, IndyCar started to look ahead and consider what a future IndyCar needed in terms of performance, safety and costs.

This search for the ‘next generation’ car led to a tender process with multiple racecar manufacturers proposing their own concept for a new IndyCar.

With a choice of cars from mild to wild, the winner of this process was Dallara, with the DW-12 design.

Incredibly this chassis remains racing to this day and will do so for another until the IR-28 debuts in 2028.

Given its 15-year tenure the DW12 chassis changed in almost every area.

Rhe initial car came with a set of spec aero configurations dependant on the track, but all included the anti-wheel-interlocking ‘fenders’ including a beam behind the rear wheels.

There then followed a period of team developed aero packages, then returning for cost reduction reasons to a Dallara set of aero configurations, which remains the format today and into 2028.

Also, during the more recent SW12 era, the aeroscreen, which is a protective screen and halo cleverly integrated into the DW12 monocoque was integrated, with minimal changes to the chassis structure.

Then latterly the integration of a hybrid system with super caps energy storage is again smartly implemented into the bellhousing twixt engine and gearbox, to a provide a modest power boost, for almost no weight penalty.

The next ‘next-generation’

Given the DW12’s incredible lifespan and the modifications made to it through that time, it’s clear that IndyCar needed to look at an all-new car.

This project has been continuing for several years with all of the key parties involved (Dallara, Honda, Chevrolet, Firestone etc).

Not without its delays along the way, but the collective needed to have full agreement between them, bringing us to the IR-28.

The broad aims were for an all new car providing; better racing, increased safety lower costs and a better platform for all the partners involved to be able to promote their products around.

Some of these latter demands meant that sustainability were considerations as well as aesthetics.

Apparently, the initial aero concepts proposed to the stakeholders weren’t universally welcomed and the careful work of balancing aero and styling was taken up by Director of Aero Development Tino Belli and British 3D artist Chris Beatty.

The result is the new car and while a considerable step away from some traditional IndyCar design cues, adopts a more modern single seater format.

Taking some ideas from F1 and Formula E, remembering that Dallara are partner for both categories with Haas F1 and Spark in in FE.

Aero

As mentioned above the aero needed to consider the overall ‘look’ of the car, not least to meet the aerodynamics aims, but also to take a step ahead of the ‘patched’ design of the DW12 and create an integrated approach to the new car.

Key amongst the technical targets were improved overtaking, by reducing the cars wake and its sensitivity to running in that wake.

These are themes that we have seen in F1 and Formula E and therefore its no surprise that the same conclusions are being reached here in IndyCar.

By focusing downforce production on the underfloor, rather than wings, but without any extreme ground effect full length tunnels.

The new car sports a long floor (within the same wheelbase) using a raised leading edge to create outwards flow expansion to create more load on the front of the car.

Then a large diffuser at the rear to create the bulk of the downforce both front and rear.

One clever trick has been to create a single spec underfloor assembly for both high downforce road course and speedway tracks.

Doing this by the simple expedient of a detachable rear section of diffuser.  Removing this cuts downforce for speedway use and presumably makes damage repair easier around road courses.

Above the floor all of the surfaces are new, based around a new wider monocoque and revised cooling package.

Firstly, looking at the wings, which are quite different to previous IndyCar incarnations.

At the front the high downforce wing looks huge, being wider and formed of three elements with large endplates.

Mounting under the nose, this sits higher from the track to reduce its performance, but also to reduce its sensitivity to car set up and running in a wake.

The speedway wings are similar but reduced to two elements.

Then at the rear the wing has been stylized into a hoop shaped format.

Mounted above the new rear crash structure (attenuator) is one surface starting with a beam wing and running up through the endplates to a three-element top wing.

This is reminiscent of the 2022-era F1 rear wing, whose aim was to reduce wake by creating softer intersections between endplate and flap. These it’s a smaller, but overall similar arrangement for speedway races.

Further aiding the reduced wake concept are the new TWCs (Tyre Wake Conditioners), which are the boxed fairings behind the front wheels and ahead of the rear wheels.

These pick up the flow off the front wheels and direct it along the car, rather than expanding outwards with outwash.

Likewise, the rear TWCs separate turbulent and clean flow either side of the rear tyre.

The effect of these is to keep the cars bodywork running clean air undisturbed by the tyres and prevent the tyre wake passing too far outboard to upset the car running behind.

These are conceptually similar to both F1 and FE designs, so the concept is sound, but have been tested with two cars in aero testing to confirm the effect.

There is a robust strut and tensioner to keep the front wheel TWC in place should there be contact with barriers or other cars to prevent this structure flying off too easily.

One observation from early tests in the wet, the spray from the front wheels exited vertically between the tyre and TWC, whether this will be a visibility problem in the wet remains to be seen.

To integrate the aeroscreen into the DW12 required a rear mounting to the roll hoop and as a result the blending of all of the surfaces was awkward and it always looked an add-on, additionally cooling for the driver was not fully incorporated.

So, the IR-28 had the opportunity to merge all the requirements of the aeroscreen into the overall car concept.

With a wider chassis, the same aeroscreen shape now looks smoothly merged into the car’s shape.

As is the structural design that properly directs the loads into the chassis.

For driver cooling there are four inlets, general cockpit cooling has two inlets, one the lower sidepod and one on the keel under the chassis.

Then there’s a bigger integrated inlet on the scuttle ahead of the aero screen and the driver helmet cooling duct on the side of the aeroscreen.

On the outside of the streamlining around the aeroscreen is a new digital LED display panel, providing the fan with car info.

A cool small detail is the new rear view mirrors that take a more complex shape with a mirror pod and wraparound vane to manage airflow downstream along the car.

Another feature improving the looks of the aeroscreen on the car are higher sidepods, these are very different geometry that of the DW12.

Being higher due to the large undercut running along the bottom edge that directs airflow over the top of the diffuser.

The new cooling package inside the pods are fed by an overbite shaped inlet.

Cooling is managed less by infills on the sidepod inlet and outlets louvers and more from a thermostat set up on the engine. Although the Indy500 spec will get an inlet blanking.

Powertrain

If the aero could be considered a radical departure, the powertrain is more evolution.

Having run the 2.2l V6 twin turbo throughout the DW12 era, the new car will get a larger capacity 2.4l V6.

This should reduce the stress on the engines, for each of the boost/power limits applied to each circuit type.

That will be 640hp on speedways, then 730-760hp on road courses and Indy500 qualifying. Both will run Shell renewable E85 fuel and rev to a high peak of 12,000rpm, with a potential peak of 800hp.

There’s also the PTT 65hp boost, with a 10% longer activation than the current system.

Each engine can be partly seen through a new clear window on the spine of the engine cover, allowing a little marketing exposure for both Honda and Chevrolet.

The DW12’s hybrid package has been controversial and has been replaced for the new car.

From a small MGU cycling energy from a super capacitor array, the new set up has more power and energy.

It remains mounted in the bellhousing, but is some 9kg (20lbs) lighter helping the cars overall reduction in weight.

The MGU is now supplied by Helix and rated at 100hp (75kw), still a modest output but twice the old specification.

While the super caps are replaced by a Battery manufactured by Bold, with 14 times the energy storage.

But as with the combustion engine there’s the potential for a more powerful or longer duration deployment, should IndyCar decide to do so.

Allied to the power unit, there’s a new Xtrac 6-speed gearbox.

Not only is this 11kg (25lb) lighter with its new casing, but the internal components are now shared with the Indy NXT development series car.

the chassis and powertrain are controlled by and displayed to the driver with a new electronics package, but with existing partners.

Motion Applied (formerly McLaren Applied) retain their position the premier motorsport ECU supplier with Cosworth supplying the display electronics including the steering wheel itself.

Chassis

As with the rest of the IR-28, the chassis elements are all new, albeit following on from the series well proven solutions.

The survival cell is new, with the aforementioned changes for the V3.0 aeroscreen.

But other aspects of safety have been included, the cockpit volume is larger to accommodate a range of driver sizes.

The crash performance has been improved in all directions, front, side and rear. Safety is also aided by the lighter overall mass of the car, with a 36-46kg (80-100lb) reduction in overall weight.

Despite the weight loss and safety increase the car remains the same basic layout and dimensions in wheelbase and track.

Suspension remains pushrod operated with steel wishbones. But the dampers are now a spec item, with even the settings restricted according to the track.

Previously IndyCar has been quite open with the development of passive dampers, indeed the series has had a far greater understanding of this area than even F1.

While this is impressive, a huge amount of development has gone into the damper set up and this along with the huge inventory of dampers and parts adds an enormous load to the team’s budget.

To reduce costs, spec units will now be provided by Axis a part of the respected Penske damper operation.

These still allow the use of inerters (J-damper – spinning mass), which have been banned from most motorsports, but are hugely beneficial for controlling the chassis.

One area IndyCar retain under the control of the driver are the anti roll (sway) bars. Currently they are manually adjusted from levers in the cockpit.

On the IR-28 they will be electronically adjusted, still under direct driver control, presumably from buttons/dials the steering wheel.

Brakes remain with the partner Performance Friction, the increase in the hybrid braking effect allows the rear brakes to be downsized, allowing another weight reduction opportunity.

Wrapped around the brakes are new wheels, the same size as before, but supplied by BBS rather than OZ and forged in Aluminium, not Magnesium.

Although these will be introduced on the current car for the 2027 season. Firestone remain the tyre supplier.

Testing and debut

Two chassis are already prepared and are testing with each of the engine partners.

As the current 2026 concludes, the teams will commence testing the IR-28 during 2027.

But the new car will not make its race debut until 2028.  During this intervening period the car will not doubt continue to develop and share its secrets.

But the step forwards for the IR-28 is already impressive and should support the IndyCar series in becoming a far more popular championship in the USA and around the world.

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Craig Scarborough

Craig Scarborough is one of the most distinguished tech illustrators and pundits in the motorsport arena, with particular expertise in F1. During a career spanning almost 4 decades, he has fronted broadcast tech analysis for F1TV and Motorsport.tv and his illustrations have featured in the world’s most prominent automotive media.

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