NASCAR’s next generation stock car

NASCAR has been testing 2021 spec racecars . The new rules will bring sweeping changes, including sequential gearboxes, modern suspension and composite bodies

The 2021 season will see a seismic shift in NASCAR, with all-new regulations moving the cars away from a template that has remained relatively unchanged since the 1970s. The current NASCAR Cup machinery retains many features that have been present for decades, not the least of which are chassis that feature ‘truck arm’ rear suspension, live rear axles and steering boxes rather than racks.

The ‘Next Gen’ Cup car will be a radical (by NASCAR standards) departure from the current Gen 6 machines. Tubeframe chassis will be retained, but the fabricated steel suspension set-ups, consisting of A-arms at the front and truck arms and live axle at the rear, will be replaced with machined uprights and double wishbones front and rear. The first prototype chassis were designed by Dallara in conjunction with NASCAR R&D.

For the first time, on-car adjustable dampers will be permitted, too, with four-way control of high and low-speed bump/rebound. The trademark 15in steel wheels, with five lug nuts, will also go the way of the dodo, to be replaced by 17in rims with centre-lock securing.

Transmission revamp

The current 358cui (5.8-litre), pushrod V8 engine package will be kept, at least until 2023, but instead of an H-pattern transmission a sequential transaxle, similar to that used in Australian Supercars, will be employed, with Xtrac awarded the contract for its supply.

There is also a tender process underway to secure a spec hybrid system for potential introduction in 2023, though details of its specification, or the engine it will be paired with, are sparse. There is also a desire for this system to be shared between both NASCAR and IMSA (which NASCAR owns).

One of the main reasons behind the move to a transaxle is safety; shifting the transmission to the rear of the car from adjacent to the drivers’ legs allows them to be seated nearer the centre of the car, therefore allowing more space for energy absorbing safety structures. The new transaxle will also help teams reduce running costs. Currently, NASCAR uses ring and pinion ratios to tune performance from track to track, meaning teams have to carry a significant number of spares at considerable expense (around $10,000 a set). With the transaxle set-up, a drop gear system will allow for fast ratio changes at much lower cost (though to accommodate the wide range of track types, from Bristol to Daytona, there will still be a need for a smaller range of ring and pinion combinations). The sequential transmission will be manually shifted and, currently, there is no plan to introduce auto engine blipping on downshifts.

Wrapping the new chassis will be all new composite bodies, with markedly different proportions to the Gen 6 machines, making them appear far closer to production models. NASCAR’s second tier Xfinity series already runs full composite shells and it was inevitable these would migrate to the top-level championship sooner rather than later.

The aerodynamic concept of the cars will also change significantly. Rather than the messy, exposed tubeframe undersides, which are ripe for exploitation by teams chasing incremental aerodynamic gains, a flat floor will be introduced with (to the undoubted horror of stock car aficionados) a rear diffuser. The hostile reception given to the CoT’s rear wing in 2007 is still fresh in many memories, so the rear spoiler is retained.

Aerodynamic parity between different bodystyles will remain a priority for NASCAR and, as such, the current process of keeping so called ‘gold’ surfaces common across cars will remain, with manufacturers permitted styling freedom in certain areas. Through NASCAR’s benchmarking and approval process, each manufacturer will have to submit its specific body designs and ensure they fall within the NASCAR window for downforce and drag, when assessed by the sanctioning body.

Though details of the new rule package are still being finalised, NASCAR, via its Research and Development department, has been track testing prototypes of a new car design, with manufacturers working on their own test chassis to develop bodywork variations since the middle of 2019. ‘We have kinda got the band back together so to speak, with the manufacturers working with the NASCAR aero guys, in a similar way to the Gen 6,’ says Suhy.

Control parts

While these changes will undoubtedly drag stock car design into at least the late 20th century (not the engineering know-how mind, as that is comparable to almost any series up to Formula 1), there is a downside. Almost every part on the cars will be spec, not simply tightly regulated, but sourced from single suppliers. NASCAR issued tenders for all of the components, from the main chassis frame, to wishbones, uprights, springs and dampers. The concept being that each of the teams will get a slice of the manufacturing pie, one making the suspension arms, one the chassis, etc. Theoretically, this means there will be no variation in componentry from one team to another, but remember, this is NASCAR. It can almost be guaranteed that the race teams are already investigating ways to add their own personal touches to the racecars, flying under the radar of NASCAR’s tech inspections.

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Racecar Engineering - February 2020


February 2020