Road cars are increasingly offering more hybrid and electric options, so it is no surprise that manufacturers want to be able to replicate that in racing. That's especially true in NASCAR and IMSA, where big changes appear to be on the horizon. While most of these hybrid discussions have happened behind closed doors, we can look across the pond at the British Touring Car Championship series to see what the future holds for stock car and sports car racing in North America.

Above: NASCAR's Next Gen car during testing.

Both NASCAR and IMSA are preparing to introduce a new generation of racers. NASCAR is working on its “Next Gen” car which will implement changes like an independent rear suspension and a sequential transaxle, seismic shifts for NASCAR. On the IMSA side, the next generation prototype is under development, known as DPi 2.0. The specs are still unknown, but we do know that manufacturers will have more styling freedom and that many are seeking an alignment with the new WEC Hypercar class.

Daytona International Speedway will likely host the debut of both cars with the NASCAR “Next Gen” car expected to first appear at the 2021 Daytona 500 and the DPi 2.0 cars hitting the track a little less than a year later for the 2022 Rolex 24 at Daytona. While these two cars could not be more different, they should share some common elements, such as the sequential transaxle. This gearbox configuration will likely be the key to a hybrid future.

BTCC’s hybrid formula. BTCC

The recently introduced hybrid regulations for BTCC can provide a window into what we can expect. Although touring cars are much different than stock cars or prototypes, the use of sequential gearboxes offers some commonality. Xtrac is a big force when it comes to sequentials in motorsport and their gearboxes appear in both the current DPi cars as well as BTCC cars. They are also rumored to be the chosen vendor for the sequential transaxle in the NASCAR “Next Gen” car.

The BTCC hybrid architecture shows a plan where one of these Xtrac boxes is mated to an electric motor generator unit (MGU) in an off-axis configuration. What this means is that the MGU is not sandwiched between the internal combustion engine and gearbox, but instead is mounted off to the side of the gearbox. We can see a diagram of this in the BTCC illustration as well as an example in a street car application in the BorgWarner diagram below:

Borg Warner

This makes sense in racing as it allows for more adaptability when dealing with various manufacturers and configurations. It's also why it makes sense for NASCAR and IMSA since it can help attract new manufacturers while controlling costs.

Specs for the BTCC system seem to fall in-line with the “mild-hybrid” application that has been rumored for NASCAR and IMSA. This system is what they consider to be a high power and low voltage system as it runs on 60 volts and supplies around 40 horsepower for push-to-pass applications. The whole system is fairly lightweight due to how the MGU integrates with the Xtrac gearbox and the fairly light 45-pound battery.

The entire hybrid system for the BTCC car comes in at just under 145 pounds, fairly lightweight for all the components considered. That's also less than the maximum success ballast weight in that series of 165 pounds. This total weight includes the MGU and battery pack as well as custom hybrid motor cooling unit, cabling, and the incorporated battery coolant system. The cost for the BTCC system is very attractive as it will be available for a full season lease for competitors for around $27,000 which ends up being around $2,700 per event.

These specs and layouts fall in line with previous news that has come out of discussions from IMSA DPi Steering Committee meetings which have suggested that a 48-volt system was under discussion, but they are also looking at higher voltage systems which could be made to work with the same architecture.

Adapting this type of system to NASCAR or IMSA would not be very complex as many of the BTCC components could be used in their current form as long as they can be made to fit the packaging The experience that Xtrac has with Cosworth in adapting the electric motor to its gearbox could be directly transferred over the these new cars. Internal combustion engine choice would not matter since the hybrid system is agnostic to what is mounted in front of the gearbox and relies on programming to interact properly.

Another series that could come into play is Australian Supercars due to the fact that they are also looking at hybrid options for their “Gen3” car that is slated for 2021. NASCAR is also rumored to use a variant of the Xtrac P1293 gearbox from the Supercars series, which means that many of the hybrid components could be shared between the two. This would go over well with the manufacturers as they would be able to have a single hybrid unit for multiple series around the world. It would also benefit the teams since a larger scale of implementation means lower cost.

Although there are a few manufacturers–such as Ford–that are pushing for a hybrid system with higher voltage and more power, it is likely that we will see smaller steps at the beginning. Based on the current specs of the BTCC system, it's likely we'll see a 48 to 60 volt system with a smaller battery pack implemented for the new series along with an electric motor that can provide 40 to 50 horsepower on demand. The electric motors and even the battery packs could possibly be developed by the individual manufacturers which is why the off-axis configuration makes sense. Multiple variants of the MGU could be used with the same gearbox as long as they have a common output flange.

This type of system would likely be most welcome by teams and fans since it would have a minimal impact on the rest of the car. Regenerative braking would be managed by the controllers for the hybrid system. Since there is no direct impact to the internal combustion engine, those could still be tuned like today and produce a similar sound. Like the BTCC implementation, the hybrid system would allow each of the series to manage Balance of Performance without having to add additional ballast or restrict the internal combustion engines since the hybrid system could be turned down using software limits in an attempt to equalize the field.

This type of system makes the most sense for a first move into hybrids. It allows for a fairly inexpensive transition that won’t change the current formula too much, but will allow manufacturers and teams to experiment and learn how to expand on it in the future.

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