Previously, all Subaru WRX STI models that raced at the Nürburgring 24 Hours used a modified version of the EJ20 that delivered around 340 horsepower and 461 Nm of torque. However, with Subaru discontinuing the EJ20, the team opted to move up to an engine based off the all-new WRX’s FA24.

Design and development began soon after the current-generation WRX (VB) was unveiled. And by enlarging its turbocharger and installing a dedicated intercooler, the power has been uprated to 380 horsepower. Even more impressive is that the cylinder block and heads are stock because they were designed with high outputs and revs in mind. They, according to STI, didn’t need any special reinforcement. It even uses a direct injection fuel delivery system, but now managed by its own dedicated ECU. Precautions were made, however, to prevent the chain-type cam driven from being starved of oil by using a baffle plate.

In addition, with the all-new WRX moving to the Subaru Global Platform (SGP), Subaru and STI engineers quickly developed the chassis for motorsports. With a higher rigidity, converting it for motorsports use was relatively easy. In its endurance race form, it uses larger front lower arm ball joints and improved aerodynamics thanks to a flat floor. Proven components such as the transmission, rear differential, and rear subframe (the same design used since 2008) were carried over from the previous-generation WRX STI (VA).

The resulting race car has a slightly shorter wheelbase than the previous NBR challenger but with similar front and rear tracks.

Said to be the toughest race course in the world with a total length of about 25 kilometers, the Subaru WRX NBR Challenge 2023 will participate in the SP4T class—a class of cars with turbocharged engines of 2.0-liter or more and less than 2.6-liter for the first time. Previously, they participated in the SP3T class. The car will be driven by an international team composed of Carlo Van Dam, Tim Schlick, Hideki Yamauchi, and Takuto Iguchi.