One is a turnkey factory car designed to race in SRO, and the other is a one-off built by volunteer Honda engineers.

The HPD Honda Civic Si will represent the company’s next generation of grassroots racing, succeeding the wildly fun-to-drive Civic Si TCA. Built from a body-in-white to adhere to the SRO TC Americas rulebook, it’s stuffed with all of the safety and performance gear necessary to perform on track. As far as drivetrain modifications go, there’s a tune for the 1.5-liter turbo inline-four, a strengthened fourth gear, a specialized exhaust, and a race-spec limited-slip differential. Other upgrades include Bilstein dampers, Eibach coil springs, adjustable control arms, and Wilwood rotors with six-piston calipers up front.

The one-off Si meant to run in this year’s 25 Hours of Thunderhill is a bit more customized, with similar safety gear but a lot more drivetrain mods. Assembled and raced by engineers across the company’s divisions, the car features a new tune for the engine, an oil cooler, a bigger radiator, a titanium exhaust, a custom gearset for the transmission, and specific engine mounts. There are Paragon brakes all around with endurance racing pads from Pagid, cooled with custom brake ducts. The dampers are KW competition units, paired to H&R race-spec coil springs. There are also custom forged wheels, a custom vented carbon hood, and custom LED exterior lights.