DPi may be the top level of sports car competition in the United States, but with its lack of a strong brand connection, it is not the most popular among automakers. The only other major manufacturers competing with Cadillac in DPi are Mazda and Acura, respected brands that have fielded excellent racecars but are far removed from the ultraluxury contingent.

The DPi cars must be built on a chassis produced by one of four manufacturers, none of which produces a mass-market road-going machine. Traditional automakers that buy a racecar chassis from one of the four can design a body, but given the limitations the format imposes, there is little visible linkage to the car company’s product line. The racecars are equipped with engines based on each automaker’s production engine, but the rest of the mechanical systems are specialized hardware.

Cadillac’s DPi racecar is on a chassis engineered and built by the Italian constructor Dallara. While the car was in development, Dallara collaborated with Cadillac. The body had to be shaped to provide the necessary downforce and cooling, while conforming to the requirements of the series and the underlying form of the monocoque chassis. Thus, only the headlights, the Cadillac-logo shape of an air inlet, the wheels and some badging identify it as a Cadillac.

The racecar is powered by a 6.2-liter naturally aspirated V-8 engine built by ECR Engines of Welcome, N.C. It uses a cylinder block, head castings and head gaskets that have Cadillac part numbers and are similar to those that were used in the engine of the now-discontinued Cadillac CTS-V and several generations of Chevrolet Corvette. But its vital components, like those of most other racing engines based on a passenger car design, are supplied by aftermarket companies.

These highly specialized parts, which were chosen in the interest of surviving a grueling 24-hour race run largely at full throttle, include a fully counterweighted crankshaft, steel H-beam connecting rods, sturdy forged pistons and valve-train parts engineered for racing.

IMSA limits horsepower to 600 or less for DPi, and that number is easily reached without getting too extreme in engine tuning and specifications. (The standard CTS-V engine produced 640 horsepower with the aid of a supercharger.) Thus, ECR was able to focus on reliability, and the powerplants have proved very durable.

The Cadillac teams usually run an engine for four races — including Daytona and Sebring — before it has to be refreshed, said Kyle Chura, a Cadillac spokesman.

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