DeMan 4.5L Porsche 718 Cayman GT4 Heads to Auction

A 2022 Porsche 718 Cayman GT4 with a DeMan Motorsport 4.5L engine conversion is listed on Bring a Trailer, featuring drivetrain upgrades and noted smog status.

A highly modified 2022 Porsche 718 Cayman GT4 has surfaced on Bring a Trailer, and this is far from a typical factory-spec example. Offered with roughly 7,000 miles, the car has been transformed with a DeMan Motorsport-built 4.5-liter flat-six, replacing the original 4.0-liter engine.

According to the listing, the factory powerplant was removed, overbored, and stroked by DeMan Motorsport in May 2023 to increase displacement to 4.5 liters. The work went well beyond the engine itself, as the car also received revised exhaust headers, DeMan over-axle pipes, and additional drivetrain upgrades aimed at matching the added performance.

The six-speed manual transaxle is said to feature shorter ratios for second through fifth gears via a close-ratio gearset, along with a DeMan limited-slip differential. A lightweight clutch and flywheel were also installed, reinforcing the impression that this build was designed as a complete package rather than a single modification.

Visually, the GT4 retains its signature aerodynamic elements, including the fixed rear wing, rear diffuser, and aggressive front bumper. This particular car adds carbon-fiber air intakes in place of the rear windows, while the seller notes that paint protection film has been applied to the exterior. Scuffs are reported on the front splitter.

The car rides on 20-inch Brixton TR05 one-piece lightweight forged monoblock wheels that were commissioned and manufactured in spring 2023. Michelin Pilot Sport 4S tires are fitted, while stopping power comes from Porsche Ceramic Composite Brakes with yellow calipers. Porsche Active Suspension Management (PASM) is also listed.

Inside, the cabin features carbon-fiber full bucket seats trimmed in black leather and Race-Tex, complete with GT4 embroidery on the headrests and Racing Yellow seatbelts. Equipment includes the Bose surround-sound system, Porsche Communication Management, Apple CarPlay, automatic climate control, and cruise control.

The listing states that the Carfax report is free of accidents or other reported damage, but one key detail stands out: the car has not passed a California smog test. Given the extensive modifications, including a Gold Leaf Performance carbon-fiber air box, this could become a major point of discussion for potential buyers—especially those planning to register the car in California.

Still, this Cayman GT4 represents a rare example of a deeply reworked build where the changes extend from the engine to the gearbox and differential. As bidding continues, questions raised in the comments about tuning and fuel requirements suggest that interest remains strong, though the final outcome may depend on how buyers weigh performance against real-world usability and emissions compliance.