The 2018 Mercedes-AMG GT C Roadster is hunting for Porsche 911 Cabriolets

Mercedes-AMG will be adding two convertibles to the GT sports car lineup this fall.

Standard GT Roadster models will have a 469-horsepower twin-turbocharged V8 engine.

The GT C Roadster features a 4.0-liter twin-turbo V8 that gets different pistons, fuel pump and turbos to push out 550 horsepower and 502 pound-feet of torque.

Mercedes-AMG says the GT C Roadster will hit 60 mph in 3.7 seconds and reach a top speed of 196 mph.

Like the coupe, the roadster models will feature a seven-speed dual-clutch transmission.

To improve stopping grunt, carbon ceramic brakes are available as an option.

Other upgrades to the GT C Roadster compared to the regular GT Roadster include wider rear body work, an electronic limited-slip differential, rear-wheel steering and wider rear tires.

To make up for the missing fixed roof, the roadster's chassis is upgraded with thicker side skirt walls, additional dashboard and windshield frame reinforcements and a rear strut tower brace.

Both the Mercedes-AMG GT Roadster and GT C Roadster will go on sale this fall.

Pricing isn't available yet, but expect the GT Roadster to be a bit more expensive than the $111,000 AMG GT, and the GT C to carry a price tag above the $131,200 GT S.