Porsche 911 GT3 RS 4.0 Explained – Video

That 4.0 in the car’s title refers to the displacement of its engine. Whereas other GT3s use a 3.8-liter flat-six, the 4.0 borrows the upsize engine from the track-only GT3 R and RSR.

The bump in displacement results from a longer stroke, as Porsche could not increase cylinder bore. Titanium connecting rods and a single-mass flywheel shave a few pounds, but all other changes relative to the GT3’s 3.8-liter six enhance airflow.

The 4.0 gets a higher-flow air filter, a modified intake manifold with shorter runners, and a less-restrictive exhaust—the last of which reduces back pressure and amps up the noise in equal measure. The result is an increase in output from 450 hp to 500 hp, with torque edging from 317 lb-ft to 339.