It’s nearly twice as expensive as a regular BMW M4 but it’s also the greatest M car on sale today. The M4 GTS does have the M4’s twin-turbo 3.0-liter inline-six but it’s undergone some surgery, and it involves much more than just that big rear spoiler
. This is the first production road car to be fitted with a water injection system, which works exactly how it sounds: water is injected as a fine spray into the intake manifold chamber where it evaporates. This lowers the intake air temperature and further reduces the final compression temperature in the combustion chamber.