With the GTS poised as a stripped-down, hardcore, go-faster iteration of BMW’s two-door sports car, it makes sense that the Bavarians would throw a water-injection system into the mix. A bit more power and better reliability will complement the vehicle’s already uncompromising attitude, and although it’s not necessarily ground-breaking technology, every little bit of efficiency from the new forced-induction engine will surely not be wasted on the track. Expect to see this system revealed in August during the Pebble Beach Auto Week.

Most interestingly, though, was that the stock turbocharged inline-six powerplant had been outfitted with a water-injection system. Now, according to Car And Driver , this system will be stock kit for the M4 GTS track model. The news comes from an unidentified insider who spoke to the publication at the Geneva Motor Show.

Late last month, we took a look at BMW’s M4 MotoGP Safety Car, the vehicle designated to set the pace for the fastest liter-bikes in the world. It has a few upgrades from the stock model, including a new coilover suspension, a lightweight M Performance titanium exhaust system, a simply superb black paint job, a few requisite racing decals, Recaro racing bucket seats, and carbon-fiber aerodynamics front to back.

Why it matters

When BMW replaced the M series’ naturally aspirated 4.0-liter V-8 powerplant with a 3.0-liter inline-six strapped with two turbochargers, the result was very, very good: not only was horsepower increased by 11 to a nice round figure of 425, but torque output gained an incredible 111 pound-feet to 406. Both peak figures occur lower in the rev range, while mileage is also bumped up by 25 percent.

Clearly, the V-8 was a dinosaur, while this new boosted straight six represents the latest in BMW’s petrol-powered technology. Now, it appears as though the Bavarians want to increase efficiency even further with water injection.

Here’s how it works: the turbochargers compress the air going into the cylinders, because as we all know, more air and more fuel equal more power. However, compressed air is hot. So hot, in fact, that it can sometimes ignite the air/fuel mix prematurely inside the cylinder, causing something called a “ping” or “knock.” Any engine that is pre-igniting the mix will eventually grenade itself to death.

To help combat this, high-octane fuel is used, as it is resistant to pre-ignition. Intercoolers are also very common, running between the compressor and intake manifold to help cool the air before it reaches the cylinders.

BMW wants to use another method of preventing knock called water injection, whereby water is sprayed into the intake tract past the intercooler, cooling both the charge and the cylinders. This allows for higher levels of boost and improved efficiency in even the most demanding environments.

The M4 Safety Car uses a 1.3-gallon tank mounted in the trunk to feed distilled water to three injectors in the intake plenum.

When BMW divided the M3 and M4 into the four-door and two-door camps respectively, the newly designated coupe found itself representing the finest of BMW’s sporting intentions. As such, the Bavarians didn’t hold back in making the new M4 one of the most track-capable road cars available, and pretty soon, its expected that an even faster GTS version will make the scene.

Details don’t yet exist, but we can look to the current M4 for ideas. The exterior will feature the typical BMW performance fair, with pumped-up fenders, a bulging hood, curvaceous aerodynamics, and lightweight 19-inch wheels. While the design looks good, it’s still quite slippery, with time spent ensuring minimal drag and a good deal of downforce, not to mention proper flow to all sections of the vehicle that require cooling. Expect additional carbon fiber aero enhancements to make the GTS stick at speed.

Curb weight on the M4 has dropped significantly to just 3,300 pounds, a reduction of 176 pounds compared to an M3 coupe with similar specification. Distribution of the heft is close to 50:50, front to back. Again, the GTS model will undoubtedly shed even more mass in the pursuit of lower lap times, utilizing components made from carbon fiber, aluminum, and titanium.

Inside the stock M4, things are plush but functional, with flat-back one-piece sport seats, a leather-wrapped steering wheel, M-design gauges, and chrome trim.

Under the hood of the M4 is a twin-turbo straight six engine mated to a standard six-speed manual gearbox with automatic throttle blip for downshifts (hey, at least there’s a clutch pedal, right?). There’s also an optional third-generation, seven-speed dual-clutch unit with integrated launch control. A carbon-fiber prop shaft and Active M differential make the power turn into go. 0-to-60 is accomplished in 4.1 seconds for the manual, and 3.9 seconds for the slushbox. Top speed is 155 mph. For the GTS, expect at least 25 extra horsepower, probably via additional boost and the water-injection system. It would be nice to see the retention of the manual six-speed, but BMW will probably prefer the quicker acceleration of the seven-speed auto.

The new M4’s suspension gets a healthy dose of trackiness, with rigid “play-free” ball joints, a carbon-fiber-reinforced plastic strut tower brace, and a rear axle that’s attached directly to the rear subframe. Clearly, comfort has no place here, which is a characteristic that’s sure to continue in the GTS.

Prices for the new M4 coupe start at $62,000, while an extra $100K will likely be tacked on for the limited-edition, track-day GTS.

Source: CarAndDriver