2016 BMW M4 GTS

BMW forges its hottest track car with a little help from a cooling injection of water. Scientists scour the ever-expanding universe for liquid water in the hope that where there is water, there will be life. Well, turn the telescopes around, eggheads and point them at Munich to see how BMW is injecting new life into its machines with water. Specifically, how H2O is squirted into the intake plenum of the M4 GTS’s S55 twin-turbo inline-six to make more power. Water injection, the process of introducing water into combustion air to increase engine output, isn’t a new technology. Military aircraft used it in World War II, and more than 50 years ago GM offered a water-injected turbo engine in the Oldsmobile Jetfire. It’s an effective way of cooling the intake charge of a boosted engine, and since cooler air is denser air, it’s richer in power-critical oxygen. In the short path from the air filter, through the turbos, up and over the dual-cam head, and through the air-to-liquid intercooler, the S55’s compressed air can heat up enough to literally boil water. Indeed, that is what BMW is counting on. The magic of water—actually any liquid—as it boils, or changes from a liquid to a gaseous state, is its cooling effect. The evaporation process converts some heat into harmless humidity. Lowering the intake temp—by about 77 degrees Fahrenheit in most driving situations in the GTS—prevents damaging engine knock, or the unwanted detonation of fuel and air. That allows BMW to both crank up the boost to 21.6 psi, versus 17.2 in the Competition-package M4, and advance the timing. The result is a 49-horse bump from the aforementioned 444-hp M4 to 493 horsepower at 6250 rpm. Explained: M4 GTS Water Injection BMW could have used an E85 injection system or an alcohol-water mix with similar if not even greater performance, but according to Jürgen Poggel, M GmbH’s head of engine development, those approaches would change the engine’s emissions. BMW didn’t want an engine that could ever be out of tailpipe compliance if the secondary tank ran dry, as a diesel does when it has consumed its urea stores. Additional water vapor in the combustion chamber does nothing to emissions because there is nothing combustible in distilled water. Run the water tank dry and the engine reverts to the 444-hp Competition- pack tune. On a racetrack, the 1.3-gallon trunk mounted water tank drains in step with the 15.9-gallon fuel tank. Water injection is only active above 5000 rpm and  under full load, so street drivers may only need to rehydrate every five or six tanks. (It is unclear if BMW dealerships will soon stock distilled “luxury” water at a commensurate price.) To reduce the chance of corrosion and to prevent the water from freezing, the car drains its lines every time the engine shuts down. BMW recommends draining the water tank completely if you plan to park the car for extended periods in temps below 41 degrees. The GTS would be special even without the magic of water injection. It is the latest in a long line of hopped-up M3 specials, until now not sold in the U.S., starting with the E30 Evolution and most recently the E92 GTS packing a 4.4-liter V-8. Perhaps you have already glanced at the specifications, eyeballed the six-figure sticker, and thought, “It had better be damn special.” Well, it is. BMW swapped out a staggering number of chassis and interior components in pursuit of track performance and to make the  GTS worthy of its $134,200 price.Carbon-ceramic brake  rotors join a carbon-fiber hood, roof, trunklid, driveshaft, rear wing, front splitter, rear bulkhead, rear diffuser, and strut brace in the GTS’s carbon pile-on. Lightweight interior trim borrowed from the i3 is standard and there to save weight. The exhaust system is titanium downstream of the catalysts, and there are no door pockets or center-console storage bins, though the cupholders remain for your own fluid injections. The water-injection system adds 22 pounds, and all the cars coming to the U.S. get fitted with a heavy four-point roll cage in place of the back seat. Also, U.S. cars don’t get the lightweight carbon-fiber seats seen in these pictures; instead, we get lighter- than-normal sport seats with manual adjustments. The result is a U.S.-spec car that weighs 3550 pounds, or just about the same as a base M4 fitted with the dualclutch transmission, which, sadly, is the only trans for the GTS. BMW tapped meaty Michelin Pilot Sport Cup 2 tires, 265/35ZR-19 up front and 285/30ZR-20 in back, to wrangle the gutpunch torque and the rest of the chassis changes. The basic suspension setup remains—struts in front and a rigidly mounted rear subframe carrying a multilink suspension—but three-way adjustable dampers with external reservoirs and adjustable spring perches (you can manually lower the car 0.8 inch for track duty) go to work here. Redesigned knuckles on the front allow for more negative camber and slightly more stability-aiding caster. The extra grip of the Cup 2s also required a subtle change to the engine: An additional quart of sump oil is spec’d to avoid starvation in high-g maneuvers. With the extra power and the additional stick from the Michelins, we expect the GTS to burn a launch-control quarter-mile run in 11.5 seconds. And if you get behind the wheel of a GTS, you’ll do a lot of these sprints because, at full tilt, this engine sounds like a feral beast saturated with adrenaline. While BMW claims 493 horsepower and 443 pound-feet of twist, our butt dyno indicates it’s more like 550 of each. Purists can rejoice that there is no artificial soundtrack pumping through the speakers here. We only sampled the car on a racetrack, with the suspension set accordingly. Curb serrations rattle the jaw, and undulations in the pavement produce head toss dangerous to those without well-developed neck muscles. BMW could have dialed back the high-speed rebound damping a bit (thereare 16 positions for it) and we still would have gotten the message. Flat-foot the gas on corner exit and the tail drifts a bit in a predictable manner, even with the stability control in its competition mode. The torque tops out at 4000 rpm, high for a modern BMW turbo, but the engine never feels peaky and it will pull hard if you roll through a second-gear corner in third. The Cup 2s enliven the M4’s steering with legitimate feedback through the suede-wrapped steering wheel, a sensation otherwise absent in this generation of M3/M4. The one thing we’d like is a larger brake pedal, or a little more spacing between the brake and throttle pedals to make left-foot braking easier. The GTS is as legit a track car as any Porsche GT car, or so says its advertised 7:27.9 lap of the Nürburgring Nordschleife, less than three seconds off the pace of the newest 911 GT3. Obviously that gap will shrink on shorter North American tracks. With a limited run of 700 GTSs worldwide, and only 300 heading to the U.S., this special M4 is indeed exclusive. BMW says dealers have already spoken for all of them and buyer vetting has begun. Which means you’d better have a house account at your local dealership if you want one. BMW has no worries about selling all of its U.S.-bound units and expects most to be used as dedicated track cars that don’t have to be trailered to the paddock. Just don’t forget to bring that distilled luxury water.

  2016 BMW M4 GTS
VEHICLE TYPE:
front-engine, rear-wheeldrive,
2-passenger,
2-door coupe
BASE PRICE: $134,200
ENGINE TYPE:
twin-turbocharged
and intercooled DOHC
24-valve inline-6,
aluminum block and
head, direct fuel
injection, port water
injection
DISPLACEMENT:
182 in, 2979 cc
POWER:
493 hp @ 6250 rpm
TORQUE:
443 lb-ft @ 4000 rpm
TRANSMISSION:
7-speed dual-clutch
automatic with manual
shifting mode
DIMENSIONS
WHEELBASE: 110.7 in
LENGTH: 185.0 in
WIDTH: 73.6 in
HEIGHT: 54.4 in
PASSENGER VOLUME:
54 cu ft
TRUNK VOLUME:
11 cu ft
CURB WEIGHT: 3550 lb
PERFORMANCE
(C/D EST)
ZERO TO 60 MPH:
3.4 sec
ZERO TO 100 MPH:
8.0 sec
1/4-MILE: 11.5 sec
TOP SPEED: 190 mph
FUEL ECONOMY
EPA COMBINED/CITY/
HWY: 19/16/23 mpg