As chief engineer Andreas Preuninger addressed a gathered throng at the New York International Auto Show, he described Porsche’s newest 911 GT3 as his group’s highest performing GT product, with “the most amazing gearbox on the planet.” Was this hyperbolic bluster, aimed at deflecting criticism of the new car for abandoning its motorsport-derived “Mezger” engine architecture and vaunted manual transmission? Immediately following the press conference I cornered “Mr. GT3” to find out.
Preuninger contends that this new engine does indeed provide a “replacement for displacement,” refuting the old muscle-car adage—it’s super-high-rev operation. Spinning an engine to 9000 rpm certainly isn’t trivial, and building in that capability drove a complete redesign of the current 911 engine that left only the raw engine block casting and the cylinder head bolts in common. The crankshaft, titanium connecting rods, and forged aluminum pistons are all newly optimized for high speed running, but it’s the valvetrain you really have to worry about at these speeds—especially in a road car with self-adjusting tappets (race engines frequently need their valve lash adjusted in between races).
To get mass out of the moving parts of the valvetrain, Preuninger’s team managed to relocate the hydraulic adjuster to the cylinder head itself. It now supports the pivot for an ultra-light cam follower that actuates the valve. Each of these little followers now weighs just over half-an ounce, slicing more than 3 pounds out of the valvetrain. He believes Porsche is the first to bring such a system to a production road car. Those race-bred cam profiles, by the way, reportedly produce a delightfully lumpy idle that gently rocks the car when standing still. The cylinder heads are configured to move mass quantities of air in and out of the cylinders at 9000 rpm, resulting in a rated output of “475-plus-plus [metric] horsepower.” This ultra-conservative rating might have been arbitrarily assigned to provide an emotional link with the outgoing GT3 RS 4.0—an identical power density of 125 PS/liter.
As for the choice to completely abandon the three-pedal stick-shift for a seven-speed PDK transmission, Preuninger claims that numerous modifications make this transmission feel like a proper racing sequential transmission (and in any case, the race-bred GT3 can no longer afford the competitive disadvantage of time-consuming manual shifts). The ratios are unique, with seventh a direct-drive gear—not an overdrive economy ratio. Top speed of 195 mph is achieved in seventh. Naturally, the powertrain executes throttle blips for ideal rev-matched downshifts. Shifting via the gear selector now happens according to racing convention—forward for downshifts, back for upshifts. The paddles themselves get stronger return springs and a more positive detent that feels sportier, and pulling both at the same time gives you neutral for as long as you hold them. This is useful for helping regain traction in a hard corner by relieving the tires of all acceleration or overrun forces, or for executing a hard launch with wheelspin. Switching off all the electronic aids activates what Preuninger calls “Hooligan mode,” for drifting and smoky burnouts. (He assures me that the system has been thoroughly tested, successfully withstanding 500 “Hooligan starts” in quick succession.) Finally, the GT3’s PDK provides no creep at idle in first gear (as the domesticated PDKs do).
Okay, Preuninger has convinced me of GT3’s fabulosity on paper, now let’s see how it fares in the crucible of Best Drivers Car competition.
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