Previous GT3s used VarioCam Plus variable intake camshaft timing, and the new car benefits from refinements to this system as well as the intake plenum to take full advantage of the added displacement. The real news, however, is that the GT3 3.8 is the first Porsche to use variable exhaust cam timing, as well. “The new cams added 3.3 pounds to engine weight, but the low-rpm torque is significantly improved and exhaust emissions are lower, as well,” says Preuninger.
As the existing exhaust-pipe diameter did not restrict the 3.8, the exhaust system was carried over. “It is a relatively light system with a good acoustic, so we saw no reason to change it,” explains Preuninger. The final numbers seem to confirm that restriction isn’t a problem in the 3.8, which is rated for 435 bhp at 7600 rpm and 317 lb-ft of torque at 6250 rpm. The specific output of 114.6 horsepower per liter is an outstanding number for a normally-aspirated engine.
Some will wonder why Porsche didn’t adopt direct fuel injection. Preuninger is ready with an answer: “We already run a very high compression ratio on this motorsport-derived engine compared to a mainstream Porsche motor. So adding DFI would have meant a lot of extra work and weight for very little gain. As it stands, we improved fuel economy and emissions over the old 3.6 motor.”
The other bit of new Porsche technology not considered for the GT3 was the PDK double-clutch gearbox. “Apart from the fact that GT3 drivers want a manual and the GT3’s short shifter selects ratios faster than a normal manual, PDK adds 66 pounds to the wrong end of the car,” offers Preuninger. “Mechanically, it does not fit the GT1 block anyway; a special flange would have to be made. Beyond that, the PDK box is longer and would create a packaging issue.”
The six-speed manual is broadly similar to the previous one. “The differences came out of our weight-savings program, where we found ways to shave a few grams here and there without compromising strength or durability,” continues Preuninger. “The one significant mechanical change is a shift in the way the gears are locked onto their shafts. A few hard-core clients asked for more easily interchangeable ratios, so we adopted the motorsport system.” The limited-slip diff is carried over unchanged and locks up 40 percent on acceleration and 28 percent on decel. Gear ratios are unchanged, so top speed only moves up one mph.
“We did not set out to make the new car faster in top speed,” says Preuninger. “Even in Germany, there is too much traffic to extend any car past 300 km/h (188 mph) for more than a few seconds unless you get up very early on a Sunday.”
Attaining such speeds is one thing, doing it in a relaxed manner is another. The 996 GT3’s nose got light beyond 155 mph and it was nervous in crosswinds at high speed. The first-generation 997 GT3 was far better and very stable at 190 mph, but the latest GT3 takes aerodynamic stability to a new level with literally five times more downforce. “The trick was to achieve this without seriously affecting drag,” explains Preuninger. “We spent weeks in the wind tunnel, and achieved the significant downforce we were looking for with the Cd climbing slightly from 0.30 to a still-good 0.32.”
The GT3 boasts 88 pounds of downforce up front and 154 pounds in the rear at 188 mph. “Where most cars have 220 pounds of lift at that speed, we have 242 pounds of downforce,” says Preuninger. “This equates to over 440 pounds more downforce than a normal car. The added stability is significant — you can do a lane change at 155 mph without feeling like you’re going to fly off the road!”