Is it all that we hoped for? Not quite. Rougher pavement throws hair in the cake. While body control is better than in the 997-1 GT3, it’s still not as good as the 997 GT2’s. The new GT3 jiggles over sections that failed to disturb the GT2. While we don’t mind being jostled, some of the vertical motions unload the tires — reducing mechanical grip or at least our perception of it. When that happens, confidence is lost and, with it, part of the thrill.
Back on perfect surfaces, we see the 2010 GT3 for what it is: a great 911 and a worthwhile improvement. It’s not a new ball game, but it is a better car, one with more power, more chassis refinement, and better handling. As to its bigger standard brakes? We suspect they’ll perform better at the track, but find the first hints of fade just as we did in the last GT3 (a 996) that we tested on the Loop with standard brakes. Whether it’s the stock pads, the stock fluid, or too many tight turns and not enough straights, we’re soon longing for the optional, fade-free PCCBs.
Time to move to the green RS, which has PCCBs and an engine that promises to work them. Its 3.9-liter six is the result of a collaboration between SharkWerks and Tempe, Arizona tuner Evolution Motorsports, with the former handling most of the mechanical aspects and the latter handling the electronics. The additional 300 cc come from a bore increase. While looking to go beyond 3.8 liters, Ross and Hendry decided against increasing the stroke early on. Cost was a consideration, but the primary reason was to preserve the GT3’s high-revving nature.
Hendry is no stanger to extreme displacement upgrades, having worked for Devek, a 928 tuner that built 6.5-liter, 600-hp V8s. Thus, he knows that bigger pistons tend to be heavier pistons, a detriment at high engine speeds. SharkWerks’ lightweight forged pistons are an exception, weighing 496 grams each with the wrist pin. By comparison, each factory 3.6-liter Mahle piston weighs 519 grams with wrist pin while each Mahle in the 3.8-liter 2010 GT3 weighs 537 grams.
“Porsche offset the 2010 GT3’s heavier pistons with a lighter, dual-mass flywheel to help it rev,” explains Ross. “Our pistons reduce rotating mass by 120 grams [over 3.6 pistons], which let us not just maintain the 8400-rpm redline but exceed it.”
To prepare the engine for life at nearly 9000 rpm, SharkWerks took one of the quieter pages from Porsche’s RSR playbook. Steel cylinder liners were installed after the aluminum cylinder blocks were bored for the larger pistons. Hendry had to fabricate special tooling to fit the liners, which is one reason the conversion will not be sold as a kit. We suspect another reason has to do with Ross’ admission that he and Hendry spent two years working with suppliers to come up with piston and camshaft specs for their 3.9.
While Ross won’t get into the specifics of either, he says the cams are the key and that both the intake and exhaust profiles were altered: “We came up with a profile that takes advantage of more displacement and higher rpm, one that matches piston valve pockets to maximize lift and duration.” He says the cams benefit from experience with 996 and 997 Turbos as well as the 3.8-liter GT3 project. “Unlike cams for a 911 Turbo, a car that doesn’t spin past 7000 rpm, we profiled these cams to be able to sustain 8800 rpm. By learning what we did from the 3.8 build, we knew how to set them up without losing performance down low.”
The compression ratio is 13.0:1, a full point up on the stock 3.6’s already high 12.0:1. The 3.9 is assembled with cylinder head studs developed by Evolution Motorsports for high-horsepower Turbo applications. Made from H-11 tool steel, they’re claimed to have 260 KSI tensile strength, 83.3-percent greater thread-surface contact, and 38-percent more clamping force than the factory studs.
