I usually cringe at the thought of a modified 911 Turbo. For every one well-executed example, there are three suffering from tuning that isn't up to par. It's daunting to try and improve something that's so good straight out of the box. What can you do to a car that doesn't really need improvement?

When GMG's 911 Turbo fires up, I don't hear the lumpy idle or stumbling misfires I've heard in the past. Instead, the car issues a low rumble-not entirely unlike stock, but with more purpose. This new attitude is achieved with GMG's own WCGT sport exhaust. It's a complete system: headers, catalysts and mufflers have all been replaced and optimized. Unlike many aftermarket twin-turbo exhausts, GMG's set-up uses a crossover tube between the two mufflers. This not only equalizes pressure between the two banks, but also adds to the unique sound. The system is constructed of TIG- and FUSE-welded T304 stainless steel. Not only does it deliver a healthy dose of power, the system weighs a scant 26 pounds. The headers use equal-length tubes, which are larger diameter than the factory runners, and empty into a TIG-welded three-into-one racing collector. They're engineered to reduce backpressure and retain more energy, reducing turbo lag and allowing faster spool-up.

Sometimes I'm too clinical, seeing assemblages of components and not the beauty of the entire machine. But even if this internal combustion engine is viewed as nothing but a reaction vessel, it's one sexy chemistry experiment. Behind the wheel, I realize the difference those headers make. A blip of the throttle demonstrates just how eager this car is to rev. The needle jumps across the tach as if electrified. You can hear the turbos spool as atmospheric gases are forced into explosive violence.

Acceleration is not as violent as you might expect. With variable geometry turbos and upgraded software, power delivery is smooth. In ballistic terms, this thing is less of an explosive-powered weapon and more like an electromagnetic rail gun. Think 474 hp of liquid-smooth propulsion. At the time of driving, it was the very first 997 Turbo to receive a chip upgrade with multiple modes. GIAC equipped the car with flip-switch technology that allows the driver to change quickly and easily between 91 and 100 octane modes. The software alone is good for roughly 50 lb-ft of torque on pump gas.

Power mods are not the whole story. GMG has applied its years of racing experience to make this car handle as well as it accelerates. To improve on what the factory has done takes real expertise, and the foundation for GMG's improvements center on keeping geometry consistent under load. Porsche engineered the Turbo to be comfortable for the average driver-serious track junkies get the GT3. So the Turbo comes with rubber bushings in all the pivot points and a non-adjustable suspension. Under high loads, those bushings tend to deflect, causing suspension geometry to be less than ideal. To counteract this, GMG designed new components, utilizing spherical bearings as pivot points. Designing new items also allowed GMG to create adjustable pieces for the owner (or the owner's tuner) to set up the car so that it suits his or her way of driving.

Besides adjustable arms and links, GMG also deploys proprietary sport springs and adjustable anti-roll bars. Such suspension work would be pointless if it retained sub-standard rolling stock. This Turbo now rides on stunning but simple Champion wheels, which look as if they've been taken from an American Le Mans Series LMP car. They are 8.5x20 inches in front, with huge 11x20 rears-sporting Michelin Pilot Sport Cup tires. Just like the car, these tires are equally at home on track and street.

To underline the car's ability as a track-day weapon, GMG also installed its GT harness bar. Looking very much like the factory Tequipment bar, it allows the owner to use racing harnesses while also adding chassis rigidity and a certain amount of driver protection. Unlike the Porsche unit, the GMG bar allows taller drivers to either slide or recline the seats back far enough to enter while wearing a helmet. The bar is constructed of chrome-moly steel, TIG-welded and normalized before powder-coating. It uses factory seatbelt anchor locations, so it can be installed or removed without any modification. GMG didn't explain that it's just about as difficult to install as the factory piece, so I would definitely recommend having it installed professionally.

GMG is far from finished with this project. Further upgrades are planned to improve engine breathing, carbon fiber bits to save a few pounds, and possibly improve aerodynamics as well. If these pieces are as well developed as the rest, I can't wait to get in the car again. I have a feeling you'll be reading more about it here.


Longitudinal rear engine, all-wheel drive

3.6-liter flat-six, dohc, 24-valve, turbocharged and intercooled, GIAC 'flip switch' software,GMG WCGT headers, 200-cell sport catalysts and sport exhaust

Six-speed manual

GMG WCGT rear upper dog bones, inner thrust arm bushings, toe steer kit, GT sport adjustable anti-roll bars, Champion Motorsport sport springs

*Wheels and Tires
Champion Motorsport RF67, 8.5x20 (f)11x20 (r)Michelin Pilot Sport Cup, 245/30 (f), 325/25 (r)

GMG GT 4130 chrome-moly harness bar

Peak Power: 474 hp
Peak Torque: 484 lb-ft
*measured at the wheels

Global Motorsports Group
Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!