2011 Porsche 911 GT2 RS - European Car Magazine

It’s a question of some import: How do you improve upon the most bad-ass 911 the Porsche factory has ever produced? A car that carries the marketing tagline “Respect required” and has earned the ominous nickname of “Widowmaker.”

If you’re GMG Racing, you take championship winning experience from World Challenge pro racing and add in several hundred hours of development research. Santa Ana-based Global Motorsports Group (GMG) earned Porsche the 2009 Manufacturers Championship in World Challenge GT competition and, at the time of this writing, currently leads both the manufacturer and drivers championships.

This car’s owner sent GMG his 2008 GT2 for a World Challenge package three years ago; he was so impressed with the first car that when he took delivery of a new GT2 RS, one of only 500 built, he elected to send it in as well to have GMG’s WC-GT2RS package installed—having only driven it a mere 75 miles after he took delivery.

Vehicle Data
Engine: 3.6-liter flat six, dohc, 24-valve, twin-turbocharged
Transmission: Six-speed manual
Current mileage: 75
Current modifications: GMG intercooler set

Dyno Data
Dyno type: Mustang MD-AWD-500
Transmission test gear: Fourth

Performance
Peak power: 495 hp @ 6300 rpm
Peak torque: 476 lb-ft @ 4305 rpm
Temperature: 65° F

Test Notes
The baseline and all subsequent testing were performed on the same day. All horsepower and torque numbers quoted were measured at all four wheels. It is also important to keep in mind that the properly calibrated Mustang dyno produces more accurate real-world horsepower and torque numbers. While these numbers might seem low when compared to figures gathered from a Dynojet what is important is the differences between each dyno run. These differences are what we use to verify the validity of the manufacturer’s horsepower and torque claims.

GIAC Software

Test 1
GIAC Pump Mode 91 Octane

Performance
Peak power: 536 hp @ 5700 rpm
Peak torque: 526 lb-ft @ 4900 rpm
Max power gain: 45 hp @ 5600 rpm
Max torque gain: 65 lb-ft @ 4700 rpm

Install process: OBD Flash
Installation time: 45 minutes
MSRP: $4,000

Pros
• OBD port flashing allows the ECU and harness to remain completely unmolested
• Increased throttle response and smoother power transitions
• Increased rev limiter
• Speed limiter is raised in Sixth gear
• 100% reversible
• Flashloader Handheld Switcher with stock, 100 octane Race, Anti-Theft and Valet modes included
• Reduced exhaust gas temperatures

Cons
• None

Test 2
GIAC Race Mode 100 Octane

Performance
Peak power: 557 hp @ 6000 rpm
Peak torque: 563 lb-ft @ 4500 rpm
Max power gain: 45 hp @ 5600 rpm
Max torque gain: 65 lb-ft @ 4700 rpm

Price: $7.59 per gallon for fuel

Test Notes
GIAC Race Mode 100 does more than just add extra timing to generate power. It is programmed to optimize every aspect of the software including fuel, timing and boost to extract more power and ensure maximum drivability.

The boost data was generated using a boost line attached directly to the intake manifold then attached to an externally mounted 3bar GM-style MAP sensor with a 0-5 volt analog output range. The signal is converted by the Powerdyne software into psi. The GIAC optimized boost curve takes full advantage of 91 or 100 octane fuel.

GMG WC-Gt2 RS Sport Exhaust

Test 3
GIAC 91 Octane & GMG Exhaust

Performance
Peak power: 545 hp @ 6210 rpm
Peak torque: 564 lb-ft @ 4200 rpm
Max power gain: 31 hp @ 6210 rpm
Max torque gain: 71 lb-ft @ 3900 rpm

Installation time: 45 minutes
MSRP: $5,595

Pros
• T304 mandrel bent tubing
• OBD-II compliant 200-cell German metal core sport catalyst
• 25% lighter than OEM exhaust system
• T304 mandrel bent stainless steel tubing
• Double normalized purge TIG welds for strength
• Proprietary center crossover section equalizes exhaust pulses and offers a scavenge effect to speed up exhaust flow

Cons
• None

Test 4
GIAC 100 Octane & GMG Exhaust

Performance
Peak power: 572 hp @ 5700 rpm
Peak torque: 610 lb-ft @ 4500 rpm
Max power gain: 47 hp @ 5300 rpm
Max torque gain: 65 lb-ft @ 4900 rpm

Price: $7.59 per gallon for fuel

Conclusion

When designing an exhaust system for a turbocharged vehicle, maintaining precise backpressure is critical to optimizing performance. It’s all about balance—you need just enough backpressure for the turbos to spool up quickly and maintain boost, yet not choke the turbos in the high rpm range. According to GMG, the OEM Porsche 997 GT2 RS exhaust maintains 10 pounds of backpressure while the T304 3.5-inch GMG World Challenge turbo-back system equipped with 200-cell German-made metal martrix sport catalysts maintains 1.5 pounds, an 85 percent reduction. The impact of the reduced backpressure on the boost curve was more than expected. On the dyno, boost pressure increased from 1-5 psi from 2500-4300 rpm and dropped 1-3.5 psi from 4350 rpm all the way to redline. The benefits from this new linear boost curve include increased turbo efficiency, reduced operating temperatures, increased horsepower and more consistent power delivery.

Cost Summary
GIAC software $4,000
GMG WC-GT2 RS exhaust $5,595
MSRP total: $9,595