991.2 GT2 RS Baseline and Cobb Accessport Dyno Results
Porsche’s latest version of the 911 GT2 RS has been highly anticipated for a number of years now. With production cars finally starting to trickle out over the past couple of months, Cobb Tuning was obviously chomping at the bit to get their hands on one. Yes, we realize this is the most powerful 911 Porsche has ever pushed through the factory doors but we simply can’t leave well enough alone.
Baseline numbers on California 91 octane (yuck) were 605hp and 520tq at the wheels (Run #3 below). Factoring in parasitic loss through the drivetrain and fuel quality, this is right in line with the 700hp figure Porsche states.
With changes to fuel injection strategy, manipulating the ignition timing curve, optimizing for fuel quality, and improving the boost profile, we were able to extract gains of 54hp and 61tq, bringing output to 659hp and 581tq to the wheels( Run #2 above). This was extremely promising as we were still utilizing standard California 91 octane fuel.
With RS owners in other areas having access to 93 octane fuel we needed to improvise in order to create a calibration optimized for 93 octane fuel. A specific amount of 100 octane VP101 fuel was added to the remaining 91 in order to achieve a blended fuel that accurately mimics 93 octane. Cobb Tuning's Porsche ECU Engineer, Mitch Mckee, then optimized the tune for the added octane before recording another power pull. To our delight, output increased even more, producing 694hp and 593tq to the wheels. That is an additional 35hp and 12tq over the 91 octane output!
With calibration work for Cobb's Stage 1 Off The Shelf Maps complete, Mitch wanted to see just how much power the completely stock GT2 RS would put down on straight 100 octane fuel. It was obvious that the car was still making power up top as boost was not falling off. This is due to two key features of the GT2 RS’s configuration.
First, intercooler sprayers. They actually work. Phenomenally. Throughout the entire tuning session, Charge Air Temperatures were never out of control.
Second, turbocharger sizing. Historically, VTG-equipped Porsches have been limited due to the small exhaust housings. The smaller housings are great for transient response and low-end torque but become a restriction up top, creating undesirably-high exhaust manifold pressure. We do not have specific sizing, but we can without a doubt, say that the GT2 RS VTG turbochargers come equipped with larger turbine housings. Volumetric efficiency is much improved, especially at the top end, resulting in decreased exhaust manifold pressure and higher power potential.
The results on 100 octane fuel were astounding! 735hp and 638tq at the wheels. At that point, we did run into signs of spark blow-out. Not surprising, as cylinder pressure at that point is definitely much higher than stock. We would definitely recommend a tighter gap on the plugs for cars wanting to push beyond the Stage 1 (91 or 93) power level.
To summarize, the GT2 RS is an animal. With a bit of fine tuning, it becomes an untamed beast.