Porsche 991 Turbo ECU Comparison - Cobb, GIAC, VR Tuned

We have been apart of the Porsche tuning community since 2005 and have definitely had our fair share of fun with cars. Many dyno test, installation articles, opinion notes, photos, have been done on the likes of our Porsche 996TT, 997TT, 997.2TTs, 997GT3RS, and now our 991 Turbo. When we got our 2014 Porsche 991 Turbo in December 2013, we went right to work with modifying it. Developing headers, an exotic sounding exhaust, high flow y-pipe, and intakes for it were just the start. But it was not until August 2014 that we had a tuning solution to really maximize the performance of our 991. Because the ECU could not be read out due to tuning encryption, the only option was the VR Tuned Tuning Box kit which is a plug and play solution. Tapping into the cars sensors, the tuning box gave the 520 horsepower 911 about 60whp and 80ft/lbs gain over stock. Combined with our Agency Power products, we added almost 100 horsepower to the crank. With these proven results, many customers picked up on our parts and had a go for themselves.

Having sold our 991 Turbo in April 2015, it circled back to us for some product development. Already equipped with the AP Y-Pipe, Intakes, Headers, Exhaust, and VR Tuned box, the new owner chatted his buddy up to come to Vivid Racing for similar mods on his 991 Turbo S. Porsche’s S version came equipped with 580 horsepower, which already gave it a 60hp advantage over our 991 Turbo. The car already had a GIAC ECU Tune, Sharkwerks muffler bypass pipes and high flow cats. So to improve the cars low end torque and throttle response, we added our Agency Power intakes, Y-Pipe, and headers to the car. After installation and some test driving, we decided to do some dyno runs of the car. We ran the car with our first run on a cool car in standard, then ran a sport run, and finally a standard run. Each run the car would lose more performance because of the increasing temperatures. Our first run in Standard Mode was our best with a peak torque of 482 ft/lbs at about 3500rpm and 474 awhp at redline. Running the Turbo S on our Mustang AWD Dyno with 91octane and a temperature of 100F, we typically see a 20-25% drivetrain loss. This would mean the car is making about 615hp to the crank up 35 from the stock 580hp. Expecting more power, I told the customer, “wait let me dyno my old 991 one right now to see where it is at.” Since the car was here, it was a perfect opportunity. Now to reiterate, both these cars had the same Agency Power add-ons except the Turbo S had straight pipes and highflow cats with a GIAC tune.

Strapping our old Project 991 Turbo down, we would get a good Apples to Apples comparison. Both being run in Standard Mode, both with 91 octane, both with the same dyno settings and calibration. We ran the same sequence of 3 runs and like the Turbo S, the first was the best. Our 991 Turbo made 525ft/lbs of torque and 493 awhp. When looking at the graph, the 991 Turbo made 43 more ft/lbs of torque and held a solid torque gain all the way to redline. Horsepower increased from 3500rpm with a gain of about 40awhp holding an increase to about 6000rpm where it tapered off. Both of the cars tapered at the same point which leads me to believe they were restricted from lack of airflow. So you are probably thinking this is a shameless VR plug… Nope these are the actual results we got that I am sharing. The runs were done within 40 minutes of each other (strapping and unstrapping the cars). How could a 991 Turbo with stock cats, aftermarket muffler, air intake, y-pipe, headers, and a plug and play Tuning box with 520hp stock, be stronger than this 991 Turbo S with a “ECU Flash”, high flow cats, muffler delete, and the same AP parts? Well it was and the customer wanted more power. With that being said, the only option would be to upgrade the turbos or maybe do a IPD plenum. But to gain real power, the VTG turbos could be modified just like we do with the 997 Turbos here.

99% of the time, when a car comes to us with Part A, Part B, and Part C, unless it is absolutely the wrong direction, we figure a way to make these parts work best for the customer. Recommending the Turbo change to the customer, he opted to not go that route, but asked, “why can’t we put that tuning box on my car”. You can’t put a tuning box on top of a tune. At the same time, since the customer had high flow cats, we did not want to have a check engine light since the Tuning Box cannot disable the O2 sensors. Then we thought, “what about the new Cobb Accessport for the 991 Turbo!“. This would be a perfect chance to have a 3 way product comparison and show off Cobb’s new product.

Famous for it’s history in the Subaru STI and Mitsubishi EVO market, Cobb quickly took over the Nissan GT-R tuning market. Also having dabbled with the Nissan 350z, Mazda 3, Ford Focus ST, and BMW N54 cars, Cobb put a hard focus on the Porsche world. Their 996 Turbo, 997 Turbo, and 997 GT3 Accessports were slow to the community since many tuning solutions were available. But the 991 Turbo was new, untapped, and this could be fun. The Accessport is like the iPhone for tuning cars. It comes preloaded with stage maps for 91 and 93 octane. For those wanting to put the hurt on, there is a 100 octane map too. These can be easily written to your cars ECU through the OBDII port. If you are thinking, “who wants an off the shelf map, its not custom”, keep reading to see results, but also Cobb Pro-Tuners can tune this platform for you. The device does not lock to 1 vendor, so no matter where you take your car, Cobb can be used. In addition to the ability to load files and return to FULL stock mapping, the Cobb Accessport for the 991 Turbo has data logging capabilities, view and clear trouble codes, live view of digital gauges, and can be connected to Cobb’s website to get the latest firmware needed.

Our first concern with the Cobb Accessport was can it overwrite the GIAC tune on the car. Typically having another tune means trouble for doing proper calibration. Its always better to start with stock firmware. Even though we have a Porsche Piwis tool here, the 991 cannot just use “programming codes” to flash it back, you have to dial into Porsche, hence the encryption issue. Cobb said this was no problem and we could flash over it. Connecting to the car was as simple as it gets. We selected the Stage 2 91 octane file to match the modifications and flashed away. The process took less than 10 minutes to write. Just for fun, I tested the factory map reset to flash back to stock and that was equally fast. Once the Cobb was on the car, it was time to test it again on the dyno. All the same variables, same dyno settings, same weather, now the difference was the tune. So how would the Cobb Accessport do compared to the VR Tuned Tuning Box and the GIAC ECU Flash? The Cobb was really strong, linear in its torque climb, and held a solid 15psi in standard mode to redline. The torque actually came on quicker than both and just edged out the VR Tuned at 536 ft/lb of torque. Its horsepower curve and midrange gains were identical to the VR Tuned with a gain of almost 50awhp at 3900 rpm holding gains to 5700 where it tapered off like the GIAC tune. The VR Tuned had slightly more top end power from 5400rpm to redline with a peak gain over both around 5900 rpm of about 15 awhp.

So with all this dyno fun and product testing, what are the final thoughts? Cobb has done it again with another hot market, this time Porsche. For $2295, you get an all in one tool that is easy to install, provides great gains, has good features, requires no shop or downtime. With few choices at the time of writing this article, it gives a good insight to what works in our tests scenario, what could be changed, and the benefits of tuning your 991 Turbo or Turbo S. Of course we like our VR Tuned Tuning Box for its simplicity and “warranty safe” plug and play feature. The Cobb Accessport is an amazing device for 991 Turbo owners looking to get that extra edge in performance.

Porsche ECU Testing Results

991 Turbo S – GIAC, Sharkwerks Muffler Delete and High Flow Cats, AP Y-Pipe, AP Intakes, AP Headers
- 474 awhp and 482 ft/lbs of torque (400 awhp at 4750 rpm)
991 Turbo S – Cobb Tuning Accessport, Sharkwerks Muffler Delete and High Flow Cats, AP Y-Pipe, AP Intakes, AP Headers
- 474 awhp 536 ft/lbs of torque (435 awhp at 4750 rpm)
991 Turbo – VR Tuned, AP Titanium Exhaust, Stock Cats, AP Y-Pipe, AP Intakes, AP Headers
- 493 awhp 525 ft/lbs of torque (440 awhp at 4750 rpm)