The Turbo Revolution is upon us and Porsche has jumped in with both feet. There are only two naturally aspirated coupe offerings sporting the Porsche crest and they are the Cayman GT4 and the 911 GT3; every other Porsche model is now turbocharged. We wanted to try and get in front of the curve with the new line of turbo charged Carreras from Porsche and see what sort of performance we could unlock from Porsche’s latest wolf in sheep’s clothing, the 2017 991.2 Carrera GTS.
AT BGB WE LIKE TO HOT-ROD THE UNDERDOG AND WELCOME A CHALLENGE
Many of our customers want something cushy for the street but able to hold its own on the track - they don’t like the big wings or the racy look of some of the GT cars and would prefer a usable back seat area. We put pen to paper to see if we could bolt some parts to a non-GT3 911 Carrera and make it lap a race track as well as its big brother while maintaining that sleeper look and comfy feel on the street.
We have spent the last 15 years racing naturally aspirated 911s and Caymans and now building them with larger 4.0L displacement engines for the street and the track. We have gone even larger recently to try and eclipse the 500-horsepower threshold, but we wanted another challenge. The underlying 911 chassis was not new to us, as we developed a 991.1 for racing homologation purposes 5 years ago; tuning modifications for turbocharged Porsches was however a new frontier. Those that follow us know that we have specialized in installing the naturally aspirated 991.1 GTS engines in Caymans, Boxsters and 911s for a few years now so it made sense to continue with a GTS model, as they are at the top of the Carrera food chain.
THE NEW TURBO ENGINES PRODUCE MORE TORQUE THAN ANY PRIOR GT3 ENGINE TO DATE
Torque is what gets a car out of the corner and down the straightaway and quite frankly, naturally aspirated Porsche engines don’t make a lot of torque relative to the other cars we have raced against over the years. The big push at the moment for Porsche is to create smaller displacement engines that are more fuel efficient but pack more punch and to do so, Porsche built the 2017 – 2018 line of Carreras with a newly designed 3.0L flat 6 turbo charged engine that produces more power and torque than the previous generation cars. Across the lineup the engines are the same in all 4 offerings; the 911 Carrera base, S, T and GTS models all have the same 3.0L powerplant but the turbo chargers and the computer programming are the major differences among them. This allows Porsche to make one engine for all Carrera models which helps save additional pennies.
Racing is everywhere in our industry and whether we are at the track or in the shop, there seems to always be a race to be at the front of the line to finish something. Much like with today’s news reporting though, the rush to be first across the line sometimes comes at the price of doing the best job possible or being the most correct and this is where we try and differentiate ourselves. As others were boasting of being the first to modify these cars, I spent about 6 months researching the race track potential of the new turbocharged Carreras from Porsche. I read reviews, test drove various models and spoke to friends that instruct at the Porsche Sport Driving School at Barber Motorsports Park in Birmingham, AL and the Porsche Experience Centers in Los Angeles and Atlanta. Stories were already spreading around the paddock about how the 991.2 GTS Porsche school cars made so much torque that they were running the same lap times as the higher horsepower 911 Turbo models on short road courses. We frequently visit the location of Porsche’s PSDS school in Alabama and during my research period I was there and when I looked up saw a fleet of yellow and red 991.2 GTS school cars, as far as the eye could see, it was a sign from above; I had never seen so many GTS 911s at one time!
Overseas there was already an instance of a 991.2 GTS lapping the famed Nürburgring faster than the previous generation 991.1 GT3. This was enough to make us jump in with both feet ourselves and we did so by finding a used, low mileage, lightly optioned speed yellow 2017 991.2 GTS that was PDK, without a sunroof, center lock wheels or rear-axle steering. To me it was the perfect candidate because it had one less driver aid for the track. The car showed up on our doorstep from Porsche of Melbourne in July and so begins the story of “Big Bird.”
THE DYNO DOES NOT LIE
The first trip we made in “Big Bird” was to the dyno to get a baseline horsepower and torque number the way we do for all engine conversion projects. My good friends at Cobb Tuning were repeatedly telling me that I would be blown away by the performance increase from their latest Off The Shelf mapping for the 991.2 and they were eager for us to sample the latest offering from their tuning platform that allowed me to perfect the drivability of our 4.0L X51 Cayman and Boxster conversions. I love learning new processes, so the mapping in the ECU was the first revision. We justified the purchase of the car to explore a new line of business for our customer offerings, specifically the ECU tuning and focused on the ECU first since it had the most potential for gains.
I am one of those people that needs to see things for themselves so before flashing the computer, we drove the car to the dyno, strapped it down and did a baseline dyno pull. It was your typical summer Florida day with high temps and high humidity, so we had set our expectations somewhat low because the car was already warm from the 30 mile drive to the dyno. I wasn’t expecting much but baseline dyno produced at the wheels what the factory advertises at the crank; the dyno does not lie. We then flashed the car with the Cobb Accessport and OTS map and did another pull and I immediately almost fell out of the driver’s seat when I saw the numbers. We picked up an astonishing 117 horsepower and 77 lb/ft of torque at the wheels from an ECU file upgrade that was the size of an email attachment! One would have to invest over $40K to see those gains from a naturally aspirated engine and we did it for less than a tenth of the cost. The ECU upgrade by itself now holds the all-time scoring record for $ per horsepower/torque test.
Since the ultimate proving ground is the race track which is technically off-road, we added an IPD plenum, BMC high flow filters and a cat bypass downpipe upgrade from our exhaust partner Cargraphic in Germany. We went back two more times to quantify each improvement and the final numbers were all triple digit gains in power and torque that equated to the car’s making an additional 20rwhp and 176 lb/ft over and above a 991.1 GT3 on the same dyno. On the highway cruising at 4K RPM, “Big Bird’s” dyno results showed his ability to make an additional 220 lb/ft of torque more than the GT3.
TRIPLE DIGIT GAINS IN POWER & TORQUE FROM BOLT-ON UPGRADES AT A FRACTION OF THE COST
We had spent over a decade trying to squeeze torque out of the naturally aspirated 3.4L and 3.8L engines by eventually increasing displacement and while these motors make plenty of horsepower, getting torque out of them was like trying to squeeze blood from a stone. The naturally aspirated flat six boxer style motors aren’t what you would call “square” in that they don’t make the same amount of torque that they do horsepower. Our best engine conversions make almost 500 horsepower but make roughly 360 lb/ft of torque and involve a lot of work. The new turbocharged motors however make big torque down low at 4K RPM which is where you want it when you’re coming out of the slow corners on a race track or cruising on the highway.
Realizing that turbo charged engines are prone to heat soak and understanding that intake air temps are a very crucial component for race track performance, we added a pair of AMS Performance Intercoolers to further cool the air going into the engine. In addition, given that Porsche has begun to make substantial usage of the car’s coolant system to cool heat exchangers for the engine and the transmission, we added a factory center 3rd radiator from the dealership to help reduce coolant temperatures and put more coolant volume in the system. Summertime at the race track in Florida means hot temperatures and high humidity, but we welcome these harsh conditions and prefer to show that our packages work anywhere in the world, not just in areas where temps are cool all year-round. The power modifications were complete; it was now time to focus on the chassis.
WE NEEDED TO MAXIMIZE GRIP BOTH IN THE MIDDLE OF THE CORNER AND IN THE BRAKING ZONES
Developing race cars has shown us that it’s not just all about power so we went to work on the brake package first because our research yielded that the new Carrera gets down the straightaway so well that it seems to chew up the brake pads on tracks with long straightaways and hard braking zones. We installed our standard track day brake package that all cars need which involves flushing the brake hydraulic fluid with Castrol SRF racing brake fluid, adding steel braided brake lines, additional brake cooling found on the GT3 / GT4 Clubsport and our tried and trusted Brembo RE10 endurance racing brake pad. A better performing brake pad means less time is spent on the brake pedal which equates to less heat in the braking components. In addition, Porsches need air ducted to the brake components because you’re asking a lot of the braking system on a race track, especially tracks that are bumpy where the ABS is active. We did make sure to essentially give it the same package a GT3 would run for the track to keep things on a level playing field. A brief test drive before going to the track showed the potential that the car would not be lacking anything in the brake zones.
The next phase was to give the car enough grip to get through the corner as well or better than anything else, so we replaced every suspension component that was not adjustable with an adjustable alternative like what is standard on the GT3. At a minimum, whether it’s a Cayman or a 911, it needs more camber up front for the race track and it needs an adjustable rear tie rod end to fine tune the rear toe settings on the alignment pad once the camber is changed. This would have been sufficient but we like to develop and test some parts for Tarett Engineering and they suggested their complete spherical kit for the 911’s 5-link rear suspension, so we upgraded everything for all of the 911’s suspension arms; we did however adjust the arm lengths to equal the stock settings so as not to create an unfair advantage relative to the GT3. Given adjustable anti-roll bars are two of the most powerful tuning tools on a current generation Porsche, we added larger adjustable Tarett sway bars and drop links.
WE WANTED TO KEEP THE DR. JEKYLL AND MR. HYDE APPROACH WITH THE SUSPENSION
We did not want to lose sight of one of our main goals of creating something equally comfortable on the highway, so we got a bit creative with the shock and spring package and how we control it. This was a car that would be driven to and from the race track, so we went the route of choosing to maintain the factory Porsche PASM dampers and their functionality and chose to upgrade them with a slip fit adjustable collar and stiffer spring from H&R; it allows you to corner balance a car with stock shocks much like an adjustable ride height coil over suspension allows. I am becoming more of a fan of this approach as opposed to spending $8K on race suspension for a dual-purpose car and the entire package from H&R can be purchased for less than $1000.
To further the dual duty approach, we pushed the edge of the envelope of Porsche’s PASM option by purchasing TPC Racing’s DSC Sport controller. They make their software available to everyone which allows the end user to maximize the PASM option in a myriad of directions. After 20 minutes on the phone with Mike Levitas and his son Harris, I was up to speed and able to create my own custom map to dial out some of the anticipated understeer and balance the car perfectly for the track yet still maintain the softness for the street. We added the same wheel studs we sell to our GT3 customers that ditch the center locks so that we could be able to add and remove the hubcentric wheel spacers as a final tuning tool. This also allows us to accommodate for different offset wheels for mounting rains vs. slicks at a track day. After doing some research, we decided that our dry tire of choice would be the 20” Pirelli PZero Trofeo R.
SAFETY FIRST, NOT LAST
While the final phase was safety, the fact that we haven’t discussed it yet is by no means an indication of how important we think it is; the car actually has to finally come off of the four post lift to have the bar, belts and seats installed so it’s last in execution and first in thought. We tell all of our customers that we have an obligation to keep them safe so safety harnesses and a 4-point bar is something we make them buy first, well before we suggest their getting into power mods. These current generation Porsches are blindingly quick around a road course and every single one of them should have something more than a standard 3-point safety belt. A few years back we developed a 4-point bolt-in bar for the 991 that did not cannibalize the back seat, so we used our bar and installed our favorite Schroth 6-point harnesses on it. I have been a fan of anything resembling a stock appearance since day one and we really wanted this car to look the part, so we chose to source the factory Porsche folding carbon fiber bucket seats found in Europe, which we received thanks to Suncoast Porsche in Sarasota, FL. At the time they were available but that is no longer the case as Porsche has put an end to that program for the U.S. Once the safety bits were installed, we spent a few hours on the alignment pad corner balancing the car and setting it up for the track and then it was time to go and see what kind of cards we were holding.
IT WAS TIME FOR BIG BIRD TO LEAVE THE NEST AND HEAD TO THE RACE TRACK
The completion of the work coincided with a trip to attend a track day event at Circuit of the Americas in Austin, TX to deliver a newly built 981 race car. Track events at COTA are chock full of GT3s, GT3RSs and all sorts of heavy machinery so we figured this would be a great place to let “Big Bird” strut his stuff. We unloaded the car, slapped some numbers on the doors and away we went. Finding some dry track time proved difficult during the first day as it kept raining every time we went out; things would look promising and then as we would roll to the grid, the skies would open up. Even in less than ideal conditions, the car showed signs of having plenty of grip. The tires generated heat easily which gave you confidence in the damp conditions. Due to the weather we only ran about four laps because we didn’t want to push our luck so we gave up on running the first day in the wet.
Around lunchtime on Sunday the sun finally showed up and we found some dry track time. I took a passenger and the first 3 laps, the sound of our laughter almost drowned out the exhaust note. Unlike the naturally aspirated cars that need to be spooled up and kept high in the RPMs, this car loved the low RPM range. As you would exit every slow corner the car would leap 2 – 3 car lengths at a time the moment you rolled into the throttle. The balance was completely neutral without any oversteer or understeer. You could rotate the car if you wanted to get overly aggressive, but it inspired confidence in every part of the corner. The brake zones seemed to be an even bigger advantage for the car. The only thing we couldn’t hold off was a prototype race car. During the session I made my way up to sandwich myself in between a pair of 991 GT3s to get some good feedback and once I got by them, they tried to hang on but you could see Big Bird gaining an advantage under braking and at the exit of the corner every time. Even though we only had one dry session before it was time to load the car up and take it home, the experiment showed signs of being a complete success. For every GT3, RS and 911 Turbo we passed there was a driver that followed us back to the garage to ask “what the heck is in this thing?” When we told them it was just bolt-on mods and our favorite iTunes playlist, they chuckled.
WE HAD TO GO TO DAYTONA INTERNATIONAL SPEEDWAY TO TRY AND BREAK THE 175MPH MARK
Our shop is based about 15 minutes from Daytona International Speedway where the terms Porsche and Rolex 24 go hand in hand and one of our biggest events is the final Porsche Club of America weekend in October. We wanted to show off Big Bird at the track one final time and let him run on the high banks to see him exceed the previously set BGB in-house top speed record. It was the same story all over again. In the tight infield hair pins he would gain tons of ground under braking and in the corners and once you got out on the banking, he would reel in the larger displacement cars. The car really showed its strong suits at this event and yet again, other 911 owners followed him back to the garage to see why it was that this car was lapping under 2 minutes and doing top speeds that most full-blown GT race cars achieve. A few corner marshals wandered into the garage at lunchtime and wanted to know why something that looked so non-descript could run as well as it had. This time we made sure to get good video.
We cannot reflect on this experiment without paying homage to the 911 GT3. It is truly an amazing car worthy of almost supercar status given how it performs on the race track in bone stock trim. We attend a lot of track events and we see a lot of high powered cars that run fast lap times and then sit in the garage suffering heat stroke and brake fade, further reiterating how Porsche builds the best dual purpose cars on the planet. Both the 991.2 GTS and the 911 GT3 do this far better than any other car out there. The GT3 makes its strides in the top end of the RPM range with an abundance of horsepower from 7K to 9K RPM while the 991.2 GTS makes it down low and pulls like a locomotive before it has to shift at its 7200 RPM redline. If the turbo cars could rev to 9K RPM like the GT3, it wouldn’t be as equal on a long straightaway. The GT3 comes with fully adjustable suspension, front and rear aero, a wide front and rear track and really is the ideal track-oriented Porsche for those that don’t need something a little less conspicuous and can have a 2nd car for the track. The goal was to create something that was on par with a GT3 and we feel we did that without exceeding the budget of the GT3 and were successful in proving that the 991.2 GTS should get the respect it deserves. With the right bolt-on parts, you can have the best of all worlds and create a true sleeper – just don’t pick yellow!