Story and Photos by Zach Mayne
If you look at the Porsche 993 Turbo Cabriolet pictured here and think to yourself that is not a model that Porsche ever produced, you’d be right… and wrong. While Porsche did not officially make a drop-top 993 Turbo, they did make around 12 or 14 examples in 1995. However, unlike the 993 Turbo Coupe, which for its time was a technological marvel thanks in part to its all wheel drive chassis, the small handful of drop-top 993 Turbos were actually based on the more basic, rear-wheel-drive 993 C2. Built by Porsche Exclusiv at the request of a Munich, Germany-based Porsche dealer, the cars are exceedingly rare and they almost never come up for sale.
So what do you do if you’re an enthusiast who wants an al fresco 993 Turbo experience? One approach is to do what Berkeley, CA resident John Mervin did and build your own. “I wanted to build the 993 Turbo that Porsche did not make, at least in any significant numbers,” he explains. His particular 993 began life as a run of the mill 993 Cabriolet that he acquired after spotting it for sale at a Kia dealer, of all places. The 993 was in solid mechanical shape but had seen better days cosmetically. Regardless, Mervin figured it would make a suitable garage mate for the Porsche 356 A Cabriolet he had spent the last several years restoring.
Ironically, when he first acquired the 993, Mervin was unaware of the handful of 993 Turbo Cabriolets that Porsche had made. But when he stumbled across some information about them he knew pretty quickly the direction he wanted to take with his newly acquired convertible 911. He charted a course to get him to his end goal and then went to work making it happen. He wisely elected to break the project into separate phases so he could still enjoy driving the car in between rounds of modifications.
Mervin knew he wanted a real, turbocharged powerplant for the car to go along with the Turbo bodywork he was planning on installing. Some research into shops that could successfully build him a forced induction motor led him to TurboKraft in Mesa, Arizona, owned by Chris Carroll. A well-respected engine builder and tuner in the Porsche world, Carroll was a great fit for the project. Early on he suggested that the best path to more power was finding a genuine 993 Turbo motor rather than using the existing 3.6-liter. LA Dismantlers provided the motor as well as the wiring harness and ECU.
Carroll rebuilt the cylinder heads with new valve guides and oversizes exhaust valves, but left the bottom end alone as it was still in good shape. The stock K16 turbos were rebuilt with larger compressor wheels used on the K24 turbos. The exhaust consists of OEM 993 Turbo mufflers that were modified for better airflow and a more aggressive exhaust note. Stainless steel exhaust tips from Dansk were also fitted. In a stroke of good luck, the engine’s ECU had already been retuned for power. When it was strapped to an engine dyno, the refreshed motor pumped out 385-hp and 425 ft/lbs of torque to the wheels, a figure that Carroll notes pushes the Porsche’s performance past that of a stock 993 Turbo and into the realm of the legendary 993 GT2 model. The added performance is paired with the 993 C2’s stock 6-speed, which has closer gearing than the Turbo gearbox and helps the car accelerate that much quicker.
Utilizing the existing gearbox presented a set of challenges however, since it's 1-inch shorter than the 993 Turbo's 6-speed. “This positions the engine farther back in the chassis and all the engine peripherals- air guide sheetmetal, motor mount, air intake plenum and tubes, intercooler and air guide, exhaust tips- all are designed to fit in this aft position,” notes Carroll. The solution was engineering a clutch spacer to position the gearbox in the proper position. The 993’s original and heavy dual mass flywheel was replaced with TurboKraft’s RS Touring flywheel that reduces parasitic drag on the engine and frees up revs. A 993 Turbo clutch assembly was used along with the Turbo-specific power steering pump, reservoir, lines and slave cylinder.
To keep the 911’s newfound power usable, TurboKraft installed a set of adjustable Bilstein PSS9 coilovers and a front strut brace. Adjustable rear toe-links ensure that the car’s alignment geometry remained correct when lowered, which helps reduce tire wear. On the stopping end of the equation, S-Car-Go Racing in San Rafael, CA installed stock 993 Turbos.
With an engine from a 993 Turbo installed in the Porsche, the next order of business was making the car look like a Turbo as well. In another stroke of good luck, Mervin sourced a complete set of the wider front and rear OEM 993 Turbo fenders, front and rear bumpers as well as the matching inner bodywork from a Porsche racer in Canada. The remaining parts, including the rear wing, rear quarters, rocker panels and underbody plastic were sourced from LA Porsche Dismantlers and Porsche. Once all the needed components were assembled, the car was shipped to Chris Jones of Canyon Auto Rebody in Oregon.
"The most difficult part was the rocker panels and the rear quarter panels,” says Mervin. “Porsche did not make (Turbo) Cabriolet rear quarters, so Chris had to modify the factory pieces to conform to the Cabriolet top mounting.” The top edge of both rear quarter panels were carefully reworked and massaged to allow the bottom edge of the soft top to fit properly for a factory quality look. “I spent a lot of time scouring the factory manuals and parts diagrams to determine just what was different about the Turbo,” recalls Mervin. “It was a lot of work for a fairly subtle change to the exterior.” The bodywork was finally sprayed in the 993’s original shade of Midnight Blue. The factory Turbo look was topped off with a set of factory hollow-spoke, 18-inch Turbo Twist wheels wrapped in sticky 225/40ZR-18 front and 285/30ZR-18 rear Michelin Pilot Sport AS Plus tires.
The Porsche’s interior hasn’t been neglected either and was fitted with a set of 993 “hardback” sport seats painted to match the exterior color. Autos International provided new carpeting as well as new black leather where appropriate. The center console was painted to match the exterior color and a three-spoke, Alcantara-wrapped steering wheel from a 996 GT2 was installed.
The twin-turbo, 3.6-liter flat-6 in the tail fire to life with a hollow whir backed up by a muted but deep timbre spilling from the exhaust. Balancing the heavy clutch with the extremely revvy engine (thanks to the light flywheel) takes some practice. Once we’re underway though, the 6-speed gearbox feels terrific, with relatively short throws and a light but positive action as we snick through the gears.
In a straight line the Porsche is way faster than it was when it left the factory, lunging down the road as RPMs quickly rise. Above 4,000 the turbos are on full boost and the acceleration is pushing me firmly back in the seat. Adding to the excitement is an exhaust that pops and bangs fantastically when we lift off the throttle for an upcoming turn. In typical 993 fashion, the front end feels light and responsive, the wheel moving back and forth as the chassis encounters dips and ruts in the road. The all-wheel-drive, stiff coilovers and sticky tires all combine to give the car plenty of grip around corners, as well as a nice, tight responsiveness as I thread through a series of corners. The chassis isn’t as sharp as a something like a 996 Turbo, particularly in the convertible form that this one is in, but that doesn’t diminish the fun that this car offers. It also feels very compact, especially when you consider how large the latest 991 has become. In our view, this is just about the perfect way to modify a convertible 993. It’s fun to drive, beautiful to look at and- perhaps most importantly- extremely unusual.
Turbo Kraft • (480) 969-0911 • Broadway Mesa Commons, 1716 W Broadway Rd #123, Mesa, AZ 85202 • www.turbokraft.com