Ruf RK Coupé

Ian Kuah takes stock of this supercharged 440bhp 3.8-litre Cayman S-based machine

Ruf RK Coupé

It's almost exactly one year since I drove the first fruits of Alfredo Stola’s partnership with Ruf, in the form of the stunning StudioTorino R Spyder, a Boxster-based roadster powered by the 355bhp Carrera S motor.

Earlier this year, I received an invitation to the premier of their second co-operative venture, the Ruf RK Coupé, which was to be unveiled on 18 August at The Quaile, a motorsport gathering in Carmel, California.

The manic number of press launches at this time of year precluded a trip to California, but I put myself down for a first drive in Pfaffenhausen as soon as the car arrived back in Germany.

It was literally the day after the car was delivered back to Ruf’s workshop when I rolled into their car park, praying that the car had not suffered any damage in transit. Thankfully, everything was in order and the RK Coupé sat in the showroom, its flawless hand-rubbed PPG paint glowing in the afternoon sunlight.

Perfectionism

As the RK Spyder is Boxster based, so the RK Coupé starts life as a Cayman S and, like the RK Spyder, its major body panels are actually low-volume hand-made even though their perfection of form and finish rivals mass production items.

Even the side sills and the intakes at their trailing edge are hand-formed from sheet steel around jigs, just as things were in the heyday of Italian coach-building. However, thanks to modern techniques, accuracy is now spot-on and the panel gaps were equal to the best we have seen in high-end production cars. Incidentally, the coach-building aspect alone occupies around 400 man-hours of each RK Coupé’s construction.

The changes include a total reshaping of the rear roofline, and the Cayman’s tailgate has given way to flying buttresses and a vertical rear screen that gives the RK Coupe a strong visual reference to the Porsche 904GTS. The new front and rear bumpers are carbon-fibre.

The level of craftsmanship involved in producing alloy components like the twin exhaust tips and fuel filler cap for instance is a true labour of love. Machined to perfection from solid aluminium billets, they are worthy of being coveted as display pieces.

If the angels are in the details, quality of design and details are what this car is all about. Alfredo is at pains to point out that while the mass-produced modern car is a great gift to the vast majority of people, its ubiquitous nature makes it less attractive to wealthy and highly individualistic souls.

This perfectionist line of thought is also carried through the interior, where the best quality Poltrona Frau leather is used on most surfaces, in this case in two shades of green. The lightweight carbon-fibre seats are from the Italian firm, Toora, which also makes StudioTornino’s alloy lightweight forged alloy wheels. Customers also have the choice of using Ruf wheels, which were on the car when we drove it.

More power

Once, StudioTorino has completed the body and interior, the car is shipped to Pfaffenhausen where Ruf removes the standard Porsche engine and begins the careful process of re-engineering it for more power.

A bespoke version of the ASA centrifugal supercharger encourages the 3.8-litre flat-six motor to produce 440bhp at 7,000rpm with 347lb-ft of torque at 5,500rpm.

Simply bolting on a supercharger is not the Ruf way however. Space-wise, the best place to install the blower on the flat-six is at the gearbox end of the motor, so it requires a driveshaft with a pulley on the end to reach the front where a Poly-Rip belt picks up the drive from the crankshaft.

As a manufacturer, Alois Ruf was adamant that the installation should look like the whole engine was designed that way, so he went to the expense of having a special housing cast for it. Optimum distribution of the pressurised air required a new cast alloy manifold and integrated intercooling system, all designed and made from scratch.

Together with a bespoke airbox, modified fuel injectors, free-flow metal catalytic converters, sports exhaust and a reprogrammed ECU, the end result looks like it was meant to be that way from day one.

Although you cannot see this incredibly thorough engineering in the RK Spyder and Coupé until you lift the internal engine lid, anyone who does will instantly see where the money has been spent.

The standard high compression ratio of the 3.8 litre base motor is reduced very slightly by means of a thick head gasket, and its inherently strong lowdown power and torque delivery feels unaffected by this or the low drag of the belt-driven supercharger. Boost pressure is 0.7 bar and fuel pressure remains unchanged.

Low inertia, torque-rich

The ASA supercharger is arguably the lowest inertia blower ever built and when you drive the RK Coupé, it really is hard to tell that there is not just a very large capacity normally aspirated motor under the engine cover. There is no supercharger whine, and because the compression ratio stays high, the motor has standard Carrera levels of low speed pickup and no meaningful loss of throttle response.

For hard-core enthusiasts, the character of a motor and its sound are just as important as bald performance figures, and in this respect the Ruf Kompressor motor delivers by the bucket load. Weighing in around 100kg less than a comparable 997 based car, the RK Coupe rockets to 62mph in just 4.0 sec, takes a tad under 13.0 sec to reach 124mph and tops out at 190mph.

The low drag supercharger allows the motor to rev hard and fast. In fact, so eagerly and smoothly does the motor chase the red line, it's hard to believe that there's another mechanical device being driven off the crankshaft.

Where the Cayman S frustrates with a fabulous chassis crying out for more power, the torque-rich supercharged 3.8 punches the car out of bends and down the straights with a thrust similar to a 996 Turbo.

With the low polar moment of inertia inherent in a mid-engined car, the RK Coupé has exquisite balance and feels lithe and nimble on a twisty road. The Ruf coil-over suspension is so well optimised that a supple secondary ride lives cheek by jowl with iron fisted high speed control.

Exclusive

Conceptually, the blend of Italian style and traditional coach building married to German engineering is both ideologically and practically perfect. However, at a whopping €200,000, the very exclusive Ruf RK Coupé is a car for wealthy connoisseurs who delight in haute couture as much as they do in fine engineering.

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