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RUF ’NATO BTR’ - Revival of the Fittest

Ruf’s famous NATO 911 is refreshed for the next lap.

Date Published: 07 Jun 2019
RUF ’NATO BTR’ - Revival of the Fittest

The passage of time does strange things to the memory. It is certainly behind the ‘rose tinted glasses’ syndrome that leaves us with a positive perspective on things we once held in great reverence.

While they can often prove to be less good when revisited many years later it is also sometimes the case that a well-sorted car will continue to impress even though the bar has been raised many times in the intervening years. The fact is that sheer speed is not everything, and fine balance endures.

RUF ‘NATO’ BTR - Revival of the Fittest

On that score I have just driven the one and only production Ruf BTR made in the image of the legendary ‘NATO’ development car, whose nickname came from its matt olive drab paintwork.

Fresh from a complete overhaul before being delivered to its new owner in the US, this Ruf BTR went down the road in a smoother and more accomplished manner than I remember the last one I drove back in the late 80s doing.

RUF ‘NATO’ BTR - Revival of the Fittest

A good drivers’ car manifests a fine balance between its chassis and engine performance, and this BTR proved outstanding in both. As we will see, the excellence of the Ruf BTR NATO cars chassis performance is based on the pillars of bodyshell stiffness, well-judged spring, damper and anti-roll bar rates, perfectly calibrated suspension geometry and state-of-the-art tyre technology.

A bodyshell with high torsional stiffness is always a better platform for the suspension, delivering improved handling and the potential for good ride quality as well.

RUF ‘NATO’ BTR - Revival of the Fittest

Here the bolt-in Matter roll cage significantly stiffens up the core of the 930 Turbo shell while the race style X-brace in the luggage compartment deals with the well-known 911 issue of flex between the front suspension towers under load.

Together these tubular metal components make a huge improvement to structural stiffness, and help to maintain the correct suspension geometry when you are pressing on.

You feel the elevated sense of structural integrity as soon as you enter the first bend with the crisp turn-in and more positive handling apparent to anyone who knows the standard car well. Feedback through the helm is exquisitely analogue, sans the trademark 911 front end bobbing over bumps.

RUF ‘NATO’ BTR - Revival of the Fittest

Old 911s also tend to tramline on uneven surfaces, particularly so when they are shod with big wheels and the wide rubber that also makes the steering heavier. The Ruf approach to the BTR suspension upgrade is a fairly classical one, but has been finessed beyond that of most others its ilk that I have driven over the years.

Rather than increasing the diameter of both front and rear torsion bars as some recommend, Ruf retains the 18.8mm front bars while increasing diameter of the rear bars from 26mm to 29mm.

RUF ’NATO BTR’ - Revival of the Fittest

The rationale here is to keeping the front end relatively soft to minimise traction loss of the lighter front end on bumpy roads. It also avoids the understeer that comes with significantly increasing front roll stiffness. At the heavier end of the car the beefed up torsion bars help to keep the tyre treads flatter on the tarmac when cornering hard.

The overall handling balance that results from altering the relative front to rear spring rates in the above way is fine-tuned by the anti-roll bars, which go up in size from the stock 20/18mm front/rear dimensions to 23/22mm.

RUF ‘NATO’ BTR - Revival of the Fittest

This stiffer front anti-roll bar offers more roll resistance, and is calculated to rebalance the bigger rear torsion bars without chipping into ride comfort to any significant degree. Rebound control is looked after by a set of Bilstein dampers with bespoke Ruf valve settings. Some of the suspension bushes were uprated to remove lost motion in the lateral plane and the ride height was lowered by 20mm for better handling, stability, and a more purposeful stance.

Suspension geometry was set up exactly to factory specifications, but with a minor tweak to the toe-in that Ruf found makes the front end noticeably less fidgety over bumps. This is part of the key to the solid and stable feel of the front-end.

Of all the elements that make up a cars chassis prowess it is tyres that have taken the greatest leap forwards since this car, based on a 1987 Turbo, was first transformed in 1990. Unlike the last BTR I drove 20 years ago this car wears the very latest Michelin Pilot Sport Cup 2 tyres renowned for their outstanding abilities in 20 and 21-inch sizes on the current Porsche GT models.

RUF ‘NATO’ BTR - Revival of the Fittest

Used in far less aggressively profiled 225/45ZR17 and 255/40ZR17 sizes wrapped around 9.0J and 10.0J x 17-inch Ruf deep dish alloy wheels they make a significant contribution to the confidence inspiring way this refreshed BTR goes down the road. The state-of-the-art rubber helps the car turn-in better, with reduced roll and slip angles, and it also helps it puts its power down much more effectively on the way out.

Behind these lovely period wheels the Ruf big brake kit scrubs off speed very effectively with great pedal feel. You just have to remember that there is no ABS safety net here and plan your driving accordingly.

Developed in the mid-1970s way before digital motor electronics became the norm for controlling fuel and spark, the original 3.0 litre and 3.3 litre turbocharged flat six motors were fuelled by the purely mechanical Bosch K-Jetronic fuel-injection system.

RUF ’NATO BTR’ - Revival of the Fittest

Fitted to a wide spread of cars of this era from the VW Golf GTI to the Porsche 930 Turbo, the K-Jetronic system did a good job even if the metering flap and warm-up regulator were not the last word in consistent fuelling precision. However, when Ruf developed the first generation BTR conversion in 1983 this was all that was available.

Realising the need for much greater control over fuelling and spark Ruf went on to develop a variation of the new Bosch Motronic system that made its debut in 1986. In fact the Ruf Motronic system was a key component for the twin-turbo engine that powered the legendary CTR ‘Yellow Bird’ of 1987, and was further developed to suit the third and final upgrade of the single-turbo Ruf BTR engine conversion of 1988.

Apart from the Motronic DME this production BTR3 benefits from uprated Mahle barrels and pistons with a very small increase in bore from 97.0 to 9.8.0mm that takes swept capacity from 3,299cc to 3,366cc on the same 7.0:1 compression ratio. It is thus now a 3.4 litre unit.

RUF ‘NATO’ BTR - Revival of the Fittest

With maximum boost pressure raised from 0.85 to 1.0 bars the output is dramatically improved from 300hp at 5,500rpm to 408hp at 6,000rpm. The peak torque of 480Nm of torque at 4,800rpm shows a similar improvement over the stock 412Nm at 4,000rpm.

The single turbo 3.3 litre BTR motor was a strong contender in its time. Ruf has always been conservative with his engine outputs and the 374hp claimed for the original BTR felt more like 400hp. The Motronic BTR3 motor feels more like 430 or 440hp, but its smooth delivery impresses as much as its raw performance.

Thanks to the mapped ignition and fuelling of the Motronic system the onset of boost is progressive, with little noticeable lag compared to the less powerful stock Turbo motor. Where the stock turbocharger reaches 0.85 bar on full boost the Ruf modified KKK K27 unit boosts at 1.0 bar, its charge air cooled more effectively by the larger and more efficient Ruf intercooler.

RUF ‘NATO’ BTR - Revival of the Fittest

The result is a palpably stronger and more consistent push in the back as the flat-six motor revs freely towards its 6,800rpm redline. Contemporary performance tests mapped out a 0-100km/h time of 4.6 sec, 0-200km/h in 15.5 sec and a top speed of 290km/h. The numbers for a stock Turbo are 5.2 sec, 21.3 sec and 257km/h respectively.

Based on the factory five-speed G50 gearbox, the Ruf six-speeder has relatively short throws and a well-oiled rifle bolt precision that allows you to select ratios with fingertip effort. This is the gearbox that Ruf originally developed to maximise the performance of the mighty CTR, and then offered it as an option for the BTR or indeed any 930 Turbo.

Together with the uprated but still medium weighted clutch this ultimate expression of the BTR philosophy is easy to drive smoothly. And despite its significantly greater speed potential the art of learning to drive it rapidly is actually less daunting than conducting a bog standard G-Series Turbo with ‘80s tyres and less finessed suspension and brakes.

The original ‘NATO’ car was a Ruf test mule and pioneer for the original BTR conversion, and was continuously being fitted with development parts right up until the BTR3 specification was settled.

RUF ‘NATO’ BTR - Revival of the Fittest

The original NATO BTR development car still wore the roof edge rain gutters, and was a rough and ready test mule with a stripped out cabin that never ventured close to being presentable as a customer spec car.

This first and only BTR3 spec production car has the sleeker de-seamed roofline pioneered by the seam-welded CTR ‘Yellow Bird’. The period Ruf front spoiler that visually balances out the factory rear wing reduces lift at speed and features an RSR style centre intake to feed the oil cooler and air ducts on either side that direct ram air at the brakes. These do not have internal ducting, as this would foul the big wheels on full lock.

RUF ‘NATO’ BTR - Revival of the Fittest

Built in late 1990 on a 1987 Turbo this car was commissioned by a Japanese client who fell in love with the look of the ‘NATO’ car that had appeared in various car magazines in the mid-‘80s.

RUF ‘NATO’ BTR - Revival of the Fittest

The car lived in Japan all this time where it even spawned a couple of replicas there amongst Ruf fans. Then last year it was sold to an American enthusiast who sent it back to Pfaffenhausen for a complete refresh before heading west to its new home.

RUF ‘NATO’ BTR - Revival of the Fittest

When the technicians pulled the motor they found that this low mileage well looked after car was in fine mechanical health so no expensive engine rebuild was required.

RUF ’NATO BTR’ - Revival of the Fittest

“While the bolted-in Matter roll cage is far less civilised for a road car than Ruf’s unobtrusive Integrated Roll Cage, as this car has historical significance the new owner wanted to retain as much of its original look as possible even if it was technically uprated under the skin,” Alois Ruf explained. “We only developed the IRC in 1991, the year after this car was completed. So the roll cage was given substantial padding and trimmed in hand-stitched colour-coded olive drab leather to match the dashboard and door panels.”

With the seats however, originality gave way to weight saving, and we surmise that at some point during its life in Japan the period Recaro seats were swapped for modern lightweight carbon-fibre ones trimmed in olive leather to match the rest of the interior.

RUF ‘NATO’ BTR - Revival of the Fittest

RUF ‘NATO’ BTR - Revival of the Fittest

RUF ‘NATO’ BTR - Revival of the Fittest

RUF ‘NATO’ BTR - Revival of the Fittest

RUF ‘NATO’ BTR - Revival of the Fittest

RUF ‘NATO’ BTR - Revival of the Fittest

Being used to practically sitting on the floor in cars with race seats I was very surprised to find myself perched a good three inches higher in this car than I expected. As this is a direct function of the specified seat base I can only assume that this was at the request of either the Japanese or American owner. .

As a street legal trackday machine the Ruf BTR can driven to and from the circuit and so has to be fairly civilised on the road. On that score because it is turbocharged and wears a Euro-legal street exhaust with a lovely flat six turbo burble the noise level, inside and out, is far from anti-social.

Despite the lack of carpets and soundproofing in the cabin its decibel count comes nowhere near the sharply enhanced aural experience that characterises a stripped-out and tuned naturally aspirated 911 with a loud aftermarket exhaust. Because of this you can cruise at a steady 140km/h (90mph) without needing to stop every now and then to re-align your earplugs.

While the full roll cage, race style X-strut brace in the front compartment, and lack of a rear seat nix any thoughts of using the NATO car as a long distance holiday machine, at a pinch you could squeeze small squashy bags in-between all the tubular metal.

RUF ‘NATO’ BTR - Revival of the Fittest

Sometimes you have to look in the rear view mirror to orientate your position in the automotive universe, and driving the only production Ruf BTR NATO in the world that afternoon did exactly this for me.

With today’s stock 992 Carrera S bi-turbo making 450hp accompanied by supercar levels of handling and grip, the sheer ability of modern Porsches is now so great that you need to go that much faster to extract the same thrills from driving it.

RUF ’NATO BTR’ - Revival of the Fittest

This brings me back to the scenario of a well-sorted late ‘80s machine that is rapid enough to satisfy an enthusiast owner but with the tactile feel and feedback that allows you to enjoy it at more modest speeds. That would be the Ruf BTR, and a coat of NATO matt olive drab only adds to its charm.

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