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Porsche 9ff GT2 RS - Rocket Science

Low flying at 366km/h.

Date Published: 18 Mar 2020
Porsche 9ff GT2 RS - Rocket Science

Papenburg, Germany - Why do people climb the highest mountains, dive to the bottom of oceans and fire themselves towards other planets? Challenge, exploration, a dare? Call it what you will, but without such pioneering spirits, we would probably still be stuck in the early stages of the industrial revolution.

 

It is the same with cars. There are always some people for whom factory stock is just the starting point. Fundamentally this is about individuality. We are all different, thank goodness, and many people express this through their cars. That premise is the foundation stone of the aftermarket tuning industry. Bigger, better, faster, more!

 

9ff GT2 RS - ROCKET SCIENCE

 

With customer individuality as a given in the tuning world, it is also important for each tuning company to be different to stand out. Having a USP attracts clientele with a similar mindset who would not naturally gravitate to a rival whose products they cannot identify with.

 

Since he set up shop in his hometown of Dortmund in 2001, Jan Fatthauer has plugged the USP of creating the fastest turbocharged 911s in the known universe. Over the years his cars have consistently won top speed shootouts organised by Germany’s Auto Bild Sportscars magazine at tracks like Nardo and Papenburg, and I have been there to witness several of these.

 

Of these the most memorable for us was the totally insane 1,086hp 997 GT3 based orange monster. Its owner, Dmitry Samorukov, CEO of SMP Racing and avid promoter of Russian motorsports, wanted a 911 that could take on the fastest cars in the annual Moscow Unlim 500+ street legal drag event, and win. He took the overall Russian street legal top speed record with this car in 2010, clocking 372km/h after just 2,500m.

 

Dmitry was keen for me to drive his car, which I did on an old airfield runway not far from 9ff’s HQ in Dortmund. I am not exaggerating when I say that the 900m long runway with an open valley at one end and a short grass runoff at the other was far too short!

 

9ff GT2 RS - ROCKET SCIENCE

9ff GT2 RS - ROCKET SCIENCE

 

Fast forward to August 2019 and we are at the German motor industry high speed test facility at Papenburg in North West Germany where there is no chance of running out of road.

 

The 900hp 9ff GT2 RS that Jan drove to Papenburg is near standard in all but its engine. Thus, it is a far cry from the purpose built 987hp 9ff GT9 that his team built for its all-out assault on the road car 400km/h Vmax record back in 2008. That GT9 prototype recorded 408.77km/h at Papenburg in May 2008, and the later 1,150hp GT9-R was even more potent.

 

In the Papenburg 3000 High Performance Event the terminal speed and acceleration numbers achieved on the way to the 3,000-metre mark are recorded and verified by third party adjudicator, TÜV Rhineland, using the industry standard Racelogic VBox data logging equipment.

 

On paper the 9ff GT2 RS was the second most powerful car in the event, giving best to the 1,050hp Klasen Audi R8 Biturbo. However, on the day the GT2 RS managed 366km/h or 227.42mph, more than sufficient to pull it clear of the Audi, which simply ran out of revs. Given the standard chassis and aero settings of the 9ff GT2 RS this illustrates the headroom built into the fastest street legal production car Porsche has ever built.

 

9ff GT2 RS - ROCKET SCIENCE

 

The basic engine block of Porsche’s 3,800cc twin-turbo flat-six has a reputation for being virtually unburstable, and as we have seen with the GT9-R and Dmitry’s GT3 bi-turbo 9ff has extracted up to 1,200hp from previous incarnations of this basic engine. Of course that level of power requires the use of a bespoke crankshaft, titanium rods, special pistons and other race grade components.

 

In parenthesis the mere 900hp that was the benchmark number for Jan Fatthauer’s team for the GT2 RS is comparatively mild, but the idea here was to offer a bolt-on road legal conversion that does not require any expensive internal work.

 

The hardware changes are all external to the engine block and centre around the two upgraded VTG turbochargers. The housings are precision machined to accommodate 4.0mm larger turbine and compressor wheels also featuring nine instead of the stock 11 blades. This improves efficiency and spool up speed as well as increasing the charge air flow rate.

 

9ff GT2 RS - ROCKET SCIENCE

 

Turbochargers use fuel to cool as well as for combustion, and a lot more fuel is required when you light the afterburners here. While the injectors themselves have sufficient headroom the fuel rail pressure is increased from 200 to 220 bar.

 

“We experimented with the boost pressure on the dyno to see where the sweet spot between output and reliability might be,” explained Jan. “We knew that the intelligent map sensor would not allow us to sustain more than 2.0 bar of boost so we aimed for a compromise just below that.”

 

“We saw 1,000hp with 2.2 bar of boost but this would not be practical. In any case we did not need anything like this level of power to make the top speed of 369km/h we were looking for in still air. Our calculations told us all we needed was 900hp and 1,000Nm of torque, which was achievable on 1.95 bar of boost.” This is a substantial increase over the 700hp and 750Nm of the stock motor on 1.55 bar of boost.

 

The exhaust system is one of 9ff’s bespoke systems from the cylinder heads back to the OE titanium silencer. This system includes swapping the catalytic convertors for 200 cell high performance units and a bespoke sound valve system.

 

9ff GT2 RS - ROCKET SCIENCE

 

The system is set up to bypass the cats when it is on full throttle, and the reduced back-pressure is so significant that the ECU mapping can dial in significantly more ignition advance. From the stock 18 degrees to as much as 26 degrees on full boost at high rpm, especially when running 102 Octane Aral fuel. With its rev limiter increased slightly from 7,200 to 7,350rpm as part of the ECU and TCU remaps, the theoretical Vmax is 369km/h.

 

The PDK gearbox controller (TCU) is also remapped accordingly so all functions and shift behaviour remain standard with the greater engine output. The mechanical components of the PDK transmission and clutch have enough headroom with this level of power so long as you do not indulge in too many hot launches or silly burnouts.

 

As this top speed shootout event was sponsored by Continental Tyres all the contestants wore the latest Continental Sport Contact 6 rubber. For the GT2 RS that means 265/35ZR20 and 325/30ZR21 tyres on the factory 9.5J x 20-inch and 12.5J x 21-inch forged alloy wheels.

 

“These tyres suit the GT2 RS very well, endowing the car with a very high degree of stability at speed,” Jan reported. “I switched off the TCS and PSM electronic safety systems during my runs to prevent any intervention that might have held the car back from achieving its best possible Vmax,” he said. “There was a little slip in first gear away from rest but after that the car was stable all the way up to top speed with no power induced movement at the rear.”

 

9ff GT2 RS - ROCKET SCIENCE

9ff GT2 RS - ROCKET SCIENCE

 

The only thing that caused Jan’s heart to beat a bit faster during the run was caused by aerodynamics. “While everything felt good flat out there was some momentary instability on the way there,” Jan recalls. “I could feel the front end go bit a light in the 330 to 350km/h range, but once past that the car hunkered down again.”

 

Interestingly I was told a similar story by Bugatti test driver, Andy Wallace when he described his 490.48km/h (304.77mph) speed record in the Chiron at Ehra Lessien, that was established about three weeks before the Papenburg 3000 event. When I spoke to Andy in September he described how he experienced a small window of instability, which quickly disappeared as he went even faster.

 

The reason for this instability in a particular speed range experienced by both drivers is rooted in aerodynamics. While an aircraft has air consistently flowing all around it whilst flying, a car experiences an additional phenomenon known as ground effect when driving at speed. What they have in common though is what is known as laminar flow, which is how airflow moves along the skin of the plane or car before it eventually departs.

 

The ideal shape for high speed and low drag is a cigar, which is of course impractical for a daily use road car. The closest any street legal production car has come to this in recent times is the McLaren Speedtail, but the cut off or Kamm (named after 1930s German aerodynamicist Wunibald Kamm) tail, is the closest practical shape to this ideal and has been featured on many production car designs since the 1960s.

 

However, a car with very low drag can have high speed aerodynamic stability issues. The reason for this is that as the vehicle goes faster it pushes its (CP) aerodynamic centre of pressure (which is variable) further and further forwards and thus ahead of its physical (CG) centre of gravity (which is fixed). The natural position of the CP at rest is behind the CG, so as it extends further forwards it tries to return to its natural position behind the CG, creating an aerodynamic turning moment and aerodynamic instability.
 

9ff GT2 RS - ROCKET SCIENCE

9ff GT2 RS - ROCKET SCIENCE

 

Those who remember the original Ford Sierra of 1982 and its then revolutionary Cd of 0.3, will also remember its high-speed instability issues. These were eventually solved by adding plastic strakes to its C-pillars, which made the airflow ‘dirtier’ and moved the CP further aft at speed.

 

While cars like the GT2 RS and Bugatti Chiron have significant downforce from their spoilers, flat bottoms and other aero devices, the flow pattern of air departing from the cars bodyshell in the null zone at the base of the front windscreen and other areas is not totally consistent and alters with speed.

 

This can change the position of the centre of pressure, moving it forwards enough to upset the fixed amount of downforce created by the front spoiler within a certain speed range, However, once that speed range is exceeded and the laminar airflow returns to the envelope within which the front and rear downforce is balanced for maximum directional stability then all is well again.

 

9ff GT2 RS - ROCKET SCIENCE

 

The front aero and rear wing of the GT2 RS are adjustable and help the car produce a total of up to 416 kg (145kg front, 271kg rear) of downforce in its ‘race’ position with four degrees angle of attack. But downforce is always a trade-off against drag, and while you need maximum downforce for fast sweeping bends on track, for a top speed run you set the aero to minimise drag.


All this this underlines the fact that the airflow around a car is a living thing that changes with speed. It is also affected by non-constants like constant or gusting crosswinds and so on. So a fixed measure of stability at speed is never a 100% given.


As for the visceral feel of driving the GT2 RS at these speeds, “Accelerating through the gears there is of course a lot of engine and exhaust noise,” Jan explained. “But once you reach very high speed in top gear it is a bit like a jet aeroplane where you are going so fast you begin to leave the noise behind you.”

 

9ff GT2 RS - ROCKET SCIENCE

9ff GT2 RS - ROCKET SCIENCE

9ff GT2 RS - ROCKET SCIENCE

 

The 25,000-euro 9ff conversion for the GT2 RS is centred around the modified turbochargers, primary exhaust and ECU reprogramming work. This is not unreasonable money for the significant gain of 200hp and 250Nm of torque on a car that cost nearly 10 times that when new and is appreciating in value at this point. “We are very pleased with this relatively ‘light’ upgrade, which has garnered a lot of interest from our clients since we set the 366km/h speed record,” says Jan.

 

9ff GT2 RS - ROCKET SCIENCE

 

A factory fresh GT2 RS laps the Nürburgring Nordscheife in a blazing 6:47.30 min, while the MR version with its stock engine tune uses uprated aero, suspension and brakes to shave a full 7.0 sec off that time. We would just love to know how fast the MR version might be when combined with 9ff’s powerhouse motor.

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