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Brabus 700 Biturbo - Power Corruption

From the German masters of Mercedes tuning mayhem.

Ian Kuah
Oct 19, 2011 SHARE

If you attended this year’s Geneva Motor Show, you could be forgiven for thinking that the Mercedes-Benz SLS AMG and Porsche Cayenne are the most-tuned cars on the planet. However, where the SLS show cars on various stands featured body styling that covered the spectrum from the sublime to the ridiculous, the gray car on the Brabus stand stood out for throwing down a power and speed challenge to the major league supercars. Dubbed the Brabus 700 Biturbo, this car has exactly what it says on the tin: 700 hp from a twin-turbocharged version of AMG’s 6.2-liter powerhaus V8.

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Because most supercar enthusiasts are not interested in SUVs, they would not automatically connect the 700 Biturbo to the Brabus ML63 Biturbo developed in 2009. But this existing engine meant that the groundwork was already laid, so the project was not a major undertaking. Since the AMG V8 in the SLS is fundamentally a tuned, dry-sump version of the V8 in the ML63, the issues simply revolved around adapting the existing ML twin-turbo system for the SLS. In practical terms, this installation was actually easier on the SLS since the engine has more space around it than in the ML. This provides better airflow for the intercoolers, and allows the use of a more efficient exhaust system.

Step one is a complete engine strip down. The major internal change is swapping out the standard pistons for a set of forged Mahle Motorsport pistons that reduce the compression ratio from 11.0:1 to 9.0:1. This allows Brabus to use a modest 0.9 bar of boost with no fear for the reliability and longevity of the motor.

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The Brabus ML63 Biturbo requires a relatively complex bespoke exhaust manifold due to packaging issues. This has one section serving three cylinders and the turbo, with the fourth pipe joined by a balance pipe.

In comparison, the SLS manifolds are very straightforward, with long, equal-length primary pipes made from high-nickel-content cast iron to withstand temperatures up to 1,200 degrees Celsius. The basic turbocharger is based on a Garrett unit, which is then heavily modified by Brabus. The scroll housing is Garrett’s, modified to relocate the oil pipe exit point from its bearing housing. Inside, the turbine wheel and compressor wheel are both bespoke units.

Brabus’ Deputy Development Chief Jorn Gander explains: “If you take a turbocharger from the manufacturer’s catalog, you will find that the innards rotate clockwise. However, in a twin-turbo arrangement, we found that the airflow in the system is only optimal if the turbochargers are mirror-imaged; otherwise the flow characteristics of two clockwise-rotating turbochargers create pulses that adversely affect response times.

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“So we have the innards of the left-hand turbocharger specially made with the blades that rotate counter-clockwise to balance things out. The tricky part on both units was getting the oil flow to the bearing housings just right. We put a lot of effort into optimizing the oil pressure and size of the feed lines.”

The twin water-to-air intercooler system is basically half of the setup used on Brabus’ most potent V12 Biturbo engines, which use four such intercoolers. With their own self-contained water circuit independent of the engine’s cooling system, these efficient intercoolers throw off heat far more effectively than an equivalent air-to-air system.

Other than the pistons, the rest of the engine internals are unchanged. The standard cylinder heads are well machined, and in any case, force-aspirated engines are less sensitive to head porting than their naturally aspirated counterparts.

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Downstream of the turbos and exhaust headers there are special catalytic converters. The rest of the exhaust system is made from titanium, the same as the normal Brabus SLS exhaust. With four 84mm outlets, this system saves 26 pounds and weighs 40 percent less than the factory stainless steel equivalent.

One useful feature of the Brabus exhaust is its pneumatic sound flap system that allows you to vary its voice at the touch of a button. In its quiet setting, the system cuts significant decibels off the factory standard level. On full noise, the system is louder than stock, thus providing the best of both worlds.

Speaking of weight, the turbochargers and intercoolers add around 66 pounds in the engine compartment. However, since the SLS is a front-mid-engine design with its motor as far back in the chassis as possible, this has minimal effect on the car’s weight distribution.

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The ECU undergoes a remap of the fuelling, spark and the variable valve timing curves, which all end up quite different to cope with the forced aspiration. The unit also features an integrated electronic boost control system.

The outputs are now 700 hp at 6600 rpm and 627 lb-ft at 4300 rpm compared to the standard 571 hp at 6800 rpm and 479 lb-ft at 4750 rpm. In terms of specific output, the numbers are 91.97 hp per liter for the factory engine, and 112.75 hp per liter for the 700 Biturbo.

Out of the box, the SLS AMG takes 3.8 seconds for the 0-62 mph sprint, and tops out at an electronically limited 197 mph. Any two-wheel-drive car will struggle to deploy such massive grunt off the line, so the 3.7-second 0-62 mph time recorded by the Brabus 700 Biturbo is not representative of how much quicker it is in real world conditions. Its 0.7-second faster 0-124 mph time of 10.2 seconds certainly is. If you can find a long enough stretch of autobahn, the extra torque and horsepower make full use of the car’s tall gearing and seven forward ratios to reach an unrestricted 213 mph. Late afternoon traffic conditions only allowed us to sneak up to around 180 mph a couple of times, but the obvious power still in hand at this speed made it clear that there was much more to come.

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Torque is also what makes the Brabus 700 Biturbo a quite different animal in everyday driving. The standard SLS is not slow or lacking in grunt if you use the revs. But if you are in a high gear and want instant go, you’ll be met by smooth but less-than-sparkling acceleration until the rev counter needle passes the 3000-rpm mark. Matching the standard car’s peak torque at just 2000 rpm on its way to its much higher plateau, the Brabus 700 Biturbo is cooking with gas much earlier in the day. The extra thrust on tap means you don’t have to pay attention to the gear you’re in so much, and it would be realistic to say that you can drive everywhere at least one gear higher for a given situation.

On the autobahn, where you can sustain long blasts of full throttle acceleration, the difference is astonishing. Where the standard SLS moves rapidly away from most other cars you’re likely to encounter, the 700 Biturbo does so to an even greater extent, and with palpably less effort. It is the difference between having to use the throttle and just tickling it. Trekkies would describe it as the difference between impulse and warp engines. The greater torque at low rpm also means that in normal light throttle driving on the road, fuel consumption is no worse than standard, and could potentially be even better as you do not need to dig deep into the throttle.

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The Brabus Ride Control system addresses the one area where the standard SLS chassis makes a compromise in the interest of its fine high-speed handling and grip. While it is widely accepted that the suspension is taut and compliant at high speed, the low speed secondary ride is a bit sudden on short, sharp bumps.

Brabus teamed with Bilstein to come up with a solution that would not compromise high-speed performance. While they were at it, they also decided to incorporate a front lift system for clearing the ramps and other obstacles that are the bane of low sports cars. Operated by a button next to the Ride Control and Exhaust valve activation, this raises the nose of the car by 50mm (2 inches), sufficient to avoid contact with most car park ramps. The final suspension solution uses bespoke coilovers with significantly increased spring rates and adjustable dampers. The front spring rate is increased by 31 percent and the rears are up by 26 percent. The variable rate damping allows a roughly 35 percent difference in damping between the Comfort and Sport settings to be achieved at the touch of a button on the center console. The antiroll bars are also uprated to further reduce roll in fast corners.

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In the final analysis, the Brabus Sport setting ends up a few percent stiffer than the factory original, although it is quite discernable with the larger wheels and tires. At the other end of the scale, the Comfort setting makes an appreciable difference to ride comfort, taking the sting out of the low-speed ride. This is a very worthwhile upgrade, even for a standard SLS, and if you stick to factory-size wheels, the ride would be even better.

As it is, our test car had the same 20- and 21-inch front and rear alloys as the Geneva Show car along with the Brabus Widestar rear wheelarch flares that add 20mm to each side. The standard SLS uses Continental ContiSportContact 5 P tires in 265/35 and 295/30 sizes on 19- and 20-inch flow-formed alloy wheels. Brabus goes up one size with 9.5x20 and 11x21-inch ultra-light forged wheels that weigh 12 percent less than the factory ones. Shod with 275/30-20 and 295/25-21 Z-rated tires from either Pirelli or Yokohama, they look terrific and give the car a more purposeful stance.

The other bodywork additions are the carbon-fiber front air splitter and a matching spoiler on the trunk lid. Both contribute to reduce lift over their respective axles for greater stability at speed. Carbon fiber is also used for the air intakes on the sides of the nose, the air outlet covers aft of the front wheel arches and the side sills with their air intakes in front of the rear arches, as well as the rear underbody diffuser, above which are air outlets for the rear valance.

As the gray Geneva Show car was sold, we used its immaculate engine bay and interior to photograph as representative of a customer’s car and drove Brabus’ red development car with its standard interior. “Plush” is the best word to describe the exquisite interior on the show car. The seats, center console, lower half of the dashboard and part of the door panels are covered in off-white leather with contrasting anthracite stitching, cross stitching in the case of the seats.

The floor and floor mats are finished in quilted anthracite leather, and the anthracite leather on the seats and steering wheel airbag have off-white stitching highlights. The dashboard top is covered in non-reflective anthracite Alcantara with off-white stitching, and this is carried through to the door cappings.

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Fine details abound, and even the buttons that clip the seatbelt retainers to the seat backrests have been replaced with ones featuring the Brabus logo. The Brabus lettering on the sills lights up blue at night in a 3D design, and LED lights under the sills light your way to the gullwing doors. The final touch is the 400-km/h speedometer.

For most people, a standard SLS AMG is the ultimate Mercedes sports car, but Brabus customers tend to look at any standard Mercedes or AMG car as just the starting point. The Brabus SLS 700 Biturbo is the result of starting at the top of the tree.

Brabus 700 Biturbo

Layout
Longitudinal front engine, rear-wheel drive

Engine
6.2-liter V8, dohc, 32-valve, twin-turbocharged. Forged Mahle pistons, custom exhaust manifold, custom Garrett turbochargers, twin water-to-air intercoolers, ported cylinder heads, custom catalytic converters, titanium exhaust, Brabus software

Transmission
Seven-speed automatic

Wheels and Tires
Brabus alloys, 9.5x20 (f), 11x21 (r)
Pirelli P Zero, 275/30 (f), 295/25 (r)

Exterior
Brabus Widestar rear wheel arch flares, carbon front splitter and rear spoiler, carbon vent accents

Interior
Custom quilted leather and Alcantara with contrasting stitching, Brabus logo accents

Performance
Peak Power: 700 hp @ 6600 rpm
Peak Torque: 627 lb-ft @ 4300 rpm
0-62 mph: 3.7 sec.
Top Speed: 213 mph (unrestricted)

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By Ian Kuah
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