Pushing an already potent supercar into uncharted territory can be a recipe for destruction. AMG was founded in 1967 by Mercedes engineers who wanted more power and racing performance than the factory was willing to offer. As an aftermarket tuner, their comprehensive body and engine modifications earned so much notoriety that Daimler purchased the company in 1999 and made them the in-house performance division.
Given the resources of Mercedes, AMG decided to build their own production car. Unencumbered by the constraints of re-working an existing chassis, they chose to build a faithful reincarnation of the iconic 300 SL Gullwing. The SLS AMG debuted in 2009 with a potent 6.2L V8 creating 563 HP and sitting behind the front wheels. An all-aluminum body and rear mounted transaxle provide an optimal 47/53 weight distribution.
It may be the modern German supercar, but since AMG became subservient to Mercedes, there has been more of an opportunity for the aftermarket to further refine their products. Enter RENNtech. Hartmut Feyhl founded the company in 1989, after twelve years at AMG, serving as their technical director for North America. His passion has been to extract every ounce of performance from all Mercedes products, even Sprinters and SmartCars.
This showroom new SLS was ordered with every option, including the rare AMG LeMans red finish. Many SLS buyers didn’t opt for the added content because it exponentially inflated the window sticker. Carbon fiber interior trim was $9,000 and the carbon-ceramic brakes were $12,000. AMG Sports Suspension is also rarely seen on the SLS because of the $1,500 price tag. At delivery to the original customer, the window sticker was $228,225, making it one of the most expensive and rare examples of the Gullwing ever built.
Performance has been pushed to stratospheric levels with more than $80,000 in RENNtech modifications. Their R3 package boosts horsepower to 635 and torque to 540 lb-ft via extensive modifications. To put that into perspective, a Corvette ZR1 was also equipped with a 6.2L V8 and it made 638 HP, but required a supercharger to do so. Even the new 2016 Mercedes-AMG GT S, which is the successor to the SLS, makes only 503 HP and it has two turbochargers.
From an engineering standpoint, no expense was spared. RENNtech hand fabricated headers that feed into an all-titanium exhaust by Akrapovic. It provides an aggressive sound and is 45 lbs lighter than the AMG system. The dual mode system can be subdued and tame for civility, but when the baffles are opened it is a symphony of power. Here is a start and idle video, uploaded to YouTube Sept. 11 by ExoticMotorsMidwest, with the exhausts open:
A large V8 that has the ability to rev so quickly implies a very free flowing system. Tuned length primaries in the headers help to retain the throaty nature of a full-on race system. The engine computer was replaced with a proprietary unit built by RENNtech. It features revised ignition timing and throttle mapping along with a leaner air/fuel ratio. Three piece forged ADV.1 wheels made exclusively for RENNtech measure a staggering 20’x10” in front and 21”x12” in the rear.
For the incredible speeds this car is capable of, much more downforce is needed to keep the rubber on the road. RENNtech used computer modeling to develop a comprehensive aero package. In addition to having the AMG carbon fiber package, RENNtech carbon comprises the splitter, side skirts and rear diffuser and is topped off by an adjustable DTM series rear wing.
With only 2,995 miles on the odometer, this is an opportunity to own the purest and most powerful example of a German Grand Tourer thanks to Exotic Motors Midwest.