US-based Mercedes tuning specialist Renntech has created a 106 kW upgrade for the Mercedes SL65 Black.

The ‘Renntech Performance Package 1′ uses a revised ECU, dual intercoolers for the bi-turbo V12 and a sports exhaust, to boost the car’s power output to a total of 592 kW. Impressive on the standard SL65 Black Series was its torque figure of 1 000 Nm, however, Renntech have increased this to a teutonic 1 356 Nm.

Obviously, deploying 1 356 N.m of torque to the tarmac via the rear wheels is easier said than done. To give the Renntech SL65 a fighting chance of not being overwhelmed by physics, the tuning company has included a transmission upgrade as part of the package. A limited-slip differential, with the ability to range from open to 100 per cent locked, is deployed between the rear wheels to help keep the power in check.

Renntech are yet to provide any revised performance figures for the upgrade, but as the SL65 Black was no slouch in standard trim, expect the results to be explosive. Of course if you don’t want to go to Renntech to have your SL65 tuned, you could always try Brabus.

I recently posted an article about two tuning packages, from Brabus and RENNtech, for the Mercedes C63 AMG.

It may have appeared at first glance that RENNtech had the upper hand with its performance package. However, Brabus are specialists of all things AMG and have been taking Mercedes and AMG’s products to the the limit since the company formed in 1977. So although the B63 S performance package may only give your standard C63 AMG an extra 54kW and 50Nm, it is by no means the end of Brabus’ efforts with the W204.

You won’t find the Brabus Bullit listed under “Performance Enhancement” in the Brabus catalogue, and there’s good reason. It’s a complete re-working of the C63 AMG to a point bordering on the insane. Perfect then to be added to the “Brabus Supercars” division.

Powered by a 6.3-litre V12 bi-turbo producing 537kW and 1100Nm the Bullit gets from zero to 100km/h in just 3.9 seconds. It’ll hit 200km/h after 10.5 seconds and 300km/h after 24.5 seconds. Keep your foot planted and you’ll be seeing 360km/h on the speedo.

To put these figures in perspective the new Lamborghini LP560-4 launches from zero to 100km/h in 3.7 seconds and hits 200km/h after 11.8 seconds. Flat out, the owner of the LP560-4 will seem like he’s out for a Sunday drive at 325km/h.

Producing 1320Nm of peak torque (limited electronically in-car to 1100Nm), the 6.3-liter V12 Biturbo Engine has been given a new turbocharging system with two larger chargers and more efficient intercoolers. Metal catalysts with low back pressure and a stainless-steel high-performance exhaust system custom-tailored for the C-Class body also allow the engine to breathe more freely.

New engine electronics have also been added along with a custom mapping and the on-board diagnostics system that delivers low exhaust emissions that meet stringent Euro IV limits.

Power is transferred to the rear wheels via a massively modified five-speed automatic transmission and a BRABUS rear locking differential with a locking rate of up to 40 percent. The Brabus Bullit is available with two different final drive ratios and includes traction and stability control systems such as ABS, ASR and ESP.

Aerodynamically, the sedan body was optimized for runs beyond 300km/h in the wind tunnel and the front apron was designed to provide maximum cooling air supply for radiators and front brakes. Cooling is also aided by a special aluminum hood with ventilation slots.

The four-door features a three-piece rear spoiler and a rear apron with integrated diffuser. Front and rear spoilers are manufactured from especially lightweight, yet high-strength, carbon fibre.

Aluminum fender flares front and back are moulded to the stock body adding 6cm to the width of the C-Class body and leave room for the large 9.5Jx19 Brabus Monoblock S light-alloy wheels with size 265/30 ZR19 tyres up front. The rear axle features 10Jx19 wheels with size 285/30 ZR19 tyres.

The coil-over suspension was custom-developed to account for the power and the weight of the engine, as well as featuring ten selectable settings each for bound and rebound.

The brake system features 12-piston aluminum fixed calipers on the front axle, which grip vented and grooved 380mm x 37mm brake discs. The rear axle stops with 360mm x 28mm discs and six-piston aluminum fixed calipers.