At 110 mph, the cabin of Renntech's SL 600 is a fairly quiet place, so quiet I can hear my co-driver's teeth grinding. The only discernable noise is a sound like a distant offshore boat heading somewhere fast. For entertainment, I drop a few gears and boot the throttle just to hear something different. Bad idea. Incessant rain has dampened the road and the slight upward slope gives the car the trajectory of a SAM missile. No, it doesn't fly off into the clouds, but rather breaks the fat Nitto rubber loose in a brilliant smoking display of high-speed power. Doing a burnout from a dead start is easy; frying the tires at triple digits ain't. It places this Mercedes in an entirely different league altogether.
I've known Hartmut Feyhl of Renntech for a long time. Nearly 15 years ago we tested a Renntech SL on a long stretch of Florida's Sawgrass Expressway. In less than an hour we had traversed nearly half of the Sunshine State. We'd never experienced a car so powerful yet so refined.
Hartmut and his company Renntech are still at it, transforming Mercedes vehicles into genuine supercars. This SL 600 project was built to showcase both Renntech's tuning prowess and Nitto's latest tire technology. Given the extreme nature of this Merc, Nitto may have gotten more that it bargained for-this beast chews through tires on a regular basis.
Invariably, people want to know two things: Who did the paint and what's the car cost? The money part is easy. Three hundred thousand dollars and it's yours. Nitto will even throw in a new set of tires. The paint part is tougher. It appears as though the entire car has been chrome plated, every fender, every sill, every panel. In truth it's a labor-intensive, high-tech paint job. The formula is a secret proprietary blend based on actual silver which must be applied in a clean-room environment to avoid contamination. After the paint sets it is repeatedly color sanded and sprayed again. Following the last rubdown, the car is sprayed with a metallic blue clear coat. The entire procedure took more than four months.
"We were inspired by cars treated with metallic foils," Hartmut recalled. "The treatment looked great but proved problematic over larger areas. This new process gives the car a more solid look, like it's carved from one piece of metal."
I can't help being reminded of the Naboo Royal Cruiser in Star Wars. The ultimate effect is stunning. And from what we saw during our testing, the paint appears to be as durable as that of standard car. Oh yeah, plan on spending $80,000 for your ride to look like this.
Although it's no slouch from the factory, Renntech squeezed another 70 bhp and 120 lb-ft of twist from the SL's twin-turbo, 5.5-liter V12. The engine has been crowned with Renntech's intake, a beautifully designed piece wrought from carbon-Kevlar. Hartmut and crew spent many hours optimizing the space under the hood and managed to create an intake that moves more air and creates more power. The intake alone netted an additional 15 bhp. Renntech's close ties to Mercedes also allowed them to write ECU code that increased horsepower (via boost, fuel and timing) and throttle response while raising the top speed limiter. At the rear, Renntech's sport mufflers lend a singular voice to this vehicle, one you cannot easily forget.
Mercedes tuners (I use that term loosely) often overlook the transmission, opting for more power without regard to its judicious use. In actuality, upgrading the gearbox is an absolute necessity as the stock tranny computer would not and could not hold the power. Renntech essentially reprogrammed the automatic five-speed transmission computer, giving it revised shift points and quicker response (a huge improvement on the 1-2 shift). Off-the-line and midrange acceleration are greatly improved while still retaining a factory-like smoothness.
The SL rides on the factory suspension altered with Renntech's electronic lowering module. At the end of the day it's nearly a full inch closer to the ground. Brakes are Renntech's own recipe comprised of Brembo, AP and Alcon components. Get this-the eight-piston calipers grip 15-inch rotors. That's bigger than most automotive production wheels. Renntech's new seven-spoke running gear measures 9x19 inches in front and 10x19 behind. Shod with Nitto's 555 high-performance rubber (245/40-19 in front and 275/35-19 behind), we're told this setup is one of the lightest currently available (like this car needs to worry about unsprung weight).
The body has been massaged with Renntech bodywork including the front splitter, decklid spoiler and rear diffuser.
"I only use stuff that works," said Hartmut. "We test all of these components. If they make no difference, why bother changing them?"
That is perhaps why Renntech cars are so special. Their understatement is a matter of form following function.
Don't ask how much the Renntech treatment costs, just ask what it can do for your Mercedes. Chances are you won't be able to find a better deal.
2004 Mercedes-Benz SL 600
DrivetrainLongitudinal front engine, rear wheel drive
Engine5.5-liter V12, single overhead cam, three valves per cylinder, twin turbocharged and intercooledModifications: Renntech intake, performance ECU
TransmissionFive-speed automaticModifications: Renntech performance upgrade
SuspensionIndependent four-link front, independent five-arm multilink rear, coil springs, electronically active hydraulic dampers, gas shocksModifications: Renntech lowering module
BrakesRenntech eight-piston calipers, 15-inch rotors
PerformancePeak Power: 625 bhpPeak Torque: 745 lb-ft0-60 mph: 3.9 secTop Speed: 198 mph